CN108696959B - Driver of light emitting diode - Google Patents

Abstract

The invention discloses a driver for a light-emitting diode, which is used for driving a light-emitting element, comprising a rectifier circuit, a current driving circuit, and a protection circuit. The rectifier circuit includes a rectifier diode for receiving an AC input power and converting it into a DC power source. The DC power source includes a DC current and a DC voltage. The current driving circuit includes a certain current unit, wherein the rectifying circuit, the current driving circuit and the light-emitting element are connected in series, and the current driving circuit is used to limit the magnitude of the direct current to drive the light-emitting element. The protection circuit includes a protection unit, wherein the protection circuit is connected across the current driving circuit and the light-emitting element, and when the DC voltage is greater than a certain value, the DC current flows to the protection circuit; wherein the rectifier diode, the constant current unit and the protection unit share a substrate.

Description

LED driver

technical field

The present invention relates to a driver of a light emitting diode, in particular to a driver of a light emitting diode with a protection unit.

Background technique

In recent years, light-emitting diodes (light-emitting diodes) have gradually replaced cathode lamps or tungsten filaments as light sources for backlights or lighting systems due to their good electro-optical conversion efficiency and small product volume. However, because of the voltage and current characteristics of light-emitting diodes (about 3 volts, DC drive), the AC input power of the general mains cannot directly drive the light-emitting diodes, but a power converter is required to convert the AC input power into an appropriate DC power supply. .

Lighting electricity often occupies a very large part of the mains power supply. Therefore, for power converters used in lighting, in addition to very low conversion losses, the regulations must also provide a good power factor (power factor between 0 and 1). The closer the power factor of an electronic device is to 1, the closer the electronic device is to a resistive load.

FIG. 1 shows a conventional lighting system 10 , which includes a bridge rectifier 12 , a power factor corrector 14 , an LED driver circuit 16 , and an LED 18 . The power factor corrector 14 may be a booster circuit, and the LED driving circuit 16 may be a buck converter. However, switching power converters such as boost circuits or buck circuits require not only bulky and expensive inductive components, but also a large number of electronic components for the entire system architecture. Therefore, lighting systems using switching power converters are relatively uncompetitive in the market due to their high production costs.

SUMMARY OF THE INVENTION

The embodiment discloses a driver for driving a light-emitting element, which includes a rectifier circuit and a current driving circuit. The rectifier circuit includes a rectifier diode, which is electrically connected to an AC input power source for generating a DC power source, and spans between the DC power source wire and a ground wire. The current drive circuit includes a certain current source. The constant current source and the light-emitting element are connected in series between the DC power line and the ground line. The constant current source can provide a certain current to drive the light-emitting element. The rectifier diode and the constant current source are jointly formed on a single semiconductor chip.

The embodiment discloses a driver for driving a light-emitting element, including a rectifier circuit, a current driving circuit, and a protection circuit. The rectifier circuit includes a rectifier diode for receiving an AC input power and converting it into a DC power source, the rectifier circuit is connected in series with the light-emitting element, and the DC power source is used for providing a DC current and a DC voltage. The current driving circuit includes a certain current unit, wherein the rectifier circuit, the current driving circuit and the light-emitting element are connected in series, and the current driving circuit is used to limit the magnitude of the direct current to drive the light-emitting element. The protection circuit includes a protection unit, wherein the protection circuit is connected across the current drive circuit and the light-emitting element, and is connected in series with the rectifier circuit. When the DC voltage is greater than a certain value, the DC current flows to the protection circuit; wherein the rectifier diode, the constant current unit and the protection circuit Units are collectively formed on a semiconductor chip.

Description of drawings

1 is a schematic diagram of an existing lighting system;

FIG. 2 is a schematic diagram of an LED driver according to an embodiment of the application;

3 is a schematic diagram of three voltage waveforms;

4A is a schematic diagram of a pattern of a metal layer on a semiconductor chip;

4B is a schematic diagram of an integrated circuit after the semiconductor chip of FIG. 4A is packaged;

5 is a cross-sectional view of the high electron mobility field effect transistor T1 in FIG. 4A along the line ST-ST;

6 is a cross-sectional view of diode DVF3 in FIG. 4A along line SD-SD;

7 is a schematic diagram of a lighting system according to an embodiment of the application;

8 is a schematic diagram of an LED driver according to another embodiment of the present application;

9A is a schematic diagram of a pattern of a metal layer on another semiconductor chip;

9B is a schematic diagram of an integrated circuit after the semiconductor chip of FIG. 9A is packaged;

10 is a schematic diagram of a lighting system according to another embodiment of the present application;

Figure 11 is a circuit diagram of an LED connected in parallel with an additional voltage-stabilizing capacitor;

12 is a schematic diagram of a pattern of a metal layer on another semiconductor chip;

13 is a cross-sectional view of a chip according to another embodiment of the diode DVF3 of FIG. 4A along the line SD-SD;

Figure 14 is a flow chart that may be used to make the diode of Figure 13;

15 is a schematic diagram illustrating the relationship between I _DS and V _DS in a metal oxide semiconductor field effect transistor (MOSFET) and a high electron mobility field effect transistor according to an embodiment of the present application;

16 is a schematic diagram of an LED driver according to another embodiment of the present application;

17 is a schematic diagram of a pattern of a metal layer on a semiconductor chip according to an embodiment of the application;

FIG. 18 is a schematic diagram of an integrated circuit after the semiconductor chip of FIG. 17 is packaged;

FIG. 19 is a schematic diagram of a lighting system implemented using the integrated circuit in FIG. 18;

20 is a schematic diagram of a circuit design of an LED driver according to an embodiment of the application;

21 is a schematic diagram of an LED driver having a plurality of LEDs according to yet another embodiment of the application;

22 is a cross-sectional view of a diode chip according to an embodiment of the application;

23 is a schematic diagram of an LED driver according to another embodiment of the present application;

Figure 24 is a schematic diagram of a bridge rectifier;

FIG. 25 illustrates a schematic diagram of a semiconductor chip that can implement the bridge rectifier in FIG. 24;

26A, 26B and 26C are chip cross-sectional views of the semiconductor chip 808 along lines CSV1-CSV1, CSV2-CSV2 and CSV3-CSV3;

Figure 27 is a schematic diagram of another bridge rectifier;

FIG. 28 illustrates a schematic diagram of a semiconductor chip that can implement the bridge rectifier in FIG. 27;

29A is a schematic diagram of an enhancement mode high electron mobility field effect transistor ME and a depletion mode high electron mobility field effect transistor MD on a semiconductor chip;

29B is a schematic diagram of the electrical connection between the high electron mobility field effect transistor MD and ME in FIG. 29A;

30 is a cross-sectional view of the chip along the line CSV4-CSV4 in FIG. 29A;

31 is a schematic diagram of an LED driver according to an embodiment of the application;

32 is a schematic diagram of the voltage waveform of the AC input power supply in FIG. 31 and a current waveform flowing through the bridge rectifier 844;

33 is a schematic diagram of an LED driver with a thermistor having a positive temperature coefficient;

34 is a schematic diagram of an LED driver with a thermistor having a negative temperature coefficient;

35 is a schematic diagram of another LED driver with a thermistor;

36A is a schematic diagram of an LED driver according to an embodiment of the application;

36B is a schematic diagram of an LED driver according to another embodiment of the present application;

37 is a voltage-current relationship diagram of a high electron mobility field effect transistor;

FIG. 38 is a top view of an LED driver according to another embodiment of the application;

FIG. 39 is a schematic cross-sectional view of the structure of the Schottky diode, the high electron mobility field effect transistor and the protection unit in FIG. 38 .

Symbol Description

10 Lighting System 12 Bridge Rectifier

14 power factor corrector 16 LED drive circuit

18, 18B, 18R LED 19 voltage regulator capacitor

60, 60a, 60b, 60c LED Drivers 62 Bridge Rectifiers

63 Protection circuit 64 Valley filling circuit

66 Current drive circuit 67 Dotted line

72, 74, 76 voltage waveforms 80 semiconductor chips

90a Semiconductor stack 91, 92 Substrate

94 buffer layer 95, 95a platform area

96 channel layer 98 high valence band gap layer

100 cap layer 102 metal layer

102a, 102b, 102c, 102d, 102e Metal sheet

102'a, 102'b, 102'c, 102'd, 102'e, 102'f sheet metal

103, 103a, 103b, 103c insulating layer 104 metal layer

104a, 104'a, 104b, 104c, 104d, 104e, 104f, 104g, 104h Metal Sheet

105 Sheath 120 Diode Symbol

130 Integrated circuits 140, 142, 144, 146, 148 steps

150, 152 curve 170 adjustment area

200 Lighting System 300LED Driver

302 Current Drive Circuit 330 Lighting System

500LED Driver 502 Bridge Rectifier

504 current drive circuit 518, 5181, 5182, 5183LED

5201, 5202, 5203, 5204 LED segment 550 semiconductor chip

552 Integrated Circuit 560 Lighting System

600LED driver 700LED driver

800 LED Driver 802 Triac Dimmer

806 Bridge Rectifier 808 Semiconductor Chip

810 Bridge Rectifier 812 Semiconductor Chip

840 LED Driver 848 LED

850 Resistor 852 Schottky Diode

900LED driver 902, 906 thermistor

910 LED driver A contact

A anode of _clamp protection unit A anode of _{sbd1～sbd4 Schottky} diode

AC-source AC input power AC+, AC AC input pins

AC1, AC2 AC power cord ARM1, ARM2 upper arm

ART, ARB upper and lower arms C contact

Cathode of C _clamp protection unit C _sbd1～sbd4 Cathode of Schottky diode

C1, C2, CF capacitor CC1, CC2, CC3, CC4 current switch

DB1, DB2, DB3, DB4 rectifier diodes DVF1, DVF2, DVF3 diodes

D terminal D _clamp protection unit

D _hemt1 , D _hemt2 drain D1, D2 drive pins

E contact F contact

GD, GE, G _hemt1 , G _hemt2 gate GND ground wire

I _c saturation current in GG gate region

I _DS drain-source current I _DC-IN DC current

IC1, IC2 segment circuit L contact

L _b p-type barrier length

ME, MD high electron mobility field effect transistor N contact

P _b p type barrier layer

PF1, PF2 correction pins

S terminal S _hemt1 , S _hemt2 source

S1, S2 drive pins

SBD1, SBD2, SBD3, SBD4 Schottky diodes

SS saturation region

TD1, TD2, TSG contacts

T _b p type barrier thickness

T1, T2, T3, T4, T5, T6, T7, T8 High Electron Mobility Field Effect Transistors

TP1, TP2, TP3 period

V _AC-IN AC voltage V _DC-IN DC voltage

V _DS drain-source voltage V _knee cut-point voltage

V _PEAK voltage peak VCC high voltage pin

VDD DC power line VSS low voltage pin

Detailed ways

In this specification, unless otherwise specified, the same symbols generally represent elements having the same or similar structures, functions, and principles, and those with ordinary knowledge in the art can infer them based on the teachings of this specification. For the sake of brevity of the description, elements with the same symbols will not be repeated.

In an embodiment of the present application, the entire LED lighting system has a simple circuit design, and the main components are only an integrated circuit packaged with a single semiconductor chip (chip), two capacitors, and an LED used as a light source. The LED lighting system of the embodiment may not need to connect additional inductive elements. Therefore, the circuit cost of the LED lighting system will be quite low. In addition, the LED lighting system of the embodiment also provides a relatively good power factor, which can meet the requirements of most specifications.

