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

Abstract

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

Description

Technical Field

[0001] The present application relates to the field of display technology, and in particular to a pixel driving circuit and a micro light emitting diode display panel. Background Art

[0002] LED (light emitting diode) display panel uses LED to realize pixel display, and its display performance has higher contrast and brightness than traditional LCD (liquid crystal display).

[0003] In an LED display panel, the LED pixel array is driven by a pixel driving circuit. The pixel driving circuit is enabled according to the row selection signal and the column driving 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 driving circuit. Due to the parasitic capacitance and parasitic resistance of the cathode of the LED, when the LED frequently switches between the on state and the off state, the pixel driving 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, thereby limiting the switching 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. Summary of the invention

[0004] The present application provides a pixel driving circuit and a micro light emitting diode Micro LED display panel, which charges the coupling point between the light emitting diode and the pixel driving circuit through a charging 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, thereby improving the switching speed of the LED.

[0005] In a first aspect, a micro light-emitting diode display panel is provided. The micro light-emitting diode display panel includes a plurality of drive circuits distributed in an array, wherein the drive circuit includes a plurality of pixel drive circuits for driving multiple pixels; wherein each of the pixels includes at least three sub-pixels, and each of the sub-pixels includes a light-emitting diode; the first sub-pixel in the pixel is coupled to the first pixel drive circuit in the plurality of pixel drive circuits, the second sub-pixel in the pixel is coupled to the second pixel drive circuit in the plurality of pixel drive circuits, and the third sub-pixel in the pixel is coupled to the third pixel drive circuit in the plurality of pixel drive circuits. For example, the drive circuit includes 12 pixel drive circuits, and 4 pixels are distributed around the drive circuit, each pixel includes three sub-pixels, and each sub-pixel includes a light-emitting diode of one color. Each pixel drive circuit is used to drive a light-emitting diode. The pixel driving circuit comprises: a light-emitting driving module cascaded between the cathode of the light-emitting diode and the ground, the light-emitting driving module comprises a gate switch and a current source, the control end of the gate switch receives a first control signal, the control end of the current source receives a bias voltage, and the anode of the light-emitting diode is coupled to the power supply; and a charging circuit coupled between the charging potential end and a first node, the first node being a coupling point between the light-emitting driving module and the cathode of the light-emitting diode.

[0006] Wherein, the charging circuit is used to charge the first node through the charging potential terminal. When the light-emitting driving module stops driving the light-emitting diode, the light-emitting diode goes out, and the charging circuit charges the cathode (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 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, 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 gating 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 a 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 less than the minimum light-emitting voltage of the light-emitting diode, as long as the first node starts to discharge slightly from the voltage of the charging potential terminal, 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 variation range of the cathode voltage of the light-emitting diode when the pixel driving circuit drives the light-emitting diode to emit light, and improves 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, thereby shortening the time it takes for the light-emitting diode to go from extinguishing to lighting up, which can improve the afterimage phenomenon when the human eye observes the light-emitting diode, and improve the display accuracy of the light-emitting diode, thereby enhancing the user experience. 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, directly setting the voltage of the first node to the voltage of the charging potential terminal, and also reducing the off time of the current signal of the light-emitting diode.

[0007] In a possible implementation, the charging circuit includes a first switch, wherein a first end of the first switch is coupled to the first node, and a second end of the first switch is coupled to the charging potential end.

[0008] In a possible implementation, the conduction enable signal of the first switch and the enable signal of the light-emitting driving module are in a logical negation relationship. 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 turn 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. When the bias voltage controls the current source to continuously output the driving current during the period when the first control signal controls the gate switch to turn on, the enable signal of the light-emitting driving module is the first control signal. The enable signal of the light-emitting driving module can be the first control signal, and the control end of the first switch is coupled to the control end of the gate switch through a negation circuit. Among them, since when the gate switch is turned on, the charging potential end stops charging the first node, and when the gate switch is turned off, the charging potential end charges the first node, therefore when the first switch and the gate switch use the same type of MOS tube, the first control signal at the control end of the gate switch is opposite in phase to the conduction enable signal of the first switch, therefore the control end of the first switch can be coupled to the control end of the gate switch through a NOT gate circuit, thereby using the first control signal to input the control end of the gate switch, and then input into the control end of the first switch after passing through the NOT gate circuit.

[0009] In a possible implementation, the first switch includes a first MOS tube, one end of the source and drain of the first MOS tube is coupled to the charging potential end, the other end of the source and drain of the first MOS tube is coupled to the first node, and the gate of the first MOS tube receives a conduction enable signal.

[0010] In a possible implementation, the gating switch includes a second MOS transistor, 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 coupled to the first node, and the gate of the gating switch receives the first control signal.

[0011] In a possible implementation, the current source includes a third MOS tube, wherein one end of the source and drain of the third MOS tube is coupled to the ground, the other end of the source and drain of the third MOS tube is coupled to the gate switch, and the gate of the third MOS tube receives the bias voltage.

[0012] In a possible implementation, the current source further includes a fourth MOS tube, wherein one end of the source and drain of the fourth MOS tube is coupled to one end of the source and drain of the third MOS tube, the other end of the source and drain of the fourth MOS tube is coupled to ground, and the gate of the fourth MOS tube receives a bias voltage.

[0013] In a possible implementation, 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 ground.

[0014] In a possible implementation manner, the first control signal is a pulse width modulation (PWM) signal.

[0015] In a second aspect, a micro light emitting diode display panel is provided. The micro light emitting diode display panel includes a plurality of driving circuits distributed in an array, wherein the driving circuit includes a plurality of pixel driving circuits for driving a plurality of pixels; wherein each of the pixels includes at least three sub-pixels, and 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 in the plurality of pixel driving circuits, the second sub-pixel in the pixel is coupled to the second pixel driving circuit in the plurality of pixel driving circuits, and the third sub-pixel in the pixel is coupled to the third pixel driving circuit in the plurality of pixel driving circuits. The pixel driving circuit includes: a light emitting driving module cascaded between the anode of the light emitting diode and a power source, the light emitting driving module includes a gate switch and a current source, the control end of the gate switch receives a first control signal, the control end of the current source receives a bias voltage, and the cathode of the light emitting diode is coupled to the ground; and a charging circuit coupled between the charging potential end and a first node, the first node being a coupling point between the light emitting driving module and the anode of the light emitting diode.

[0016] The charging circuit is used to charge the first node through the charging potential terminal. When the light-emitting driving module stops driving the light-emitting diode, the light-emitting diode goes out, and the charging potential terminal charges the anode (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 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, 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 power supply charges the parasitic capacitance of the first node through the gating switch and the current source until the voltage of the first node is the same as the power supply. Since in this process, the first node starts to charge from a 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 less than the minimum light-emitting voltage of the light-emitting diode, as long as the voltage of the first node is slightly increased from the voltage of the charging potential terminal, that is, the voltage difference between the voltage of the first node and the ground can meet the minimum light-emitting voltage of the light-emitting diode, the light-emitting diode starts to emit light, which reduces 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, and improves 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, thereby shortening the time it takes for the light-emitting diode to go from extinguishing to lighting up, which can improve the afterimage phenomenon when the human eye observes the light-emitting diode, and improve the display accuracy of the light-emitting diode, thereby enhancing the user experience. 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, directly setting the voltage of the first node to the voltage of the charging potential terminal, and also reducing the off time of the current signal of the light-emitting diode.

