WO2022040879A1

WO2022040879A1 - Pixel driving circuit and micro light emitting diode display panel

Info

Publication number: WO2022040879A1
Application number: PCT/CN2020/110889
Authority: WO
Inventors: 赵公元; 方黎明
Original assignee: 华为技术有限公司
Priority date: 2020-08-24
Filing date: 2020-08-24
Publication date: 2022-03-03
Also published as: CN115917633A

Abstract

The present application relates to the technical field of display, and provides a pixel driving circuit and a micro light emitting diode (LED) display panel. A charging circuit (1001) charges a coupling point of an LED (D1) and the pixel driving circuit (1000), thereby reducing a change range of a cathode voltage of the LED (D1) when the pixel driving circuit (1000) drives the LED (D1) to emit light, and improving the switching speed of the LED. The micro LED display panel comprises a plurality of driving circuits, and each driving circuit comprises a plurality of pixel driving circuits (1000). Each pixel driving circuit (1000) comprises: a light-emitting driving module (1002) cascaded between a cathode of the LED (D1) and the ground, the light-emitting driving module (1002) comprising a gating switch (Ks) and a current source (Is), a control terminal of the gating switch (Ks) receiving a first control signal (PWM), a control terminal of the current source (IS) receiving a bias voltage (Vbias), and an anode of the LED (D1) being coupled to a power supply; and the charging circuit (1001) coupled between a charging potential terminal (VA1) and a first node (A), the first node (A) being a coupling point of the light-emitting driving module (1002) and the cathode of the LED (D1).

Description

A pixel drive circuit and a miniature light-emitting diode display panel

technical field

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

Background technique

LED (light emitting diode, light emitting diode) display panel adopts LED to realize pixel display, and its display performance has higher contrast and brightness than traditional LCD (liquid crystal display, liquid crystal display).

In an LED display panel, an array of LED pixels is driven by a pixel driver circuit. The pixel driving circuit is gated according to the row gate signal and the column drive signal, thereby driving the LED to emit light. The anode of the LED is coupled to the power supply, and the cathode is coupled to the pixel drive circuit. Due to the parasitic capacitance and parasitic resistance of the cathode of the LED, when the LED is frequently switched between the on state and the off state, the pixel drive circuit needs to charge or discharge the cathode of the LED at a high speed, and the charging and discharging time affects the switching time of the LED switch, thus Limits the switching speed of the LEDs. When the LED switching speed is slow, the human eye can easily observe the afterimage phenomenon, which affects the user experience.

SUMMARY OF THE INVENTION

The present application provides a pixel driving circuit and a micro light-emitting diode Micro LED display panel. The charging circuit charges the coupling point between the light-emitting diode and the pixel driving circuit, thereby reducing the variation range of the cathode voltage of the light-emitting diode when the pixel driving circuit drives the light-emitting diode to emit light. , to improve the switching speed of the LED.

In a first aspect, a miniature light emitting diode display panel is provided. The miniature light-emitting diode display panel includes a plurality of driving circuits distributed in an array, and the driving circuits include a plurality of pixel driving circuits for driving multiple pixels; wherein each of the pixels includes at least three sub-pixels, and each of the sub-pixels includes at least three sub-pixels. The pixel includes a light emitting diode; the first sub-pixel in the pixel is coupled to the first pixel driving circuit of the plurality of pixel driving circuits, and the second sub-pixel in the pixel is coupled to the plurality of the pixel driving circuits A second pixel driving circuit in the pixel, and a third sub-pixel in the pixel is coupled to a plurality of third pixel driving circuits in the pixel driving circuit. 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 to drive one light emitting diode. The pixel drive circuit includes: a light-emitting drive module cascaded between the cathode of the light-emitting diode and the ground, the light-emitting drive module includes a gate switch and a current source, the control end of the gate switch receives a first control signal, and the control of the current source The terminal receives the bias voltage, and the anode of the light-emitting diode is coupled with the power supply; and the charging circuit is coupled between the charging potential terminal and the first node, and the first node is the coupling point between the light-emitting driving module and the cathode of the light-emitting diode.

Wherein, 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 extinguished, and the charging circuit charges the cathode (the first node) of the light-emitting diode through the charging potential terminal until the voltage of the first node is equal to the voltage of the charging potential terminal, and the charging potential terminal is equal to the voltage of the charging potential terminal. The voltage difference of the power supply is less than the minimum light-emitting voltage of the light-emitting device, and the voltage of the charging potential terminal is less than the voltage of the power supply, so the light-emitting diode does not 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 gate switch and the current source until the voltage of the first node is the same as the ground. In this process, the first node starts to discharge from the voltage lower than the power supply (the voltage of the charging potential terminal), and when the voltage difference between the charging potential terminal and the power supply is slightly smaller than the minimum light-emitting voltage of the light-emitting diode, as long as the first node is discharged from the charging potential The voltage of the terminal begins to discharge slightly, then 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, and the light-emitting diode starts to emit light, which reduces the change of the cathode voltage of the light-emitting diode when the pixel driving circuit drives the light-emitting diode to emit light. range, increasing the switching speed of the LEDs. When the variation range of the cathode voltage of the light-emitting diode becomes smaller, the establishment time of the current signal of the light-emitting diode becomes shorter, and the refresh frequency of the light-emitting diode becomes higher, so that the time for the light-emitting diode from extinguishing to lighting is shortened. The afterimage phenomenon when the human eye observes the light-emitting diode can be improved, the display accuracy of the light-emitting diode can be improved, and the user experience can be 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 terminal, and directly sets the voltage of the first node to the voltage of the charging potential terminal, which also reduces the Turn-off time of the current signal of the light-emitting diode.

In a possible implementation manner, 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 a possible implementation manner, the turn-on enable signal of the first switch and the enable signal of the light-emitting driving module are in a logical negation relationship. Wherein, the enable signal of the light-emitting driving module is the 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; when the first control signal controls the gate switch to turn 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. Wherein, when the bias voltage controls the current source to continuously output the driving current during the conduction period of the gate 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 the first control signal, and the control end of the first switch is coupled to the control end of the gating switch through the NOT circuit. Among them, when the gate switch is turned on, the charging potential terminal stops charging the first node, and when the gate switch is turned off, the charging potential terminal charges the first node, so the first switch and the gate switch use the same type of MOS When the first switch is turned on, the phase of the first control signal of the control terminal of the gate switch is opposite to that of the turn-on enable signal of the first switch. The first control signal is input to the control terminal of the strobe switch, and is input to the control terminal of the first switch after passing through the NOT gate circuit.

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

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

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

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

In a possible implementation manner, the pixel driving circuit further includes a capacitor, one end of the capacitor is coupled to the control end of the current source, and the other end is coupled to ground.