FIG. 2 shows an LED driver 60 that can be used to drive the LEDs 18 according to an embodiment of the present application. The LED 18 may be a high voltage LED formed by connecting a number of micro LEDs (micro LEDs) in series. For example, in one embodiment, the forward voltage of each micro-LED is about 3.4 volts, and the LED 18 is formed by connecting more than 10 micro-LEDs in series, and the equivalent forward voltage V _ef-led (forward voltage) is about 50V.

The LED driver 60 has roughly three parts. The first part connected to the AC input power supply (AC-source) is the bridge rectifier 62 . The second part is a valley-fill circuit 64 , which acts as a power factor corrector and can improve the power factor of the entire LED driver 60 . The third part has two high electron mobility transistors (HEMTs) T1 and T2 as the current driving circuit 66 . The high electron mobility field effect transistors T1 and T2 can each be used as a constant current source or can be connected in parallel as a constant current source that can provide a larger current value. Taking the high electron mobility field effect transistor T1 as an example, when its drain-to-source voltage (V _DS ) is large enough, the drain-to-source current (I _DS ), that is, from The current flowing from the drain to the source will be approximately constant and will hardly vary with V _DS . The high electron mobility field effect transistor T1 provides approximately a certain current to drive the LED 18 .

The bridge rectifier 62 includes four rectifier diodes DB1-DB4. As will be explained below, the four rectifier diodes may all be Schottky Barrier Diodes (SBD). The bridge rectifier 62 rectifies the AC input power to generate the DC power, which spans between the DC power line VDD and the ground line GND. The AC input power source includes an AC voltage V _AC-IN , and the DC power source includes a DC current I _DC-IN and a DC voltage V _DC-IN . For example, the AC input power supply can be general 110V or 220V AC mains.

The valley filling circuit 64 is electrically connected between the DC power line VDD and the ground line GND, and includes three diodes DVF1-DVF3 and capacitors C1 and C2. The diodes DVF1-DVF3 are connected in reverse series between the DC power line VDD and the ground line GND. In this embodiment, the capacitance values of the capacitors C1 and C2 are approximately equal, but the present application is not limited thereto. Theoretically, the capacitor voltages VC1 and VC2 of the capacitors C1 and C2 can be charged to about half of the voltage peak value V _PEAK of the DC voltage VDC-IN (0.5×V _PEAK ). When the absolute value of the AC voltage V _AC-IN is lower than 0.5×V _PEAK , the capacitors C1 and C2 can discharge the DC power line VDD and the ground line GND. As long as the capacitors C1 and C2 are large enough, the valley filling circuit 64 can make the minimum value of the DC voltage V _DC-IN approximately equal to 0.5V _PEAK , providing enough DC voltage V _DC-IN to keep the LED 18 emitting light.

Both the high electron mobility field effect transistors T1 and T2 are depletion mode transistors, which means that their threshold voltages (threshold voltage, VTH) are both negative. Each high electron mobility field effect transistor has a gate and two channels, and the two channels are commonly referred to as a source and a drain. The gate and source of each of the high electron mobility field effect transistors T1 and T2 are shorted to each other. Taking the high electron mobility field effect transistor T1 as an example, when its drain-to-source voltage (V _DS ) is large enough, the drain-to-source current (I _DS ), that is, from The drain-to-source current will be approximately constant, almost independent of V _DS . Therefore, regardless of whether the high electron mobility field effect transistor T1 or T2 can be used as a constant current source, it can provide a stable constant current to drive the LED 18, so that the luminous intensity of the LED 18 can be maintained constant without flickering. In FIG. 2, the high electron mobility field effect transistor T1 drives the LED 18, and the two together act as a load and are connected in series between the DC power line VDD and the ground line GND. FIG. 2 connects the high electron mobility field effect transistor T2 and the LED 18 with a dotted line 67, indicating that the high electron mobility field effect transistor T2 can selectively drive the LED 18 together with the high electron mobility field effect transistor T1, which will be detailed later. illustrate.

3 shows the time-varying voltage waveform 72 of the AC voltage V _AC-IN of the AC input power supply, the time-varying voltage waveform 74 of the DC voltage V _DC-IN of the DC power supply without the valley filling circuit 64 , and the valley filling circuit Time-varying voltage waveform 76 of the DC voltage V _DC-IN of the DC power supply at 64 . For example, the AC input voltage V _AC-IN is 220VAC, which is a sine wave, as shown in FIG. 3 . The voltage waveform 74 is represented as a virtual result without the valley fill circuit 64 . Without the valley-fill circuit 64, the bridge rectifier 62 would provide simple full-wave rectification, and so would convert the negative voltage portion of the voltage waveform 72 to positive, as shown by the voltage waveform 74. The valley filling circuit 64 will fill in the valleys in the voltage waveform 74 , or make the valleys in the voltage waveform 74 less deep, as shown by the voltage waveform 76 . For the convenience of description, the following description will sometimes use the voltage waveform 74 to explain the timing of event occurrence. For example, when the voltage waveform 74 reaches a peak, it represents when the voltage waveform 72 (the AC input voltage V _AC-IN ) reaches a peak or a valley.

Period TP1 begins when voltage waveform 74 is greater than or equal to voltage waveform 76 until voltage waveform 74 rises over time until peak V _PEAK ends. During time period TP1, the power to illuminate the LED 18 will come directly from the AC input power source, so the voltage waveform 76 of the DC voltage V _DC-IN is equal to the voltage waveform 74 . At this time, once the DC voltage V _DC-IN is greater than the sum of the capacitor voltages VC1 and VC2, the capacitors C1 and C2 will be charged by the AC input power. When the voltage waveform 74 reaches the peak value V _PEAK , the capacitor voltages VC1 and VC2 are both approximately 0.5V _PEAK .

Period TP2 begins when the voltage waveform 74 reaches the peak value V _PEAK until the voltage waveform 74 drops to half the peak value (1/2V _PEAK ). During time period TP2, the voltage waveform 74 begins to drop over time, and the power to illuminate the LED 18 will come directly from the AC input power source, so the voltage waveform 76 is equal to the voltage waveform 74. Because the capacitors C1 and C2 are not charged or discharged, the capacitor voltages VC1 and VC2 will both remain at 0.5V _PEAK .

Period TP3 begins after the voltage waveform 74 falls below 0.5V _PEAK , which is approximately the time when the valley of the voltage waveform 74 occurs. During the period TP3, the capacitor C1 is discharged through the diode DVF3 to supply power to the high electron mobility field effect transistor T1 and the LED 18. Similarly, the capacitor C2 will discharge through the diode DVF1 to supply power to the high electron mobility field effect transistor T1 and the LED 18 as well. The capacitor voltages VC1 and VC2 will decrease with time, and the rate of decrease depends on the capacitance values of the capacitors C1 and C2. Period TP3 ends when voltage waveform 74 is higher than capacitor voltage VC1 or VC2 after bouncing off the valley. It is then continued by another time period TP1. As shown in the voltage waveform 76 of FIG. 3, as long as the capacitors C1 and C2 are large enough, the DC power supply may provide enough DC voltage V _DC-IN to keep the LED 18 lit.

As long as the capacitors C1 and C2 are large enough, the power factor achieved by the valley filling circuit 64 can meet the power factor requirements of most countries.

In one embodiment, the rectifier diodes DB1-DB4, the diodes DVF1-DVF3, and the high electron mobility field effect transistors T1 and T2 in FIG. 2 are all formed together on a single semiconductor chip. FIG. 4A shows a pattern of a metal layer 104 on a semiconductor chip 80 and indicates the relative positions of the diode and the high electron mobility field effect transistor in FIG. 2 on the semiconductor chip 80 . The semiconductor chip 80 may be a monolithic microwave integrated circuit (MMIC) using gallium nitride as a conduction channel material (GaN-based). In FIG. 4A , the element structure of each diode is approximately similar, that is, a Schottky diode, and the element structures of the high electron mobility field effect transistors T1 and T2 are also similar. FIG. 5 shows a chip cross-sectional view of the high electron mobility field effect transistor T1 in FIG. 4A along the line ST-ST; FIG. 6 shows a chip cross-sectional view of the diode DVF3 in FIG. 4A along the line SD-SD. The element structures of other diodes and high electron mobility field effect transistors in the figure can be obtained by analogy.

In the example of FIG. 5 , the buffer layer 94 on the silicon substrate 92 may be C-doped intrinsic GaN. The channel layer 96 may be intrinsic GaN on which a high-bandgap layer 98 is formed, and the material may be intrinsic AlGaN. The capping layer 100 may be intrinsic GaN. The cap layer 100 , the high valence bandgap layer 98 and the channel layer 96 are patterned to form a mesa 95 (mesa). A two-dimensional electron gas (2D-electron gas) may be formed in a quantum well in the channel layer 96 adjacent to the high-valence bandgap layer 98 as a conductive channel. The material of the patterned metal layer 102 may be titanium, aluminum, or a laminate of these two materials. In FIG. 5 , the metal layer 102 forms two metal strips 102 a and 102 b above the mesa region 95 , and forms two ohmic contacts with the mesa region 95 respectively, so that the metal strips 102 a and 102 b serve as two ohmic contacts respectively. The source and drain of the high electron mobility field effect transistor T1. The material of the metal layer 104 may be titanium, gold or a laminate of these two materials. For example, from bottom to top, the metal layer 104 has a nickel layer (Ni), a copper layer (Cu), and a platinum layer (Pt), wherein the platinum layer can increase the adhesion of the protective layers 105 formed later to each other. Adhesion to prevent peeling problems during the pad fabrication process. In other embodiments, the metal layer 104 may also be a stack of nickel (Ni), gold (Au) and platinum (Pt) layers, or a nickel (Ni), gold (Au) and titanium (Ti) layer ) stack. In FIG. 5, the patterned metal layer 104 forms metal sheets 104a, 104b and 104c. The metal sheet 104b contacts the upper center of the mesa region 95 to form a schottky contact, which serves as the gate of the high electron mobility field effect transistor T1. 104a and 104c in FIG. 5 are in contact with 102a and 102b, respectively, to provide electrical connection between the source and drain of the high electron mobility field effect transistor T1 to other electronic components. Please refer to FIG. 5 and FIG. 4A at the same time, it can be found that the gate (metal sheet 104b) of the high electron mobility field effect transistor T1 is short-circuited to the metal sheet 104a through the metal layer 104, and is also short-circuited to the high electron mobility field effect transistor T1 the source. The right part of FIG. 5 shows the equivalent circuit diagram of the high electron mobility field effect transistor T1. There is a protective layer 105 above the metal layer 104, and the material thereof may be silicon oxynitride (SiON). The protective layer 105 is patterned to form bonding pads required for packaging. For example, in FIG. 5, the left half of the protective layer 105 does not cover the part, which can be soldered to the bonding wire of the low voltage pin VSS (which will be explained later); and the right half of the protective layer 105 is not covered. , which can be soldered to the bond wire of the drive pin D1 (explained later).