[0017] In a possible implementation, the charging circuit includes a first switch, wherein a first end of the first switch is coupled to the first node, and a second end of the first switch is coupled to the charging potential end.

[0018] In a possible implementation, the conduction enable signal of the first switch and the enable signal of the light-emitting driving module are in a logical negation relationship. 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 turn 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. When the bias voltage controls the current source to continuously output the driving current during the period when the first control signal controls the gate switch to turn on, the enable signal of the light-emitting driving module is the first control signal. The enable signal of the light-emitting driving module can be the first control signal, and the control end of the first switch is coupled to the control end of the gate switch through a negation circuit. Among them, since when the gate switch is turned on, the charging potential end stops charging the first node, and when the gate switch is turned off, the charging potential end charges the first node, therefore when the first switch and the gate switch use the same type of MOS tube, the first control signal at the control end of the gate switch is opposite in phase to the conduction enable signal of the first switch, therefore the control end of the first switch can be coupled to the control end of the gate switch through a NOT gate circuit, thereby using the first control signal to input the control end of the gate switch, and then input into the control end of the first switch after passing through the NOT gate circuit.

[0019] In a possible implementation, the first switch includes a first MOS tube, one end of the source and drain of the first MOS tube is coupled to the charging potential end, the other end of the source and drain of the first MOS tube is coupled to the first node, and the gate of the first MOS tube receives a conduction enable signal.

[0020] In a possible implementation, the gate switch includes a second MOS tube, one end of the source and drain of the second MOS tube is coupled to a current source, the other end of the source and drain of the second MOS tube is electrically coupled to the anode of the light-emitting diode at the first node, and the gate of the second MOS tube receives a first control signal.

[0021] In a possible implementation, 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 gate of the third MOS transistor receives a bias voltage.

[0022] In a possible implementation, the current source further includes a fourth MOS tube, wherein one end of the source and drain of the fourth MOS tube is coupled to one end of the source and drain of the third MOS tube, the other end of the source and drain of the fourth MOS tube is coupled to the power supply, and the gate of the fourth MOS tube receives the bias voltage.

[0023] In a possible implementation, 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 source.

[0024] In a possible implementation manner, the control signal is a pulse width modulation (PWM) signal.

[0025] In a third aspect, an AMOLED display panel is provided. The display panel includes pixels distributed in an array, wherein the pixels include a pixel driving circuit and a light-emitting diode, wherein 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 to drive the light-emitting diode; the pixel also includes: a charging circuit coupled between the charging potential terminal and a first node, wherein 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 will not be described in detail here.

[0026] In a possible implementation, the voltage difference between the charging potential terminal and the ground is smaller than the minimum light-emitting voltage of the light-emitting diode, and the voltage at the charging potential terminal is smaller than the voltage of the power supply.

[0027] In a possible implementation, the charging circuit includes a third switch, wherein a first end of the third switch is coupled to the first node, and a second end of the third switch is coupled to the charging potential end.

[0028] In a possible implementation, the pixel driving circuit includes a first MOS tube and a second MOS tube, one end of the source and drain of the first MOS tube receives a data voltage, the other end of the source and drain of the first MOS tube is coupled to the gate of the second MOS tube, the gate of the first MOS tube receives a scan signal, one end of the source and drain of the second MOS tube is coupled to a power supply, and the other end of the source and drain of the second MOS tube is coupled to the first node.

[0029] In a possible implementation, the third switch includes a third MOS tube, one end of the source and drain of the third MOS tube is coupled to the charging potential end, and the other end of the source and drain of the third MOS tube is coupled to the first node.

[0030] In a possible implementation, the pixel driving circuit further includes a capacitor, one end of which is coupled to the gate of the second MOS transistor, and the other end of which is coupled to the ground.

[0031] In a fourth aspect, an AMOLED display panel is provided. The display panel includes pixels distributed in an array, wherein the pixels include a pixel driving circuit and a light emitting diode, wherein 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 to drive the light emitting diode; the pixel also includes: a charging circuit coupled between a charging potential terminal and a first node, wherein 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 will not be described in detail here.

[0032] In a possible implementation manner, a voltage difference between the charging potential terminal and the power supply is smaller than a minimum light-emitting voltage of the light-emitting device, and a voltage at the charging potential terminal is smaller than a voltage of the power supply.

[0033] In a possible implementation, the charging circuit includes a third switch, wherein a first end of the third switch is coupled to the first node, and a second end of the third switch is coupled to the charging potential end.

[0034] In a possible implementation, the pixel driving circuit includes a first MOS tube and a second MOS tube, one end of the source and drain of the first MOS tube receives a data voltage, the other end of the source and drain of the first MOS tube is coupled to the gate of the second MOS tube, the gate of the first MOS tube receives a scan signal, one end of the source and drain of the second MOS tube is coupled to a power supply, and the other end of the source and drain of the second MOS tube is coupled to the first node.

[0035] In a possible implementation, the third switch includes a third MOS tube, one end of the source and drain of the third MOS tube is coupled to the charging potential end, and the other end of the source and drain of the third MOS tube is coupled to the first node.

[0036] In a possible implementation, the pixel driving circuit further includes a capacitor, one end of which is coupled to the gate of the second MOS tube, and the other end of which is coupled to the power supply.

[0037] In a fifth aspect, a pixel driving circuit is provided. 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, the control end of the gate switch receives a first control signal, the control end of the current source receives a bias voltage, and the anode of the light-emitting diode is coupled to the power supply; and a charging circuit coupled between the charging potential end and a first node, the first node being a coupling point between the light-emitting driving module and the cathode of the light-emitting diode.

[0038] In a possible implementation, the charging circuit includes a first switch, wherein a first end of the first switch is coupled to the first node, and a second end of the first switch is coupled to the charging potential end.

[0039] In a possible implementation manner, the conduction enable signal of the first switch and the enable signal of the light-emitting driving module are in a logical negation relationship.

[0040] In a possible implementation, the first switch includes a first MOS tube, one end of the source and drain of the first MOS tube is coupled to the charging potential end, the other end of the source and drain of the first MOS tube is coupled to the first node, and the gate of the first MOS tube receives a conduction enable signal.

[0041] The pixel driving circuit of the fifth aspect has similar effects to the Micro LED display panel of the first aspect, and will not be described in detail here.

[0042] In a sixth aspect, a pixel driving circuit is provided. The pixel driving circuit includes: a light-emitting driving module cascaded between an anode of a light-emitting diode and a power supply, the light-emitting driving module includes a gate switch and a current source, a control end of the gate switch receives a first control signal, a control end of the current source receives a bias voltage, and a cathode of the light-emitting diode is coupled to ground; and a charging circuit coupled between a charging potential end and a first node, the first node being a coupling point between the light-emitting driving module and the anode of the light-emitting diode.