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

In a second aspect, a miniature light emitting diode display panel is provided. The miniature light emitting diode display panel includes a plurality of driving circuits distributed in an array, the driving circuits include a plurality of pixel driving circuits for driving a plurality of pixels; wherein each of the pixels includes at least three sub-pixels, each of the sub-pixels The pixel includes a light emitting diode; the first sub-pixel in the pixel is coupled to the first pixel driving circuit of the plurality of pixel driving circuits, and the second sub-pixel in the pixel is coupled to the plurality of the pixel driving circuits A second pixel driving circuit in the pixel, and a third sub-pixel in the pixel is coupled to a plurality of third pixel driving circuits in the pixel driving circuit. The pixel drive circuit includes: a light-emitting drive module cascaded between the anode of the light-emitting diode and the power supply, the light-emitting drive module includes a gate switch and a current source, the control end of the gate switch receives the first control signal, and the control end of the current source receiving bias voltage, the cathode of the light emitting diode is coupled to ground; and a charging circuit is coupled between the charging potential terminal and a first node, where the first node is a coupling point between 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 extinguished, and the charging potential terminal will charge 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 terminal, and the voltage of the charging potential terminal is equal to the ground The voltage difference is less than the minimum light-emitting voltage of the light-emitting diode, and the voltage of the charging potential terminal is less than the voltage of the power supply, so the light-emitting diode will not 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 the parasitic capacitance of the first node through the gate 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 the voltage lower than the power supply (the voltage of the charging potential terminal), and when the voltage difference between the charging potential terminal and the ground is slightly smaller than the minimum light-emitting voltage of the light-emitting diode, as long as the first node is charged from the The voltage of the potential terminal begins to increase slightly, 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, and the light-emitting diode starts to emit light, which reduces the cathode voltage of the light-emitting diode when the pixel driving circuit drives the light-emitting diode to emit light. Variation range to increase the switching speed of the LEDs. When the variation range of the cathode voltage of the light-emitting diode becomes smaller, the establishment time of the current signal of the light-emitting diode becomes shorter, and the refresh frequency of the light-emitting diode becomes higher, so that the time for the light-emitting diode from extinguishing to lighting is shortened. The afterimage phenomenon when the human eye observes the light-emitting diode can be improved, the display accuracy of the light-emitting diode can be improved, and the user experience can be 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 terminal, and directly sets the voltage of the first node to the voltage of the charging potential terminal, which also reduces the Turn-off time of the current signal of the light-emitting diode.

In a possible implementation manner, the turn-on enable signal of the first switch and the enable signal of the light-emitting driving module are in a logical negation relationship. Wherein, the enable signal of the light-emitting driving module is the 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; when the first control signal controls the gate switch to turn 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. Wherein, when the bias voltage controls the current source to continuously output the driving current during the conduction period of the gate 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 the first control signal, and the control end of the first switch is coupled to the control end of the gating switch through the NOT gate circuit. Among them, when the gate switch is turned on, the charging potential terminal stops charging the first node, and when the gate switch is turned off, the charging potential terminal charges the first node, so the first switch and the gate switch use the same type of MOS When the first switch is turned on, the phase of the first control signal of the control terminal of the gate switch is opposite to that of the turn-on enable signal of the first switch. The first control signal is input to the control terminal of the strobe switch, and is input to the control terminal of the first switch after passing through the NOT gate circuit.

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

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

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

In a possible implementation manner, the pixel driving circuit further includes a capacitor, one end of the capacitor is coupled to the control end of the current source, and the other end of the capacitor is coupled to the power supply.

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

In a third aspect, an AMOLED display panel is provided. The display panel includes pixels distributed in an array, the pixels include a pixel driving circuit and a light emitting diode, the pixel driving circuit is coupled between the anode of the light emitting diode and the power supply, and the cathode of the light emitting diode is coupled to the ground, wherein the pixel driving circuit is used for driving the light emitting diode; The pixel also includes: a charging circuit, which is coupled between the charging potential terminal and the first node, where the first node is a coupling point between the pixel driving circuit and the anode of the light emitting diode. The AMOLED display panel of the third aspect has similar effects to the Micro LED display panel of the second aspect, and details are not described herein again.

In a possible implementation, the voltage difference between the voltage of the charging potential terminal and the ground is less than the minimum light-emitting voltage of the light emitting diode, and the voltage of the charging potential terminal is less than the voltage of the power supply.

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

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

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

In a fourth aspect, an AMOLED display panel is provided. The display panel includes pixels distributed in an array, the pixels include a pixel driving circuit and a light emitting diode, the pixel driving circuit is coupled between the cathode of the light emitting diode and the ground, and the anode of the light emitting diode is coupled to a power supply, wherein the pixel driving circuit is used for driving the light emitting diode; The pixel also includes: a charging circuit, which is coupled between the charging potential terminal and the first node, where the first node is a coupling point between the pixel driving circuit and the anode of the light emitting diode. The AMOLED display panel of the fourth aspect has similar effects to the Micro LED display panel of the first aspect, and details are not repeated here.

In a possible implementation manner, the voltage difference between the charging potential terminal and the power supply is less than the minimum light-emitting voltage of the light-emitting device, and the voltage of the charging potential terminal is less than the voltage of the power supply.

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

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

In a possible implementation manner, the turn-on enable signal of the first switch and the enable signal of the light-emitting driving module are in a logical negation relationship.

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

The pixel driving circuit of the fifth aspect has similar effects to the Micro LED display panel of the first aspect, and details are not repeated here.

In a sixth aspect, a pixel driving circuit is provided. The pixel drive circuit includes: a light-emitting drive module cascaded between the anode of the light-emitting diode and the power supply, the light-emitting drive module includes a gate switch and a current source, the control end of the gate switch receives the first control signal, and the control end of the current source receiving bias voltage, the cathode of the light emitting diode is coupled to ground; and a charging circuit is coupled between the charging potential terminal and a first node, where the first node is a coupling point between the light emitting driving module and the anode of the light emitting diode.

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

The pixel driving circuit of the sixth aspect has similar effects to the Micro LED display panel of the second aspect, and details are not repeated here.

In a seventh aspect, a terminal device includes a rear case, a middle frame, and the Micro LED display panel as described in the first aspect or the second aspect, wherein the rear case 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 the AMOLED LED display panel according to the third aspect or the fourth aspect, wherein 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 aspect or the eighth aspect has a similar effect to the Micro LED display panel in the first aspect or the second aspect, and details are not repeated here.

Description of 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 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 provided by an embodiment of the present application;

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

FIG. 7 is a schematic structural diagram of a driving circuit provided by an embodiment of the present application;

FIG. 8 is a schematic structural 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;

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

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;

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 provided by another embodiment of the present application;

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

FIG. 18 is a schematic structural diagram of a pixel driving circuit provided by still another embodiment of the present application;

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

detailed description

The making and using of the various embodiments are discussed in detail below. It should be appreciated, however, that many of the applicable inventive concepts provided herein can 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 the technology, and do not limit the scope of the application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art.

In the embodiments of the present application, "at least one" refers to one or more, and "a plurality" refers to two or more. "And/or", which describes the association relationship of the associated objects, indicates that there can be three kinds of relationships, for example, A and/or B, which can indicate: the existence of A alone, the existence of A and B at the same time, and the existence of B alone, where A, B can be singular or plural. The character "/" generally indicates that the associated objects are an "or" relationship. "At least one item(s) below" or similar expressions thereof refer to any combination of these items, including any combination of single item(s) or plural items(s). For example, at least one (a) of a, b or c may represent: a, b, c, a and b, a and c, b and c or a, b and c, where a, b and c can be It can be single or multiple. In the embodiments of the present application, the terms "first", "second", etc. are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implying the number of indicated technical features. In addition, the term "coupling" may refer to a manner of electrical connection for signal transmission, and "coupling" may be a direct electrical connection or an indirect electrical connection through an intermediate medium. For example, connections made through resistors, inductors, or other electrical components. When used to describe 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, metal oxide semiconductor) tube, the control terminal may refer to the gate of the MOS tube, the first terminal may refer to the source of the MOS tube, and the second terminal It refers to the drain of the MOS tube, or the first end may refer to the drain of the MOS tube, and the second end refers to the source of the MOS tube.

