CN102761260B - With the booster circuit of low-voltage driving and correlation technique - Google Patents

Abstract

The invention relates to a boost circuit driven by low voltage and a related method; the boost circuit includes an inductor, a diode, a capacitor, a first switch and a second switch. The second switch is coupled between the first switch and the anode of the diode. The first switch is selectively turned on according to a switch signal, and the second switch is turned on when the first switch is turned on.

Description

Boost circuit driven by low voltage and related method

technical field

The present invention relates to a low-voltage driven boost circuit and a related method, and in particular to a low-voltage driven boost circuit and related method which are provided with stacked switching transistors and can be controlled by a low-voltage switching signal.

Background technique

The boost circuit is used to boost a lower DC voltage to a higher DC voltage, and is widely used in various applications requiring high voltage.

Please refer to FIG. 1 , which illustrates a known boost circuit 10 . The boost circuit 10 is provided with an inductor L0 , a diode D0 , a transistor M0 and a capacitor C0 for boosting the lower DC voltage Vi to a higher DC voltage Vo at the node nd4 . The transistor M0 is a switch transistor, the gate of which is controlled by a switch signal sw1, and selectively conducts between the node nd3 and the ground voltage GND according to the switch signal sw1. FIG. 1 also shows the timing sequence of the waveform of the switch signal sw1, the horizontal axis is time, and the vertical axis is the voltage of the signal. The switch signal sw1 can periodically control the transistor M0 according to a period T; in each period T, the switch signal sw1 turns on the transistor M0 with the voltage Vi0 in the period Ton, and turns off the transistor M0 with the ground voltage GND in the rest of the time Not conducting.

When the transistor M0 is turned on, the node nd3 is turned on to the ground voltage GND, and the voltage Vi will charge magnetic energy in the inductor L0. When the switching signal sw1 turns off the transistor M0 and stops conduction, the magnetic energy of the inductor L0 can be released to the capacitor C0 through the forward-conducting diode D0 to support the voltage Vo at the node nd4, so that the voltage Vo can be higher than the voltage Vi. The ratio of the period Ton to the period T (the so-called duty cycle) can control the ratio between the voltage Vo and the voltage Vi; the closer the period Ton is to the period T, the higher the control voltage Vo is. For example, the voltage Vi can be 12 volts; the voltage Vo can be 60 volts through the duty cycle control of the switching signal sw1.

However, when the transistor M0 is not turned on, the voltage of the node nd3 will be the voltage across the diode D0 plus the voltage Vo, so that the drain voltage of the transistor M0 at the node nd3 will exceed the voltage Vo; at this time, due to the drain voltage of the transistor M0 Both the electrode voltage and the gate voltage are equal to the ground terminal voltage GND, so each electrode of the transistor M0 needs to withstand a large voltage difference. Therefore, the transistor M0 must be a power transistor with a high voltage rating and can withstand high voltage. However, the higher rated transistor M0 also has a higher threshold voltage when it is to be driven on. To cope with the higher threshold voltage of the transistor M0 , the switch signal sw1 also needs to have a higher voltage Vi0 in the period Ton to turn on the transistor M0 . For example, in an application where the voltages Vi and Vo are 12 and 60 volts respectively, the threshold voltage of the transistor M0 will be 5 volts or higher.

The boost circuit 10 is equipped with a control chip 14 to control the magnitude of the voltage Vo; the control chip 14 adjusts the duty cycle (and frequency) of the switch signal sw1 to control the voltage Vo. However, since the voltage Vi0 required by the switching signal sw1 has exceeded the output signal voltage of the control chip 14 , the control chip 14 cannot directly control the boost circuit 10 . The switch signal sw0 output by the control chip 14 can only vary between the voltage VH and GND, but the voltage VH does not exceed the threshold voltage of the transistor M0, which is not enough to turn on the transistor M0.