[0043] In a possible implementation, the charging circuit includes a first switch, wherein a first end of the first switch is coupled to an anode of the light emitting diode, and a second end of the first switch is coupled to a charging potential end.

[0044] In a possible implementation manner, the conduction enable signal of the first switch and the enable signal of the light-emitting driving module are in a logical negation relationship.

[0045] In a possible implementation, the first switch includes a first MOS tube, one end of the source and drain of the first MOS tube is coupled to the charging potential end, the other end of the source and drain of the first MOS tube is coupled to the first node, and the gate of the first MOS tube receives a conduction enable signal.

[0046] The pixel driving circuit of the sixth aspect has similar effects to the Micro LED display panel of the second aspect, and will not be described in detail here.

[0047] In the seventh aspect, a terminal device includes a back cover, a middle frame, and the Micro LED display panel as described in the first aspect or the second aspect, the back cover and the Micro LED display panel are arranged relative to each other and connected by a frame.

[0048] In an eighth aspect, a terminal device includes a back cover, a middle frame, and the AMOLED LED display panel as described in the third aspect or the fourth aspect, wherein the back cover and the Micro LED display panel are arranged relative to each other and connected by a frame.

[0049] The terminal device in the seventh aspect or the eighth aspect has similar effects to the Micro LED display panel in the first aspect or the second aspect, and will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 A schematic diagram of the structure of a terminal device provided in an embodiment of the present application;

[0051] Figure 2 A schematic diagram of the structure of a terminal device provided in another embodiment of the present application;

[0052] Figure 3 A schematic diagram of the structure of a display panel provided in an embodiment of the present application;

[0053] Figure 4 A schematic diagram of a connection method between a pixel driving circuit and an LED provided in an embodiment of the present application;

[0054] Figure 5 A schematic diagram of the structure of a pixel driving circuit provided in an embodiment of the present application;

[0055] Figure 6 A schematic diagram of the structure of a display panel provided in another embodiment of the present application;

[0056] Figure 7 A schematic diagram of the structure of a driving circuit provided in an embodiment of the present application;

[0057] Figure 8 A schematic structural diagram of a pixel driving circuit provided in another embodiment of the present application;

[0058] Fig. 9 A schematic diagram of a waveform of a node signal of a pixel driving circuit provided in an embodiment of the present application;

[0059] Fig.10 A schematic structural diagram of a pixel driving circuit provided in yet another embodiment of the present application;

[0060] Fig.11 A schematic diagram of a waveform of a node signal of a pixel driving circuit provided in yet another embodiment of the present application;

[0061] Fig.12 A schematic structural diagram of a pixel driving circuit provided in another embodiment of the present application;

[0062] Fig.13 A schematic structural diagram of a pixel driving circuit provided in yet another embodiment of the present application;

[0063] Fig.14A schematic structural diagram of a pixel driving circuit provided in yet another embodiment of the present application;

[0064] Fig.15 A schematic diagram of a waveform of a node signal of a pixel driving circuit provided in yet another embodiment of the present application;

[0065] Fig.16 A schematic structural diagram of a pixel driving circuit provided in another embodiment of the present application;

[0066] Fig.17 A schematic structural diagram of a pixel driving circuit provided in yet another embodiment of the present application;

[0067] Fig.18 A schematic structural diagram of a pixel driving circuit provided in yet another embodiment of the present application;

[0068] Fig.19 A schematic structural diagram of a pixel driving circuit provided in another embodiment of the present application. DETAILED DESCRIPTION

[0069] The making and use of various embodiments will be discussed in detail below. However, it should be understood that many applicable inventive concepts provided by this application can be implemented in a variety of specific environments. The specific embodiments discussed are merely illustrative of specific ways to implement and use this description and technology, and do not limit the scope of this application. Unless otherwise defined, all scientific and technological terms used herein have the same meaning as those known to those of ordinary skill in the art.

[0070] In the embodiments of the present application, "at least one" refers to one or more, and "plurality" refers to two or more. "And / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone, where A and B can be singular or plural. The character " / " generally indicates that the associated objects before and after are in an "or" relationship. "At least one of the following" or its similar expressions refers to any combination of these items, including any combination of single items or plural items. For example, at least one of a, b or c can 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 single or multiple. In the embodiments of the present application, the terms "first", "second", etc. are used only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. In addition, the term "coupling" can be a way of achieving electrical connection for signal transmission. "Coupling" can be a direct electrical connection or an indirect electrical connection through an intermediate medium. For example, a connection achieved through a resistor, an inductor, or other electrical components. When used to describe a three-terminal switch element, the "first end" and the "second end" can refer to the connection ends of the three-terminal switch element, respectively, and the "control end" can refer to the control end of the three-terminal switch element. For example, for a MOS (metal-oxide-semiconductor) tube, the control end can refer to the gate of the MOS tube, the first end can refer to the source of the MOS tube, and the second end can refer to the drain of the MOS tube, or the first end can refer to the drain of the MOS tube, and the second end can refer to the source of the MOS tube.

[0071] An embodiment of the present application provides a terminal device, which may be an electronic device with a display screen, such as a mobile phone, a tablet computer, a laptop computer, an ultra-mobile personal computer (UMPC), a netbook, a personal digital assistant (PDA), a vehicle-mounted mobile device, etc.

[0072] Figure 1 The following is a schematic diagram of an exemplary terminal device architecture provided in an embodiment of the present application. Figure 1 As shown, 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 Figure 1The structure of the terminal device shown in the figure does not constitute a limitation on the terminal device, and the terminal device may include, for example Figure 1 More or fewer components may be shown, or they may be combined as shown. Figure 1 Some of the components shown may be combined with Figure 1 The components shown are arranged differently.

[0073] The processor 11 is the control center of the terminal device. It uses various interfaces and lines to connect various parts of the entire terminal device. By running or executing software programs and / or modules stored in the memory 14 and calling data stored in the memory 14, it executes various functions of the terminal device and processes data, thereby monitoring the terminal device 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, and the modem processor mainly processes wireless communications. It is understandable that the above-mentioned modem processor may not be integrated into the processor 11.

[0074] The RF circuit 12 can be used for receiving and sending signals during information transmission or calls. In particular, after receiving the downlink information of the base station, it is sent to the processor 11 for processing; in addition, the uplink data is sent to the base station. Generally, the RF circuit includes but is not limited to an antenna, at least one amplifier, a transceiver, a coupler, a low noise amplifier (LNA), a duplexer, etc. In addition, the RF circuit 12 can also communicate with the network and other devices through wireless communication. Wireless communication can use any communication standard or protocol, including but not limited to the global system of mobile communication (GSM), general packet radio service (GPRS), code division multiple access (CDMA), wideband code division multiple access (WCDMA), long term evolution (LTE), email, short messaging service (SMS), etc.

[0075] The terminal device includes a power source 13 (such as a battery) for supplying power to various components. Optionally, the power source can be logically connected to the processor 11 through a power management system, so that the power management system can manage functions such as charging, discharging, and power consumption.