An embodiment of the present 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, and a personal digital assistant (personal digital assistant). assistant, PDA), in-vehicle mobile devices, etc.

FIG. 1 is a schematic structural diagram of an exemplary terminal device according to an embodiment of the present application. As shown in FIG. 1, the terminal device 01 includes: a processor 11, a radio frequency (RF) circuit 12, a power supply 13, a memory 14, an input unit 15, a display device 16, an audio circuit 17 and other components. Those skilled in the art can understand that the structure of the terminal device shown in FIG. 1 does not constitute a limitation on the terminal device, and the terminal device may include more or less components than those shown in FIG. 1 , or may be combined Some of the components shown in FIG. 1 , or may be arranged differently from the components shown in FIG. 1 .

The processor 11 is the control center of the terminal device, using various interfaces and lines to connect various parts of the entire terminal device, by running or executing the software programs and/or modules stored in the memory 14, and calling the software programs stored in the memory 14. Data, perform various functions of the terminal equipment and process data, so as to monitor the terminal equipment as a whole. Optionally, the processor 11 may include one or more processing units; preferably, the processor 11 may integrate an application processor and a modem processor, wherein the application processor mainly processes the operating system, user interface, and application programs, etc. , the modem processor mainly deals with wireless communication. It can be understood that, the above-mentioned modulation and demodulation processor may not be integrated into the processor 11 .

The RF circuit 12 can be used for receiving and sending signals during transmission and reception of information or during a call. In particular, after receiving the downlink information of the base station, it is processed by the processor 11; in addition, the uplink data is sent to the base station. Typically, RF circuits include, but are not limited to, antennas, at least one amplifier, transceivers, couplers, low noise amplifiers (LNAs), duplexers, and the like. In addition, the RF circuit 12 may also communicate with the network and other devices via wireless communication. Wireless communication can use any communication standard or protocol, including but not limited to global system of mobile communication (GSM), 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 so on.

The terminal device includes a power supply 13 (such as a battery) that supplies power to various components. Optionally, the power supply can be logically connected to the processor 11 through a power management system, so that functions such as managing charging, discharging, and power consumption can be implemented through the power management system. .

The memory 14 can be used to store software programs and modules, and the processor 11 executes various functional applications and data processing of the terminal device by running the software programs and modules stored in the memory 14 . The memory 14 may mainly include a stored program area and a stored data area, wherein the stored program area may store an operating system, an application program (such as a sound playback function, an image playback function, etc.) required for at least one function, and the like; Data created by the use of the mobile phone (such as audio data, image data, phone book, etc.), etc. Additionally, 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 may be used to receive input numerical or character information, and generate key signal input related to user setting and function control of the terminal device. Specifically, the input unit 15 may include a touch screen 151 and other input devices 152 . The touch screen 151, also known as a touch panel, can collect the user's touch operations on or near the touch screen (such as the user's operations on or near the touch screen 151 using a finger, a stylus, or any suitable object or accessory), and according to the The preset program drives the corresponding connection terminal device. Optionally, the touch screen 151 may include two parts, a touch detection device and a touch controller. Among them, the touch detection device detects the user's touch orientation, detects the signal brought by the touch operation, and transmits the signal to the touch controller; the touch controller receives the touch information from the touch detection device, converts it into contact coordinates, and then sends it to the touch controller. To the processor 11, and can receive the command sent by the processor 11 and execute it. In addition, the touch screen 151 may be implemented in various types such as resistive, capacitive, infrared, and surface acoustic waves. Other input devices 152 may include, but are not limited to, one or more of a physical keyboard, function keys (such as volume control keys, power switch keys, etc.), trackballs, mice, joysticks, and the like.

The display device 16 may be used to display information input by the user or information provided to the user and various menus of the terminal device. The display device 16 may include a display panel 161, and in the present application, the display panel 161 may adopt an AMOLED display panel or a Micro LED display panel. Further, the touch screen 151 can cover the display panel 161. When the touch screen 151 detects a touch operation on or near the touch screen 151, it transmits it to the processor 11 to determine the type of the touch event, and then the processor 11 displays the touch event according to the type of the touch event. Corresponding visual outputs are provided on panel 161 . Although in FIG. 1, the touch screen 151 and the display panel 161 are used as two independent components to realize the input and output functions of the device, in some embodiments, the touch screen 151 and the display panel 161 can be integrated to realize the input of the device and output functions.

The audio circuit 17, the speaker 171 and the microphone 172 are used to provide an audio interface between the user and the terminal device. The audio circuit 17 can transmit the received audio data converted electrical signal to the speaker 171, and the speaker 171 converts it into a sound signal for output; on the other hand, the microphone 172 converts the collected sound signal into an electrical signal, which is converted by the audio circuit 17 After reception, it is converted into audio data, and the audio data is output to the RF circuit 12 for transmission to, for example, another terminal device, or the audio data is output to the memory 14 for further processing.

Optionally, the terminal device shown in FIG. 1 may further include various sensors. For example, a gyroscope sensor, a hygrometer sensor, an infrared sensor, a magnetometer sensor, etc., will not be repeated here. 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 repeated here.

It can be understood that, in the embodiments of the present application, the terminal device may perform some or all of the steps in the embodiments of the present application, these steps or operations are only examples, and the embodiments of the present application may also perform other operations or variations of various operations. In addition, various steps may be performed in different orders presented in the embodiments of the present application, and may not be required to perform all the operations in the embodiments of the present application. Each embodiment of the present application may be implemented independently or in any combination, which is not limited in this application.

The specific form of the above-mentioned terminal device 01 is not particularly limited in this embodiment of the present application. For the convenience of description, the following description is made by taking the terminal device 01 as a mobile phone as an example. The structure of the above-mentioned terminal device 01 is 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 connected through the middle frame 22 . In the embodiment of the present application, the above-mentioned display panel 21 is an organic light-emitting diode (organic light-emitting diode, OLED), an active-matrix organic light-emitting diode or an active-matrix organic light-emitting diode (active-matrix organic light-emitting diode), AMOLED), flexible light-emitting diode (flex light-emitting diode, FLED), Miniled, MicroLed, Micro-oLed, quantum dot light emitting diode (quantum dot light emitting diodes, QLED), micro light emitting diode (Micro LED) and other display panels.

In the AMOLED display panel solution, a pixel driving circuit composed of two or more TFTs is usually used to drive the light-emitting diodes in the pixels to realize the display function. As shown in FIG. 3 , the display panel 30 includes an active display area (AA) 100 and a non-display area 101 located around the AA area 100 . The AA area 100 includes a plurality of pixels 31 . For the convenience of description, in the present application, the above-mentioned plurality of pixels 31 are arranged in a matrix form as an example for description.

It should be noted that, in the embodiment of the present application, the pixels 31 arranged in a row along the horizontal direction X in FIG. 3 are called pixels in the same row, and the pixels 31 arranged in a row along the vertical direction Y are called pixels in the same column. In the embodiment of the present application, the above-mentioned display panel 30 may be an AMOLED display panel. The AMOLED display panel can realize self-luminescence. In this case, the pixel 31 in the AA area 100 is provided with an LED as shown in FIG. 4 and a pixel driving circuit 301 for driving the LED to emit light.

