CN115917633B

CN115917633B - A pixel driving circuit and a micro light emitting diode display panel

Info

Publication number: CN115917633B
Application number: CN202080103250.1A
Authority: CN
Inventors: 赵公元; 方黎明
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2020-08-24
Filing date: 2020-08-24
Publication date: 2025-05-09
Anticipated expiration: 2040-08-24
Also published as: CN115917633A; WO2022040879A1

Abstract

Provided are a pixel drive circuit and a micro light emitting diode display panel, relating to the field of display technology. A charging circuit (1001) is used to charge a coupling point between a light emitting diode (D1) and a pixel drive circuit (1000), thereby reducing a variation range of a cathode voltage of the light emitting diode (D1) when the pixel drive circuit (1000) drives the light emitting diode (D1) to emit light, thereby increasing the switching speed of the LED. The micro light emitting diode display panel comprises a plurality of driving circuits, wherein the driving circuits comprise a plurality of pixel driving circuits (1000), wherein the pixel driving circuit (1000) comprises: a light emitting driving module (1002) cascaded between the cathode of a light emitting diode (D1) and ground, wherein the light emitting driving module (1002) comprises a gate switch (Ks) and a current source (Is), wherein the control end of the gate switch (Ks) receives a first control signal (PWM), the control end of the current source (Is) receives a bias voltage (Vbias), and the anode of the light emitting diode (D1) is coupled to a power supply; and a charging circuit (1001) coupled between a charging potential end (VA1) and a first node (A), wherein the first node (A) is a coupling point between the light emitting driving module (1002) and the cathode of the light emitting diode (D1).

Description

Pixel driving circuit and miniature light-emitting diode display panel

Technical Field

The present application relates to the field of display technologies, and in particular, to a pixel driving circuit and a micro light emitting diode display panel.

Background

An LED (LIGHT EMITTING diode) display panel implements pixel display using LEDs, and its display performance has higher contrast and brightness than a conventional LCD (liquid CRYSTAL DISPLAY).

In an LED display panel, an LED pixel array is driven by a pixel driving circuit. The pixel driving circuit is gated according to the row gate signal and the column driving signal, thereby driving the LEDs to emit light. The anode of the LED is coupled to a power source and the cathode is coupled to a pixel drive circuit. Because parasitic capacitance and parasitic resistance exist at the cathode of the LED, when the LED is frequently switched between an on state and an off state, the pixel driving circuit needs to charge or discharge the cathode of the LED at a high speed, and the charge and discharge time influences the switching time of the LED switch, so that the switching speed of the LED is limited. When the LED switch speed is slower, the afterimage phenomenon is easily observed by human eyes, and the user experience is affected.

Disclosure of Invention

The application provides a pixel driving circuit and a Micro light emitting diode Micro LED display panel, wherein a coupling point between a light emitting diode and the pixel driving circuit is charged through a charging circuit, so that the variation range of the cathode voltage of the light emitting diode is reduced when the pixel driving circuit drives the light emitting diode to emit light, and the switching speed of the LED is improved.

In a first aspect, a micro light emitting diode display panel is provided. The micro light emitting diode display panel comprises a plurality of driving circuits which are distributed in an array, wherein each driving circuit comprises a plurality of pixel driving circuits and is used for driving a plurality of pixels, each pixel comprises at least three sub-pixels, each sub-pixel comprises a light emitting diode, a first sub-pixel in the pixel is coupled with a first pixel driving circuit in the pixel driving circuits, a second sub-pixel in the pixel is coupled with a second pixel driving circuit in the pixel driving circuits, and a third sub-pixel in the pixel is coupled with a third pixel driving circuit in the pixel driving circuits. For example, the driving circuit includes 12 pixel driving circuits, 4 pixels are distributed around the driving circuit, each pixel includes three sub-pixels, and each sub-pixel includes a light emitting diode of one color. Each pixel driving circuit is used for driving one light emitting diode. The pixel driving circuit comprises a light-emitting driving module and a charging circuit, wherein the light-emitting driving module is cascaded between the cathode of the light-emitting diode and the ground, the light-emitting driving module comprises a gating switch and a current source, the control end of the gating switch receives a first control signal, the control end of the current source receives a bias voltage, the anode of the light-emitting diode is coupled with a power supply, the charging circuit is coupled between a charging potential end and a first node, and the first node is a coupling point of the light-emitting driving module and the cathode of the light-emitting diode.

The charging circuit is used for charging the first node through the charging potential end. When the light-emitting driving module stops driving the light-emitting diode, the light-emitting diode is turned off, the charging circuit charges the cathode (the first node) of the light-emitting diode through the charging potential end until the voltage of the first node is equal to the voltage of the charging potential end, the voltage difference between the charging potential end and the power supply is smaller than the minimum light-emitting voltage of the light-emitting device, and the voltage of the charging potential end is smaller than the voltage of the power supply, so that the light-emitting diode cannot emit light. When the light-emitting driving module drives the light-emitting diode, the charging circuit stops charging the first node, and the charge in the parasitic capacitance of the first node is discharged through the gating switch and the current source until the voltage of the first node is the same as the ground. In the process, the first node starts discharging from a voltage lower than the power supply (the voltage of the charging potential end), and when the voltage difference between the charging potential end and the power supply is slightly smaller than the minimum light-emitting voltage of the light-emitting diode, the voltage difference between the voltage of the first node and the power supply can meet the minimum light-emitting voltage of the light-emitting diode as long as the first node starts slightly discharging from the voltage of the charging potential end, the light-emitting diode starts emitting light, the variation range of the cathode voltage of the light-emitting diode is narrowed when the pixel driving circuit drives the light-emitting diode to emit light, and the switching speed of the light-emitting diode is improved. When the change range of the cathode voltage of the light-emitting diode is reduced, the establishment time of the current signal of the light-emitting diode is shortened, and the refreshing frequency of the light-emitting diode is increased, so that the time from extinction to lighting of the light-emitting diode is shortened, the afterimage phenomenon when the light-emitting diode is observed by human eyes can be improved, the display precision of the light-emitting diode is improved, and the user experience is improved. In addition, when the light-emitting driving module changes from the state of driving the light-emitting diode to the state of stopping driving the light-emitting diode, the charging circuit charges the first node through the charging potential end, and the voltage of the first node is directly set as the voltage of the charging potential end, so that the turn-off time of a current signal of the light-emitting diode is also reduced.

In one possible embodiment, the charging circuit comprises a first switch, wherein a first terminal of the first switch is coupled to the first node and a second terminal of the first switch is coupled to the charging potential terminal.

In one possible embodiment, the on enable signal of the first switch is in logical non-relationship with the enable signal of the light emitting driving module. The light-emitting driving module drives the light-emitting diode when the first control signal controls the gating switch to be turned on and the bias voltage controls the current source to output driving current, or when the first control signal controls the gating switch to be turned off or the bias voltage controls the current source to stop outputting driving current, the light-emitting driving module stops driving the light-emitting diode. When the bias voltage controls the current source to continuously output the driving current in the on period of the gating switch controlled by the first control signal, the enabling signal of the light-emitting driving module is the first control signal. The enable signal of the light emitting driving module may be a first control signal, and the control terminal of the first switch is coupled to the control terminal of the gate switch through the not gate circuit. When the gate switch is turned on, the charging potential end stops charging the first node, and when the gate switch is turned off, the charging potential end charges the first node, so that when the first switch and the gate switch adopt MOS tubes of the same type, the first control signal of the control end of the gate switch is opposite to the conduction enabling signal of the first switch, the control end of the first switch can be coupled with the control end of the gate switch through the NOT circuit, and the control end of the gate switch is input by using the first control signal and is input into the control end of the first switch after passing through the NOT circuit.

In one possible implementation manner, the first switch includes a first MOS transistor, one end of a source/drain of the first MOS transistor is coupled to the charging potential end, the other end of the source/drain of the first MOS transistor is coupled to the first node, and a gate of the first MOS transistor receives the turn-on enable signal.

In one possible implementation manner, the gate switch includes a second MOS transistor, one end of a source/drain of the second MOS transistor is coupled to the current source, the other end of the source/drain of the second MOS transistor is coupled to the cathode of the light emitting diode and is coupled to the first node, and a gate of the gate switch receives the first control signal.

In one possible implementation manner, the current source includes a third MOS transistor, wherein one end of a source-drain electrode of the third MOS transistor is coupled to ground, the other end of the source-drain electrode of the third MOS transistor is coupled to the gate switch, and a gate electrode of the third MOS transistor receives the bias voltage.

In one possible implementation manner, the current source further includes a fourth MOS transistor, wherein one end of the source-drain electrode of the fourth MOS transistor is coupled to one end of the source-drain electrode of the third MOS transistor, the other end of the source-drain electrode of the fourth MOS transistor is coupled to ground, and the gate electrode of the fourth MOS transistor receives the bias voltage.