[0076] The memory 14 can be used to store software programs and modules. 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 can mainly include a program storage area and a data storage area, wherein the program storage area can store an operating system, an application required for at least one function (such as a sound playback function, an image playback function, etc.), etc.; the data storage area can store data created according to the use of the mobile phone (such as audio data, image data, phone book, etc.), etc. In addition, the memory 14 can include a high-speed random access memory, and can also include a non-volatile memory, such as at least one disk storage device, a flash memory device, or other volatile solid-state storage devices.

[0077] The input unit 15 can be used to receive input digital or character information, and generate key signal input related to the user settings 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 operation on or near the touch screen (such as the user's operation on or near the touch screen 151 using any suitable object or accessory such as a finger, stylus, etc.), and drive the corresponding connected terminal device according to a pre-set program. 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 direction, 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 the touch point coordinates, and then sends it to the processor 11, and can receive and execute the command sent by the processor 11. In addition, the touch screen 151 can be implemented in various types such as resistive, capacitive, infrared and surface acoustic wave. Other input devices 152 may include, but are not limited to, one or more of a physical keyboard, function keys (such as a volume control button, a power switch button, etc.), a trackball, a mouse, a joystick, and the like.

[0078] The display device 16 can 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. In the present application, the display panel 161 may be an AMOLED display panel or a Micro LED display panel. Furthermore, the touch screen 151 may cover the display panel 161. When the touch screen 151 detects a touch operation on or near the touch screen 151, it is transmitted to the processor 11 to determine the type of touch event. Then, the processor 11 provides a corresponding visual output on the display panel 161 according to the type of touch event. Although in Figure 1In the embodiment, the touch screen 151 and the display panel 161 are used as two independent components to implement the input and output functions of the device. However, in some embodiments, the touch screen 151 and the display panel 161 can be integrated to implement the input and output functions of the device.

[0079] 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 electrical signal converted from the received audio data to the speaker 171, which is converted into a sound signal for output; on the other hand, the microphone 172 converts the collected sound signal into an electrical signal, which is received by the audio circuit 17 and converted into audio data, and then outputs the audio data to the RF circuit 12 to be sent to, for example, another terminal device, or outputs the audio data to the memory 14 for further processing.

[0080] Optional, such as Figure 1 The terminal device shown may also include various sensors, such as a gyroscope sensor, a hygrometer sensor, an infrared sensor, a magnetometer sensor, etc., which will not be described in detail here. Figure 1 The terminal device shown may also include a wireless fidelity (WiFi) module, a Bluetooth module, etc., which will not be described in detail here.

[0081] It is understandable that in the embodiment of the present application, the terminal device can perform some or all of the steps in the embodiment of the present application, and these steps or operations are only examples. The embodiment of the present application can also perform other operations or variations of various operations. In addition, each step can be performed in a different order presented in the embodiment of the present application, and it is possible not to perform all the operations in the embodiment of the present application. The various embodiments of the present application can be implemented separately or in any combination, and the present application is not limited to this.

[0082] The present application embodiment does not impose any special restrictions on the specific form of the terminal device 01. For the convenience of description, the following description is based on the example of a mobile phone as the terminal device 01. Figure 2As shown, it mainly includes a display panel 21, a middle frame 22 and a rear shell 23. The rear shell 23 and the display panel 21 are arranged relative to each other and connected through the middle frame 22. In an embodiment of the present application, the display panel 21 is an organic light-emitting diode (OLED), an active-matrix organic light-emitting diode or an active-matrix organic light-emitting diode (AMOLED), a flexible light-emitting diode (FLED), Miniled, MicroLed, Micro-oLed, quantum dot light-emitting diodes (QLED), a micro light-emitting diode (Micro LED) and the like display panel.

[0083] 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. Figure 3 As shown, 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, the plurality of pixels 31 are described in this application by arranging in a matrix form as an example.

[0084] It should be noted that in the embodiments of the present application, Figure 3 The pixels 31 arranged in a row along the horizontal direction X are called the same row of pixels, and the pixels 31 arranged in a row along the vertical direction Y are called the same column of pixels. In the embodiment of the present application, the display panel 30 may be an AMOLED display panel. The AMOLED display panel can realize self-luminescence. In this case, the pixels 31 in the AA area 100 are provided with the following Figure 4 The LED shown in FIG. 1 and the pixel driving circuit 301 for driving the LED to emit light.

[0085] In addition, the above device may further include a display driving circuit for driving the display panel 30 to display, and the display driving circuit may be coupled to the display panel 30. Exemplarily, the display driving circuit may be a display driver integrated circuit (DDIC). Figure 3As shown, DDIC 32 is arranged in the non-display area 101 of the display panel 30. The pixel driving circuit 301 in the same column of pixels 31 is coupled to DDIC 32 via the same data line (DL). In other embodiments of the present application, the DDIC 32 can also be arranged independently of the display panel 30. The terminal device also includes a printed circuit board (PCB) and a system on chip (SoC) installed on the PCB. The SoC can be provided with an application processor (AP), which can be Figure 1 Processor 11 in. Figure 3 The DDIC 32 in the embodiment is coupled to the SoC via a flexible printed circuit (FPC).

[0086] In this way, the display data output by the SoC is converted into a data voltage Vdata after passing through the DDIC 32 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 to drive the LED in the pixel 31 to emit light. Specifically, Figure 5 As shown, a schematic diagram of a pixel driving circuit is provided, which includes a first MOS tube M1 and a second MOS tube M2, wherein the gate g of M1 is coupled to the scan line SCAN, 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 (wherein the anode of the LED is coupled to VDD, and the cathode is coupled to the drain of M2), the source s of M2 is coupled to the ground VEE, and the coupling capacitor Cst is between the source s and the gate g of M2. In this way, usually when the pixel is selected by the scan signal of the scan line SCAN, the data voltage (Vdata) is applied to the LED through M2, and M2 generates a current (Idata) flowing through the LED to emit light. The above is explained by taking the LED common anode connection mode as an example, wherein M2 is an NMOS tube. When a PMOS tube is used, in order to ensure the stability of the source voltage of M2 and avoid the source voltage floating problem, 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 between 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 LED realizes a common cathode connection mode. Figure 5 This is only an example of a pixel driving circuit. Those skilled in the art can also Figure 5 The pixel circuit shown is replaced with other forms of pixel driving circuits.

[0087] The pixel driving circuit 301, LED and data line DL in each pixel 31 in the display panel 30 can be made on a substrate. The substrate can be made of a flexible resin material. In this case, the AMOLED display panel can be used as a folding display screen. Alternatively, the substrate in the AMOLED display panel can also be made of a hard material, such as glass. In this case, the AMOLED display panel is a hard display screen.