For the sake of brevity, the same or similar parts of FIG. 6 as those of FIG. 5 are not repeated. In FIG. 6 , the metal layer 102 forms two metal sheets 102 c and 102 d above the platform region 95 , and the patterned metal layer 104 forms the metal sheets 104 d , 104 e and 104 f . Similar to FIG. 5, the metal sheet 104e can be used as the gate of a high electron mobility field effect transistor. Although the metal sheet 102d can be used as a source of a high electron mobility field effect transistor, the metal sheet 102d is not in contact with the metal layer 104 . In another embodiment, the metal sheet 102d may be omitted and not formed. The metal sheet 104f contacts a part of the upper surface and a side wall of the platform region 95 to form another Schottky contact, which can be used as a Schottky diode, the cathode of which is equivalently short-circuited to the high electron mobility field effect transistor of FIG. 6 . source. Please refer to FIG. 6 and FIG. 4A at the same time. Metal sheet 104e, through metal layer 104, is shorted to metal sheet 104f, which is the anode of the Schottky diode. The right part of Figure 6 shows the equivalent circuit connection diagram of the left half, which behaves as a diode. The right part of FIG. 6 also shows a special diode symbol 120 to represent the equivalent circuit in FIG. 6 . Diode symbol 120 is also used in FIG. 2 to represent rectifier diodes DB1-DB4 and diodes DVF1-DVF3, each of which is a composite diode of a high electron mobility field effect transistor and a Schottky diode.

FIG. 4B shows an integrated circuit 130 after the semiconductor chip 80 is packaged, which has only 8 pins, which are: a high-voltage pin VCC, calibration pins PF1 and PF2, a low-voltage pin VSS, and an AC input pin Pins AC+ and AC-, drive pins D1 and D2. Please refer to FIG. 4A , which also shows that each pin is electrically shorted by a bonding wire to a metal sheet patterned by the metal layer 104 , and these metal sheets are also provided in the semiconductor chip 80 . The corresponding input or output terminals of the electronic components are connected to each other. For example, the drive pin D1 is electrically connected to the drain of the high electron mobility field effect transistor T1, and the correction pin PF1 is electrically connected to the cathode of the diode DVF3.

FIG. 7 shows a lighting system 200 implemented in accordance with the present application. The integrated circuit 130 is mounted on the printed circuit board 202 . Through the metal wires on the printed circuit 202, the capacitor C1 is electrically connected between the high-voltage pin VCC and the calibration pin PF1, the capacitor C2 is electrically connected between the low-voltage pin VSS and the calibration pin PF2, and the LED 18 is electrically connected to the Between the high voltage pin VCC and the driving pin D1, the AC input pins AC+ and AC- are electrically connected to the AC input power supply (the AC voltage V _AC-IN ). It can be understood from the previous explanation that the lighting system 200 in FIG. 7 is very simple, and only uses four electronic components (two capacitors C1 and C2, the integrated circuit 130 and the LED 18) to realize the LED driver 60 in FIG. 2 . . Without expensive and bulky inductive components, the cost of the lighting system 200 can be reduced, and the overall product volume can also be reduced.

In FIG. 7 , the driving pin D2 of the integrated circuit 130 (electrically connected to the drain of the high electron mobility field effect transistor T2 ) can be electrically connected to the LED 18 depending on the AC voltage V _AC-IN . In other words, the integrated circuit 130 can selectively use a single high electron mobility field effect transistor (T1), or use two high electron mobility field effect transistors (T1 and T2) in parallel to drive the LED 18 to emit light. For example, assuming that the high electron mobility field effect transistors T1 and T2 in the integrated circuit 130 have the same size, each can provide about the same constant current of 1u. When the lighting system 200 of FIG. 7 is applied to an AC input power supply of 110VAC, an LED with a forward voltage of 50V can be selected as the LED 18, and the driving pins D1 and D2 are connected to the LED 18. At this time, the LED 18 is The power consumed is about 2u×50 (=100u). When the lighting system 200 of FIG. 7 is applied to an AC input power supply of 220VAC, an LED with a forward voltage of 100V can be selected as the LED 18 , and the driving pin D1 is connected to the LED 18 only, and the driving pin D2 is left floating and free. , the power consumed by the LED18 at this time is about 1u×100 (=100u). In this way, although the AC voltage V _AC-IN of the AC input power supply is different, as long as LEDs with different forward voltages are selected, the power consumed by the LEDs 18 can be approximately the same (all are approximately 100u), and the illumination brightness generated by the lighting system 200 is equal to It will be about the same. In other words, the integrated circuit 130 is not only suitable for the AC input power of 220VAC, but also suitable for the AC input power of 110VAC. This is very convenient for the manufacturer of the lighting system 200 , and can save the cost of managing the parts inventory of the lighting system 200 .

In FIG. 2, the current driving circuit 66 is connected between the LED 18 and the ground line GND, but the present application is not limited thereto. FIG. 8 shows another LED driver 300 implemented in accordance with the present application for driving the LEDs 18 . In FIG. 8, the current driving circuit 302 has high electron mobility field effect transistors T3 and T4, the drains of the high electron mobility field effect transistors T3 and T4 are electrically connected to the DC power line VDD together, and the LED 18 is electrically connected to the ground line Between GND and the current drive circuit 302 . FIG. 9A shows the pattern of the metal layer 140 on a semiconductor chip 310 and indicates the relative positions of the diode and the high electron mobility field effect transistor in FIG. 8 . 5 may also represent a chip cross-sectional view of the high electron mobility field effect transistor T3 in FIG. 9A along the line ST-ST; FIG. 6 may also represent a chip cross-sectional view of the diode DVF3 in FIG. 9A along the line SD-SD. FIG. 9B shows an integrated circuit 320 after the semiconductor chip 310 is packaged, which has only 8 pins, which are: high voltage pin VCC, calibration pins PF1 and PF2, low voltage pin VSS, and AC input pin Pins AC+ and AC-, drive pins S1 and S2. FIG. 10 shows another lighting system 330 implemented in accordance with the present application, which implements the LED driver 300 of FIG. 8 . Fig. 8, Fig. 9A, Fig. 9B and Fig. 10, you can refer to the previous Fig. 2, Fig. 4A, Fig. 4B and Fig. 7 and the related explanations to know the principle, operation, and advantages. .

As shown in the embodiment of FIG. 11 , an additional stabilizing capacitor 19 can be connected in parallel with the LED 18 . The voltage stabilizing capacitor 19 can reduce the variation of the voltage VLED of the LED 18, and even increase the duty cycle or light-emitting time of the LED 18 within one cycle of the AC input power supply, thereby reducing the possibility of flickering of the LED 18.

The pattern in FIG. 4A is only an example, and the present application is not limited thereto. FIG. 12 shows a pattern of a metal layer 104 on another semiconductor chip. FIG. 12 is substantially similar to FIG. 4A, and for the sake of brevity, parts that are the same or similar to each other are not repeated. In FIG. 4A, a gate located in the middle of each diode is only connected to its anode through an upper arm ARM1 of a patterned metal layer 104 (such as the metal sheet 104f in FIG. 6); located in each high electron A gate in the middle of the mobility field effect transistor is also connected to its source through an upper arm ARM2 of a patterned metal layer 104 (eg, the metal sheet 104a in FIG. 5 ). However, in FIG. 12, like the gate region GG illustrated, the gate at the middle position of each diode is connected to its anode through the upper and lower arms ART and ARB of the patterned metal layer 104; A gate in the middle of the field effect transistor is also connected to its source through the upper and lower arms of the patterned metal layer 104 . Compared with the design of FIG. 4A , the structure of the upper and lower arms of the diode in FIG. 12 is relatively symmetrical in fabrication, and is less likely to be affected by the structure between the upper and lower arms during the development, exposure, epitaxy, etching and other fabrication processes. Compressed space, the width (the upper and lower arms) will be more consistent, and the structure is less likely to be damaged or deformed; while the structure in Figure 4A has only a single arm, it is easy to cause the whole arm width to be inconsistent when making other parts. , and this situation is also likely to lead to the accumulation of large current or large voltage and cause breakdown. Therefore, the structures of the upper and lower arms of FIG. 12 are not easily deformed by other structures because the width of the entire structure is relatively consistent, so that the structure of FIG. 12 has a higher breakdown voltage withstand capability.

The cross-sectional views in FIGS. 5 and 6 are not intended to limit the protection scope of the present application. For example, FIG. 13 shows a chip cross-sectional view of the diode DVF3 in FIG. 4A along the line SD-SD according to another embodiment. 13 and FIG. 6, for the sake of brevity, the parts that are the same or similar to each other will not be described again. Different from FIG. 6 , an insulating layer 103 is sandwiched between the metal sheet 104e and the cap layer 100 in FIG. 13 , the material of which is, for example, silicon oxide. The presence of the insulating layer 103 can also enhance the breakdown voltage withstand capability of the diode.

FIG. 14 shows a flow chart for making the diode of FIG. 13 . Step 140 firstly forms a platform area. For example, the channel layer 96 , the high-valence band gap layer 98 , and the cap layer 100 are respectively formed on the buffer layer 94 first. The three layers are then patterned by inductively coupled plasma etching or the like to complete the mesa region 95 . Step 142 forms an ohmic contact. For example, titanium/aluminum/titanium/gold are respectively deposited as the metal layer 102, and then the metal layer 102 is patterned to form metal sheets 102a, 102b, and the like. Step 144 forms the insulating layer 103 . For example, a silicon dioxide layer is first deposited and then patterned, and the remaining silicon dioxide layer becomes the insulating layer 103 . Step 146 forms Schottky contacts and patterning. For example, in step 146, nickel/gold/platinum is sequentially deposited as the metal layer 104, and then the metal layer 104 is patterned to form metal sheets 104a, 104b, 104c, and the like. There is an ohmic contact between the metal layer 104 and the metal layer 102 , but a Schottky contact between the metal layer 104 and the mesa region 95 . Step 148 forms the capping layer 105 and pattern it to form pad openings. Of course, the flow chart of FIG. 14 is also suitable for fabricating the high electron mobility field effect transistor in FIG. 12 . With proper adjustment, the flowchart in FIG. 14 can also be used to fabricate the diode and the high electron mobility field effect transistor in FIG. 4A , for example, step 144 is omitted, or other fabrication processes are added.

Although the high electron mobility field effect transistors T1 and T2 in FIGS. 2 and 5 can be regarded as constant current sources, they may not be completely ideal current sources. The drain-source current (I _DS ) of the high electron mobility field effect transistors T1 and T2 may still be somewhat related to the drain-source voltage (V _DS ) in the saturation region. Figure 15 shows I _DS versus V _DS for metal oxide semiconductor field effect transistors (MOSFETs) and high electron mobility field effect transistors. Curves 150 and 152 are for a silicon-based metal oxide semiconductor field effect transistor (MOSFET) and a high electron mobility field effect transistor, respectively. It can be found from the curve 150 that in the MOSFET, I _DS and V _DS are approximately both positively correlated, that is, the greater the V _DS , the greater the I _DS . But high electron mobility field effect transistors are different. It can be found from the curve 152 that in the high electron mobility field effect transistor, when V _DS exceeds a certain value, the relationship between I _DS and it will change from positive correlation to negative correlation. And this specific value can be set through the parameters of the manufacturing process. The characteristics of this high electron mobility field effect transistor have a special advantage. When the V _DS suddenly rises due to the unstable mains voltage, the I _DS will drop instead, which may reduce the consumption of the high electron mobility field effect transistor. electrical power, so avoid high electron mobility field effect transistors from being burned out.