In a possible embodiment, the pixel driving circuit further comprises a capacitor, one end of which is coupled to the control terminal of the current source, and the other end of which is coupled to ground.

In one possible embodiment, the first control signal is a pulse width modulated PWM signal.

In a second aspect, a micro light emitting diode display panel is provided. The miniature light-emitting diode display panel comprises a plurality of driving circuits which are distributed in an array, wherein each driving circuit comprises a plurality of pixel driving circuits and is used for driving a plurality of pixels, each pixel comprises at least three sub-pixels, each sub-pixel comprises a light-emitting diode, a first sub-pixel in each pixel is coupled with a first pixel driving circuit in the plurality of pixel driving circuits, a second sub-pixel in each pixel is coupled with a second pixel driving circuit in the plurality of pixel driving circuits, and a third sub-pixel in each pixel is coupled with a third pixel driving circuit in the plurality of pixel driving circuits. The pixel driving circuit comprises a light-emitting driving module and a charging circuit, wherein the light-emitting driving module is cascaded between an anode of a light-emitting diode and a power supply, the light-emitting driving module comprises a gating switch and a current source, a control end of the gating switch receives a first control signal, a control end of the current source receives a bias voltage, a cathode of the light-emitting diode is coupled with the ground, the charging circuit is coupled between a charging potential end and a first node, and the first node is a coupling point of the light-emitting driving module and the anode of the light-emitting diode.

The charging circuit is used for charging the first node through the charging potential terminal. When the light-emitting driving module stops driving the light-emitting diode, the light-emitting diode is turned off, the charging potential end charges the anode (the first node) of the light-emitting diode until the voltage of the first node is equal to the voltage of the charging potential end, the voltage difference between the voltage of the charging potential end and the ground is smaller than the minimum light-emitting voltage of the light-emitting diode, and the voltage of the charging potential end is smaller than the voltage of the power supply, so that the light-emitting diode cannot emit light. When the light-emitting driving module drives the light-emitting diode, the charging circuit stops charging the first node, and the power supply charges parasitic capacitance of the first node through the gating switch and the current source until the voltage of the first node is the same as the power supply. In this process, the first node starts to charge from a voltage lower than the power supply (the voltage at the charging potential end), and when the voltage difference between the charging potential end and the ground is slightly smaller than the minimum light-emitting voltage of the light-emitting diode, as long as the first node starts to slightly increase from the voltage at the charging potential end, that is, the voltage difference between the voltage of the first node and the ground can meet the minimum light-emitting voltage of the light-emitting diode, the light-emitting diode starts to emit light, so that the variation range of the cathode voltage of the light-emitting diode is reduced when the pixel driving circuit drives the light-emitting diode to emit light, and the switching speed of the light-emitting diode is increased. When the change range of the cathode voltage of the light-emitting diode is reduced, the establishment time of the current signal of the light-emitting diode is shortened, and the refreshing frequency of the light-emitting diode is increased, so that the time from extinction to lighting of the light-emitting diode is shortened, the afterimage phenomenon when the light-emitting diode is observed by human eyes can be improved, the display precision of the light-emitting diode is improved, and the user experience is improved. In addition, when the light-emitting driving module changes from the state of driving the light-emitting diode to the state of stopping driving the light-emitting diode, the charging circuit charges the first node through the charging potential end, and the voltage of the first node is directly set as the voltage of the charging potential end, so that the turn-off time of a current signal of the light-emitting diode is also reduced.

In one possible embodiment, the charging circuit includes a first switch, wherein a first terminal of the first switch is coupled to the first node, and a second terminal of the first switch is coupled to the charging potential terminal.

In one possible implementation manner, the gating switch includes a second MOS transistor, one end of a source/drain of the second MOS transistor is coupled to the current source, the other end of the source/drain of the second MOS transistor and an anode of the light emitting diode are electrically coupled to the first node, and a gate of the second MOS transistor receives the first control signal.

In one possible implementation manner, the current source includes a third MOS transistor, wherein one end of a source-drain electrode of the third MOS transistor is coupled to the power supply, the other end of the source-drain electrode of the third MOS transistor is coupled to the gate switch, and a gate electrode of the third MOS transistor receives the bias voltage.

In one possible implementation manner, the current source further includes a fourth MOS transistor, wherein one end of a source-drain electrode of the fourth MOS transistor is coupled to one end of a source-drain electrode of the third MOS transistor, the other end of the source-drain electrode of the fourth MOS transistor is coupled to the power supply, and a gate electrode of the fourth MOS transistor receives the bias voltage.

In a possible embodiment, the pixel driving circuit further comprises a capacitor, one end of which is coupled to the control terminal of the current source and the other end of which is coupled to the power supply.

In one possible embodiment, the control signal is a pulse width modulated PWM signal.

In a third aspect, an AMOLED display panel is provided. The display panel comprises pixels distributed in an array, wherein the pixels comprise pixel driving circuits and light emitting diodes, the pixel driving circuits are coupled between anodes of the light emitting diodes and a power supply, cathodes of the light emitting diodes are coupled to ground, the pixel driving circuits are used for driving the light emitting diodes, the pixels further comprise charging circuits which are coupled between a charging potential end and a first node, and the first node is a coupling point of the pixel driving circuits and anodes of the light emitting diodes. The AMOLED display panel of the third aspect has similar effects to the Micro LED display panel of the second aspect, and is not described here again.

In one possible embodiment, the voltage difference between the voltage at the charging potential end and ground is smaller than the minimum light emitting voltage of the light emitting diode, and the voltage at the charging potential end is smaller than the voltage of the power supply.

In one possible embodiment, the charging circuit comprises a third switch, wherein a first terminal of the third switch is coupled to the first node and a second terminal of the third switch is coupled to the charging potential terminal.

In one possible implementation manner, the pixel driving circuit includes a first MOS transistor and a second MOS transistor, one end of a source/drain of the first MOS transistor receives the data voltage, the other end of the source/drain of the first MOS transistor is coupled to a gate of the second MOS transistor, the gate of the first MOS transistor receives the scan signal, one end of the source/drain of the second MOS transistor is coupled to a power supply, and the other end of the source/drain of the second MOS transistor is coupled to a first node.

In one possible implementation manner, the third switch includes a third MOS transistor, one end of a source/drain of the third MOS transistor is coupled to the charging potential end, and the other end of the source/drain of the third MOS transistor is coupled to the first node.

In one possible implementation, the pixel driving circuit further includes a capacitor, one end of which is coupled to the gate of the second MOS transistor, and the other end of which is coupled to ground.

In a fourth aspect, an AMOLED display panel is provided. The display panel comprises pixels distributed in an array, wherein the pixels comprise pixel driving circuits and light emitting diodes, the pixel driving circuits are coupled between cathodes of the light emitting diodes and ground, anodes of the light emitting diodes are coupled with a power supply, the pixel driving circuits are used for driving the light emitting diodes, the pixels further comprise charging circuits which are coupled between charging potential ends and first nodes, and the first nodes are coupling points of the pixel driving circuits and anodes of the light emitting diodes. The AMOLED display panel of the fourth aspect has similar effects to the Micro LED display panel of the first aspect, and will not be described here again.

In one possible embodiment, a voltage difference between the charging potential terminal and the power supply is smaller than a minimum light emitting voltage of the light emitting device, and a voltage of the charging potential terminal is smaller than a voltage of the power supply.

In one possible implementation, the pixel driving circuit further includes a capacitor, one end of which is coupled to the gate of the second MOS transistor, and the other end of which is coupled to the power supply.

In a fifth aspect, a pixel driving circuit is provided. The pixel driving circuit comprises a light-emitting driving module and a charging circuit, wherein the light-emitting driving module is cascaded between the cathode of the light-emitting diode and the ground, the light-emitting driving module comprises a gating switch and a current source, the control end of the gating switch receives a first control signal, the control end of the current source receives a bias voltage, the anode of the light-emitting diode is coupled with a power supply, the charging circuit is coupled between a charging potential end and a first node, and the first node is a coupling point of the light-emitting driving module and the cathode of the light-emitting diode.

In one possible embodiment, the on enable signal of the first switch is in logical non-relationship with the enable signal of the light emitting driving module.

The pixel driving circuit of the fifth aspect has similar effects to those of the Micro LED display panel of the first aspect, and will not be described here again.

In a sixth aspect, a pixel driving circuit is provided. The pixel driving circuit comprises a light-emitting driving module and a charging circuit, wherein the light-emitting driving module is cascaded between an anode of a light-emitting diode and a power supply, the light-emitting driving module comprises a gating switch and a current source, a control end of the gating switch receives a first control signal, a control end of the current source receives a bias voltage, a cathode of the light-emitting diode is coupled with the ground, the charging circuit is coupled between a charging potential end and a first node, and the first node is a coupling point of the light-emitting driving module and the anode of the light-emitting diode.