[0088] In Micro LED display panels, Figure 6 As shown, it generally includes an array of pixels 61, each pixel including at least three sub-pixels. Figure 6 In the example, a pixel 61 includes three sub-pixels R (red), G (green) and B (blue), and each sub-pixel includes an LED. The diodes in the same pixel 61 emit light of different colors. Figure 6 As shown, it also includes: a driving circuit 62 arranged in an array, the driving circuit 62 includes a plurality of pixel driving circuits, and four pixels are distributed around the driving circuit 62; the first sub-pixel in the pixel 61 is connected to the first pixel driving circuit in the plurality of pixel driving circuits, the second sub-pixel in the pixel 61 is connected to the second pixel driving circuit in the plurality of pixel driving circuits, and the third sub-pixel in the pixel is connected to the third pixel driving circuit in the plurality of pixel driving circuits. A plurality of pixels are distributed around any driving circuit 62 (wherein, Figure 6 The driving circuit 62 includes a plurality of pixel driving circuits, each of which is coupled to an LED to drive the coupled LED. Specifically, Figure 7 As shown, the driving circuit 62 includes an analog circuit part 622 and a digital circuit part 621. For a pixel composed of RGB three-primary color sub-pixels, the analog circuit part includes 12 pixel driving circuits. Figure 8 As shown, the pixel driving circuit is usually composed of a current source 81 and a gate switch 82. The current source 81 is coupled to the Micro LED ( Figure 8D1 in the figure), each pixel driving circuit supplies power to a sub-pixel Micro LED. The external timing control chip controls the digital circuit part 621 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. The control signal is used to select the output of the current source 81 (equivalent to the DDIC in the AMOLED display panel selecting the pixel through the scanning line), and the bias voltage is used to control the output power of the current source 81 (equivalent to the use of data voltage (Vdata) in the AMOLED display panel to drive the transistor to generate current (Idata)), thereby realizing the light emission control of the corresponding Micro LED. Figure 8 As shown, a schematic diagram of a pixel driving circuit is provided, including MOS tubes M1, M2 and M3, wherein M1 is used as a selection switch and is connected in series between a current source 81 and a Micro LED, and the current source 81 includes two MOS tubes M2 and M3 connected in series, wherein the gate of M1 is used to receive a control signal, 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, the cathode is coupled to the drain of M1, and the power supply VDD provides a high level VH). The gate of M2 is coupled to the gate of M3 and is used to receive a bias voltage, the source of M2 is coupled to the drain of M3, and the source of M3 is coupled to the ground VEE (the ground VEE provides a low level VL). In addition, the above current source is described by taking the MOS tubes M2 and M3 connected in series as an example. In some examples, the current source may include only one MOS tube M2, in which case the source of M2 is directly coupled to the ground VEE; of course, the current source may also include 3 or more MOS tubes connected in series. The above is described by taking the common anode connection method of LED as an example, Figure 8 M1, M2 and M3 are NMOS tubes. When PMOS tubes are used, D1 needs to be connected in a common cathode mode. Figure 8 This is only an example of a pixel driving circuit. Those skilled in the art can also Figure 8 The pixel circuit shown is replaced with other forms of pixel driving circuits.

[0089] Whether it is the above-mentioned AMOLED display panel solution or the Micro LED display panel solution, refer to Figure 5 , Figure 8 As shown in Figure 1, due to the cathode of the LED ( Figure 5 Node X in Figure 8 There is parasitic capacitance at node A in Figure 8Cp in the figure 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). During each LED switching process, the pixel driving circuit must first charge and discharge node A (or node X), resulting in a certain amount of time required for the LED switching process. This limits the speed of LED switching. 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. Figure 8 , Fig. 9 For illustration, the pixel driving circuit uses a current source 81 to provide a driving current for the LED. Under the control of the PWM signal, M1 controls the opening or closing of the LED. Fig. 9The timing curve of the PWM signal shown in FIG. 1 shows that the NMOS tube is usually 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 turned off, the voltage VA of node A becomes higher than VH (node ​​A is floating and equal to the level of VDD), the current (ID1) of the LED is 0, and the charge is stored on the parasitic capacitor Cp of node A; when the PWM signal becomes high, M1 is turned on, and node A is first discharged through M1, M2, and M3. When the voltage at point A decreases, the current flows through the LED. For example, referring to the voltage curve VA of node A, when the voltage at node A drops to VA0, VDD-VA0 is equal to the turn-on voltage of the LED. Then, as the voltage at node A continues to drop, ID1 gradually increases. When the PWM signal becomes low, M1 is turned off, and VDD charges the parasitic capacitor Cp again until ID1 becomes 0 (at this time, the voltage of the parasitic capacitor is greater than VA0), and then the LED can be turned off. In this way, when the LED is turned on, node A needs to be discharged from VH to VL. At the beginning of discharge, ID1 is completely absorbed by Cp until the voltage of node A drops below VA0, and then current starts to flow through the LED. When the LED is working normally and stably, the voltage of node A is VL. Due to the parasitic capacitance of node A, when the LED is turned off, VDD charges node A, and the voltage of node A slowly increases until it reaches VH. That is, node A needs to be discharged first each time the LED is turned on; by comparing the ideal current waveform of ID1 and the actual current waveform, it can be seen that when the LED is turned off, node A is charged to a high level HV, resulting in a discharge delay time of T1 (where T1 is the time for node A to discharge from VH to VA0) during the LED turn-off process, and a charge delay time of T2 (where T2 is the time for node A to charge from VEE to VA0) during the LED turn-off process. In this way, there is a certain delay in the opening and closing of the LED, which 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, using PWM signal to control M1 to turn the LED on or off requires a higher switching speed. The existing technology limits the frequency of refreshing the LED, and the current technology cannot meet the demand.

[0090] In view of the above problems, an embodiment of the present application provides a pixel driving circuit 1000, such as Fig.10As shown, it includes: 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 to both ends of 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 gating switch Ks and a current source Is, wherein the control end of the gating switch Ks receives a first control signal. In one embodiment, the first control signal may be a PWM signal, and the control end of the current source Is receives a bias voltage.

[0091] 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 voltage of the power supply VDD. The pixel driving circuit 1000 may also include a capacitor Cst electrically coupled between the control terminal of the current source Is and the ground VEE.

[0092] When the voltage of the node A is lower than a certain threshold VA0, the voltage VDD-VA0 applied to the light-emitting diode D1 is greater than the minimum light-emitting voltage of D1, and the light-emitting diode D1 is turned on. The threshold is mainly related to the forward conduction voltage (i.e., the minimum light-emitting voltage) of the light-emitting diode D1. For example, for a silicon (Si) tube, its forward conduction voltage is about 0.7V, while that of a germanium (Ge) tube is about 0.3V.

[0093] In some embodiments, Fig.10 As shown, 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 other end of the source and drain of M3 is coupled to the current source Is (that is, the other end of the source and drain of M3 is coupled to one end of the source and drain of M2), and the other end of the source and drain of M2 is coupled to the cathode of the light-emitting diode D1 at the first node A, the gate of M2 receives the first control signal, and the gate of M3 receives the bias voltage.