In the previous embodiments, the LED driver has a valley filling circuit, but the present application is not limited to this. FIG. 16 shows another LED driver 500 for driving an LED 518, which includes several LED segments 5201, 5202, 5203 connected in series. There is no valley filling circuit in the LED driver 500 . The bridge rectifier 502 and the current driving circuit 504 in the LED driver 500 can be integrated together on a semiconductor chip and packaged into an integrated circuit. FIG. 17 shows a pattern of a metal layer 104 on a semiconductor chip 550 , and indicates the relative positions of the diode and the high electron mobility field effect transistor in FIG. 16 on the semiconductor chip 550 . The semiconductor chip 550 integrates the bridge rectifier 502 and the current driving circuit 504 in the LED driver 500 . FIG. 18 shows an integrated circuit 552 after the semiconductor chip 550 is packaged. FIG. 19 shows a lighting system 560 implementing the LED driver 500 using the integrated circuit 552 of FIG. 18 . Figures 16-19 can be learned from the previous teachings, so their details are not repeated here. It can be seen from FIG. 19 that the entire lighting system 560 uses a very small number of electronic components (a capacitor CF, the integrated circuit 552 and the LED 518). The cost of the lighting system 560 will be reduced and the overall product will be more streamlined.

16 and 19 are not intended to limit the application of the integrated circuit 552 . FIG. 20 illustrates an LED driver 600 that can be used to illustrate another application of an integrated circuit including a bridge rectifier 502 and a current driver circuit 504 . In FIG. 20 , the HMETs T1 and T2 in the current drive circuit 504 can be selectively used to drive the LED 518 , which includes several LED segments 5201 , 5202 , 5203 . The LED driver 600 further has segmented circuits IC1 and IC2, which can be short-circuited or open-circuited according to the level of the DC voltage V _DC-IN . For example, when the DC voltage V _DC-IN is slightly higher than the forward voltage of the LED segment 5203, the segment circuits IC1 and IC2 are both short circuits, so the LED segment 5203 emits light, while the LED segments 5201 and 5202 do not emit light; when When the DC voltage V _DC-IN increases beyond the sum of the forward voltages of LED segments 5202 and 5203, segment circuit IC1 is a short circuit and segment circuit IC2 is an open circuit, so LED segments 5202 and 5203 emit light, while LED segment 5201 does not. Lighting; when the DC voltage V _DC-IN increases to exceed the sum of the forward voltages of the LED segments 5201, 5202 and 5203, the segment circuit IC1 also becomes an open circuit, so the LED segments 5201, 5202 and 5203 all emit light. Therefore, the electro-optical conversion efficiency of the LED driver 600 is better, and the power factor and the total harmonic distortion rate can be well controlled.

An integrated circuit implemented according to the present application is not limited to only integrating a bridge rectifier and a current driving circuit. The previously described integrated circuits 130 and 552 are by way of example only. For example, in addition to the bridge rectifier and the current driving circuit, an integrated circuit implemented according to the present application also integrates some diodes or high electron mobility field effect transistors, which can be used for the segmented circuits IC1 and IC1 in FIG. 20 . IC2.

The integrated circuits implemented in this application are not limited to depletion mode high electron mobility field effect transistors. In some embodiments, the integrated circuit includes enhancement-mode high electron mobility field effect transistors, the on-current of which can be controlled by supplying an appropriate gate voltage, thereby changing the amount of LED segments being driven. The intensity of light emitted. For example, while the activated LED segments 5201, 5202, 5203 are adjusted using segment circuits IC1 and IC2 in FIG. 20, the gate voltage of the enhancement mode high electron mobility field effect transistor can be adjusted to change the high electron mobility field effect transistor input. The current to the LED segments 5201, 5202, 5203 changes the light intensity emitted by the LED segments 5201, 5202, 5203.

Although the previously disclosed LED drivers or lighting systems are each used to drive a single LED 518, the present application is not so limited. In some embodiments, two or more LEDs may be driven separately at different currents. FIG. 21 illustrates an LED driver 700 in which the high electron mobility field effect transistors T1 and T2 in the current driving circuit 504 drive the LEDs 18R and 18B, respectively. For example, the driving current provided by the high electron mobility field effect transistor T1 is smaller than the driving current provided by the high electron mobility field effect transistor T2, and the LED 18R is substantially a red LED, and the LED 18B is substantially a blue LED.

The diodes in FIG. 6 and FIG. 13 are respectively formed on a single mesa region 95, but the present application is not limited thereto. FIG. 22 shows a chip cross-sectional view of a diode in another embodiment. Parts in FIG. 22 that are the same as or similar to those in FIG. 6 and FIG. 13 will not be repeated for the sake of brevity. In Figure 22 there are two land areas 95 and 95a. The metal sheet 102e forms an ohmic contact on the mesa region 95a, and the metal sheet 102d forms another ohmic contact on the mesa region 95. The metal sheets 102d and 102e are electrically short-circuited to each other through the metal sheet 104g. The metal piece 104f serves as an anode of the diode, and the metal piece 104d serves as a cathode of the diode. The structure in Figure 22 can enhance the breakdown voltage withstand capability of the diode.

The previously taught current drive circuits 66, 302 and 504 are used to drive light emitting diodes (LEDs), but the present application is not so limited. FIG. 23 shows an LED driver 800 according to another embodiment of the present application, which is similar to FIG. 16 , and the similarities with each other can be understood with reference to the previous description, and are not described again for the sake of brevity. Different from the LED driver 500 in FIG. 16 , the LED driver 800 in FIG. 23 has an additional TRIAC dimmer 802, and the high electron mobility field effect transistor T1 in the current driving circuit 804 is directly connected Between the DC power line VDD and the ground line GND, no LED is driven. When a triac dimmer is turned off and appears to be an open circuit, a certain amount of holding current is required to avoid malfunction. In FIG. 23 , the high electron mobility field effect transistor T1 can provide the holding current required by the triac dimmer 802 . In terms of design, the high electron mobility field effect transistor T2 can provide a relatively large current to make the LED 518 emit light; while the high electron mobility field effect transistor T1 can provide a relatively small current, when the LED 518 does not emit light, it is used as a bidirectional The holding current required by the thyristor dimmer 802.

The diodes in the previous embodiments are represented by diode symbols 120 in FIG. 6 , which are diodes formed by a combination of a high electron mobility field effect transistor and a Schottky diode. However, the present application is not limited to this. The diodes in all the embodiments can be replaced in whole or in part with other kinds of diodes. For example, FIG. 24 shows a bridge rectifier 806 composed of four Schottky diodes SBD1, SBD2, SBD3, SBD4.

FIG. 25 illustrates, by way of example, the pattern of the metal layer 104 and the mesa 95 on a semiconductor chip 808, which can implement the bridge rectifier 806 of FIG. 24. FIG. 26A, 26B, and 26C show chip cross-sectional views of the semiconductor chip 808 along lines CSV1-CSV1, CSV2-CSV2, and CSV3-CSV3. For example, the Schottky diode SBD1 in FIG. 24 is connected between the AC power line AC1 and the ground line GND. 25 and 26A show high electron mobility field effect transistors having a multi-finger structure. The gate terminal of the high electron mobility field effect transistor is used as the anode of the Schottky diode SBD1, and the channel terminal of the high electron mobility field effect transistor is used as the cathode of the Schottky diode SBD1. Equivalently, the Schottky diode SBD1 consists of many small Schottky diodes in parallel. The high electron mobility field effect transistor with multi-finger structure can provide larger driving current in a limited chip area.

In the previous embodiment, each diode can also be implemented with several diodes connected in series, as exemplified in FIG. 27 . FIG. 27 shows another bridge rectifier 810 . For example, between the AC power line AC1 of the bridge rectifier 810 and the ground line GND, there are two Schottky diodes connected in series. FIG. 28 illustrates, by way of example, the pattern of the metal layer 104 and the mesa region 95 on a semiconductor chip 812, which can implement the bridge rectifier 810 of FIG. 27 . 26A, 26B and 26C can also be used to show chip cross-sectional views of the semiconductor chip 812 along the lines CSV1-CSV1, CSV2-CSV2 and CSV3-CSV3.

As mentioned above, the semiconductor chips of the embodiments of the present application are not limited to the high electron mobility field effect transistors and Schottky diodes that can only have depletion mode, but can also include enhancement mode (enhancement mode, E-mode) high electron mobility field effect transistor. FIG. 29A shows the pattern of the metal layer 104 and the mesa 95 of an enhancement mode high electron mobility field effect transistor ME and a depletion mode high electron mobility field effect transistor MD on a semiconductor chip. FIG. 29B shows the electrical connection between the high electron mobility field effect transistor MD and ME in FIG. 29A. FIG. 30 shows a cross-sectional view of the chip along the line CSV4-CSV4 in FIG. 29A. As shown in FIG. 30 , the left half is an enhancement mode high electron mobility field effect transistor ME, wherein an insulating layer 103 is sandwiched between the metal sheet 104h serving as the gate GE and the cap layer 100 . An adjustment region 170 is formed at the portion of the cap layer 100 and the high-valence bandgap layer 98 below the metal sheet 104h. For example, the adjustment region 170 may be formed by locally implanting fluorine ions into the cap layer 100 and the high-valence bandgap layer 98 . Compared with the depletion mode high electron mobility field effect transistor MD in the left half of FIG. 22 , the enhancement mode high electron mobility field effect transistor ME in the left half of FIG. Used to adjust or increase the threshold voltage Vt (threshold voltage) of a high electron mobility field effect transistor.

As shown in FIGS. 29A , 29B and 30 , the gate GD of the depletion mode high electron mobility field effect transistor MD is short-circuited to the terminal of the enhancement mode high electron mobility field effect transistor ME through the electrical connection of the metal layer 104 S.

In the circuit of FIG. 29B, when the high electron mobility field effect transistor ME is turned off (open circuit), the high electron mobility field effect transistor ME together with the high electron mobility field effect transistor MD can undertake to disperse the distance from the terminal D to the terminal S Therefore, it can have quite good pressure resistance. When the high electron mobility field effect transistor ME is turned on (conducted), the high electron mobility field effect transistor MD can act as a constant current source, limiting the maximum amount of current between the terminal D and the terminal S.

The enhancement mode high electron mobility field effect transistor in FIGS. 29A and 29B can also be used as an active switch in a semiconductor chip. FIG. 31 shows a circuit design of an LED driver 840 according to an embodiment of the present application, which has an enhancement mode high electron mobility field effect transistor and a depletion mode high electron mobility field effect transistor. In addition to some Schottky diodes and resistors, the LED driver 840 also includes current switches CC1 , CC2 , CC3 , and a depletion mode high electron mobility field effect transistor T8 , the electrical connections of which are shown in FIG. 31 . On a semiconductor chip, the current switches CC1 , CC2 , and CC3 can be implemented with the device structures shown in FIGS. 29A and 30 . In one embodiment, the current switches CC1 , CC2 , CC3 and the depletion mode high electron mobility field effect transistor T8 , the maximum currents that can be turned on are the current values I1 , I2 , I3 and I4 respectively, and I1<I2< I3<I4. Each of the current switches CC1, CC2, CC3 has a control terminal (that is, the gate terminal of an enhancement mode high electron mobility field effect transistor), which is commonly connected to the Schottky diode 852 through a corresponding resistor, which has The other end is connected to the ground wire GND.