In one possible embodiment, the charging circuit includes a first switch, wherein a first terminal of the first switch is coupled to an anode of the light emitting diode, and a second terminal of the first switch is coupled to a charging potential terminal.

The pixel driving circuit of the sixth aspect has similar effects to those of the Micro LED display panel of the second aspect, and will not be described here again.

A seventh aspect, a terminal device, including a rear housing, a middle frame, and a Micro LED display panel according to the first or second aspect, where the rear housing and the Micro LED display panel are disposed opposite to each other and connected by a frame.

In an eighth aspect, a terminal device includes a rear case, a middle frame, and an AMOLED display panel according to the third aspect or the fourth aspect, where the rear case and the Micro LED display panel are disposed opposite to each other and connected by a frame.

The terminal device in the seventh or eighth aspect has effects similar to those of the Micro LED display panel in the first or second aspect, and will not be described here again.

Drawings

Fig. 1 is a schematic structural diagram of a terminal device according to an embodiment of the present application;

fig. 2 is a schematic structural diagram of a terminal device according to another embodiment of the present application;

Fig. 3 is a schematic structural diagram of a display panel according to an embodiment of the present application;

Fig. 4 is a schematic diagram of a connection manner between a pixel driving circuit and an LED according to an embodiment of the present application;

Fig. 5 is a schematic structural diagram of a pixel driving circuit according to an embodiment of the present application;

fig. 6 is a schematic structural diagram of a display panel according to another embodiment of the application;

Fig. 7 is a schematic structural diagram of a driving circuit according to an embodiment of the present application;

fig. 8 is a schematic diagram of a pixel driving circuit according to another embodiment of the present application;

fig. 9 is a schematic waveform diagram of a node signal of a pixel driving circuit according to an embodiment of the present application;

Fig. 10 is a schematic structural diagram of a pixel driving circuit according to still another embodiment of the present application;

fig. 11 is a schematic waveform diagram of a node signal of a pixel driving circuit according to another embodiment of the present application;

fig. 12 is a schematic diagram of a pixel driving circuit according to another embodiment of the present application;

fig. 13 is a schematic structural diagram of a pixel driving circuit according to another embodiment of the present application;

fig. 14 is a schematic structural diagram of a pixel driving circuit according to still another embodiment of the present application;

fig. 15 is a schematic waveform diagram of a node signal of a pixel driving circuit according to another embodiment of the present application;

Fig. 16 is a schematic structural diagram of a pixel driving circuit according to another embodiment of the present application;

fig. 17 is a schematic diagram of a pixel driving circuit according to another embodiment of the present application;

Fig. 18 is a schematic diagram of a pixel driving circuit according to still another embodiment of the present application;

fig. 19 is a schematic diagram of a pixel driving circuit according to another embodiment of the application.

Detailed Description

The making and using of the various embodiments are discussed in detail below. It should be appreciated that the numerous applicable inventive concepts provided by the present application may be embodied in a wide variety of specific contexts. The specific embodiments discussed are merely illustrative of specific ways to make and use the description and technology, and do not limit the scope of the application. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art.

In embodiments of the present application, "at least one" means one or more, and "a plurality" means two or more. "and/or" describes an association of associated objects, meaning that there may be three relationships, e.g., A and/or B, and that there may be A alone, while A and B are present, and B alone, where A, B may be singular or plural. The character "/" generally indicates that the context-dependent object is an "or" relationship. "at least one of" or the like means any combination of these items, including any combination of single item(s) or plural items(s). For example, at least one (a, b or c) of a, b, c, a and b, a and c, b and c or a, b and c may be represented, wherein a, b and c may be single or plural. In embodiments of the application, the terms "first," "second," and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. In addition, the term "coupled" may be used to implement an electrical connection for signal transmission, where "coupled" may be a direct electrical connection or an indirect electrical connection via an intermediary. Such as connections made through resistors, inductors, or other electrical components. When describing the three-terminal switching element, the "first terminal" and the "second terminal" may refer to the connection terminal of the three-terminal switching element, respectively, and the "control terminal" may refer to the control terminal of the three-terminal switching element. For example, for a MOS (metal-oxide-semiconductor) transistor, the control terminal may refer to the gate (gate) of the MOS transistor, the first terminal may refer to the source (source) of the MOS transistor, the second terminal may refer to the drain (drain) of the MOS transistor, or the first terminal may refer to the drain of the MOS transistor, and the second terminal may refer to the source of the MOS transistor.

The embodiment of the application provides a terminal device, which can be an electronic device with a display screen, such as a mobile phone, a tablet computer, a notebook computer, an ultra-mobile personal computer (UMPC), a netbook, a Personal Digital Assistant (PDA), a vehicle-mounted mobile device and the like.

Fig. 1 is a schematic architecture diagram of an exemplary terminal device according to an embodiment of the present application. As shown in fig. 1, the terminal apparatus 01 includes a processor 11, a Radio Frequency (RF) circuit 12, a power source 13, a memory 14, an input unit 15, a display device 16, an audio circuit 17, and the like. It will be appreciated by those skilled in the art that the structure of the terminal device shown in fig. 1 does not constitute a limitation of the terminal device, and the terminal device may include more or less components than those shown in fig. 1, or may combine some of the components shown in fig. 1, or may be arranged differently from the components shown in fig. 1.

The processor 11 is a control center of the terminal device, connects respective parts of the entire terminal device using various interfaces and lines, and performs various functions of the terminal device and processes data by running or executing software programs and/or modules stored in the memory 14 and calling data stored in the memory 14, thereby performing overall monitoring of the terminal device. Alternatively, the processor 11 may comprise one or more processing units, and preferably the processor 11 may integrate an application processor and a modem processor, wherein the application processor primarily handles operating systems, user interfaces, application programs, etc., and the modem processor primarily handles wireless communications. It will be appreciated that the modem processor described above may not be integrated into the processor 11.

The RF circuit 12 is used for receiving and transmitting signals during the process of receiving and transmitting information or communication, specifically, receiving downlink information of a base station, processing the downlink information by the processor 11, and transmitting uplink data to the base station. Typically, RF circuitry includes, but is not limited to, antennas, at least one amplifier, transceivers, couplers, low noise amplifiers (low noise amplifier, LNAs), diplexers, and the like. In addition, RF circuit 12 may also communicate with networks and other devices via wireless communications. The wireless communication may use any communication standard or protocol including, but not limited to, global system for mobile communications (global system of mobile communication, GSM), general packet radio service (GENERAL PACKET radio service, GPRS), code division multiple access (code division multiple access, CDMA), wideband code division multiple access (wideband code division multiple access, WCDMA), long term evolution (long term evolution, LTE), email, short message service (short MESSAGING SERVICE, SMS), and the like.

The terminal device comprises a power supply 13, such as a battery, for powering the various components, which may optionally be logically connected to the processor 11 via a power management system, whereby charging, discharging, power consumption management, etc. functions are performed via the power management system.

The memory 14 may be used to store software programs and modules, and the processor 11 performs various functional applications of the terminal device and data processing by running the software programs and modules stored in the memory 14. The memory 14 may mainly include a storage program area that may store an operating system, an application program required for at least one function (such as a sound playing function, an image playing function, etc.), etc., and a storage data area that may store data created according to the use of the cellular phone (such as audio data, image data, phonebook, etc.), etc. In addition, memory 14 may include high-speed random access memory, and may also include non-volatile memory, such as at least one magnetic disk storage device, flash memory device, or other volatile solid-state storage device.

The input unit 15 is operable to receive input numeric or character information and to generate key signal inputs related to user settings and function control of the terminal device. In particular, the input unit 15 may include a touch screen 151 and other input devices 152. The touch screen 151, also referred to as a touch panel, may collect touch operations of a user on or near the touch screen (such as operations of the user on or near the touch screen 151 using any suitable object or accessory such as a finger, a stylus, etc.), and drive the corresponding connection terminal device according to a preset program. Alternatively, the touch screen 151 may include two parts, a touch detection device and a touch controller. The touch controller receives touch information from the touch detection device, converts the touch information into touch point coordinates, sends the touch point coordinates to the processor 11, and can receive and execute commands sent by the processor 11. In addition, the touch screen 151 may be implemented in various types of resistive, capacitive, infrared, surface acoustic wave, and the like. Other input devices 152 may include, but are not limited to, one or more of a physical keyboard, function keys (e.g., volume control keys, power switch keys, etc.), a trackball, mouse, joystick, etc.

The display device 16 may be used to display information input by a user or information provided to the user and various menus of the terminal apparatus. The display device 16 may include a display panel 161, and in the present application, the display panel 161 may be an AMOLED display panel or a Micro LED display panel. Further, the touch screen 151 may overlay the display panel 161, and when the touch screen 151 detects a touch operation on or near the touch screen 151, the touch is transmitted to the processor 11 to determine the type of touch event, and then the processor 11 provides a corresponding visual output on the display panel 161 according to the type of touch event. Although in fig. 1, the touch screen 151 and the display panel 161 are provided as two separate components to implement the input and output functions of the device, in some embodiments, the touch screen 151 and the display panel 161 may be integrated to implement the input and output functions of the device.