[0094] like Fig.10As shown, the charging circuit 1001 includes a first switch M1, wherein the first end of the first switch M1 is coupled to the first node A, and the second end of the first switch M1 is coupled to the charging potential terminal VA1. In one embodiment, the above-mentioned M1 is a first MOS tube, 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 receives a conduction enable signal. M1 is in an on or off state under the control of the conduction enable signal. When M1 is in the on state, the charging circuit charges the first node A through the charging potential terminal VA1, and when M1 is in the off state, the charging circuit stops charging the first node A.

[0095] The conduction enable signal of M1 and the enable signal of the light-emitting driver module 1002 are in a logical negation relationship. The enable signal of the light-emitting driver 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 turn on, and the bias voltage controls the current source to output the driving current, the light-emitting driver 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 driver module stops driving the light-emitting diode. When the bias voltage controls the current source to continuously output the driving current during the period when the first control signal controls the gate switch to turn on, the enable signal of the light-emitting driver module is the first control signal. The enable signal of the light-emitting driver module can be the first control signal, and the control end of the first switch is coupled to the control end of the gate switch through a negation circuit.

[0096] In the working state, the M2 is turned on or off under the control of the received first control signal, and the M3 is kept on under the control of the received bias voltage Vbias. When the first control signal controls M2 to be turned off, the voltage of node A (i.e., 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 node A (the parasitic capacitance Cp is mainly the capacitance generated by the drain of M1, the cathode of D1, and the connection between the cathode of D1 and the drain of M1, Fig.10(not shown) will accumulate charge. When the first control signal controls M2 to turn on, the parasitic capacitor Cp is discharged through M2 and M3. When the voltage of node A is lower than a certain threshold VA0 (depending on the characteristics of the light-emitting diode D1), the light-emitting diode D1 is turned on. In the embodiment of the present application, after M2 is disconnected, the charging circuit 1001 can charge the parasitic capacitor of node A through the charging potential terminal VA1 until the voltage of node A is equal to the voltage of the charging potential terminal VA1, and the difference between the voltage of the charging potential terminal VA1 and the voltage of the power supply VDD is less than the minimum light-emitting voltage (VDD-VA0) of the light-emitting diode D1, and the voltage of the charging potential terminal VA1 is less than the voltage of the power supply VDD, so the light-emitting diode D1 will not emit light. Since the voltage of the charging potential terminal VA1 is greater than VA0, the leakage current of M2 can also be guaranteed to be low. When M2 is turned on, the charging circuit 1001 stops charging the first node A, and the charge in the parasitic capacitor of the first node A is discharged through M2 and M3 until the voltage of the first node A is the same as the ground VEE. Since in 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 less 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, the light-emitting diode D1 starts to emit light, which reduces 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, and improves 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, thereby shortening the time it takes for the light-emitting diode to go from extinguishing to lighting, which can improve the afterimage phenomenon when the human eye observes the light-emitting diode, and improve the display accuracy of the light-emitting diode, thereby enhancing the user experience. 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 directly sets the voltage of the node A to VA1, which also reduces the turn-off time of the current signal of the light emitting diode.

[0097] Combination Fig.10 and Fig.11 The working principle of the pixel driving circuit is described as follows: In a charge and discharge cycle, Fig.11 (a) shows a waveform diagram of a PWM signal in a conventional pixel driving circuit, a voltage waveform diagram of a node A, and a waveform diagram of a current ID1 in a light-emitting diode D1; Fig.11(b) shows the waveform of the PWM signal in the optimized pixel driving circuit, the voltage waveform of node A, and the waveform of the current ID1 in the light-emitting diode D1. The present application embodiment is described by taking the selection signal as a PWM signal and M1, M2 and M3 as NMOS tubes as an example.

[0098] 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 the off state at this time. Therefore, the voltage of node A (VH) is higher than the threshold voltage VA0, and the current ID1 in the light-emitting diode D1 is 0, and the light-emitting diode D1 is in the off state. At t1, the PWM signal changes from a low level to a high level, and M2 switches from the off state to the on state. Since both M2 and M3 are in the on state, the voltage of node A will drop rapidly to 0 (VL) in an ideal state, and the current ID1 in the light-emitting diode D1 will increase rapidly to a larger value, such as Fig.11 The "ideal current waveform" curve in (a) is shown in the figure. In actual work, Fig.11 As shown in the "actual current waveform" curve in (a), in the conventional circuit of the prior art, due to the presence of parasitic capacitance Cp at node A, when M2 is in the off state, VDD will charge the voltage of node A to VH. When M2 switches 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 threshold voltage VA0. At t2, the current ID1 in the light-emitting diode D1 begins to increase to the maximum value, and then maintains the maximum value until t3. At t3, the PWM signal changes from a high level to a low level, the current ID1 in the light-emitting diode D1 begins to decrease, and Cp at node A begins to charge until the voltage at node A is higher than the threshold voltage VA0, and the current ID1 becomes 0 (i.e., at t4). Correspondingly, as Fig.11 As shown in (a), due to the slow discharge, after M2 is turned on, node A in the conventional circuit of the prior art needs T1 (t2-t1) time to complete signal establishment, and after M2 is turned off, it takes T2 (t4-t3) time to complete signal shutdown. Fig.11 From (a), we can see that from t1 to t2, the parasitic capacitor Cp is in the discharge process, which causes the light-emitting diode D1 to take a long time to turn from off to on. From t3 to t4, the parasitic capacitor Cp is in the charging process, which causes the light-emitting diode D1 to take a long time to turn from on to off. The larger the parasitic capacitor Cp, the longer the time from t1 to t2 and the time from t3 to t4, and the easier it is for the human eye to observe the afterimage phenomenon, which affects the user experience.

[0099] The charging circuit 1001 coupled to the node A in the pixel driving circuit provided in 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, since the voltage difference between VA1 and VDD is less than the minimum light-emitting voltage of the light-emitting diode D1 (that is, VA1 is greater than VA0), Fig.11 As shown in (b), from time 0 to t1, the current ID1 is 0, D1 does not emit light, from t1 to t2, M2 is turned on, and the parasitic capacitor Cp starts to discharge directly from VA1. Compared with the traditional pixel driving circuit, Fig.11 In (a) of FIG. 1 , the voltage of Cp at time t1 to t2 needs to be discharged from VDD to VA0 before current flows through D1. In the optimized solution, Fig.11 In (b) of FIG. 1 , the voltage of Cp at time t1 to t2 only needs to discharge from VA1 to VA0, and current will flow through D1, reducing the voltage change at node A, that is, the range of ΔVA changes from VH to VL ( Fig.11 (a)) in becomes VA1~VL( Fig.11 (b) in the above example, Fig.11 The "actual current waveform" shown in (b) is closer to the "ideal current waveform", thereby accelerating the signal establishment time of the light-emitting diode D1 and increasing the switching frequency of the light-emitting diode D1, thereby achieving the purpose of eliminating residual images, improving display accuracy, and improving user experience. Fig.11 In (a), the voltage of Cp at time t3 to t4 needs to be charged from VEE to VA0, so that the current ID1 of D1 will be zero. In the optimized solution, Fig.11 In (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.