FIG. 32 shows the voltage waveform of the AC input power supply in FIG. 31 and a current waveform flowing through the bridge rectifier 844 . As the voltage across the DC power line VDD to the ground line GND gradually increases from 0V, the current switches CC1, CC2, and CC3 are all turned on. At this time, only the LED segment 5201 emits light, and the LED segments 5202, 5203, and 5204 do not emit light. The driving current flowing through the LED segment 5201 is limited by the current switch CC1, and the maximum is the current value I1. As the cross-voltage between the DC power line VDD and the ground line GND continues to increase, the current switch CC1 is turned off and the LED segment 5202 emits light. At this time, the driving current flowing through the LED segments 5201 and 5202 is limited by the current switch CC2. The maximum is the current value I2. When the cross-voltage between the DC power line VDD and the ground line GND continues to rise, the current switch CC2 is turned off and the LED segment 5203 lights up. Limit, the maximum is the current value I3. When the cross-voltage between the DC power line VDD and the ground line GND exceeds a certain level, the current switches CC1, CC2, and CC3 will all be turned off, and the LED segments 5201, 5202, 5203, and 5204 will all light up. At this time, the driving current flowing through the LED segments 5201 , 5202 , 5203 , and 5204 is limited by the depletion mode high electron mobility field effect transistor T8 , and the maximum is the current value I4 . When the cross-voltage between the DC power line VDD and the ground line GND gradually decreases from the highest point, the current switches CC3, CC2, and CC1 will gradually turn on and conduct in sequence. It can be found from FIG. 32 that the LED driver 840 of FIG. 31 not only has a good power factor, but also has a relatively low total harmonic distortion (THD).

In FIG. 31, corresponding to each current switch CC3, CC2, CC1, there are two Schottky diodes connected in reverse series, connected between a control terminal and a high voltage terminal of each current switch. In another embodiment, these Schottky diodes (there are 6 in total in FIG. 31 ) can be omitted to reduce cost.

The Schottky diode 852 connected between the resistor 850 and the ground line GND can be used to limit the maximum voltage of the control terminals of the current switches CC3, CC2, CC1. The Schottky diode 852 can prevent an enhancement mode high electron mobility field effect transistor from being damaged due to a high gate voltage when a high voltage surge occurs on the DC power line VDD.

In the LED driver 840 shown in FIG. 31, all Schottky diodes and high electron mobility field effect transistors can be integrated into a single crystal microwave integrated circuit with GaN-based conduction channel material. For example, the Schottky diode can be implemented with the device structure shown in FIG. 6 or FIG. 26A , and the enhancement mode high electron mobility field effect transistor and the depletion mode high electron mobility field effect transistor can be implemented with the device structure shown in FIG. 30 , respectively. The component structure of the left half and the right half is realized. In other words, when implementing the LED driver 840, only a single crystal microwave integrated circuit, some resistance elements, an LED 848 and a printed circuit board (PCB) may be required, and the cost is very low.

As the ambient temperature increases, the luminous brightness of an LED driven by a constant current may decrease. In order to compensate for the brightness attenuation caused by high temperature, in some embodiments of the present application, a thermistor with a positive temperature coefficient or a negative temperature coefficient can be used to adjust the driving current to the LED.

FIG. 33 shows an LED driver 900 with a thermistor having a positive temperature coefficient, wherein the two ends of the thermistor 902 are respectively connected to a gate of the enhancement mode high electron mobility field effect transistor ME1 in the current switch CC4 end and a channel end. The depletion mode high electron mobility field effect transistor T5 is used as a certain current source to provide a certain current to flow through the positive temperature coefficient thermistor 902, and the enhancement mode high electron mobility field effect transistor ME1 operates in the linear region. As the ambient temperature increases, the resistance of the thermistor 902 rises and, therefore, the voltage on the control gate of the current switch CC4 also rises, increasing the current through the LED 518. In this way, the amount of light emitted by the LED 518 can be kept approximately unchanged with temperature.

FIG. 34 shows an LED driver 906 with a thermistor having a negative temperature coefficient, wherein the depletion mode high electron mobility field effect transistor T6 can be used as a constant current source, which provides a constant current approximately determined by its source voltage decided. When the ambient temperature increases, the resistance of the thermistor 906 decreases, therefore, the source voltage of the depletion-mode high electron mobility field effect transistor T6 becomes lower, and the gate-to-source ( gate to source) voltage increases, thus increasing the current through LED 518. In this way, the amount of light emitted by the LED 518 can be kept approximately unchanged with temperature.

The LED driver implemented according to the present application is not limited to having only one LED or only one thermistor. FIG. 35 shows LED driver 910 with LEDs 5181, 5182 and 5183. Similar to what is taught in Figure 33, the drive current through LED 5181, controlled by thermistor 902, increases with increasing temperature. Similar to what is taught in Figure 34, the drive current through LED 5182, controlled by thermistor 906, increases with increasing temperature. The driving current flowing through the LED 5183 is controlled by the depletion mode high electron mobility field effect transistor T7, and is substantially invariant with temperature. In one embodiment, LED 5183 is a blue LED and LED 5181 or 5182 is a red LED.

FIG. 36A shows an LED driver 60a according to an embodiment of the present application, which can be used to drive a light-emitting element. The light-emitting element may be the LED 18 in FIG. 2 that is formed by connecting a plurality of LEDs in series. The equivalent forward direction of the LED 18 is The voltage V _ef-led can be between 50V and 140V according to actual needs. Similar to the LED driver 60 in FIG. 2 , the LED driver 60 a of this embodiment also roughly includes three parts. The first part is a bridge rectifier 62 electrically connected to the LED 18 and the AC input power source AC-source; the second part is a bridge rectifier 62 . A protection circuit 63 between the bridge rectifier 62 and the LED 18; the third part is a current drive circuit 66 connected across the LED 18 and the bridge rectifier 62, which includes two high electron mobility field effect transistors T1, T2. Among them, the bridge rectifier 62 is used as a rectifying circuit for converting an alternating current input power (AC-source) into a direct current power (DC-source). The DC power source includes a DC current I _DC-IN and a DC voltage V _DC-IN provided to the LED 18 . The high electron mobility field effect transistors T1 and T2 are used to limit the magnitude of the DC current I _DC-IN to provide approximately a certain current to drive the LED 18 . The protection circuit 63 includes a protection unit D _clamp . The protection circuit 63 is connected across the current driving circuit 66 and the LED 18, and is connected in series with the rectifier circuit (bridge rectifier 62). When the DC voltage V _DC-IN is greater than a certain value, the DC current I _{DC -IN} flows to the protection circuit 63 . The difference between this embodiment and the previous embodiment is that this embodiment focuses on the protection of components, so the protection circuit 63 is used to replace the valley filling circuit 64 in the previous embodiment. However, the present application is not limited to the above, and in other embodiments, the LED driver may include a protection circuit and a valley filling circuit at the same time. Please refer to FIG. 36B. FIG. 36B shows an LED driver 60b according to another embodiment of the present application. The LED driver 60b roughly includes four parts. The first part is a bridge rectifier 62 electrically connected to the LED 18 and the AC input power source AC-source; The second part is the protection circuit 63 connected across the bridge rectifier 62 and the LED 18; the third part is the current drive circuit 66 connected across the LED18 and the bridge rectifier 62; the fourth part is the valley filling circuit 64 . In short, compared with the LED driver 60a, the LED driver 60b further includes a valley filling circuit 64 connected in parallel with the protection circuit 63 and the current driving circuit 66, respectively.

In the LED driver 60a of FIG. 36A, the bridge rectifier 62 is connected to the AC input power source AC-source through the contacts N, L, and the bridge rectifier 62 is also connected in series with the LED 18 through the contacts C, A. The bridge rectifier 62 includes four rectifier diodes DB1-DB4, which are used to convert the AC input power AC-source into DC power, wherein the voltage waveforms of the AC input power (AC-source) and the DC power supply (DC-source), Please refer to the voltage waveforms 72 and 74 of FIG. 3 , respectively. The DC power supply can provide the DC current I _DC-IN and the DC voltage V _DC-IN to the LED 18 . For example, the AC input power AC-source may be a general 110V AC mains or a 220V AC mains.

Referring to FIG. 36A , the current driving circuit 66 is connected in series with the LED 18 , and the magnitude of the DC current I _DC-IN is limited by the current driving circuit 66 to provide a certain current to the LED 18 approximately. The high electron mobility field effect transistors T1 and T2 in the current driving circuit 66 can be depletion mode transistors as described above, which means that their threshold voltages (V _TH ) are both negative, and Each has a gate, source and drain. In this embodiment, the gate and source of each of the high electron mobility field effect transistors T1 and T2 are connected. In addition, as mentioned above (please refer to the seventh paragraph in the "Detailed Description of Embodiments" of this case), the high electron mobility field effect transistors T1 and T2 can also be used as a certain current source respectively or can be used in parallel to provide A constant current source with a larger current value, in FIG. 36A , similar to FIG. 2 , the high electron mobility field effect transistor T2 and the LED 18 are also connected by a dotted line 67 , thus indicating that the high electron mobility field effect transistor T2 can be selectively The LED 18 is driven together with the high electron mobility field effect transistor T1. To further understand the characteristics of the high electron mobility field effect transistor, take the high electron mobility field effect transistor T1 as an example, please refer to FIG. 37 , which is a voltage-current relationship diagram of the high electron mobility field effect transistor T1 . It can be seen from FIG. 37 that when the drain-source voltage V _DS of the high electron mobility field effect transistor T1 is greater than the cut-in voltage V _knee (knee voltage) of the high electron mobility field effect transistor T1, at this time, the high electron mobility field effect transistor T1 operates in the saturation region SS, and the drain-source current I _DS of the high electron mobility field effect transistor T1 is about a constant I _C , which is generally called the saturation current. The magnitude of the drain-source voltage V _DS of the high electron mobility field effect transistor T1 is approximately equal to the DC voltage V _DC-IN minus the equivalent forward voltage V _ef-led of the LED 18 (in this embodiment, it is set to 50V ), and then subtract the voltage V _DBi (about 1.5V) of a single rectifier diode, where i=1, 2, 3, 4, that is, V _DS =V _DC-IN -V _ef-led -V _DBi .

The protection circuit 63 is connected across the current drive circuit 66 and the LED 18, and the rectifier circuit (bridge rectifier 62) is connected in reverse. The protection circuit 63 includes a protection unit D _clamp , which is mainly used to protect the current driving circuit 66 , that is, to protect the high electron mobility field effect transistors T1 and T2 . Taking the high electron mobility field effect transistor T1 as an example, in order to achieve the above purpose of effectively protecting the high electron mobility field effect transistor T1, the reverse conduction voltage V _clamp of the protection unit D _clamp selected in this embodiment will be less than high. The breakdown voltage V _break of the electron mobility field effect transistor T1 . For example, when the breakdown voltage V _break of the high electron mobility field effect transistor T1 is 600V, a protection unit D _clamp with a reverse conduction voltage V _clamp of 560V can be selected. In this embodiment, the protection unit D _clamp is, for example, a clamp diode, and the characteristic of the clamp diode as the protection unit D _clamp is that its reverse conduction voltage V _clamp (ranging from tens of volts to hundreds of volts) is more conductive than forward conduction The voltage (on the order of a few volts) is much higher, and when it conducts in reverse, the resistance of the protection unit D _clamp is extremely small. When a surge occurs and the DC voltage V _DC-IN exceeds the reverse conduction voltage V _{clamp of the protection unit D clamp (} V _DC-IN >V _clamp ), the protection unit D _clamp is turned on. The resistance is extremely small, so most of the DC current I _DC-IN will flow to the protection unit D _clamp , and the reverse conduction voltage V _clamp of the protection unit D _clamp selected in this embodiment is smaller than the strike of the high electron mobility field effect transistor T1 The breakdown voltage V _break can effectively prevent the high electron mobility field effect transistors T1 and T2 from being short-circuited due to the excessive DC voltage V _DC-IN causing the drain-source voltage V _DS to exceed the breakdown voltage V _break . In addition, the reverse conduction voltage V _clamp of the protection unit D _clamp of this embodiment is higher than the equivalent forward voltage V _ef-led of the LED 18. Generally speaking, in the absence of a surge, the DC voltage V _DC-IN will be When the reverse conduction voltage V clamp of the protection unit D _clamp is smaller than the reverse conduction voltage V _clamp of the protection unit D clamp , the protection unit D _clamp is not conductive at this time, and the DC current I _DC-IN will flow to the LED 18 without affecting the operation of the LED 18 .