Audio circuitry 17, speaker 171 and microphone 172 for providing an audio interface between the user and the terminal device. The audio circuit 17 may transmit the received electrical signal converted from audio data to the speaker 171 for conversion to a sound signal for output by the speaker 171, while the microphone 172 may convert the collected sound signal to an electrical signal for receipt by the audio circuit 17 for conversion to audio data for output to the RF circuit 12 for transmission to, for example, another terminal device, or for output to the memory 14 for further processing.

Optionally, the terminal device as shown in fig. 1 may also include various sensors. Such as gyroscopic sensors, hygrometric sensors, infrared sensors, magnetometer sensors, etc., are not described in detail herein. Optionally, the terminal device shown in fig. 1 may further include a wireless fidelity (WIRELESS FIDELITY, wiFi) module, a bluetooth module, etc., which will not be described herein.

It will be understood that, in the embodiment of the present application, the terminal device may perform some or all of the steps in the embodiment of the present application, these steps or operations are merely examples, and the embodiment of the present application may also perform other operations or variations of various operations. Furthermore, the various steps may be performed in a different order presented in accordance with embodiments of the application, and it is possible that not all of the operations in the embodiments of the application may be performed. The embodiments of the present application may be implemented alone or in any combination, and the present application is not limited thereto.

The embodiment of the present application does not particularly limit the specific form of the terminal device 01. For convenience of explanation, the following description will be made taking the terminal device 01 as an example of a mobile phone. The terminal device 01 is structured as shown in fig. 2, and mainly includes a display panel 21, a middle frame 22, and a rear case 23. The rear case 23 and the display panel 21 are disposed opposite to each other and are connected by the middle frame 22. In the embodiment of the present application, the display panel 21 is an organic light-emitting diode (OLED), an active-matrixorganic LIGHT EMITTING diode (AMOLED), a flexible light-emitting diode (FLED), miniled, microLed, micro-oLed, a quantum dot light-emitting diode (quantum dot lightemitting diodes, QLED), a Micro light-emitting diode (Micro LED), or the like.

In the AMOLED display panel scheme, a pixel driving circuit composed of two or more TFTs is generally used to drive light emitting diodes in pixels to realize a display function. As shown in fig. 3, the display panel 30 includes an effective display area (ACTIVE AREA, AA) 100 and a non-display area 101 located at the periphery of the AA area 100. The AA area 100 includes a plurality of pixels (pixels) 31. For convenience of explanation, the plurality of pixels 31 are described as being arranged in a matrix form.

In the embodiment of the present application, the pixels 31 arranged in a row along the horizontal direction X in fig. 3 are referred to as pixels in the same row, and the pixels 31 arranged in a row along the vertical direction Y are referred to as pixels in the same column. In an embodiment of the present application, the display panel 30 may be an AMOLED display panel. The AMOLED display panel can realize self-luminescence. In this case, an LED as shown in fig. 4 and a pixel driving circuit 301 for driving the LED to emit light are provided in the pixel 31 in the AA region 100.

In addition, the apparatus may further include a display driving circuit for driving the display panel 30 to display, and the display driving circuit may be coupled with the display panel 30. The display driving circuit may be a display driving chip (DISPLAY DRIVER INTEGRATED circuits, DDIC), for example. In some embodiments of the present application, as shown in fig. 3, DDIC32 is disposed in non-display area 101 of display panel 30. The pixel driving circuits 301 in the same column of pixels 31 are coupled to the DDIC32 through the same Data Line (DL). In other embodiments of the present application, the DDIC32 may also be provided independently of the display panel 30. The terminal device further includes a printed circuit board (printed circuit board, PCB), and a System on Chip (SoC) mounted on the PCB. An application processor (application processor, AP), which may be the processor 11 in fig. 1, may be provided within the SoC. DDIC32 in fig. 3 is coupled to the SoC through a flexible circuit board (flexible printed circuit, FPC).

In this way, the display data outputted from the SoC is converted into the data voltage Vdata after passing through the DDIC32, and is transferred to the pixel driving circuit 301 of each pixel 31 to which each data line DL is coupled. Next, each pixel driving circuit 301 generates a driving current I matching the data voltage Vdata by the data voltage Vdata on the data line DL to drive the LEDs in the pixels 31 to emit light. Specifically, as shown in fig. 5, a schematic diagram of a pixel driving circuit is provided, which includes a first MOS transistor M1 and a second MOS transistor M2, wherein a gate g of M1 is coupled to a SCAN line SCAN, a source s of M1 is coupled to a data line DL, a drain d of M1 is coupled to a gate g of M2, a drain d of M2 is coupled to a power supply VDD (wherein an anode of the LED is coupled to VDD and a cathode of the LED is coupled to a drain of M2), a source s of M2 is coupled to ground VEE, and a capacitor Cst is coupled between a source s of M2 and the gate g. Thus, generally, when the pixel is addressed by the SCAN signal of the SCAN line SCAN, the data voltage (Vdata) is applied to the LED through M2, and the M2 generates a current (Idata) to flow through the LED to emit light. The above description is given by taking an LED common anode connection mode as an example, where M2 is an NMOS tube. When the PMOS transistor is adopted, in order to ensure that the source voltage of M2 is stable and avoid the problem of floating the source voltage, so as to affect the unstable gate-source (gs) voltage of M2, the source s of M2 is usually coupled to VDD, and the LED is coupled between VEE and the drain d of M2 (where the anode of the LED is coupled to the drain d of M2 and the cathode is coupled to VEE), so that the LED realizes a common cathode connection mode. Fig. 5 is only an example of a pixel driving circuit, and those skilled in the art can replace the pixel circuit shown in fig. 5 with other forms of pixel driving circuits.

The pixel driving circuit 301, the LEDs, the data lines DL, etc. in each pixel 31 in the display panel 30 may be fabricated on a substrate. The substrate base plate may be made of a flexible resin material. In this case, the AMOLED display panel may function as a folding display screen. Alternatively, the substrate in the AMOLED display panel may be made of a harder material, such as glass. In this case, the AMOLED display panel is a hard display screen.

In a Micro LED display panel, as shown in fig. 6, an array-type pixel 61 is generally included, and the pixel includes at least three sub-pixels. In fig. 6, three sub-pixels R (red), G (green), and B (blue) are illustrated as being included in the pixel 61, each sub-pixel including an LED, and the diodes in the same pixel 61 emit light of different colors. The display device further comprises a driving circuit 62 arranged in an array, wherein the driving circuit 62 comprises a plurality of pixel driving circuits, four pixels are distributed around the driving circuit 62, a first sub-pixel in the pixel 61 is connected with a first pixel driving circuit in the plurality of pixel driving circuits, a second sub-pixel in the pixel 61 is connected with a second pixel driving circuit in the plurality of pixel driving circuits, and a third sub-pixel in the pixel is connected with a third pixel driving circuit in the plurality of pixel driving circuits. Taking as an example a plurality of pixels (of which 4 are illustrated in fig. 6) are distributed around any of the driving circuits 62. The drive circuit 62 includes a plurality of pixel drive circuits, each coupled to one LED, to drive the coupled LED. Specifically, as shown in fig. 7, the driving circuit 62 internally includes an analog circuit portion 622 and a digital circuit portion 621. For a pixel composed of RGB ternary sub-pixels, the analog circuit portion includes 12 pixel driving circuits. Referring to fig. 8, the pixel driving circuit is generally composed of a current source 81 and a gate switch 82, wherein the current source 81 is coupled to the Micro LED (D1 in fig. 8) through the gate switch 82, and each pixel driving circuit supplies power to the Micro LED of one sub-pixel. The control signal (typically, a pulse width modulation (pulse width modulation, PWM) signal) to the gate switch 82 and the bias voltage (Vbias) of the current source are externally controlled and generated by the timing control chip to the digital circuit portion 621, the gate output by the current source 81 is realized by the control signal (which is equivalent to that the DDIC addresses the pixel through the scanning line in the AMOLED display panel), and the control of the output power of the current source 81 is realized by the bias voltage (which is equivalent to that the current (Idata) is generated by using the data voltage (Vdata) driving transistor in the AMOLED display panel), thereby realizing the light emission control of the corresponding Micro LED. As shown in fig. 8, a schematic diagram of a pixel driving circuit is provided, which includes MOS transistors M1, M2 and M3, wherein M1 is used as a gate switch and is connected in series between a current source 81 and a Micro LED, the current source 81 includes two MOS transistors M2 and M3 connected in series, wherein a gate of M1 is used for receiving a control signal, a source of M1 is coupled to a drain of M2, and a drain of M1 is coupled to a power supply VDD through D1 (wherein an anode of D1 is coupled to VDD, a cathode of D1 is coupled to a drain of M1, and the power supply VDD provides a high level VH). The gate of M2 is coupled to the gate of M3 for receiving a bias voltage, the source of M2 is coupled to the drain of M3, and the source of M3 is coupled to ground VEE (ground VEE provides a low level VL). In addition, the above current source is exemplified by the MOS transistors M2 and M3 connected in series, and in some examples, the current source may include only one MOS transistor M2, where the source of M2 is directly coupled to VEE, and of course, the current source may also include 3 or more MOS transistors connected in series. In the above description, the LED common anode connection is taken as an example, and M1, M2, and M3 in fig. 8 are NMOS transistors. When a PMOS tube is adopted, D1 needs to be connected by adopting a common cathode. Fig. 8 is only an example of a pixel driving circuit, and those skilled in the art can replace the pixel circuit shown in fig. 8 with other forms of pixel driving circuits.