Therefore, the conventional boost circuit 10 needs to be equipped with a potential shifter 12 . The potentiometer 12 operates between the voltage Vi0 and the ground voltage GND, and is provided with resistors Rp1, Rp2, and Rp3 and transistors Q1, Q2, and Q3 to convert the low-voltage switch signal sw0 at the node nd1 into a high-voltage switch at the node nd2 Signal sw1. Through the operation of the potentiometer 12, the switch signal sw1 can turn on the transistor M0 with a higher voltage Vi0 (higher than the voltage VH). For example, in order to have a sufficient rating in an application where the voltage Vo is 60 volts, the threshold voltage of the transistor M0 will be increased to more than 5 volts, but in the switching signal sw0 output by the control chip 14, the voltage VH is only 3 volts, which is insufficient to directly drive transistor M0. Therefore, the prior art needs to use the potentiometer 12 to increase the voltage Vi0 of the switch signal sw1 to 12 volts.

Because the known boost circuit 10 needs to be equipped with the potential shifter 12 , the known boost technology shown in FIG. 1 needs to use more circuit components, occupies a larger circuit area, and increases the cost of the boost technology. Furthermore, more circuit elements will slow down the response time due to the delay effect of resistors and capacitors; when the switching signal sw0 is input into the potentiometer 12, the rising and falling edges of the switching signal sw1 generated at the output end will be delayed accordingly. , affects the response speed of the switch signal sw1, making it impossible to quickly switch between the voltage Vi0 and GND; jointly, the period T cannot be shortened, and the frequency of the switch signal sw1 cannot be increased.

In the boost technology using an inductor with a switching transistor, driving the switching transistor with a high-frequency switching signal for high-frequency switching can bring many advantages; for example, the size of the inductor can be reduced, the electromagnetic interference (EMI) can be reduced, and the energy utilization efficiency can also be improved. However, the known boost technology shown in Fig. 1 cannot be applied to high-frequency switching. The preferred switching signal frequency is around one million hertz, but the switching signal frequency in the known technology shown in FIG. 1 can only reach tens of thousands of hertz.

Furthermore, when the transistor M0 is switched between on and off, the voltage variation of the node nd3 is not conducive to high-frequency switching. There is a parasitic capacitance Cgd between the gate and the drain of the transistor M0, as shown in FIG. 1 . When the transistor M0 is turned on, the voltages of the nodes nd2 and nd3 are respectively the voltage Vi0 and the voltage GND at both ends of the capacitor Cgd; when the transistor M0 is not turned on, the voltage of the node nd2 changes to the voltage GND, and the voltage of the node nd3 becomes To transition to a voltage exceeding Vo. For example, in the case where Vo is 60 volts, when the transistor M0 is switched from on to off, the voltage of the node nd3 will increase from 0 volts of the ground voltage GND to over 60 volts. That is to say, when the transistor M0 switches, the voltage difference between the nodes nd2 and nd3 changes dramatically; the switching signal sw1 needs to spend a long time charging and discharging the capacitor Cgd to achieve this change, and then achieve the switching of the driving transistor M0. This has also become one of the reasons why the known boost technology cannot be switched at high frequency.

Contents of the invention

The invention provides a voltage boosting circuit and a related method to improve the disadvantages of the known technology and realize the voltage boosting technology with simplified circuit and high-frequency switching.

The purpose of the present invention is to provide a boost circuit driven by low voltage, which is provided with an inductor, a diode, a capacitor, a first switch and a second switch. The inductor is coupled between a first voltage and a first node, and the anode and cathode of the diode are respectively coupled to the first node and a second node. The capacitor is coupled to the second node. The first switch may include a first transistor having a first drain, a first source and a first gate, respectively coupled to a first channel terminal, a second channel terminal and a first control terminal of the first switch . The first control end is coupled to a switch signal, and the first switch selectively conducts between the first channel end and the second channel end according to the switch signal. The second switch may include a second transistor having a second drain, a second source and a second gate, respectively coupled to a third channel terminal, a fourth channel terminal and a second control terminal of the second switch . The third channel terminal, the fourth channel terminal and the second control terminal are respectively coupled to the first node, the first channel terminal and a second voltage. When the first switch conducts between the first channel end and the second channel end, the second switch conducts between the third channel end and the fourth channel end; when the first switch stops between the first channel end and the second channel end The second switch stops conducting between the third channel end and the fourth channel end.