In order to briefly explain the operation principle of the LED driver 60a, the following operation principle is for the example of driving the LED 18 only with the high electron mobility field effect transistor T1, that is, the dotted line 67 does not connect the high electron mobility field effect transistor T2 and the LED. 18. The case where the high electron mobility field effect transistor T1 is not connected in parallel with the high electron mobility field effect transistor T2. As described above, when the direct current voltage V _DC-IN is lower than the reverse conduction voltage V _clamp of the protection unit D _clamp , the protection unit D _clamp is not turned on. After the bridge rectifier 62 converts the AC input power AC-source into a DC power source, the DC power source provides the DC current I _DC-IN and the DC voltage V _DC-IN to the LED 18 . Due to the electrical connection between the LED 18 and the high electron mobility field effect transistor T1, the magnitude of the DC current I _DC-IN flowing to the LED 18 will be limited by the high electron mobility field effect transistor T1. After the LED 18 is turned on (the DC voltage V _DC-IN is greater than the equivalent forward voltage V _ef-led ), and the drain-source voltage V _DS of the high electron mobility field effect transistor T1 is greater than the high electron mobility field effect transistor T1 The case of the cut-in voltage V _knee (knee voltage) is discussed. In the above case, since the high electron mobility field effect transistor T1 operates in the saturation region SS (as shown in FIG. 37 ), its drain-source current I _DS is about a constant _IC (called saturation current). According to Kirchhoff's current law, it can be known that the magnitude of the drain-source current I _DS will be equal to the magnitude of the DC current I _DC-IN flowing through the LED 18 (Ic=I _DC-IN ), so the high electron mobility field can be The effective transistor T1 is used as a constant current source to limit the magnitude of the DC current I _DC-IN to provide a stable constant current to drive the LED 18, so that the luminous intensity of the LED 18 is maintained constant. The above situation is illustrated with actual values. In this embodiment, the voltage V _DBi of a single rectifier diode is about 1.5V, the equivalent forward voltage V _ef-led of the LED 18 is about 50V, and the high electron mobility field effect transistor The breakdown voltage V _break and cut-in voltage V _knee of T1 are about 600V and 5V, respectively, and the saturation current Ic is about 110mA. The above numerical description about the high electron mobility field effect transistor T1 still follows the curve characteristics of FIG. 37 , and the above numerical value is only an embodiment, and is not intended to limit the present invention. When the DC voltage V _DC-IN is between 60V and 110V, the drain-source voltage V _DS is approximately between 8V and 55V (V _DS =V _1st -V _ef-led -V _DBi ), which is greater than the cut-in voltage V _knee . At this time, the drain-source voltage V _DS of the high electron mobility field effect transistor T1 is in the saturation region SS (between 5V and 700V), so the magnitude of the DC current I _DC-IN can be limited, thereby providing the LED 18 with a certain current Ic= 110mA. On the other hand, when a surge occurs, if the DC voltage V _DC-IN corresponding to the surge is greater than the reverse conduction voltage V _clamp of the protection unit D _clamp by 560V, the protection unit D _clamp is turned on, and most of the current flows to the protection unit The unit D _clamp can achieve the effect of protecting the high electron mobility field effect transistor T1 and avoid short circuit of the high electron mobility field effect transistor T1 .

In order to simplify the manufacturing process of the above LED driver 60a, in an embodiment of the present application, the rectifier diodes DB1-DB4, the high electron mobility field effect transistors T1, T2, and the protection unit D _clamp in FIG. 36A can also be formed together on a substrate 91 . Figure 38 shows a top view of the LED driver 60c. In FIG. 38 , the LED driver 60 c includes a bridge rectifier 62 , a protection circuit 63 and a current drive circuit 66 . In this embodiment, the current driving circuit includes two high electron mobility field effect transistors T1 and T2, and the protection circuit 63 includes a protection unit D _clamp . The bridge rectifier 62 , the two high electron mobility field effect transistors T1 and T2 and the protection unit D _clamp share the substrate 91 . In other words, the LED driver 60c is a monolithic structure, and each unit of the LED driver 60c is formed from a single semiconductor chip through different fabrication processes. The electrical connection of the bridge rectifier 62 , the two high electron mobility field effect transistors T1 and T2 , and the protection unit D _clamp is the same as that in FIG. 36A . Please refer to FIG. 36A and the above description. In this embodiment, the four rectifier diodes of the bridge rectifier 62 are composed of four Schottky diodes SBD1 , SBD2 , SBD3 , and SBD4 with a multi-finger structure and are arrayed on the substrate 91 . The two high electron mobility field The effect transistors T1 and T2 are, for example, high electron mobility field effect transistors with a multi-finger structure, and the protection unit D _clamp is, for example, a clamping diode with a multi-finger structure. The bridge rectifier 62 is electrically connected to an AC input power source (not shown) using the contacts N and L, and is connected across the AC input power source and a light-emitting element (not shown). Equivalently, the Schottky diodes SBD1 , SBD2 , SBD3 , and SBD4 in the bridge rectifier 62 are respectively composed of many small Schottky diodes in parallel. The high electron mobility field effect transistor with multi-finger structure can provide larger driving current in a limited chip area. In one embodiment, each of the Schottky diodes SBD1 , SBD2 , SBD3 , and SBD4 can also be formed by connecting a plurality of diodes in series as shown in FIG. 27 . In another embodiment, the high electron mobility field effect transistors T1 and T2 are not limited to be in depletion mode, and one of them can be an enhancement mode (E-mode) and the other is a depletion mode, which is described in detail. Please refer to FIG. 29A , FIG. 29B , and FIG. 30 . In yet another embodiment, the high electron mobility field effect transistors T1/T2 of the LED driver 60c may also be connected to a thermistor. Please refer to the descriptions of FIGS. 33 to 35 for detailed descriptions, which will not be repeated here.

Please refer to Figure 38 and Figure 39 at the same time. FIG. 39 is a schematic cross-sectional view of the structure of the Schottky diode SBD1 , the high electron mobility field effect transistor T1 and the protection unit D _clamp in FIG. 38 . As shown above and in FIG. 38, the LED driver 60c includes a bridge rectifier 62 formed by four arrays of Schottky diodes SBD1, SBD2, SBD3, SBD4, two high electron mobility field effect transistors T1, T2 and Protection unit D _clamp , and multiple contacts A, C, E, F, N, L, TD1, TD2, TSG. The anodes A _sbd1-sbd4 and the cathodes C _sbd1-sbd4 are respectively formed on the Schottky diodes SBD1, SBD2, SBD3, SBD4; the drains D _hemt1 , D _hemt2 , the gates G _hemt1 , G _hemt2 , the sources S _hemt1 , S _{The hemt2} is formed on the high electron mobility field effect transistors T1 and T2 respectively; the anode A _clamp and the cathode C _clamp are respectively formed on the protection unit D _clamp . Schottky diodes SBD1, SBD2, SBD3, SBD4, high electron mobility field effect transistors T1, T2 and protection unit D _clamp are formed together with multiple contacts A, C, E, F, N, L, TD1, TD2, TSG on the base 91 . In this embodiment, since the structures of the Schottky diodes SBD1, SBD2, SBD3, and SBD4 are the same, and the structures of the high electron mobility field effect transistors T1 and T2 are the same, in order to simplify the description, in FIG. Taking the Schottky diode SBD1 and the high electron mobility field effect transistor T1 as examples to illustrate the structure, FIG. 39 is only a schematic diagram for the structure description, not the actual structure size and layout. As shown in FIG. 39, the Schottky diode SBD1 on the substrate 91 includes a semiconductor stack 90a, and insulating layers 103a, 103b on the semiconductor stack 90a, an anode _Asbd1 and a cathode _Csbd1 , wherein the anode _Asbd1 and the cathode are C _sbd1 is connected to the contacts A and N, respectively; the high electron mobility field effect transistor T1 on the substrate 91 includes the semiconductor stack 90a, the insulating layers 103a, 103b on the semiconductor stack 90a, the source S _hemt1 , the drain The electrode D _hemt1 and the gate G _hemt1 , wherein the source S _hemt1 and the gate G _hemt1 are connected to the contact TSG, and the drain D _hemt1 is connected to the contact TD1; the protection unit D _clamp located on the substrate 91 includes a semiconductor stack 90a , and the insulating layers 103a and 103b on the semiconductor stack 90a and the anode A _clamp and the cathode C _clamp , wherein the anode A _clamp and the cathode C _clamp are connected to the contacts E and F, respectively.

The Schottky diode SBD1, the high electron mobility field effect transistor T1 and the protection unit D _clamp of the present embodiment share the substrate 91, and each have the same semiconductor stack 90a. Therefore, in the fabrication of the Schottky diode SBD1, When the high electron mobility field effect transistor T1 and the protection unit D _clamp are used, the three semiconductor stacks 90a can be fabricated at the same time, and the three semiconductor stacks 90a can also be fabricated on the same substrate 91, which simplifies production process. In this embodiment, before forming the semiconductor stack 90a of this embodiment, a substrate 91 is provided first, and the thickness of the substrate 91 is about 175-1500 μm. The material of the substrate 91 itself may include semiconductor material, oxide material and/or metal material. The above-mentioned semiconductor material can include, for example, silicon (Si), silicon carbide (SiC), gallium nitride (GaN), gallium arsenide (GaAs), aluminum nitride (AlN), etc.; the above-mentioned oxide material can include, for example, sapphire ( sapphire); the above-mentioned metal material may contain copper (Cu), molybdenum (Mo), for example. In addition, when distinguished by electrical conductivity, the base 91 itself may be a conductive substrate or an insulating substrate, and the above-mentioned conductive substrates include substrates such as silicon (Si) substrates, gallium nitride (GaN) substrates, and gallium arsenide (GaAs) substrates. The above-mentioned insulating substrates include sapphire (sapphire) substrates, silicon on insulator (SOI) substrates, aluminum nitride (AlN) and other substrates. In addition, the substrate 91 can be selectively doped with substances therein to change its conductivity to form a conductive substrate or a non-conductive substrate. For a silicon (Si) substrate, boron (B), arsenic (As) can be doped with ), or phosphorus (P) to make it conductive.