In addition, the above-mentioned apparatus may further include a display driving circuit for driving the display panel 30 to perform display, and the display driving circuit may be coupled with the display panel 30 . Exemplarily, the display driver circuit may be a display driver integrated circuit (DDIC). In some embodiments of the present application, as shown in FIG. 3 , the DDIC 32 is disposed in the non-display area 101 of the display panel 30 . The pixel driving circuits 301 in the same column of pixels 31 are coupled to the DDIC 32 through the same data line (DL). In other embodiments of the present application, the above-mentioned DDIC 32 may also be provided independently of the display panel 30 . The above-mentioned terminal equipment also includes a printed circuit board (printed circuit board, PCB), and a system on chip (System on Chip, SoC) mounted on the PCB. An application processor (application processor, AP) may be provided in the SoC, and the AP may be the processor 11 in FIG. 1 . The DDIC 32 in FIG. 3 is coupled to the SoC through a flexible printed circuit (FPC).

In this way, after the display data output by the SoC passes through the DDIC 32, it is converted into a data voltage Vdata and transmitted to the pixel driving circuit 301 of each pixel 31 coupled to each data line DL. Next, each pixel driving circuit 301 generates a driving current I matching the data voltage Vdata through the data voltage Vdata on the data line DL, so as to drive the LED in the pixel 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 the gate g of M1 is coupled to the scan line SCAN, and the source s of M1 is coupled to The data line DL, the drain d of M1 is coupled to the gate g of M2, the drain d of M2 is coupled to the power supply VDD through the LED (the anode of the LED is coupled to VDD, the cathode is coupled to the drain of M2), and the source s of M2 is coupled to the ground VEE , the coupling capacitance Cst between the source s and the gate g of M2. In this way, usually 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 is described by taking the LED common anode connection as an example, wherein M2 is an NMOS transistor. When using a PMOS transistor, in order to ensure the stability of the source voltage of M2 and avoid the problem of source voltage floating, which affects the instability of the gate-source (gs) voltage of M2, the source s of M2 is usually coupled to VDD, and the LED is coupled to VEE and the drain d of M2 (wherein, the anode of the LED is coupled to the drain d of M2, and the cathode is coupled to VEE), so that the LEDs realize a common cathode connection. FIG. 5 is only an example of a pixel driving circuit, and those skilled in the art can also replace the pixel circuit shown in FIG. 5 with other forms of pixel driving circuits.

The pixel driving circuits 301 , LEDs, and data lines DL in each pixel 31 of the display panel 30 can be fabricated on a base substrate. The base substrate may be formed of a flexible resin material. In this case, the AMOLED display panel can be used as a folding display. Alternatively, the base substrate in the above-mentioned AMOLED display panel may also be made of a material with a relatively hard texture, such as glass. In this case, the above-mentioned AMOLED display panel is a hard display panel.

In a Micro LED display panel, as shown in FIG. 6 , it usually includes pixels 61 in an array manner, and the pixels include at least three sub-pixels. In FIG. 6 , the pixel 61 includes three sub-pixels R (red, red), G (green, green) and B (blue, blue) as an example for illustration, each sub-pixel includes an LED, and the same pixel 61 Diodes emit different colors of light. Wherein, as shown in FIG. 6 , it also includes: a drive circuit 62 arranged in an array, the drive circuit 62 includes a plurality of pixel drive circuits, and four pixels are distributed around the drive circuit 62; the first sub-pixel in the pixel 61 is connected to a plurality of pixels The first pixel driving circuit in the pixel driving circuit, the second sub-pixel in the pixel 61 is connected to the second pixel driving circuit of the plurality of pixel driving circuits, and the third sub-pixel in the pixel is connected to the plurality of pixel driving circuits. the third pixel driving circuit. It is assumed that a plurality of pixels are distributed around any driving circuit 62 (wherein, four pixels are taken as an example for illustration in FIG. 6 ). The driving circuit 62 includes a plurality of pixel driving circuits, each of which is coupled to an LED, to drive the coupled LEDs. Specifically, as shown in FIG. 7 , the driving circuit 62 internally includes an analog circuit part 622 and a digital circuit part 621 . For a pixel composed of RGB three-color sub-pixels, the analog circuit part includes 12 pixel driving circuits. Referring to FIG. 8, the pixel drive circuit is usually composed of a current source 81 and a gate switch 82. The current source 81 is coupled to the Micro LED (D1 in FIG. 8) through the gate switch 82, and each pixel drive circuit is a sub- Pixel's Micro LED powered. Externally, the digital circuit part 621 is controlled by the timing control chip to generate a control signal (usually a pulse width modulation (PWM) signal) for the gate switch 82 and a bias voltage (Vbias) of the current source, which is realized by the control signal. The strobe of the output of the current source 81 (equivalent to the DDIC in the AMOLED display panel selecting the pixel address through the scan line), and the control of the output power of the current source 81 through the bias voltage (equivalent to the data voltage (Vdata) used in the AMOLED display panel. ) to drive the transistor to generate a current (Idata)), thereby realizing the light-emitting control of the corresponding Micro LED. As shown in FIG. 8, a schematic diagram of a pixel driving circuit is provided, including MOS transistors M1, M2 and M3, wherein M1 is used as a gate switch and is connected in series between the current source 81 and the Micro LED, and the current source 81 includes two series-connected The MOS transistors M2 and M3, where the gate of M1 is used to receive control signals, the source of M1 is coupled to the drain of M2, and the drain of M1 is coupled to the power supply VDD through D1 (wherein the anode of D1 is coupled to VDD, and the cathode of M1 is coupled to Drain, 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 described by taking the series-connected MOS transistors M2 and M3 as an example. In some examples, the current source may only include one MOS transistor M2. At this time, the source of M2 is directly coupled to VEE; of course, the current source can also be Including 3 or more MOS tubes connected in series. The above description is given by taking the LED common anode connection as an example. M1, M2 and M3 in FIG. 8 are NMOS transistors. When using a PMOS tube, it is necessary to use a common cathode connection method for D1. FIG. 8 is only an example of a pixel driving circuit, and those skilled in the art can also replace the pixel circuit shown in FIG. 8 with other forms of pixel driving circuits.