Whether the aforementioned AMOLED display panel scheme or the Micro LED display panel scheme, referring to fig. 5 and 8, since parasitic capacitance (Cp in fig. 8, mainly including the cathode of the LED, the connection line of the cathode of the LED and the drain of M1, and the parasitic capacitance generated by the drain of M1) exists at the cathode of the LED (node X in fig. 5, node a in fig. 8), the pixel driving circuit first charges and discharges the node a (or node X) during each LED switching process, resulting in a certain time required for the LED switching process. The speed of the LED switch is limited, and when the speed of the LED switch is low, the afterimage phenomenon is easily observed by human eyes, so that the user experience is influenced. Taking a Micro LED display panel as an example, the specific principle is as follows, and referring to fig. 8 and 9, a current source 81 is used in a pixel driving circuit to provide a driving current for an LED, and under the control of a PWM signal, M1 controls the LED to be turned on or off, and referring to a timing curve of the PWM signal shown in fig. 9, normally an NMOS transistor is turned on when a gate is at a high level and turned off when the gate is at a low level. when the PWM signal is at a low level, M1 is disconnected, the voltage VA of the node A becomes high VH (the node A floats to be at a level equal to VDD), the current (ID 1) of the LED is 0, charges are stored on the parasitic capacitance Cp of the node A, when the PWM signal is at a high level, M1 is conducted, the node A is firstly discharged through M1, M2 and M3, the LED only has current to pass after the voltage at the point A is reduced, for example, according to the voltage curve VA of the node A, when the voltage of the node A is reduced to VA0, VDD-VA0 is equal to the opening voltage of the LED, and then the ID1 is gradually increased along with the continuous reduction of the voltage of the node A. When the PWM signal goes low, M1 is turned off, VDD again charges the parasitic capacitance Cp until ID1 becomes 0 (at which time the voltage of the parasitic capacitance is greater than VA 0), and the LED can be turned off. Thus, when the LED is on, it is necessary to discharge node a from VH to VL. At the beginning of the discharge, ID1 is completely absorbed by Cp until the voltage at node a drops below VA0, and the LED begins to have current through. When the LED normally and stably works, the voltage of the node A is VL, and when the LED is turned off, VDD charges the node A due to the parasitic capacitance influence of the node A, and the voltage of the node A slowly rises until VH. The ideal current waveform and the actual current waveform of the ID1 are compared, so that when the LED is turned off, the node A is charged to a high level HV, so that the Cp discharge delay time T1 (T1 is the time for discharging the node A from VH to VA 0) in the LED turning-on process, and the Cp charge delay time T2 (T2 is the time for charging the node A from VEE to VA 0) in the LED turning-off process are caused, and therefore, certain delay exists between the on and off of the LED, the switching response speed of the LED is influenced, and when the switching speed of the LED is slower, the afterimage phenomenon is easily observed by human eyes, and the user experience is influenced. Especially for Micro LED display panel scheme, use PWM signal control M1 to realize that the LED is opened or shut down, to the switching speed requirement higher, prior art has limited the frequency of refreshing the LED, and current technique can not satisfy the demand.

In view of the above, an embodiment of the present application provides a pixel driving circuit 1000, as shown in fig. 10, including a light emitting driving module 1002 cascaded between a cathode of a light emitting diode D1 and a ground VEE, and a charging circuit 1001. Wherein the anode of the light emitting diode D1 is coupled to the power supply VDD to provide a voltage difference applied across the light emitting diode D1. The charging circuit 1001 is coupled between the charging potential terminal VA1 and a first node a, which is a coupling point between the first switch M1 and the cathode of the light emitting diode D1. The light emitting driving module 1002 includes a gate switch Ks and a current source Is, wherein a control terminal of the gate switch Ks receives a first control signal, which may be a PWM signal in one embodiment, and a control terminal of the current source Is receives a bias voltage.

The charging circuit 1001 is configured to charge the first node a through a charging potential terminal VA1, wherein a voltage difference between the charging potential terminal VA1 and the power supply VDD is smaller than a minimum light emitting voltage of the light emitting diode D1, and a voltage of the charging potential terminal VA1 is smaller than a voltage of the power supply VDD. The pixel driving circuit 1000 may further include a capacitor Cst electrically coupled between the control terminal of the current source Is and ground VEE.

When the voltage at the node A is lower than a threshold VA0, the voltage VDD-VA0 applied to the light emitting diode D1 is greater than the minimum light emitting voltage of D1, and the light emitting diode D1 is turned on. The threshold is mainly related to the forward on voltage (i.e., the minimum light emission voltage) of the light emitting diode D1. For example, the forward turn-on voltage is about 0.7V for silicon (Si) tubes, while the forward turn-on voltage is about 0.3V for germanium (Ge) tubes.

In some embodiments, as shown in fig. 10, the gate switch Ks includes a second MOS transistor M2, the current source Is includes a third MOS transistor M3, wherein one end of a source/drain of M3 Is coupled to ground VEE, the other end of the source/drain of M3 Is coupled to the current source Is (i.e., the other end of the source/drain of M3 Is coupled to one end of the source/drain of M2), the other end of the source/drain of M2 Is coupled to a cathode of the light emitting diode D1 to receive the first control signal, a gate of M2 receives the bias voltage, and a gate of M3 receives the bias voltage.

As shown in fig. 10, the charging circuit 1001 includes a first switch M1, wherein a first terminal of the first switch M1 is coupled to the first node a, and a second terminal of the first switch M1 is coupled to the charging potential terminal VA1. In an embodiment, the above-mentioned M1 is a first MOS transistor, one end of the source/drain of the M1 is coupled to the charging potential terminal VA1, and the other end of the source/drain of the first switch M1 is coupled to the gate of the first node a, M1 to receive the on enable signal. M1 is in an on or off state under control of an on enable signal. When M1 is in an on state, the charging circuit charges the first node A through the charging potential terminal VA1, and when M1 is in an off state, the charging circuit stops charging the first node A.

The on enable signal of M1 is in logical non relationship with the enable signal of the light emitting driving module 1002. The enable signal of the light emitting driving module 1002 is an intersection of the first control signal and the bias voltage, that is, when the first control signal controls the gate switch to be turned on and the bias voltage controls the current source to output the driving current, the light emitting driving module drives the light emitting diode, and when the first control signal controls the gate switch to be turned off or the bias voltage controls the current source to stop outputting the driving current, the light emitting driving module stops driving the light emitting diode. When the bias voltage controls the current source to continuously output the driving current in the on period of the gating switch controlled by the first control signal, the enabling signal of the light-emitting driving module is the first control signal. The enable signal of the light emitting driving module may be a first control signal, and the control terminal of the first switch is coupled to the control terminal of the gate switch through the not gate circuit.