After the substrate 91 is provided, the semiconductor stack 90a is formed over the substrate 91 . The semiconductor stack 90 a includes a buffer layer 94 , a channel layer 96 , a high-valence band gap layer 98 and a cap layer 100 , and each layer of the semiconductor stack 90 a may be formed on the substrate 91 by epitaxial growth. In addition, before the buffer layer 94 is formed, a nucleation layer (not shown) can also be selectively formed on the substrate 91. The thickness of the nucleation layer is about 20 nm to 200 nm. The epitaxial quality of the buffer layer 94 , the channel layer 96 , the high-valence bandgap layer 98 and the cap layer 100 is good. The nucleation layer is, for example, a Group III and V semiconductor material, including materials such as aluminum nitride (AlN), gallium nitride (GaN), or aluminum gallium nitride (AlGaN). The semiconductor stack 90a can be grown on the substrate 91 by means of epitaxy, including but not limited to metal-organic chemical vapor deposition (MOCVD) or molecular-beam epitaxy (MBE). However, the present application is not limited to an epitaxial manner, that is, the substrate 91 of the present application is not limited to a growth substrate. In other embodiments, the semiconductor stack 90a can be epitaxially grown on other growth substrates, and then the semiconductor stack 90a is combined with the substrate 91, and the substrate 91 includes metal, dielectric material, insulating material or composite material. The bonding methods include gluing, welding, hot pressing and so on. Alternatively, the semiconductor stack 90 a epitaxially formed on a growth substrate is directly aligned and bonded to the substrate 91 , and then the growth substrate is completely or partially removed so that the semiconductor stack 90 a is located on the substrate 91 . Alternatively, the semiconductor stack 90a is first epitaxially grown on another growth substrate, then the growth substrate is thinned, and then the thinned growth substrate and the semiconductor stack 90a thereon are combined with the substrate 91 to make the semiconductor stack 90a is formed on a composite substrate consisting of a thinned growth substrate and substrate 91 .

After the nucleation layer is formed, a buffer layer 94 is formed thereon. The buffer layer 94 may be C-doped intrinsic GaN as previously described. The buffer layer 94 is used for the channel layer 96 and the high-valence bandgap layer 98 formed thereon to have better epitaxial quality, and its thickness is about 1 μm˜10 μm. The buffer layer 94 may be a single layer or a multi-layer, and when the buffer layer 94 is a multi-layer, it may include a super lattice multilayer or two or more layers with different materials. The material of the single-layer or multi-layer buffer layer 94 may include Group III and V semiconductor materials, such as aluminum nitride (AlN), gallium nitride (GaN), or aluminum gallium nitride (AlGaN) and other materials, and may be doped with other elements , such as carbon or iron, in which the doping concentration can be graded or fixed according to the growth direction. In addition, when the buffer layer 94 is a superlattice stack, it can be composed of two multi-layer epitaxial layers with different materials alternately stacked, and its material can be a Group III or V semiconductor material, such as an aluminum nitride layer (AlN ) and an aluminum gallium nitride layer (AlGaN), the sum of the two layers of the aluminum nitride layer and the gallium nitride layer is about 2 nm to 30 nm, and the overall thickness is about 1 μm to 5 μm.

After the buffer layer 94 is formed, the channel layer 96 and the high-valence bandgap layer 98 are formed on the buffer layer 94 by epitaxy. The channel layer 96 has a thickness in the range of 50-300 nm, is formed on the buffer layer 94, and has a first energy gap. The high-valence band gap layer 98 has a thickness ranging from 20 to 50 nm, is formed on the channel layer 96, and has a second energy gap, the second energy gap is higher than the first energy gap, and the lattice constant of the high-valence band gap layer 98 is higher than that of the channel layer. 96 small. In this embodiment, the channel layer 96 includes indium gallium nitride (In _x Ga _(1-x) N), 0≤x<1, and the material of the high-valence band gap layer 98 is aluminum gallium nitride (A _y Ga ₍ 1-x) N) _-y) N), y is between 0.1 and 0.3, the channel layer 96 and the high-valence bandgap layer 98 can be intrinsic semiconductors; in other embodiments, the material of the high-valence bandgap layer 98 can be aluminum indium gallium nitride ( Al _w In _z Ga _(1-z) N), 0<w<1, 0≤z<1. As previously discussed, a two-dimensional electron cloud may be formed within channel layer 96 adjacent to the junction of channel layer 96 and high valence bandgap layer 98 as a conductive channel. In detail, the formation of the two-dimensional electron cloud is due to the spontaneous polarization of the energy band by the high-valence bandgap layer 98 and the mismatch of lattice constants from the channel layer 96 and the high-valence bandgap layer 98 The piezoelectric polarization (piezoelectric polarization) is formed to bend, so that part of the energy band is located below the Fermi level, and a two-dimensional electron cloud is formed at the junction between the channel layer 96 and the high-valence band gap layer 98 .

After the high-valence bandgap layer 98 is formed on the channel layer 96 , the buffer layer 94 , the channel layer 96 , the high-valence bandgap layer 98 , and the cap layer may be patterned by means of inductively coupled plasma etching or the like with reference to step 140 in FIG. 14 . 100 to complete the platform area 95. Before this step, the Schottky diode SBD1, the semiconductor stack 90a of the high electron mobility field effect transistor T1, and the semiconductor stack 90a of the protection unit D _clamp are connected to each other. The semiconductor stack 90a, the semiconductor stack 90a of the high electron mobility field effect transistor T1 and the semiconductor stack 90a of the protection unit D _clamp can be separated from each other, thereby achieving the purpose of electrical insulation between the semiconductor stacks 90a. However, the present application is not limited to the above, and the formation timing and formation method of the platform region 95 may be adjusted according to the requirements of the manufacturing process. For example, in other embodiments, when the buffer layer 94 is a high-resistance layer, the When the mesa region 95 is used, it is not necessary to completely etch the buffer layer 94, and only the channel layer 96, the high-valence bandgap layer 98, and the cap layer 100 on the buffer layer 94 can be etched to achieve electrical insulation between the semiconductor stacks 90a. Purpose. In other words, in the above case, the buffer layer 94 can be completely or partially retained, and the Schottky diode SBD1 , the high electron mobility field effect transistor T1 and the protection unit D _clamp share the buffer layer 94 . 90a can still be electrically isolated from each other.

In this embodiment, in order to prevent the protection unit D _clamp from conducting when the DC voltage V _DC-IN is lower than the reverse conduction voltage V _clamp of the protection unit D _clamp , a high valence band gap layer 98 is formed on the channel layer 96 . After that, a p-type barrier layer Pb is further formed in the high-valence band gap layer 98 of the protection unit D _clamp , and the p-type barrier layer Pb is used to completely deplete the two-dimensional electron cloud in the channel layer 96 under the p-type barrier layer. The above-mentioned purpose of preventing the protection unit D _clamp from being turned on is achieved when the DC voltage V _DC-IN is less than the reverse conduction voltage V _clamp of the protection unit D _clamp . In this embodiment, the p-type barrier layer Pb is formed by doping the high-valence band gap layer 98 of the protection unit D _clamp as an example. When the p-type barrier layer Pb layer is formed in the high valence band gap layer 98, the p-type barrier layer Pb will change the position of the Fermi level, so that the Fermi level where the p-type barrier layer Pb is located is far away from the conduction band Moving in the direction of the valence band, once the Fermi level of the p-type barrier layer Pb is located below the conduction band, the two-dimensional electron cloud in the channel layer 96 below it is completely depleted. Generally speaking, the doping concentration of the p-type barrier layer Pb is positively correlated with the carrier concentration, while the carrier concentration and thickness of the p-type barrier layer Pb are negatively correlated with the concentration of the two-dimensional electron cloud, respectively. In the case where the Pb layer of the p-type barrier layer is formed on the high-valence band gap layer 98, the higher the carrier concentration of the p-type barrier layer Pb layer or the thicker the thickness Tb of the p-type barrier layer Pb layer, the higher the p-type barrier layer Pb layer. The Fermi level at the position of the barrier layer Pb will move to the direction of the valence band, so that the concentration of the two-dimensional electron cloud below it will be lower. In this embodiment, by making the thickness Tb of the p-type barrier layer Pb greater than or equal to the thickness of the high-valence band gap layer 98 , the Fermi levels at the position of the p-type barrier layer Pb are all located below the conduction band without It overlaps with the conduction band, so that the two-dimensional electron cloud under the p-type barrier layer Pb is completely depleted, or by increasing the carrier concentration of the p-type barrier layer Pb, the conduction band at the position of the p-type barrier layer Pb is different from that of the p-type barrier layer Pb. The Fermi levels do not overlap, so that the 2D electron cloud under the p-type barrier Pb is completely depleted. In other words, the carrier concentration and thickness Tb of the p-type barrier layer Pb will affect the polarity of the p-type barrier layer Pb, and then change the energy band position of the p-type barrier layer Pb, so that the Fermi level and the The distance between the valence bands changes accordingly, and the concentration of the two-dimensional electron cloud under the p-type barrier layer Pb also changes accordingly.

In addition, the carrier concentration and length Lb of the p-type barrier layer Pb also affect the width of the depletion region between the p-type barrier layer Pb and the channel layer 96 . Since the reverse conduction voltage V _clamp of the protection unit D _clamp is affected by the concentration of the two-dimensional electron cloud and the width of the depletion region between the p-type barrier layer Pb and the channel layer 96, the p-type resistance can also be adjusted by adjusting the The carrier concentration, length Lb, and thickness Tb of the barrier layer Pb change the magnitude of the reverse conduction voltage V _clamp . In detail, the reverse conduction voltage V _clamp of the protection unit D _clamp is negatively correlated with the carrier concentration of the p-type barrier layer Pb, and positively correlated with the length Lb of the p-type barrier layer Pb. The lower or the longer the length Lb, the wider the depletion region of the protection unit D _clamp , so the reverse conduction voltage V _clamp is higher. The depletion region mentioned here means that the depletion region is close to the p-type barrier layer Pb and is connected to the channel layer 96. At the surface, there is no region of mobile carriers. By properly adjusting the carrier concentration of the p-type barrier layer Pb and the length Lb of the p-type barrier layer Pb, the reverse conduction voltage V _clamp of the protection unit D _clamp can be smaller than that of the high electron mobility field effect transistor T1 Breakdown voltage V _break requirement. To sum up, since the p-type barrier layer Pb in this embodiment can change the concentration of the two-dimensional electron cloud below it, and can also adjust the reverse conduction voltage V _clamp of the protection unit D _clamp , the p-type barrier layer Pb can be adjusted appropriately The carrier concentration and length Lb can be achieved at the same time when the reverse conduction voltage Vclamp of the protection unit D _clamp is smaller than the breakdown voltage V _break of the high electron mobility field effect transistor T1, and when the DC voltage V _DC-IN is smaller than the protection unit D _clamp In the case of the reverse conduction voltage V _clamp , the purpose of the protection unit D _clamp not to conduct conduction. The present application is not limited to the above-mentioned method, and other methods can also be used to achieve the above-mentioned purpose. For example, in other embodiments, the p-type barrier layer Pb can also be additionally formed on the high-valence band gap layer of the protection unit D _clamp . Above 98 (not shown), as the above-mentioned principle, when the p-type barrier layer Pb layer is formed on the high-valence band gap layer 98, the p-type barrier layer Pb will change the position of the Fermi level, so that the p-type barrier layer Pb will change the position of the Fermi level. The Fermi energy level at the position of the barrier layer Pb moves away from the conduction band to the direction of the valence band. Once the Fermi energy level at the position of the p-type barrier layer Pb is located below the conduction band, the lower part is located in the channel layer 96 The 2D electron cloud is completely depleted. Generally speaking, the doping concentration of the p-type barrier layer Pb is positively correlated with the carrier concentration, and the carrier concentration of the p-type barrier layer Pb affects the concentration of the two-dimensional electron cloud respectively. It is particularly noted that when the p-type barrier layer Pb layer is formed on the high-valence band gap layer 98, the thickness of the p-type barrier layer Pb layer is relatively independent of the concentration of the two-dimensional electron cloud, and is mainly adjusted by adjusting the p-type barrier layer. The carrier concentration of the barrier layer Pb makes the two-dimensional electron cloud located in the channel layer 96 under the p-type barrier layer Pb completely depleted, and is adjusted by adjusting the carrier concentration, thickness Tb and length Lb of the p-type barrier layer Pb. The principle of changing the magnitude of the reverse conduction voltage V _clamp capable of protecting the unit D _clamp is as described above and will not be repeated here.