[0100] The current source further includes a fourth MOS tube, wherein one end of the source and drain of the fourth MOS tube is coupled to one end of the source and drain of the third MOS tube, the other end of the source and drain of the fourth MOS tube is coupled to the ground, and the gate of the fourth MOS tube receives a bias voltage. Fig.12 As shown, a pixel driving circuit is provided, M4 is coupled between the source of M3 and the ground VEE, when M4 is an NMOS tube, the source of M4 is coupled to the ground VEE, the drain of M4 is coupled to the source of M2, and the gate of M4 is coupled to the gate of M2. M2 and M4 form a current source, and a similar current source can also include more MOS tubes connected in series.

[0101] like Fig.13As shown, a pixel driving circuit is provided, wherein the control end of M1 is coupled to the control end of M2 through a NOT gate circuit 1003. Wherein, since when M2 is turned on, the charging potential end stops charging the first node A, and when M2 is turned off, the charging potential end VA1 charges the first node A, therefore, when M2 and M1 use the same type of MOS tube, the conduction enable signal of the control end of M1 is opposite in phase to the first control signal of the control end of M2, and therefore the control end of M2 can be coupled to the control end of M1 through the NOT gate circuit 1003, so that the first control signal is input to the control end of M2, and then input to the control end of M1 after passing through the NOT gate circuit 1002.

[0102] The above mainly describes the pixel driving circuit by taking the common anode connection mode of the light-emitting diodes in the Micro LED display panel as an example. Fig.14 A method for connecting a common cathode of a light emitting diode is also provided. Fig.14 As shown, the pixel driving circuit 2000 includes: a light-emitting driving module 2002 cascaded between the anode of the light-emitting diode D1 and the power supply VDD, the light-emitting driving module 2002 includes a selection switch Ks and a current source Is, the control end of the selection switch Ks receives a first control signal, in one embodiment, the first control signal can be a PWM signal, the control end of the current source Is receives a bias voltage Vbias, and the cathode of the light-emitting diode D1 is coupled to the ground VEE; and a charging circuit 2001, coupled between the charging potential 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.

[0103] 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 also include a capacitor Cst electrically coupled between the control terminal of the current source Is and the power supply VDD.

[0104] In some embodiments, Fig.14 As shown, 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 other end of the source and drain of M3 is coupled to the current source Is (that is, the other end of the source and drain of M3 is coupled to one end of the source and drain of M2), the other end of the source and drain of M2 is coupled to the anode of the light-emitting diode D1 at the first node A, the gate of M2 receives the first control signal, and the gate of M3 receives the bias voltage.

[0105] like Fig.14As shown, the charging circuit 2001 includes a first switch M1, wherein the first end of M1 is coupled to the first node A, and the second end of M1 is coupled to the charging potential terminal VA1. In one embodiment, the above-mentioned M1 is a first MOS tube, 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 a conduction enable signal. M1 is in an on or off state under the control of the conduction enable signal. When M1 is in the on state, the charging circuit charges the first node A through the charging potential terminal VA1, and when M1 is in the off state, the charging circuit stops charging the first node A.

[0106] The conduction enable signal of M1 and the enable signal of the light-emitting driver module 2002 are in a logical negation relationship. The enable signal of the light-emitting driver 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 turn on, and the bias voltage controls the current source to output the driving current, the light-emitting driver 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 driver module stops driving the light-emitting diode. When the bias voltage controls the current source to continuously output the driving current during the period when the first control signal controls the gate switch to turn on, the enable signal of the light-emitting driver module is the first control signal. The enable signal of the light-emitting driver module can be the first control signal, and the control end of the first switch is coupled to the control end of the gate switch through a negation circuit.

[0107] In the working state, the M2 is turned on or off under the control of the received first control signal, and the M3 is kept on under the control of the received bias voltage Vbias. When the first control signal controls M2 to be turned off, the voltage of node A (i.e., 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 extinguished, and the charging potential terminal VA1 will charge the parasitic capacitance Cp on node A (the parasitic capacitance Cp is mainly the capacitance generated by the drain of M1, the anode of D1, and the connection between the anode of D1 and the drain of M1, Fig.15(not shown) until the voltage of the first node is equal to the voltage of the charging potential terminal VA1, and the voltage difference between the voltage of the charging potential terminal VA1 and the ground VEE is 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 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. Since in this process, the first node A starts to charge 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 less than the minimum light-emitting voltage of the light-emitting diode, as long as the first node A starts to increase 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 ground VEE can meet the minimum light-emitting voltage of the light-emitting diode, the light-emitting diode starts to emit light, which reduces 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, and improves 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 from the light-emitting diode to the light-emitting diode is shortened, which can improve the afterimage phenomenon when the human eye observes the light-emitting diode, and improve the display accuracy of the light-emitting diode and enhance the user experience. In addition, when M2 changes from the on state to the off state, the charging circuit directly charges node A through the charging potential terminal VA1, and directly sets the voltage of node A to VA1, which also reduces the off time of the current signal of the light-emitting diode.

[0108] Combination Fig.14 and Fig.15 The working principle of the pixel driving circuit is described in detail as follows: In a charge and discharge cycle, Fig.15 (a) shows a waveform diagram of a PWM signal in a conventional pixel driving circuit, a voltage waveform diagram of a node A, and a waveform diagram of a current ID1 in a light-emitting diode D1; Fig.15 (b) shows the waveform of the PWM signal in the optimized pixel driving circuit, the voltage waveform of node A, and the waveform of the current ID1 in the light-emitting diode D1. The present application embodiment is described by taking the selection signal as a PWM signal and M1, M2 and M3 as PMOS tubes as an example.

[0109] When the pixel driving circuit is working normally, M3 is turned on. 1At the moment, the PWM signal is at a high level, and M2 is in the off state. Therefore, the voltage (VL) of node A is lower than the threshold voltage VA0, and the current ID1 in the light-emitting diode D1 is 0, and the light-emitting diode D1 is in the off state. At the moment t1, the PWM signal changes from a high level to a low level, and the first switch M1 switches from the off state to the on state. Since both M2 and M3 are in the on state, the voltage of node A will rise rapidly to VH in an ideal state, and the current ID1 in the light-emitting diode D1 will rapidly increase to a larger value, such as Fig.15 The "ideal current waveform" curve in (a) is shown in the figure. In actual work, Fig.15 As shown in the "actual current waveform" curve in (a), in the conventional circuit of the prior art, due to the presence of parasitic capacitance Cp at node A, when M2 is in the off state, the voltage at node A is 0 (VL). When M2 switches from the off state to the on state, the parasitic capacitance Cp first needs to be charged through M2 and M3 from time t1 to t2 until the voltage at node A is higher than the threshold voltage VA0. At time t2, the current ID1 in the light-emitting diode D1 begins to increase until it reaches the 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 Cp at node A begins to discharge until the voltage at node A is lower than the threshold voltage VA0, and the current ID1 becomes 0 (i.e., at time t4). Correspondingly, as Fig.15 As shown in (a), due to the slow charging and discharging, after the first switch M1 is turned on, node A in the conventional circuit of the prior art needs T1 (t2-t1) time to complete the signal establishment, and after M2 is turned off, it takes T2 (t4-t3) time to complete the signal shutdown. Fig.15 From (a), we can see that from t1 to t2, the parasitic capacitor Cp is in the charging process, which causes the light-emitting diode D1 to take a long time to turn from off to on. From t3 to t4, the parasitic capacitor Cp is in the discharging process, which causes the light-emitting diode D1 to take a long time to turn from on to off. The larger the parasitic capacitor Cp, the longer the time from t1 to t2 and the time from t3 to t4, and the easier it is for the human eye to observe the afterimage phenomenon, which affects the user experience.