In the operating state, the M2 is turned on or off under the control of the received first control signal, and the M3 is kept on under the control of the received bias voltage Vbias. When the first control signal controls M2 to turn off, the voltage at the node a (i.e., the cathode of the light emitting diode D1) becomes high, the current in the light emitting diode D1 becomes 0, and the parasitic capacitance Cp at the node a (the parasitic capacitance Cp is mainly the capacitance generated by the drain of M1, the cathode of D1, and the line between the cathode of D1 and the drain of M1, which is not shown in fig. 10) accumulates charges. When the first control signal controls M2 to be turned on, the parasitic capacitance Cp is discharged through M2 and M3. When the voltage at node a is below a certain threshold VA0 (depending on the characteristics of the light emitting diode D1), the light emitting diode D1 is turned on. In the embodiment of the application, after the charging circuit 1001 is turned off at M2, the parasitic capacitor of the node a can be charged through the charging potential terminal VA1 until the voltage of the node a is equal to the voltage of the charging potential terminal VA1, and the voltage difference between the voltage of the charging potential terminal VA1 and the voltage of the power supply VDD is smaller than the minimum light emitting voltage (VDD-VA 0) of the light emitting diode D1, and the voltage of the charging potential terminal VA1 is smaller than the voltage of the power supply VDD, so that the light emitting diode D1 will not emit light. Since the voltage of the charging potential terminal VA1 is greater than VA0, the leakage current of M2 can be also ensured to be low. When M2 is turned on, the charging circuit 1001 stops charging the first node a, and the charge in the parasitic capacitance of the first node a is discharged through M2 and M3 until the voltage of the first node a is the same as the ground VEE. Because in this process, the first node a starts discharging from a voltage lower than the power supply VDD (the voltage of the charging potential terminal VA 1), and when the voltage difference between the charging potential terminal VA1 and the power supply VDD is slightly smaller than the minimum light-emitting voltage of the light-emitting diode D1, only the first node a starts slightly discharging from the voltage of the charging potential terminal VA1, i.e., the voltage difference between the voltage of the first node a and the power supply VDD can satisfy the minimum light-emitting voltage of the light-emitting diode D1, the light-emitting diode D1 starts emitting, so that the variation range of the cathode voltage of the light-emitting diode is narrowed when the pixel driving circuit drives the light-emitting diode to emit light, and the switching speed of the LED is improved. When the change range of the cathode voltage of the light-emitting diode is reduced, the establishment time of the current signal of the light-emitting diode is shortened, and the refreshing frequency of the light-emitting diode is increased, so that the time from extinction to lighting of the light-emitting diode is shortened, the afterimage phenomenon when the light-emitting diode is observed by human eyes can be improved, the display precision of the light-emitting diode is improved, and the user experience is improved. In addition, when the M2 is changed from the on state to the off state, the charging circuit directly charges the node a through the charging potential terminal VA1, and directly sets the voltage of the node a to VA1, so that the turn-off time of the current signal of the light emitting diode is also reduced.

The working principle of the pixel driving circuit is specifically described with reference to fig. 10 and 11, in which (a) in fig. 11 shows a waveform of a PWM signal in a conventional pixel driving circuit, a voltage waveform of a node a, a waveform of a current ID1 in a light emitting diode D1, and (b) in fig. 11 shows a waveform of a PWM signal in an optimized pixel driving circuit, a voltage waveform of a node a, and a waveform of a current ID1 in a light emitting diode D1 in one charge-discharge period. In the embodiment of the application, the gating signal is taken as a PWM signal, and M1, M2 and M3 are all NMOS transistors for illustration.

When the pixel driving circuit works normally, M3 is conducted. At the time 0to t1, the PWM signal is at a low level, and at this time M2 is in an off state, so that the Voltage (VH) at the node a is higher than the threshold voltage VA0, the current ID1 in the light emitting diode D1 is 0, and the light emitting diode D1 is in an off state. At time t1, the PWM signal changes from low to high, and M2 switches from off to on. Since M2 and M3 are both on, the voltage at node a will drop rapidly to 0 (VL) in an ideal state, and the current ID1 in led D1 will increase rapidly to a larger value, as shown by the "ideal current waveform" curve in fig. 11 (a). In actual operation, as shown in the "actual current waveform" curve in fig. 11 (a), the parasitic capacitance Cp of the conventional circuit in the prior art is due to the parasitic capacitance Cp of the node a, when M2 is in the off state, the voltage of the node a is charged to VH by VDD, and when M2 is switched from the off state to the on state, the parasitic capacitance Cp needs to be discharged through M2 and M3 at times t1 to t2 first until the voltage of the node a is lower than the threshold voltage VA0. At time t2, the current ID1 in the light emitting diode D1 starts to increase up to a maximum value, and then the maximum value is held until time t 3. At time t3, the PWM signal changes from high to low, the current ID1 in the light emitting diode D1 starts to decrease, the Cp of the node a starts to charge, and the current ID1 changes to 0 until the voltage of the node a is higher than the threshold voltage VA0 (i.e., time t 4). Accordingly, as shown in fig. 11 (a), since the discharging is slow, the node a in the conventional circuit in the prior art needs time T1 (T2-T1) to complete the signal establishment after M2 is turned on, and needs time T2 (T4-T3) to complete the signal turn-off after M2 is turned off. As can be seen from fig. 11 (a), at the time t1 to t2, the parasitic capacitance Cp is in the discharge process, resulting in the light emitting diode D1 going from off to on for a long time. At the time t3 to t4, the parasitic capacitance Cp is in the charging process, so that the light emitting diode D1 is turned on to off for a longer time, and when the parasitic capacitance Cp is larger, the time t1 to t2 and the time t3 to t4 are longer, the human eyes can observe the ghost phenomenon more easily, and the user experience is affected.

In the pixel driving circuit provided by the embodiment of the application, the charging circuit 1001 coupled to the node a can charge the voltage of the node a to VA1 when M2 is turned off (e.g. 0-t 1), so that, because the voltage difference between VA1 and VDD is smaller than the minimum light-emitting voltage of the light-emitting diode D1 (i.e. VA1 is greater than VA 0), as shown in (b) in fig. 11, the current ID1 is 0 at time 0 to t1, D1 does not emit light, and M2 is turned on at time t1 to t2, and the parasitic capacitor Cp directly starts discharging from VA1, compared with the conventional pixel driving circuit, as shown in (a) in fig. 11, the voltage of the Cp from VDD to VA0 at time t2 needs to be discharged from VDD, and D1 needs to have current to pass through in the optimized scheme, as shown in (b) in fig. 11, the voltage of the Cp from VA1 to VA0 at time t2 needs to be discharged from VA1, and D1 needs to have current to pass, thus the voltage change of the node a is reduced, i.e. the range of Δva change from VH to VL (a) in fig. 11) to VL (a) is turned on, and the voltage of the v 1 to v 1 is shown in (b) in fig. 11, and the waveform of the light-emitting diode D1 is improved, thereby improving the actual waveform of the light-emitting diode is more to achieve the purpose of improving the waveform, and the display accuracy, and improving the display accuracy. And in the optimized scheme, as in the case of time t3 to time t4 in (b) in fig. 11, the voltage of Cp is directly set to VA1, and as VA1 is larger than VA0, the current ID1 of D1 can be turned off quickly.

The current source also comprises a fourth MOS tube, wherein one end of the source drain electrode of the fourth MOS tube is coupled with one end of the source drain electrode of the third MOS tube, the other end of the source drain electrode of the fourth MOS tube is coupled with the ground, and the grid electrode of the fourth MOS tube receives the bias voltage. As shown in fig. 12, a pixel driving circuit is provided, wherein M4 is further coupled between the source of M3 and ground VEE, and when M4 is an NMOS transistor, the source of M4 is coupled to ground VEE, the drain of M4 is coupled to the source of M2, and the gate of M4 is coupled to the gate of M2. Wherein M2 and M4 constitute the current source, and similar current source can also include more MOS pipes of establishing ties.

As shown in fig. 13, a pixel driving circuit is provided, wherein the control terminal of M1 is coupled to the control terminal of M2 through a nor circuit 1003. When M2 is turned on, the charging potential end stops charging the first node a, when M2 is turned off, the charging potential end VA1 charges the first node a, so when M2 and M1 adopt MOS transistors of the same type, the on enable signal of the control end of M1 is opposite to the first control signal of the control end of M2, and therefore the control end of M2 can be coupled to the control end of M1 through the not gate 1003, so that the first control signal is input to the control end of M2, and is input to the control end of M1 after passing through the not gate 1002.

In the above description, taking the connection mode of the common anode of the light emitting diode in the Micro LED display panel as an example, in fig. 14, a connection mode of the common cathode of the light emitting diode Is also provided, as shown in fig. 14, the pixel driving circuit 2000 includes a light emitting driving module 2002 cascaded between the anode of the light emitting diode D1 and the power supply VDD, the light emitting driving module 2002 includes a gate switch Ks and a current source Is, a control end of the gate switch Ks receives a first control signal, in an embodiment, the first control signal may be a PWM signal, a control end of the current source Is receives a bias voltage Vbias, a cathode of the light emitting diode D1 Is coupled with a ground VEE, and a charging circuit 2001 coupled between a charging potential end VA1 and a first node a, where the first node a Is a coupling point between the light emitting driving module 2002 and the anode of the light emitting diode D1.

The charging circuit 2001 is configured to charge the first node a through a charging potential terminal VA1, wherein a voltage difference between the charging potential terminal VA1 and the ground VEE is smaller than a minimum light emitting voltage of the light emitting diode, and a voltage of the charging potential terminal VA1 is smaller than a voltage of the power supply VDD. The pixel driving circuit 2000 may further include a capacitor Cst electrically coupled between the control terminal of the current source Is and the power supply VDD.

In some embodiments, as shown in fig. 14, the gate switch Ks includes a first MOS transistor M2, the current source Is includes a third MOS transistor M3, wherein one end of a source/drain of M3 Is coupled to the power supply VDD, the other end of the source/drain of M3 Is coupled to the current source Is (i.e., the other end of the source/drain of M3 Is coupled to one end of the source/drain of M2), the other end of the source/drain of M2 Is coupled to an anode of the light emitting diode D1 to receive the first control signal, a gate of M2 receives the bias voltage, and a gate of M3 receives the bias voltage.