The second voltage may be a DC voltage, and may be equal to the first voltage. When the cross voltage between the first gate and the first source is greater than a first threshold voltage, the first transistor is turned on between the first drain and the first source. When the cross voltage between the second gate and the second source is greater than a second threshold voltage, the second transistor is turned on between the second drain and the second source. When the first switch stops conducting between the first channel end and the second channel end, the second switch makes the voltage at the first channel end less than the second voltage. Therefore, the first transistor may be a low-rated, low-threshold voltage transistor, ie, the first threshold voltage may be smaller than the second threshold voltage. Therefore, the first transistor can be directly controlled by the low-voltage switching signal of the control chip.

Cooperating with the control chip, a voltage detection circuit and/or a current detection circuit can be added in the boost circuit. The voltage detection circuit provides a voltage detection signal at a voltage dividing node according to the voltage of the second node. For example, a first resistor and a second resistor can be set in the voltage detection circuit, the first resistor is coupled between the second node and the voltage dividing node, and the second resistor is coupled between the voltage dividing node and the ground terminal voltage between. The current detection circuit is coupled to the first switch, and provides a current detection signal according to the current at the second channel end; for example, the current detection circuit can be provided with a resistor, coupled between the second channel end and a ground voltage, so The magnitude of the current at the second channel end is related to the voltage at the second channel end, and the voltage at the second channel end can be used as a current detection signal. The voltage detection signal and the current detection signal can be transmitted to the control chip, so that the control chip adjusts the timing (such as duty cycle and/or frequency) of the switching signal accordingly, and feedback controls the output voltage of the boost circuit at the second node.

Another object of the present invention is to provide a method of controlling/driving a boost circuit at low voltage. The boost circuit receives a first voltage to provide an output voltage, and is provided with a second transistor, and the second transistor has a second gate and a second source. The method includes: providing a first transistor, which has a first gate and a first drain, and the first drain is coupled to the second source; and, using the chip to provide a low-voltage switching signal to the first gate pole to selectively turn on the first transistor; when the switch signal makes the first transistor and the second transistor non-conductive, the output voltage is higher than the first voltage. Furthermore, the second gate is coupled to a second voltage, and the second voltage can be a DC voltage, or can be equal to the first voltage. For feedback control, a voltage detection circuit can be provided, coupled to the second node of the boost circuit to provide the output voltage, a voltage detection signal is provided according to the output voltage, and the voltage detection signal is received by the chip. And/or, provide a current detection circuit, coupled to the first transistor, provide a current detection signal according to the current of the first drain, and receive the current detection signal by the chip.

In order to have a better understanding of the above-mentioned and other aspects of the present invention, the preferred embodiments are specifically cited below, together with the accompanying drawings, and are described in detail as follows:

Description of drawings

FIG. 1 illustrates a known boost circuit.

FIG. 2 is a boost circuit according to an embodiment of the invention.

FIG. 3 is a boost circuit according to another embodiment of the present invention.

Description of main component symbols

10, 20, 30: boost circuit

12: Potential shifter

14, 36: chip

22, 24: switch

32: Voltage detection circuit

34: Current detection circuit

Vi0, Vi, Vi2, Vo, VH, GND, Vn4, Vn5: Voltage

nd1-nd4, n1-n5: nodes

Q1-Q3, M0-M2: Transistors

D0, D: diode

C0, C, Cc, Cgd: capacitance

L0, L: inductance

Rp1-Rp3, R1-R3: Resistors

sw0-sw1, sw: switch signal

Ton: time period

T: period

detailed description

Please refer to FIG. 2 , which illustrates a boost circuit 20 according to an embodiment of the present invention. The boost circuit 20 draws the voltage Vi to provide an output voltage Vo at the node n2. The boost circuit 20 is provided with an inductor L, a diode D, a capacitor C and two switches 22 and 24 .