Whether it is the above-mentioned AMOLED display panel solution or the Micro LED display panel solution, referring to FIG. 5 and FIG. 8 , since the cathode of the LED (node X in FIG. 5 and node A in FIG. 8 ) has parasitic capacitance (in FIG. 8 ) The Cp mainly includes the cathode of the LED, the connection between the cathode of the LED and the drain of M1, and the parasitic capacitance generated by the drain of M1). X) Charge and discharge, causing the LED switching process to take a certain time. The speed of LED switching is limited. When the LED switching speed is slow, the human eye can easily observe the afterimage phenomenon, which affects the user experience. Taking the Micro LED display panel as an example, the specific principle is as follows, referring to FIG. 8 and FIG. 9 for description, the pixel driving circuit uses the current source 81 to provide the driving current for the LED, and under the control of the PWM signal, M1 controls the on or off of the LED, Referring to the timing curve of the PWM signal shown in FIG. 9 , the NMOS transistor is generally turned on when the 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 node A becomes high VH (node A is floating at the same level as VDD), the LED current (ID1) is 0, and the parasitic capacitance Cp of node A stores charge; When the PWM signal changes to high level, M1 is turned on, and node A is first discharged through M1, M2, and M3. When the voltage at point A decreases, the LED can only pass current. For example, referring to the voltage curve VA of node A, when When the voltage of node A drops to VA0, VDD-VA0 is equal to the turn-on voltage of the LED, and then as the voltage of node A continues to drop, ID1 gradually increases. When the PWM signal changes to a low level, M1 is disconnected, and VDD charges the parasitic capacitor Cp again until ID1 becomes 0 (the voltage of the parasitic capacitor is greater than VA0 at this time), and the LED can be turned off. In this way, node A needs to be discharged from VH to VL when the LED is on. At the beginning of the discharge, ID1 is completely absorbed by Cp, and when the voltage of node A drops below VA0, the LED begins to flow current. When the LED is working normally and stably, the voltage of node A is VL. Due to the influence of the parasitic capacitance of node A, when the LED is turned off, VDD charges node A, and the voltage of node A rises slowly until VH. That is, every time the LED is turned on, the node A needs to be discharged first; comparing the ideal current waveform and the actual current waveform of ID1, it can be seen that when the LED is turned off, the node A is charged to a high level HV, resulting in the Cp discharge delay time T1 during the LED turn-on process (where T1 is the time when node A is discharged from VH to VA0), and the LED turn-off process Cp charging delay time T2 (where T2 is the time when node A is charged from VEE to VA0), so that there is a certain delay in turning on and off the LED, It affects the switching response speed of the LED. When the LED switching speed is slow, the human eye can easily observe the afterimage phenomenon, which affects the user experience. Especially for the Micro LED display panel solution, the use of PWM signal to control M1 to turn on or off the LED requires higher switching speed. The existing technology limits the frequency of refreshing the LED, and the current technology cannot meet the demand.

In response to the above problems, 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 the cathode of the light-emitting diode D1 and the ground VEE, and a charging circuit 1001 . 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 the first node A, and the first node A is the 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 the control terminal of the gate switch Ks receives a first control signal. In one embodiment, the first control signal may be a PWM signal. The control of the current source Is terminal receives the bias voltage.

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

When the voltage of the node A is lower than a certain threshold value 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 at this time. The threshold is mainly related to the forward conduction voltage (ie, the minimum light-emitting voltage) of the light-emitting diode D1. For example, the forward conduction voltage of a silicon (Si) tube is about 0.7V, while that of a germanium (Ge) tube is about 0.3V.

In some embodiments, as shown in FIG. 10 , the gate switch Ks includes a second MOS transistor M2, and the current source Is includes a third MOS transistor M3; wherein, one end of the source and drain of M3 is coupled to the ground VEE, and the source of M3 The other end of the drain is coupled with the current source Is (that is, the other end of the source and drain of M3 is coupled with one end of the source and drain of M2), and the other end of the source and drain of M2 is coupled with the cathode of the light emitting diode D1 to the first node A, the gate of M2 receives the first control signal, and the gate of M3 receives the bias voltage.

As shown in FIG. 10 , the charging circuit 1001 includes a first switch M1 , wherein the first terminal of the first switch M1 is coupled to the first node A, and the second terminal of the first switch M1 is coupled to the charging potential terminal VA1 . In one embodiment, the above-mentioned M1 is a first MOS transistor, one end of the source and drain of M1 is coupled to the charging potential terminal VA1, the other end of the source and drain of the first switch M1 is coupled to the first node A, and the gate of M1 The pole receives the turn-on enable signal. M1 is turned on or off under the control of the turn-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 and the enable signal of the light-emitting driving module 1002 are in a logical negation relationship. Wherein, the enable signal of the light-emitting driving module 1002 is the 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 driving the light-emitting diode; 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. Wherein, when the bias voltage controls the current source to continuously output the driving current during the conduction period of the gate 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 the first control signal, and the control end of the first switch is coupled to the control end of the gating switch through the NOT circuit.

In the working state, the above-mentioned M2 is turned on or off under the control of the received first control signal, and the above-mentioned M3 is kept on under the control of the received bias voltage Vbias. When the first control signal controls M2 to be turned off, the voltage of node A (ie, the cathode of the light-emitting diode D1) becomes high, the current in the light-emitting diode D1 is 0, and the parasitic capacitance Cp on the node A (the parasitic capacitance Cp is mainly the The drain, the cathode of D1, and the capacitance created by the connection between the cathode of D1 and the drain of M1 (not shown in Figure 10) accumulate charge. When the first control signal controls M2 to be turned on, the parasitic capacitance Cp is discharged through M2 and M3. When the voltage of the node A is lower than a certain threshold value VA0 (depending on the characteristics of the light emitting diode D1), the light emitting diode D1 is turned on. In the embodiment of the present application, after M2 is disconnected, the charging circuit 1001 can charge the parasitic capacitance of the node A 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 charging potential terminal VA1 has the same voltage. The difference between the voltage and the power supply VDD is less than the minimum light-emitting voltage (VDD-VA0) of the LED D1, and the voltage of the charging potential terminal VA1 is less than the voltage of the power supply VDD, so the LED D1 does not emit light. Since the voltage of the charging potential terminal VA1 is greater than VA0, the leakage current of M2 can also be guaranteed to be low. When M2 is turned on, the charging circuit 1001 stops charging the first node A, and the charges in the parasitic capacitance of the first node A are discharged through M2 and M3 until the voltage of the first node A is the same as the ground VEE. During this process, the first node A starts to discharge from a voltage lower than the power supply VDD (the voltage of the charging potential terminal VA1), 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 , as long as the first node A starts to discharge slightly from the voltage of the charging potential terminal VA1, that is, the voltage difference between the voltage of the first node A and the power supply VDD can meet the minimum light-emitting voltage of the light-emitting diode D1, and the light-emitting diode D1 starts to emit light, reducing the size of the pixel. When the driving circuit drives the light-emitting diode to emit light, the variation range of the cathode voltage of the light-emitting diode increases the switching speed of the LED. When the variation range of the cathode voltage of the light-emitting diode becomes smaller, the establishment time of the current signal of the light-emitting diode becomes shorter, and the refresh frequency of the light-emitting diode becomes higher, so that the time for the light-emitting diode from extinguishing to lighting is shortened. The afterimage phenomenon when the human eye observes the light-emitting diode can be improved, the display accuracy of the light-emitting diode can be improved, and the user experience can be improved. In addition, when M2 changes from the on state to the off state, the charging circuit directly charges the node A through the charging potential terminal VA1, and the voltage of the node A is directly set to VA1, which also reduces the turn-off of the current signal of the light-emitting diode. time.

The working principle of the pixel drive circuit is described in detail with reference to Fig. 10 and Fig. 11 as follows: In one charge and discharge cycle, (a) in Fig. 11 shows the waveform diagram of the PWM signal in the traditional pixel drive circuit. Voltage waveform diagram, the waveform diagram of the current ID1 in the LED D1; Figure 11 (b) shows the waveform diagram of the PWM signal in the optimized pixel drive circuit, the voltage waveform diagram of node A, in the LED D1 The waveform diagram of the current ID1. The embodiments of the present application are described by taking the strobe signal as a PWM signal, and M1, M2, and M3 all being NMOS transistors as an example.