As shown in fig. 14, the charging circuit 2001 includes a first switch M1, wherein a first terminal of M1 is coupled to the first node a, and a second terminal of M1 is coupled to the charging potential terminal VA1. In an embodiment, the above-mentioned M1 is a first MOS transistor, one end of the source/drain of the M1 is coupled to the charging potential terminal VA1, and the other end of the source/drain of the M1 is coupled to the gate of the first node a, and the gate of the M1 receives the on enable signal. M1 is in an on or off state under control of an on enable signal. When M1 is in an on state, the charging circuit charges the first node A through the charging potential terminal VA1, and when M1 is in an off state, the charging circuit stops charging the first node A.

The on enable signal of M1 is logically non-related to the enable signal of the light-emitting driving module 2002. The enable signal of the light emitting driving module 2002 is an intersection of the first control signal and the bias voltage, that is, when the first control signal controls the gate switch to be turned on and the bias voltage controls the current source to output the driving current, the light emitting driving module drives the light emitting diode, and when the first control signal controls the gate switch to be turned off or the bias voltage controls the current source to stop outputting the driving current, the light emitting driving module stops driving the light emitting diode. When the bias voltage controls the current source to continuously output the driving current in the on period of the gating switch controlled by the first control signal, the enabling signal of the light-emitting driving module is the first control signal. The enable signal of the light emitting driving module may be a first control signal, and the control terminal of the first switch is coupled to the control terminal of the gate switch through the not gate circuit.

In the operating state, the M2 is turned on or off under the control of the received first control signal, and the M3 is kept on under the control of the received bias voltage Vbias. When the first control signal controls M2 to turn off, the voltage of the node a (i.e., the anode of the light emitting diode D1) becomes low, the current in the light emitting diode D1 becomes 0, the light emitting diode is turned off, the charging potential terminal VA1 will couple the parasitic capacitance Cp (the parasitic capacitance Cp is mainly the drain of M1, the anode of D1 and the capacitance generated by the connection between the anode of D1 and the drain of M1, not shown in fig. 15) on the node a until the voltage of the first node is equal to the voltage of the charging potential terminal VA1, and the voltage difference between the voltage of the charging potential terminal VA1 and the ground VEE is smaller than the minimum light emitting voltage of the light emitting diode, and the voltage of the charging potential terminal is smaller than the voltage of the power supply, so that the light emitting diode will not emit light. When M2 is turned on, the charging circuit 2001 stops charging the first node a, and the power supply VDD charges the parasitic capacitance of the first node a through M2 and M3 until the voltage of the first node a is the same as the power supply. In this process, the first node a starts to charge from a voltage lower than the power supply (the voltage of the charging potential end VA 1), and when the voltage difference between the charging potential end VA1 and the power supply VDD is slightly smaller than the minimum light-emitting voltage of the LED, as long as the first node a starts to slightly increase from the voltage of the charging potential end VA1, i.e. the voltage difference between the voltage of the first node a and the ground VEE can meet the minimum light-emitting voltage of the LED, the LED starts to emit light, so that the variation range of the cathode voltage of the LED is narrowed when the pixel driving circuit drives the LED to emit light, and the switching speed of the LED is increased. When the change range of the anode voltage of the light-emitting diode is reduced, the establishment time of the current signal of the light-emitting diode is shortened, and the refreshing frequency of the light-emitting diode is increased, so that the time from extinction to lighting of the light-emitting diode is shortened, the afterimage phenomenon when the light-emitting diode is observed by human eyes can be improved, the display precision of the light-emitting diode is improved, and the user experience is improved. In addition, when the M2 is changed from the on state to the off state, the charging circuit directly charges the node a through the charging potential terminal VA1, and directly sets the voltage of the node a to VA1, so that the turn-off time of the current signal of the light emitting diode is also reduced.

The operation principle of the pixel driving circuit is described in detail with reference to fig. 14 and 15, in which (a) in fig. 15 shows a waveform of a PWM signal in the conventional pixel driving circuit, a voltage waveform of a node a, a waveform of a current ID1 in the light emitting diode D1, and (b) in fig. 15 shows a waveform of a PWM signal in the optimized pixel driving circuit, a voltage waveform of a node a, and a waveform of a current ID1 in the light emitting diode D1 in one charge-discharge period. In the embodiment of the application, the gating signal is taken as a PWM signal, and M1, M2 and M3 are all PMOS tubes for illustration.

When the pixel driving circuit works normally, M3 is conducted. At time 0 to t ₁, the PWM signal is at high level, and at this time M2 is in the off state, so that the Voltage (VL) at the node a is lower than the threshold voltage VA0, the current ID1 in the light-emitting diode D1 is 0, and the light-emitting diode D1 is in the off state. At time t1, the PWM signal changes from high level to low level, and the first switch M1 is switched from off state to on state. Since M2 and M3 are both on, the voltage at node a will rise rapidly to VH in the ideal state, and the current ID1 in led D1 will rise rapidly to a larger value, as shown by the "ideal current waveform" curve in fig. 15 (a). In actual operation, as shown in the "actual current waveform" curve in fig. 15 (a), the parasitic capacitance Cp of the conventional circuit in the prior art is due to the parasitic capacitance Cp existing at the node a, when the voltage at the node a is 0 (VL) and the voltage at the node a is switched from the off state to the on state, the parasitic capacitance Cp needs to be charged through M2 and M3 at time t1 to t2 until the voltage at the node a is higher than the threshold voltage VA0. At time t2, the current ID1 in the light emitting diode D1 starts to increase up to a maximum value, and then the maximum value is held until time t 3. At time t3, the PWM signal changes from low level to high level, the current ID1 in the light emitting diode D1 starts to decrease, the Cp of the node a starts to discharge, and the current ID1 changes to 0 until the voltage of the node a is lower than the threshold voltage VA0 (i.e., time t 4). Accordingly, as shown in fig. 15 (a), since the charge and discharge are slow, the node a in the conventional circuit in the prior art needs time T1 (T2-T1) to complete the signal establishment after the first switch M1 is turned on, and needs time T2 (T4-T3) to complete the signal turn-off after the switch M2 is turned off. As can be seen from fig. 15 (a), at the time t1 to t2, the parasitic capacitance Cp is in the charging process, resulting in the light emitting diode D1 going from off to on for a long time. At the time t3 to t4, the parasitic capacitance Cp is in a discharging process, so that the light emitting diode D1 is turned on to off for a longer time, and when the parasitic capacitance Cp is larger, the time t1 to t2 and the time t3 to t4 are longer, the human eyes can observe the ghost phenomenon more easily, and the user experience is affected.

In the pixel driving circuit provided by the embodiment of the application, when M2 is turned off, the charging circuit 2001 coupled to the node a can charge the voltage of the node a to VA1, so that, because the voltage difference between VA1 and VEE is smaller than the minimum light emitting voltage of the light emitting diode D1 (VA 1 is smaller than VA 0), that is, as shown in (b) of fig. 15, the current ID1 is 0 from 0 to t1, D1 does not emit light, and at the time of t1 to t2, M2 is turned on, parasitic capacitor Cp directly starts to charge from VA1, compared with the conventional pixel driving circuit, as shown in (a) of fig. 15, the voltage of Cp needs to charge from VL to VA0 at the time of t1 to t2, and in the optimized scheme, as shown in (b) of fig. 15, the voltage of Cp only needs to charge from VA1 to VA0 at the time of t2, and D1 needs to have current to pass, so that the voltage change of the node a is reduced, that is, as shown in (a) of fig. 15, the voltage change range of Δva is from VL to VH (a) to 1 (a) of fig. 1 to 1 (b) of fig. 15), the current is improved, and the actual waveform of the light emitting diode is improved, and the waveform of the light emitting diode is improved, as shown in the time of fig. 15, and the waveform of the light emitting diode is more has been improved. And in the optimized scheme, as in the case of time t3 to t4 in (b) in fig. 15, the voltage of Cp is directly set to VA1, and as VA1 is smaller than VA0, the current ID1 of D1 can be turned off quickly.

The current source also comprises a fourth MOS tube, wherein one end of the source drain electrode of the fourth MOS tube is coupled with one end of the source drain electrode of the third MOS tube, the other end of the source drain electrode of the fourth MOS tube is coupled with a power supply, and the grid electrode of the fourth MOS tube receives bias voltage. As shown in fig. 16, there is provided a pixel driving circuit, wherein M4 is further coupled between the source of M3 and the power supply VDD, and when M4 is a PMOS transistor, the source of M4 is coupled to the power supply VDD, the drain of M4 is coupled to the source of M2, and the gate of M4 is coupled to the gate of M2. Wherein M2 and M4 constitute the current source, and similar current source can also include more MOS pipes of establishing ties.