After the platform region 95 is completed, referring to step 144 in FIG. 14, the insulating layer 103a can be grown on the Schottky diode SBD1 in one manufacturing process by epitaxial growth or sputtering and patterning process. Above the high valence band gap layer 98 of the high electron mobility field effect transistor T1, and above the high valence band gap layer 98 of the protection unit D _clamp , for example, metal organic chemical vapor phase epitaxy (metal -organic chemical vapor deposition, MOCVD) or molecular beam epitaxy (molecular-beamepitaxy, MBE) and other methods to epitaxially grow the insulating layer 103a. In this embodiment, the insulating layer 103 a substantially covers the surface of the high-valence bandgap layer 98 , which functions to improve the surface leakage current and protect the surface of the high-valence bandgap layer 98 . The insulating layer 103a may be an insulating material or a high-resistance material, including a nitride insulating material, such as silicon nitride (SiN _x ), an oxide insulating material, such as silicon dioxide (SiO ₂ ), or a p-type III-V group Semiconductors, such as p-type gallium nitride layers (p-GaN).

However, the present application is not limited to the above, and other materials with the same characteristics can also be substituted for it. In addition, the position of the insulating layer 103a is not limited to the disclosure of the present application.

After the insulating layer 103a is fabricated, in the same fabrication process (please refer to step 142 in FIG. 14 ), the insulating layers 103b of the Schottky diode SBD1, the high electron mobility field effect transistor T1 and the protection unit D _clamp are respectively placed over the insulating layer 103b. A metal layer (not shown) is deposited and patterned to form a plurality of metal sheets 102'a, 102'b, 102'c, 102'd, 102'e. In this embodiment, the plurality of metal sheets 102'a, 102'b may be formed by selecting an appropriate metal layer material (eg, titanium/aluminum/titanium/gold) and/or by a fabrication process (eg, thermal annealing). Ohmic contacts are formed between , 102 ′ c , 102 ′ d , 102 ′ e , 102 ′ f and the high valence band gap layer 98 . The metal sheets 102'a and 102'b are used as the anode A _sbd1 and the cathode C _sbd1 of the Schottky diode SBD1; the metal sheets 102'c and 102'd are used as the source electrodes S _hemt1 and C sbd1 of the high electron mobility field effect transistor T1. The drain D _hemt1 ; the metal sheets 102'e and 102'f serve as the anode A _clamp and the cathode C _{clamp of the protection unit D clamp .} After the multiple electrodes _Asbd1 , C _sbd1 , _Shemt1 , D _hemt1 , A _clamp and C _clamp are fabricated, referring to step 146 in FIG. 14 , a metal layer (not shown) is deposited over the high electron mobility field effect transistor T1 , and patterning the metal layer to form a metal sheet 104'a. In this embodiment, a Schottky contact can be formed between the metal sheet 104 ′ a and the high-valence bandgap layer 98 by selecting an appropriate metal layer material (eg, nickel/gold/platinum). The metal sheet 104'a is used as the gate G _hemt1 of the high electron mobility field effect transistor T1.

After the above-mentioned gate G _hemt1 is formed, an insulating layer 103b may be further formed to cover the high-valence bandgap layer 98 to prevent the high-valence bandgap layer 98 from deteriorating due to moisture, which may affect electrical properties. In this embodiment, for the material of the insulating layer 103b, please refer to the previous description of the insulating layer 103a, which will not be repeated here. In addition, in order to facilitate the electrical connection between the above-mentioned electrodes and the outside world, after the insulating layer 103b is fabricated, a plurality of contacts C, N, L, A, TD1, TD2, TSG as shown in FIG. 38 can be formed on the substrate 91 respectively. , E, F. The contacts C, N, L, and A are used to connect the anodes A _{sbd1 to sbd4} of Schottky diodes SBD1, SBD2, SBD3, and SBD4 with the cathodes C _{sbd1 to sbd4} (for detailed connection methods, please refer to the following); contacts TD1 and TD2 are respectively Used to connect with the drains D _hemt1 and D _hemt2 of the high electron mobility field effect transistors T1 and T2; the contact TSG is connected to the source S _hemt1 and the gate G _hemt1 of the high electron mobility field effect transistor T1, and the high electron mobility The source S _hemt2 and the gate G _hemt2 of the field effect transistor T2 are connected; the contacts E and F are respectively connected to the anode A _clamp and the cathode C _clamp of the protection unit D _clamp . In FIG. 39, only the contacts A, N, TD1, TSG, E, and F related to the Schottky diode SBD1, the high electron mobility field effect transistor T1, and the protection unit D _clamp are listed. Among them, the contact point A and the contact point N are respectively connected with the anode A _sbd1 and the cathode C _sbd1 of the Schottky diode SBD1; the contact TSG is connected with the source S _hemt1 and the gate G _hemt1 of the high electron mobility field effect transistor T1, and the contact TD1 is connected with the high The drain D _hemt1 of the electron mobility field effect transistor T1 is connected; the contact point E and the contact point F are respectively connected to the anode A _clamp and the cathode C _clamp of the protection unit D _clamp . The structure and formation of the Schottky diodes SBD2, SBD3, SBD4 and the high electron mobility field effect transistor T2 are the same as those of the Schottky diode SBD1 and the high electron mobility field effect transistor T1. Please refer to the above The description of the Schottky diode SBD1 and the high electron mobility field effect transistor T1 will not be repeated here.

In this application, in order to realize the electrical connection relationship in FIG. 36A, as shown in FIG. 38, the contact point A is connected to the anode _Asbd2 of the Schottky diode SBD2 in addition to the anode Asbd1 of the Schottky diode _SBD1 ; the contact point N In addition to connecting the cathode C _sbd1 of the Schottky diode SBD1, the anode A _sbd4 of the Schottky diode SBD4 will also be connected; the contact point L connects the anode A _sbd3 of the Schottky diode SBD3 and the cathode C _sbd2 of the Schottky diode SBD2; the contact point C connects the cathode C sbd3 of the Schottky diode SBD3 and the cathode C _sbd4 of the Schottky diode _SBD4 ; the contact TSG not only connects the source S _hemt1 and the gate G _hemt1 of the high electron mobility field effect transistor T1, but also connects with the high electron The source S _hemt2 and the gate G _hemt2 of the mobility field effect transistor T2 are connected; the contact TD1 is connected with the drain D _hemt1 of the high electron mobility field effect transistor T1; the contact TD2 is connected with the drain of the high electron mobility field effect transistor T2 D _hemt2 is connected; the contacts E and F are respectively connected to the anode A _clamp and the cathode C _clamp of the protection unit D _clamp as described above.

After the above-mentioned multiple contacts A, C, E, F, L, N, TD1, TD2, and TSG are formed, an insulating layer 103c can also be selectively formed on the side surface of the mesa region 95 and the multiple contacts A, C, E, On the surface of F, L, N, TD1, TD2, TSG, to prevent the deterioration of components due to moisture, and expose contacts A, C, E, F, L, N, TD1, TD2, TSG as appropriate Part of the surface is used for power connection. After the above-mentioned insulating layer is completed, the LED driver 60c of the present application is completed. In actual operation, please refer to FIGS. 36A and 38 , one end of the AC input power source AC-source is electrically connected to the contact L of the bridge rectifier 62 , and the other end of the AC input power source AC-source is electrically connected to the bridge rectifier 62 . The contact point N is electrically connected; one end of the LED 18 is electrically connected to the contact points TD1 and TD2 of the current drive circuit 66, and the other end of the LED 18 is electrically connected to the contact point C of the bridge rectifier 62; the contact point TSG of the current drive circuit 66 is electrically connected It is electrically connected to the contact point A of the bridge rectifier 62 ; the contact point E of the protection circuit 63 is connected to the contact point A of the bridge rectifier 62 ; the contact point F of the protection circuit 63 is connected to the contact point C of the bridge rectifier 62 .

To sum up, the LED driver of an embodiment of the present application includes a valley filling circuit, which can maintain the minimum voltage of the DC power supply at half of the peak voltage, thereby providing sufficient voltage to keep the light-emitting element emitting light. The LED driver of another embodiment of the present application includes a protection unit, which can prevent the high electron mobility field effect transistor of the current driving circuit in the LED driver from breaking down due to surge, thereby achieving the effect of protecting the light-emitting element. The LED driver of another embodiment of the present application includes a valley-fill circuit and a protection unit, and can achieve the effect of providing sufficient voltage to keep the light-emitting element emitting light and protecting the light-emitting element. The above descriptions are only preferred embodiments of the present invention, and all equivalent changes and modifications made according to the claims of the present invention shall fall within the scope of the present invention.

Claims (9)

1. A driver for driving a light-emitting element, comprising: a rectifier circuit, comprising a rectifier diode for receiving an AC input power and converting it into a DC power supply, the DC power supply comprising a DC current and a DC voltage; a current driving circuit, comprising a constant current unit, wherein the rectifier circuit, the current driving circuit and the light-emitting element are connected in series, and the current driving circuit is used to limit the magnitude of the direct current to drive the light-emitting element; and a protection circuit, including a protection unit, wherein the protection circuit bridges the current driving circuit and the light-emitting element, and when the DC voltage is greater than a certain value, the DC current flows to the protection circuit; Wherein, the rectifier diode, the constant current unit and the protection unit share a substrate; Wherein, the rectifier diode, the constant current unit and the protection unit respectively comprise semiconductor stacks, and the structures and constituent materials of the semiconductor stacks are the same. 2. The driver of claim 1, wherein the semiconductor stacks are epitaxially formed on the substrate. 3. The driver of claim 2, wherein the semiconductor stacks respectively comprise a buffer layer on the substrate, a channel layer on the buffer layer, and a high valence bandgap layer on the channel layer. 4. The driver of claim 3, wherein the protection unit further comprises a p-type barrier layer over the channel layer. 5. The driver of claim 4, wherein the p-type barrier layer is thicker than the high valence bandgap layer. 6. The driver of claim 3, wherein the protection unit is a clamping diode. 7 . The driver of claim 1 , wherein the constant current unit, the protection unit or the rectifier diode is a high electron mobility field effect transistor with a multi-finger structure. 8 . 8 . The driver of claim 1 , wherein the number of the rectifier diodes is plural, and the number of the constant current unit is plural. 9 . 9. The driver of claim 8, wherein the plurality of rectifier diodes are arranged in an array.

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