When the pixel driving circuit works normally, M3 is turned on. From 0 to t1, the PWM signal is at a low level, and M2 is in an off state at this time, so the voltage (VH) of node A is higher than the above-mentioned threshold voltage VA0, the current ID1 in the LED D1 is 0, and the LED D1 is in off state. At time t1, the PWM signal changes from a low level to a high level, and M2 switches from an off state to an on state at this time. Since M2 and M3 are both on, ideally, the voltage of node A will drop rapidly to 0 (VL), and the current ID1 in LED D1 will rapidly increase to a larger value, as shown in Figure 11 The "ideal current waveform" curve in (a) is shown. In actual work, as shown in the "actual current waveform" curve in (a) of Figure 11, the conventional circuit in the prior art has parasitic capacitance Cp at node A, when M2 is in the off state, VDD has a negative effect on node A. The voltage will be charged to VH, and when M2 is switched from the off state to the on state, the parasitic capacitance Cp first needs to be discharged through M2 and M3 from t1 to t2 until the voltage of node A is lower than the above-mentioned threshold voltage VA0. At time t2, the current ID1 in the light-emitting diode D1 begins to increase until it reaches a maximum value, and then maintains the maximum value until time t3. At time t3, the PWM signal changes from high level to low level, the current ID1 in the light-emitting diode D1 begins to decrease, and the Cp of node A starts to charge until the voltage of node A is higher than the above-mentioned threshold voltage VA0, and the current ID1 becomes 0 (ie time t4). Correspondingly, as shown in (a) of FIG. 11 , due to the slow discharge, the node A in the conventional circuit in the prior art needs T1 (t2-t1) time to complete the signal establishment after M2 is turned on, and M2 After disconnection, the time of T2 (t4-t3) is required to complete the turn-off of the signal. It can be seen from (a) in FIG. 11 that from t1 to t2, the parasitic capacitance Cp is in the discharging process, which causes the light-emitting diode D1 to take a long time from extinguishing to lighting. From t3 to t4, the parasitic capacitance Cp is in the charging process, which causes the light-emitting diode D1 to take a long time from turning on to turning off. When the parasitic capacitance Cp is larger, the time from t1 to t2 and the time from t3 to t4 are longer. , the human eye is more likely to observe the afterimage phenomenon, which affects the user experience.

The charging circuit 1001 coupled to the node A in the pixel driving circuit provided by the embodiment of the present application can charge the voltage of the node A to VA1 when M2 is turned off (for example, 0-t1). In this way, due to the voltage difference between VA1 and VDD It is less than the minimum light-emitting voltage of LED D1 (that is, VA1 is greater than VA0), as shown in (b) of Figure 11, from 0 to t1, the current ID1 is 0, D1 does not emit light, and from t1 to t2, M2 is turned on, The parasitic capacitance Cp starts to discharge directly from VA1. Compared with the traditional pixel driving circuit, the voltage of Cp from t1 to t2 in Figure 11 (a) needs to be discharged from VDD to VA0, and current will flow through D1. After optimization In the solution, as shown in (b) in Figure 11, the voltage of Cp only needs to be discharged from VA1 to VA0 from time t1 to t2, and D1 will have a current passing through, reducing the voltage change of node A, that is, the change range of △VA is from VH ~VL ((a) in Fig. 11) becomes VA1 ~ VL ((b) in Fig. 11), the "actual current waveform" as shown in (b) in Fig. 11 has been closer to the "ideal current waveform", Therefore, the signal establishment time of the light emitting diode D1 is accelerated, and the switching frequency of the light emitting diode D1 is increased, so as to achieve the purpose of eliminating afterimages, improving display accuracy and improving user experience. And in Figure 11 (a), the voltage of Cp needs to be charged from VEE to VA0 from t3 to t4, and the current ID1 of D1 will be zero. In the optimized solution, as shown in Figure 11 (b) From t3 to t4, the voltage of Cp is directly set to VA1. Since VA1 is greater than VA0, the current of D1 can be quickly turned off.

The current source further includes a fourth MOS transistor, wherein one end of the source and drain of the fourth MOS transistor is coupled with one end of the source and drain of the third MOS transistor, the other end of the source and drain of the fourth MOS transistor is coupled to the ground, and the fourth The gate of the MOS transistor receives the bias voltage. As shown in FIG. 12, a pixel driving circuit is provided. M4 is also coupled between the source of M3 and the ground VEE. When the M4 is an NMOS transistor, the source of M4 is coupled to the ground VEE, and the drain of M4 is coupled to M2. The source of M4 is coupled to the gate of M2. Among them, M2 and M4 form a current source, and similar current sources can also include more MOS tubes connected in series.

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 the NOT gate circuit 1003 . Among them, when M2 is turned on, the charging potential terminal stops charging the first node A, and when M2 is turned off, the charging potential terminal VA1 charges the first node A. Therefore, when M2 and M1 use the same type of MOS tube, M1's The conduction enable signal of the control terminal is opposite to the phase of the first control signal of the control terminal of M2, so the control terminal of M2 can be coupled to the control terminal of M1 through the NOT gate circuit 1003, so as to use the first control signal to input the control terminal of M2, and After passing through the NOT gate circuit 1002, it is input to the control terminal of M1.

The above mainly takes the common anode connection method of light emitting diodes in the Micro LED display panel as an example to describe the pixel driving circuit. In FIG. 14, a common cathode connection method of light emitting diodes is also provided. As shown in FIG. 14, the pixel The 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, and the control terminal of the gate switch Ks receives the first control In one embodiment, the first control signal may be a PWM signal, the control terminal of the current source Is receives the bias voltage Vbias, the cathode of the light-emitting diode D1 is coupled to the ground VEE; and the charging circuit 2001 is coupled to the charging potential Between the terminal VA1 and the first node A, the first node A is the coupling point of the light-emitting driving module 2002 and the anode of the light-emitting diode D1.

The charging circuit 2001 is used to charge the first node A through the charging potential terminal VA1, wherein the voltage difference between the charging potential terminal VA1 and the ground VEE is less than the minimum light-emitting voltage of the light emitting diode, and the voltage of the charging potential terminal VA1 is less than the 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, and the current source Is includes a third MOS transistor M3; wherein, one end of the source and drain of M3 is coupled to the power supply VDD, and the source of M3 The other end of the drain is coupled with the current source Is (that is, the other end of the source and drain of M3 is coupled with one end of the source and drain of M2), and the other end of the source and drain of M2 is coupled with the anode of the light emitting diode D1 to the first node A, the gate of M2 receives the first control signal, and the gate of M3 receives the bias voltage.

As shown in FIG. 14 , the charging circuit 2001 includes a first switch M1 , wherein the first terminal of M1 is coupled to the first node A, and the 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 and drain of M1 is coupled to the charging potential terminal VA1, the other end of the source and drain of M1 is coupled to the first node A, and the gate of M1 receives the conduction pass enable signal. M1 is turned on or off under the control of the turn-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 and the enable signal of the light-emitting driving module 2002 are in a logical negation relationship. Wherein, the enable signal of the light-emitting driving module 2002 is the 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 driving the light-emitting diode; 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. Wherein, when the bias voltage controls the current source to continuously output the driving current during the conduction period of the gate 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 the first control signal, and the control end of the first switch is coupled to the control end of the gating switch through the NOT circuit.