In the boost circuit 20, the inductor L is coupled between the voltage Vi and the node n1. The diode D can be a Schottky diode, and its anode and cathode are coupled to the node n1 and the node n2 respectively. The capacitor C is coupled between the node n2 and the ground voltage GND. The switch 22 can be realized by a transistor M1; the transistor M1 can be an n-channel metal-oxide-semiconductor transistor, and its drain, source, and gate serve as two channel ends and a control end of the switch 22, and are respectively coupled to the nodes n3, n4 and the switch signal sw, so that the switch 22 can be selectively turned on between the nodes n3 and n4 according to the switch signal sw. Another switch 24 can be realized by transistor M2; transistor M2 can be an n-channel metal oxide semi-transistor, and its drain, source and gate are two channel terminals and a control terminal of switch 24, respectively coupled to nodes n1, n3 and a Voltage Vi2. The voltage Vi2 may be a DC voltage; in one embodiment, the voltage Vi2 may be equal to the voltage Vi.

In an embodiment, the transistor M1 may be a transistor with a lower rated voltage, a smaller area, and a lower threshold voltage; the transistor M2 may be a power transistor with a higher rated voltage and a larger threshold voltage. Since the threshold voltage of the transistor M1 is relatively low, it can be directly controlled to be turned on by a low-voltage switching signal.

The operation of the boost circuit 20 can be described as follows. The transistor M1 is controlled by the switch signal sw; when the switch signal sw turns on the transistor M1, the transistor M1 turns on the node n3 to the ground voltage GND of the node n4. For the transistor M2, the source voltage of the node n3 is turned on to the ground voltage GND, but the gate maintains the voltage Vi2, so the cross voltage between the gate and the source is sufficient to exceed the threshold voltage of the transistor M2, The transistor M2 is also turned on together with the transistor M1, and the node n1 is turned on to the ground voltage GND. In this way, the voltage Vi will charge the magnetic energy in the inductor L.

When the switch signal sw makes the transistor M1 off and non-conductive, the node n3 is no longer conductive to the ground voltage GND. The transistor M2 will charge the node n3 to increase the voltage of the node n3; as the voltage of the node n3 increases, the cross voltage between the gate and the source of the transistor M2 will gradually decrease. When the voltage across the gate and source of the transistor M2 is lower than the threshold voltage of the transistor M2, the transistor M2 is turned off and stops conducting. In this way, the magnetic energy in the inductor L can be released through the diode D to support the voltage Vo at the node n2 to achieve the purpose of boosting the voltage.

In one embodiment, the voltages Vi and Vi2 can be equal to 12 volts; in accordance with the setting of the duty cycle of the switch signal sw, the voltage Vo can be as high as 60 volts. Therefore, the transistor M2 can be a power transistor with a high voltage rating, which is sufficient to withstand the high voltage of the node n1. For the transistor M2, when the transistor M1 conducts the node n3 to the ground voltage GND, the gate voltage Vi2 (such as 12 volts) of the transistor M2 is sufficient to exceed the threshold voltage of the transistor M2 (such as 5 volts), so that the transistor M2 M2 can be successfully turned on.

Furthermore, since the transistor M1 is cascaded under the source of the transistor M2, the drain of the transistor M1 at the node n3 does not need to withstand the high voltage of the voltage Vo. When the transistors M2 and M1 are not conducting, the voltage of the node n3 will be lower than the voltage Vi2 (such as 12 volts), so the transistor M1 does not need to be a high-rated power transistor; the transistor M1 can be a small-area, low-rated transistor, Therefore, its threshold voltage is also lower. Because the threshold voltage of the transistor M1 is relatively low, it can be directly turned on by a low-voltage switching signal sw. For example, the switch signal sw may be a signal directly output by the control chip; for example, the switch signal sw is a signal switched between 0 volts and 3 volts. In this way, the control chip can directly control the operation of the booster through the combination of the transistor M1 driven by the low voltage and the transistor M2 driven by the high voltage, without going through a circuit such as a potential shifter to control the operation of the booster circuit.