As shown in fig. 17, a pixel driving circuit is provided in which a control terminal of M1 is coupled to a control terminal of M2 through a not gate 2003. When M2 is turned on, the charging potential end stops charging the first node a, when M2 is turned off, the charging potential end VA1 charges the first node a, so when M1 and M2 adopt MOS transistors of the same type, the first control signal of the control end of M2 is opposite to the conduction enable signal of the control end of M1, and therefore the control end of M2 can be coupled to the control end of M1 through the not gate 2003, so that the first control signal is input to the control end of M2, and is input to the control end of M1 after passing through the not gate 2003.

In one embodiment, a pixel driving circuit is described as an example of a pixel driving circuit in an AMOLED display panel scheme. In a connection mode of a light emitting diode common anode, as shown in fig. 18, a pixel driving circuit 3000 includes a first MOS transistor M1, a second MOS transistor M2, and a charging circuit 3001, wherein a control end of M1 is coupled to a SCAN line SCAN, a first end of M1 is coupled to a data line DL, a second end of M1 is coupled to a control end of M2, a first end of M2 is coupled to a power supply VDD (wherein an anode of the LED is coupled to VDD, a cathode of the LED is coupled to a first end of M2), a second end of M2 is coupled to a ground VEE, and a capacitor Cst is coupled between the second end of M2 and a gate. Thus, typically, when a pixel is addressed by the SCAN line SCAN, a data voltage (Vdata) on the data line DL is applied to the LED through M2, and a current (Idata) is generated by M2 to flow through the LED to emit light. The charge/discharge circuit 3001 is coupled between the cathode (i.e., node X) of the light emitting device D1 and the charge potential terminal VA1. The charging circuit 1001 is configured to charge the node X through the charging potential terminal VA1, wherein a voltage difference between the charging potential terminal VA1 and the power supply VDD is smaller than a minimum light emitting voltage of the light emitting diode D1, and a voltage of the charging potential terminal VA1 is smaller than a voltage of the power supply VDD. The charging circuit 3001 includes a third switch M3, a first terminal of the third switch M3 is coupled to a second terminal of the light emitting diode D1, and a second terminal of the third switch M3 is coupled to the charging potential terminal VA1, wherein the second voltage terminal V2 inputs the predetermined voltage value VA1. Wherein M1, M2 and M3 may be NMOS, wherein the control terminal of M1 is the gate, the first terminal of M1 is the drain, and the second terminal is the source. The control end of M2 is the grid, and the first end of M2 is the drain electrode, and the second end is the source electrode. The control end of M3 is a grid electrode, the first end of M3 is a source electrode, and the second end of M3 is a drain electrode. The analysis of the working principle of the pixel driving circuit provided in fig. 18 may be performed with reference to (b) in fig. 11, and will not be described herein.

In the above description, taking the common anode connection mode of the light emitting diode D1 as an example, when the light emitting diode D1 implements the common cathode connection mode, as shown in fig. 19, the M1, M2 and M3 adopt PMOS, in order to ensure that the source voltage of the M2 is stable and avoid the floating problem of the source voltage, so as to affect the unstable voltage of the gate source (gs) of the M2, the source s of the M2 is generally coupled to VDD, the light emitting diode D1 is coupled between VEE and the drain D of the M2 (where the anode of the light emitting diode D1 is coupled to the drain D of the M2 and the cathode is coupled to VEE), so that the light emitting diode D1 implements the common cathode connection mode, as shown in fig. 19. The analysis of the working principle of the pixel driving circuit provided in fig. 19 may be performed with reference to (b) in fig. 15, and will not be described herein.

The above, whether the pixel driving circuit under the AMOLED display panel scheme and the Micro LED display panel scheme are just some examples, and those skilled in the art may implement the pixel driving circuit in other ways.

It should be noted that the above description is only a specific embodiment of the present application, but the scope of the present application is not limited thereto, and any changes or substitutions within the technical scope of the present application should be covered by the scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims

1. The miniature light-emitting diode display panel is characterized by comprising a plurality of driving circuits distributed in an array, wherein each driving circuit comprises a plurality of pixel driving circuits and is used for driving a plurality of pixels, each pixel comprises at least three sub-pixels, each sub-pixel comprises a light-emitting diode, a first sub-pixel in the pixels is coupled with a first pixel driving circuit in the plurality of pixel driving circuits, a second sub-pixel in the pixels is coupled with a second pixel driving circuit in the plurality of pixel driving circuits, and a third sub-pixel in the pixels is coupled with a third pixel driving circuit in the plurality of pixel driving circuits;

The pixel driving circuit comprises a light-emitting driving module, a charging circuit and a driving circuit, wherein the light-emitting driving module is cascaded between a cathode of a light-emitting diode and the ground, the light-emitting driving module comprises a gating switch and a current source, a control end of the gating switch receives a first control signal, a control end of the current source receives a bias voltage, an anode of the light-emitting diode is coupled with a power supply, and the charging circuit is coupled between a charging potential end and a first node, and the first node is a coupling point of the light-emitting driving module and the cathode of the light-emitting diode;

The charging circuit is configured to charge the first node through the charging potential end when the light-emitting driving module stops driving the light-emitting diode to emit light, the voltage difference between the charging potential end and the power supply is smaller than the minimum light-emitting voltage of the light-emitting diode, and the voltage of the charging potential end is smaller than the voltage of the power supply;

And when the first node is stopped from being charged, the voltage of the first node is charged to the voltage of the charging potential end, and the voltage difference between the charging potential end and the power supply is slightly smaller than the minimum light-emitting voltage of the light-emitting diode.

2. The micro light emitting diode display panel of claim 1, wherein the charging circuit comprises a first switch, wherein a first terminal of the first switch is coupled to the first node and a second terminal of the first switch is coupled to a charging potential terminal.

3. The led display panel of claim 2, wherein the on enable signal of the first switch is logically non-related to the enable signal of the light-emitting driver module.

4. The micro light emitting diode display panel according to claim 2 or 3, wherein the first switch comprises a first MOS transistor, one end of a source/drain of the first MOS transistor is coupled to the charging potential end, the other end of the source/drain of the first MOS transistor is coupled to the first node, and a gate of the first MOS transistor receives a turn-on enable signal.

5. The micro light emitting diode display panel according to claim 2, wherein the gate switch comprises a second MOS transistor, one end of a source/drain of the second MOS transistor is coupled to the current source, the other end of the source/drain of the second MOS transistor is coupled to the cathode of the light emitting diode and is coupled to the first node, and a gate of the gate switch receives the first control signal.

6. The micro light emitting diode display panel of claim 2, wherein the current source comprises a third MOS transistor, wherein one end of a source-drain electrode of the third MOS transistor is coupled to ground, the other end of the source-drain electrode of the third MOS transistor is coupled to the gate switch, and a gate electrode of the third MOS transistor receives the bias voltage.

7. The micro light emitting diode display panel of claim 6, wherein the current source further comprises a fourth MOS transistor, wherein one end of a source-drain electrode of the fourth MOS transistor is coupled to one end of a source-drain electrode of the third MOS transistor, the other end of the source-drain electrode of the fourth MOS transistor is coupled to ground, and a gate electrode of the fourth MOS transistor receives the bias voltage.

8. The micro light emitting diode display panel of claim 1, wherein the pixel driving circuit further comprises a capacitor having one end coupled to a control terminal of the current source and the other end coupled to ground.

9. The micro light emitting diode display panel of claim 1, wherein the first control signal is a pulse width modulated PWM signal.

10. A pixel driving circuit, comprising:

the light-emitting driving module is cascaded between the cathode of the light-emitting diode and the ground and comprises a gating switch and a current source, wherein the control end of the gating switch receives a first control signal, the control end of the current source receives a bias voltage, the anode of the light-emitting diode is coupled with a power supply, and

The charging circuit is coupled between a charging potential end and a first node, and the first node is a coupling point of the light-emitting driving module and the cathode of the light-emitting diode;

11. The pixel driving circuit of claim 10, wherein the charging circuit comprises a first switch, wherein a first terminal of the first switch is coupled to a cathode of the light emitting diode and a second terminal of the first switch is coupled to a charging potential terminal.

12. The pixel driving circuit according to claim 11, wherein the on enable signal of the first switch is in logical-to-logical-not relationship with the enable signal of the light-emitting driving module.

13. The pixel driving circuit according to claim 11 or 12, wherein the first switch comprises a first MOS transistor, one end of a source-drain electrode of the first MOS transistor is coupled to the charging potential end, the other end of the source-drain electrode of the first MOS transistor is coupled to the first node, and a gate electrode of the first MOS transistor receives a turn-on enable signal.

14. A terminal device comprising a rear housing, a center frame, and a micro light emitting diode display panel according to any one of claims 1 to 9, the rear housing and the micro light emitting diode display panel being disposed opposite each other and connected by the center frame.