In the working state, the above-mentioned M2 is turned on or off under the control of the received first control signal, and the above-mentioned 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 node A (that is, the anode of the light-emitting diode D1) becomes low, the current in the light-emitting diode D1 is 0, the light-emitting diode is turned off, and the charging potential terminal VA1 will reduce the parasitic voltage on the node A. Capacitance Cp (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 Figure 15), until the voltage and charging of the first node The voltage of the potential terminal VA1 is equal, and the voltage difference between the voltage of the charging potential terminal VA1 and the ground VEE is less than the minimum light-emitting voltage of the LED, and the voltage of the charging potential terminal is less than the voltage of the power supply, so the LED 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 be charged from a voltage lower than the power supply (the voltage of the charging potential terminal VA1), 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, as long as The voltage of the first node A starts to increase slightly from the charging potential terminal VA1, that is, the voltage difference between the voltage of the first node A and the ground VEE can meet the minimum light-emitting voltage of the light-emitting diode, and the light-emitting diode starts to emit light, which reduces the size of the pixel drive circuit. When the diode emits light, the variation range of the cathode voltage of the light-emitting diode increases the switching speed of the LED. When the variation range of the anode voltage of the light-emitting diode becomes smaller, the establishment time of the current signal of the light-emitting diode becomes shorter, and the refresh frequency of the light-emitting diode becomes higher, so that the time for the light-emitting diode from extinguishing to lighting is shortened. The afterimage phenomenon when the human eye observes the light-emitting diode can be improved, the display accuracy of the light-emitting diode can be improved, and the user experience can be improved. In addition, when M2 changes from the on state to the off state, the charging circuit directly charges the node A through the charging potential terminal VA1, and the voltage of the node A is directly set to VA1, which also reduces the turn-off of the current signal of the light-emitting diode. time.

The working principle of the pixel drive circuit is described in detail with reference to Fig. 14 and Fig. 15 as follows: In one charge and discharge cycle, (a) in Fig. 15 shows the waveform diagram of the PWM signal in the traditional pixel drive circuit. Voltage waveform diagram, the waveform diagram of the current ID1 in the LED D1; Figure 15(b) shows the waveform diagram of the PWM signal in the optimized pixel drive circuit, the voltage waveform diagram of the node A, the LED D1 The waveform diagram of the current ID1 in . The embodiments of the present application are described by taking the strobe signal as a PWM signal, and M1, M2, and M3 all being PMOS transistors as an example.

When the pixel driving circuit works normally, M3 is turned on. From 0 to _t1 , the PWM signal is at a high level, and M2 is in an off state at this time, so the voltage (VL) of node A is lower than the above-mentioned threshold voltage VA0, the current ID1 in the LED D1 is 0, and the LED D1 is off. At time t1, the PWM signal changes from a high level to a low level, and at this time, the first switch M1 switches from an off state to an on state. Since M2 and M3 are both on, ideally, the voltage of node A will rapidly rise to VH, and the current ID1 in LED D1 will rapidly increase to a larger value, as shown in (a) in Figure 15 shown in the "Ideal Current Waveform" curve. In actual work, as shown in the "actual current waveform" curve in (a) of Figure 15, the conventional circuit in the prior art has parasitic capacitance Cp at node A, when M2 is in the off state, the voltage at node A is 0 (VL), when M2 is switched from the off state to the on state, the parasitic capacitance Cp first needs to be charged through M2 and M3 from t1 to t2 until the voltage of node A is higher than the above-mentioned threshold voltage VA0. At time t2, the current ID1 in the light-emitting diode D1 begins to increase until it reaches a maximum value, and then maintains the maximum value until time t3. At time t3, the PWM signal changes from a low level to a high level, the current ID1 in the light-emitting diode D1 begins to decrease, and the Cp of the node A begins to discharge until the voltage of the node A is lower than the above-mentioned threshold voltage VA0, and the current ID1 becomes 0 (ie time t4). Correspondingly, as shown in (a) of FIG. 15 , due to slow charging and discharging, the node A in the conventional circuit in the prior art needs T1 (t2-t1) time to complete after the first switch M1 is turned on. After the signal is established and M2 is disconnected, it takes T2 (t4-t3) time to complete the signal turn-off. It can be seen from (a) in FIG. 15 that from t1 to t2, the parasitic capacitance Cp is in the charging process, which causes the light-emitting diode D1 to take a long time from extinguishing to lighting. From t3 to t4, the parasitic capacitance Cp is in the discharge process, which causes the light-emitting diode D1 to go through a long time from turning on to turning off. When the parasitic capacitance Cp is larger, the time from t1 to t2 and the time from t3 to t4 are longer. , the human eye is more likely to observe the afterimage phenomenon, which affects the user experience.

The charging circuit 2001 coupled to the node A in the pixel driving circuit provided by the embodiment of the present application can charge the voltage of the node A to VA1 when M2 is turned off. In this way, since the voltage difference between VA1 and VEE is smaller than the minimum light emission of the light-emitting diode D1 Voltage, that is (VA1 is less than VA0), that is, as shown in (b) of Figure 15, from 0 to t1, the current ID1 is 0, D1 does not emit light, and from t1 to t2, M2 is turned on, and the parasitic capacitance Cp directly from VA1 Start charging, compared with the traditional pixel drive circuit, the voltage of Cp from t1 to t2 in Figure 15 (a) needs to be charged from VL to VA0, and D1 will have current flow, and in the optimized scheme, as shown in the figure The voltage of Cp from t1 to t2 in (b) in 15 only needs to be charged from VA1 to VA0, and D1 will have a current flow through, which reduces the voltage change of node A, that is, the ΔVA changes from VL to VH (Figure 15). (a)) becomes VA1~VH ((b) in Figure 15), as shown in (b) in Figure 15, the "actual current waveform" has been closer to the "ideal current waveform", thereby speeding up the LED D1 The signal establishment time increases the switching frequency of the light-emitting diode D1, so as to eliminate afterimages, improve display accuracy, and improve user experience. And in Figure 15 (a), the voltage of Cp needs to be discharged from VH to VA0 from t3 to t4, and the current ID1 of D1 will be zero. In the optimized scheme, as shown in Figure 15 (b) From t3 to t4, the voltage of Cp is directly set to VA1. Since VA1 is smaller than VA0, the current of D1 can be quickly turned off.

The current source further includes a fourth MOS transistor, wherein one end of the source and drain of the fourth MOS transistor is coupled to one end of the source and drain of the third MOS transistor, the other end of the source and drain of the fourth MOS transistor is coupled to the power supply, and the fourth The gate of the MOS transistor receives the bias voltage. As shown in FIG. 16, a pixel driving circuit is provided. M4 is coupled between the source of M3 and the power supply VDD. When M4 is a PMOS transistor, the source of M4 is coupled to the power supply VDD, and the drain of M4 is coupled to the source of M2. pole, the gate of M4 is coupled to the gate of M2. Among them, M2 and M4 form a current source, and similar current sources can also include more MOS tubes connected in series.

As shown in FIG. 17 , a pixel driving circuit is provided, wherein the control terminal of M1 is coupled to the control terminal of M2 through the NOT gate circuit 2003 . Among them, when M2 is turned on, the charging potential terminal stops charging the first node A, and when M2 is turned off, the charging potential terminal VA1 charges the first node A, so when M1 and M2 use the same type of MOS tube, M2's The first control signal of the control terminal is opposite in phase to the conduction enable signal of the control terminal of M1, so the control terminal of M2 can be coupled to the control terminal of M1 through the NOT gate circuit 2003, so as to use the first control signal to input the control terminal of M2, and After passing through the NOT gate circuit 2003, it is input to the control terminal of M1.