Since the voltage boosting technology of the present invention does not need a potentiometer, high-frequency switching can be applied, so that the boosting circuit 20 can realize various advantages of high-frequency switching. Furthermore, the circuit architecture design of the boost circuit of the present invention is also helpful for realizing high-frequency switching. When the transistor M1 is switched from on to off, the drain voltage at the node n3 will not be higher than the voltage Vi2 (eg, 12V), and much lower than the voltage Vo (eg, 60V). That is to say, when the transistor M1 is switched between on and off, its drain voltage does not change much. Therefore, for the transistor M1, the Miller effect on its gate-drain parasitic capacitance will be reduced; the switching signal sw can quickly complete the necessary charging and discharging of the gate-drain parasitic capacitance of the transistor M1, so that the transistor M1 can quickly switch between on and off, thereby realizing a high-frequency switching boost.

Please refer to FIG. 3 , which is a boost circuit 30 according to another embodiment of the present invention. The boost circuit 30 can be directly controlled by a chip 36; the chip 36 can be a control chip or a driver chip. Similar to the boost circuit 20 in FIG. 2, the boost circuit 30 is provided with an inductor L, a diode D, a capacitor C, and transistors M1 and M2 as switches to draw the voltage Vi to provide an output voltage Vo; the boost operation of the boost circuit 30 It can be derived by analogy from the principle of the boost circuit 20 , and will not be repeated here.

As shown in FIG. 3 , the boost circuit 30 is directly controlled by the switch signal sw output by the chip 36 . In order to cooperate with the chip 36 to control the boosting operation, the boosting circuit 30 can be provided with a voltage detection circuit 32 and a current detection circuit 34 . The voltage detection circuit 32 provides a voltage detection signal according to the voltage Vo to reflect the magnitude of the voltage Vo. In the embodiment of FIG. 3, the voltage detection circuit 32 is provided with two resistors R1, R2 and a capacitor Cc; the resistor R1 is coupled between the nodes n2 and n5, and the resistor R2 is coupled between the node n5 and the ground voltage GND , the capacitor Cc is also coupled between the node n5 and the ground voltage GND. The node n5 between the resistors R1 and R2 can be regarded as a voltage dividing node, both of which divide the voltage Vo, and the voltage Vn5 of the node n5 can be used as a voltage detection signal to reflect the voltage of the voltage Vo. The voltage Vn5 can be transmitted to the chip 36 as a basis for feedback control; the capacitor Cc is used to maintain the stability of the feedback system.

The current detection circuit 34 is coupled to the transistor M1, and provides a current detection signal according to the current of the transistor M1. In the embodiment of FIG. 3, a resistor R3 is provided in the current detection circuit 34, which is coupled between the node n4 and the ground voltage GND, so that the current of the transistor M1 is related to the voltage Vn4 of the node n4, and the voltage Vn4 can be as a current sense signal. The voltage Vn4 can also be transmitted to the chip 36 as another basis for feedback control.

According to the voltage detection signal and current detection signal of the voltages Vn5 and Vn4, the chip 36 can adjust the timing (such as the duty cycle and/or frequency) of the switching signal sw, thereby feedback-controlling the boosting operation of the boosting circuit 30 (such as the voltage size of Vo).

To sum up, compared with the known boost circuit and boost technology, the boost circuit of the present invention adopts the structure of double switching transistor stacking, so the boost circuit of the present invention can be directly controlled by the switch signal of the chip, not only can The cost and circuit area of the boost operation are saved, and the switching frequency of the boost boost can be increased to realize high-frequency switching. The boosting technology of the present invention is applicable to various applications requiring high voltage, for example, it is used to drive LED strings of display panels.

To sum up, although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Those skilled in the art of the present invention may make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention should be defined by the claims.

Claims (15)

1., with a booster circuit for low-voltage driving, comprise:

One inductance, is coupled between one first voltage and a primary nodal point；

One diode, has an anode and a negative electrode, and this anode couples this primary nodal point, and this negative electrode couples a secondary nodal point；

One electric capacity, couples this secondary nodal point；

One first switch, has a first passage end, a second channel end and one first control end；This first control end couples a switching signal, and this first switch optionally turns on according to this switching signal between this first passage end and this second channel end；