In one embodiment, the pixel driving circuit is an example in which the pixel driving circuit is an AMOLED display panel scheme for description. In a connection mode of common anode of light-emitting diodes, as shown in FIG. 18 , the pixel driving circuit 3000 includes a first MOS transistor M1, a second MOS transistor M2 and a charging circuit 3001, wherein the control end of M1 is coupled to the scan line SCAN, M1 The first end of M1 is coupled to the data line DL, the second end of M1 is coupled to the control end of M2, the first end of M2 is coupled to the power supply VDD through the LED (the anode of the LED is coupled to VDD, and the cathode is coupled to the first end of M2), and the first end of M2 is coupled to the power supply VDD. Two terminals are coupled to ground VEE, and a capacitor Cst is coupled between the second terminal of M2 and the gate. In this way, usually when the pixel is addressed by the scan line SCAN, the data voltage (Vdata) on the data line DL is applied to the LED through M2, and M2 generates a current (Idata) to flow through the LED to emit light. The charging and discharging circuit 3001 is coupled between the cathode of the light emitting device D1 (ie, the node X) and the charging potential terminal VA1. The charging circuit 1001 is used to charge the node X through the charging potential terminal VA1, wherein the voltage difference between the charging potential terminal VA1 and the power supply VDD is less than the minimum light emission voltage of the LED D1, and the voltage of the charging potential terminal VA1 is less than the voltage of the power supply VDD. Exemplarily, the charging circuit 3001 includes a third switch M3, the first terminal of M3 is coupled to the second terminal of the light emitting diode D1, the second terminal of the third switch M3 is coupled to the charging potential terminal VA1, and the second voltage terminal V2 inputs a predetermined voltage. value VA1. 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 terminal of M2 is the gate, the first terminal of M2 is the drain, and the second terminal is the source. The control terminal of M3 is the gate, the first terminal of M3 is the source, and the second terminal of M3 is the drain. The analysis of the working principle of the pixel driving circuit provided in FIG. 18 can be analyzed with reference to (b) in FIG. 11 , which will not be repeated here.

Figure 18 above takes the common anode connection mode of the light-emitting diode D1 as an example to illustrate. When the light-emitting diode D1 realizes the common cathode connection mode, as shown in Figure 19, M1, M2 and M3 use PMOS, in order to ensure the stability of the source voltage of M2 To avoid the problem of source voltage floating, which affects the instability of the gate-source (gs) voltage of M2, usually the source s of M2 is coupled to VDD, and the light-emitting diode D1 is coupled between VEE and the drain d of M2 (wherein the luminous The anode of the diode D1 is coupled to the drain d of M2, and the cathode is coupled to VEE), so that the light-emitting diode D1 realizes a common-cathode connection, as shown in FIG. 19 . The analysis of the working principle of the pixel driving circuit provided in FIG. 19 can be performed with reference to (b) in FIG. 15 , which will not be repeated here.

Above, the pixel drive circuits under the AMOLED display panel solution and the Micro LED display panel solution are only some examples, and those skilled in the art can also implement pixel drive circuits in other ways.

Finally, it should be noted that: the above are only specific embodiments of the present application, but the protection scope of the present application is not limited to this, and any changes or replacements within the technical scope disclosed in the present application should be covered by the present application. within the scope of protection of the application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

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

The pixel driving circuit includes: a light-emitting driving module cascaded between the cathode of the light-emitting diode and the ground, the light-emitting driving module includes a gate switch and a current source, and the control end of the gate switch receives the first a control signal, the control terminal of the current source receives the bias voltage, the anode of the light-emitting diode is coupled to the power supply; and the charging circuit is coupled between the charging potential terminal and the first node, the first node is the light-emitting diode The coupling point of the driving module and the cathode of the light emitting diode.
The miniature light-emitting diode display panel according to claim 1, wherein the voltage difference between the charging potential terminal and the power supply is less than the minimum light-emitting voltage of the light-emitting device, and the voltage of the charging potential terminal is smaller than the power supply voltage.
The miniature light emitting diode display panel of claim 1, wherein the charging circuit comprises a first switch, wherein a first end of the first switch is coupled to the first node, and the first switch The second terminal of the is coupled to the charging potential terminal.
The miniature light-emitting diode display panel according to claim 3, wherein the turn-on enable signal of the first switch and the enable signal of the light-emitting driving module are in a logical negation relationship.
The miniature light-emitting diode display panel according to claim 3 or 4, wherein the first switch comprises a first MOS transistor, and one end of the source and drain of the first MOS transistor is coupled to the charging potential terminal, The other end of the source and drain of the first MOS transistor is coupled to the first node, and the gate of the first MOS transistor receives a turn-on enable signal.
The miniature light-emitting diode display panel according to any one of claims 3-5, wherein the gate switch comprises a second MOS transistor, and one end of the source and drain of the second MOS transistor is coupled to the current source , the other end of the source and drain of the second MOS transistor is coupled to the cathode of the light emitting diode and is coupled to the first node, and the gate of the gate switch receives the first control signal.
The miniature light-emitting diode display panel according to any one of claims 3-5, wherein the current source comprises a third MOS transistor, wherein one end of the source and drain of the third MOS transistor is coupled to the ground, so The other end of the source and drain of the third MOS transistor is coupled to the gate switch, and the gate of the third MOS transistor receives the bias voltage.
The miniature light-emitting diode display panel according to claim 7, wherein the current source further comprises a fourth MOS transistor, wherein one end of the source and drain of the fourth MOS transistor is connected to the source of the third MOS transistor. One end of the drain is coupled, the other end of the source and drain of the fourth MOS transistor is coupled to ground, and the gate of the fourth MOS transistor receives the bias voltage.
The miniature light-emitting diode display panel according to any one of claims 1 to 8, wherein the pixel driving circuit further comprises a capacitor, one end of the capacitor is coupled to the control end of the current source, and the other end is coupled to the control end of the current source. land.
The miniature light emitting diode display panel according to any one of claims 1 to 9, wherein the first control signal is a pulse width modulated PWM signal.
A pixel drive circuit, comprising:

A light-emitting drive module cascaded between the cathode of the light-emitting diode and the ground, the light-emitting drive module includes a gate switch and a current source, the control terminal of the gate switch receives the first control signal, and the control terminal of the current source receiving a bias voltage, the anode of the light emitting diode is coupled to a power supply; and

The charging circuit is coupled between the charging potential terminal and a first node, where the first node is a coupling point between the light-emitting driving module and the cathode of the light-emitting diode.
The pixel driving circuit according to claim 11, wherein the charging circuit comprises a first switch, wherein a first end of the first switch is coupled to a cathode of the light emitting diode, and a first end of the first switch is coupled to the cathode of the light emitting diode. The second terminal is coupled to the charging potential terminal.
13. The pixel driving circuit according to claim 12, wherein the turn-on enable signal of the first switch and the enable signal of the light-emitting driving module are in a logical negation relationship.
The pixel driving circuit according to claim 12 or 13, wherein the first switch comprises a first MOS transistor, one end of the source and drain of the first MOS transistor is coupled to the charging potential terminal, and the The other end of the source and drain of the first MOS transistor is coupled to the first node, and the gate of the first MOS transistor receives a turn-on enable signal.
A terminal device, comprising a rear casing, a middle frame, and the miniature light-emitting diode display panel according to any one of claims 1-9, wherein the rear casing and the miniature light-emitting diode display panel are arranged opposite to each other and pass through the middle frame. box connection.