One second switch, have a third channel end, a fourth lane end and one second controls end, it is respectively coupled to this primary nodal point, this first passage end and one second voltage, wherein, when this first switch between this first passage end and this second channel end conducting time, this second switch turns between this third channel end and this fourth lane end；Turning between this first passage end and this second channel end when this first switch stops at, this second switch stops at and turns between this third channel end and this fourth lane end；

Wherein this first switch comprises a first transistor, has one first drain electrode, one first source electrode and a first grid, is respectively coupled to this first passage end, this second channel end and this first control end；When cross-pressure when between this first grid and this first source electrode is more than first limit voltage, the conducting between this first drain electrode and this first source electrode of this first transistor；This second switch comprises a transistor seconds, and this transistor seconds has one second drain electrode, one second source electrode and a second grid, is respectively coupled to this third channel end, this fourth lane end and this second control end；When cross-pressure when between this second grid and this second source electrode is more than second limit voltage, the conducting between this second drain electrode and this second source electrode of this transistor seconds；Wherein this first limit voltage is less than this second limit voltage, and this first limit voltage is low to moderate makes this first transistor can be turned on by the cross-pressure of 3 volts between this first grid and this first source electrode, and this second limit voltage is equal to 5 volts.

2. booster circuit as claimed in claim 1, it is characterised in that this second voltage is a DC voltage.

3. booster circuit as claimed in claim 1, it is characterised in that this second voltage is equal to this first voltage.

4. booster circuit as claimed in claim 1, it is characterised in that when this first switch stops at conducting between this first passage end and this second channel end, this second switch makes the voltage of this first passage end less than this second voltage.

5. booster circuit as claimed in claim 1, it is characterised in that also comprise:

One voltage detecting circuit, provides a voltage detection signal according to the voltage of this secondary nodal point in a divider node.

6. booster circuit as claimed in claim 5, it is characterized in that, this voltage detecting circuit comprises one first resistance and one second resistance, and this first resistance is coupled between this secondary nodal point and this divider node, and this second resistance is coupled between this divider node and a ground terminal voltage.

7. booster circuit as claimed in claim 1, it is characterised in that also comprise:

One current detection circuit, is coupled to this first switch, provides a current detection signal according to the electric current of this second channel end.

8. booster circuit as claimed in claim 7, it is characterised in that this current detection circuit comprises a resistance, is coupled between this second channel end and a ground terminal voltage.

9., with a method for low-voltage driving one booster circuit, this booster circuit receives one first voltage to provide an output voltage, and includes a transistor seconds, and this transistor seconds has a second grid and one second source electrode；And the method comprises:

Thering is provided a first transistor, have a first grid, one first source electrode and one first drain electrode, this first drain electrode couples this second source electrode；And

There is provided a low tension switch signal to this first grid, to selectively turn on this first transistor, when the first transistor turns on, this transistor seconds turns on, when this first transistor stops conducting, this transistor seconds stops conducting, when this low tension switch signal makes the first transistor and this transistor seconds be not turned on, cause this output voltage higher than this first voltage, wherein this first transistor has the first limit voltage, this transistor seconds has the second limit voltage, this first limit voltage is less than this second limit voltage, this first limit voltage is low to moderate makes this first transistor can be turned on by the cross-pressure of 3 volts between this first grid and this first source electrode, this second limit voltage is equal to 5 volts.

10. method as claimed in claim 9, it is characterised in that this low tension switch signal is provided by a chip.

11. method as claimed in claim 9, it is characterised in that also comprise:

This second grid is made to be coupled to one second voltage.

12. method as claimed in claim 11, it is characterised in that this second voltage is equal to this first voltage.

13. method as claimed in claim 11, it is characterised in that this second voltage is a DC voltage.

14. method as claimed in claim 10, it is characterised in that this booster circuit provides this output voltage in a secondary nodal point, and the method also comprises:

One voltage detecting circuit is provided, couples this secondary nodal point, provide a voltage detection signal according to this output voltage；And

This voltage detection signal is received with this chip.

15. method as claimed in claim 10, it is characterised in that also comprise:

One current detection circuit is provided, is coupled to this first transistor, provide a current detection signal according to the electric current of this first drain electrode；And

This current detection signal is received with this chip.