[0110] The charging circuit 2001 coupled to the node A in the pixel driving circuit provided in 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 less than the minimum light-emitting voltage of the light-emitting diode D1, that is, (VA1 is less than VA0), Fig.15 As shown in (b), 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 capacitor Cp is charged directly from VA1. Compared with the traditional pixel driving circuit, Fig.15 In (a) of FIG. 1 , the voltage of Cp from t1 to t2 needs to be charged from VL to VA0 before current can flow through D1. In the optimized solution, Fig.15 In (b) of FIG. 1 , the voltage of Cp from time t1 to t2 only needs to be charged from VA1 to VA0, and current will flow through D1, reducing the voltage change of node A, that is, the range of ΔVA changes from VL to VH ( Fig.15 (a)) in becomes VA1~VH( Fig.15 (b) in the above example, Fig.15 The "actual current waveform" shown in (b) is closer to the "ideal current waveform", thereby accelerating the signal establishment time of the light-emitting diode D1 and increasing the switching frequency of the light-emitting diode D1, thereby achieving the purpose of eliminating residual images, improving display accuracy, and improving user experience. Fig.15 In (a) of FIG. 1 , the voltage of Cp at time t3 to t4 needs to be discharged from VH to VA0, so that the current ID1 of D1 will be zero. In the optimized solution, Fig.15 In (b), from t3 to t4, the voltage of Cp is directly set to VA1. Since VA1 is less than VA0, the current of D1 can be quickly turned off.

[0111] The current source further includes a fourth MOS tube, wherein one end of the source and drain of the fourth MOS tube is coupled to one end of the source and drain of the third MOS tube, the other end of the source and drain of the fourth MOS tube is coupled to the power supply, and the gate of the fourth MOS tube receives a bias voltage. Fig.16 As shown, a pixel driving circuit is provided, wherein M4 is coupled between the source of M3 and the power supply VDD, and when M4 is a PMOS tube, the source of M4 is coupled to the power supply VDD, the drain of M4 is coupled to the source of M2, and the gate of M4 is coupled to the gate of M2. M2 and M4 form a current source, and a similar current source can also include more MOS tubes connected in series.

[0112] like Fig.17 As shown, a pixel driving circuit is provided, wherein the control end of M1 is coupled to the control end of M2 through a NOT gate circuit 2003. Wherein, since when M2 is turned on, the charging potential end stops charging the first node A, and when M2 is turned off, the charging potential end VA1 charges the first node A, when M1 and M2 use the same type of MOS tube, the first control signal of the control end of M2 is opposite in phase to the conduction enable signal of the control end of M1, and therefore the control end of M2 can be coupled to the control end of M1 through the NOT gate circuit 2003, so that the first control signal is input to the control end of M2, and then input to the control end of M1 after passing through the NOT gate circuit 2003.

[0113] In one implementation, the pixel driving circuit is an AMOLED display panel solution. Fig.18 As shown, the pixel driving circuit 3000 includes a first MOS transistor M1 and a second MOS transistor M2 and a charging circuit 3001, wherein the control end of M1 is coupled to the scan line SCAN, 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 (wherein the anode of the LED is coupled to VDD, and the cathode is coupled to the first end of M2), the second end of M2 is coupled to the ground VEE, and a capacitor Cst is coupled between the second end of M2 and the gate. In this way, usually when the pixel is selected 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) flowing through the LED to emit light. The charging and discharging circuit 3001 is coupled between the cathode (i.e., node X) of the light-emitting device D1 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-emitting voltage of the light-emitting diode 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, a first end of M3 is coupled to the second end of the light-emitting diode D1, a second end of the third switch M3 is coupled to the charging potential end VA1, and a second voltage end V2 inputs a predetermined voltage value VA1. M1, M2 and M3 can be NMOS, wherein the control end of M1 is a gate, the first end of M1 is a drain, and the second end is a source. The control end of M2 is a gate, the first end of M2 is a drain, and the second end is a source. The control end of M3 is a gate, the first end of M3 is a source, and the second end of M3 is a drain. Wherein, Fig.18 The analysis of the working principle of the pixel driving circuit provided can refer to Fig.11 (b) in the figure is analyzed and will not be repeated here.

[0114] above Fig.18 The following is an example of a common anode connection mode for light emitting diode D1. When light emitting diode D1 is connected in a common cathode mode, Fig.19 As shown, M1, M2 and M3 use PMOS. In order to ensure the stability of the source voltage of M2 and avoid the source voltage floating problem, thereby affecting the instability of the gate-source (gs) voltage of M2, the source s of M2 is usually coupled to VDD, and the light-emitting diode D1 is coupled between VEE and the drain d of M2 (wherein the anode of the light-emitting diode D1 is coupled to the drain d of M2, and the cathode is coupled to VEE). In this way, the light-emitting diode D1 realizes a common cathode connection mode, as shown in the following figure. Fig.19 As shown. Among them, Fig.19 The analysis of the working principle of the pixel driving circuit provided can refer to Fig.15 (b) in the figure is analyzed and will not be repeated here.

[0115] The pixel driving circuits described above, whether in the AMOLED display panel solution or the Micro LED display panel solution, are merely some examples, and those skilled in the art may also implement the pixel driving circuit in other ways.

[0116] Finally, it should be noted that the above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A micro light emitting diode display panel, characterized in that: The invention comprises a plurality of driving circuits distributed in an array, wherein 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, and each of the sub-pixels includes a light-emitting diode; a first sub-pixel in the pixel is coupled to a first pixel driving circuit in the plurality of pixel driving circuits, a second sub-pixel in the pixel is coupled to a second pixel driving circuit in the plurality of pixel driving circuits, and a third sub-pixel in the pixel is coupled to a third pixel driving circuit in the plurality of pixel driving circuits; The pixel driving circuit comprises: a light-emitting driving module cascaded between the cathode of the light-emitting diode and the ground, the light-emitting driving module comprising a gate switch and a current source, the control end of the gate switch receives a first control signal, the control end of the current source receives a bias voltage, and the anode of the light-emitting diode is coupled to a power supply; and a charging circuit coupled between a charging potential end and a first node, the first node being a coupling point between the light-emitting driving module and the cathode of the light-emitting diode; The charging circuit is configured to charge the first node through the charging potential terminal when the light driving module stops driving the light emitting diode to emit light, the voltage difference between the charging potential terminal and the power supply 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; Furthermore, the charging circuit is further configured to stop charging the first node when the light-emitting driving module drives the light-emitting diode to emit light; and when charging the first node is stopped, the voltage of the first node is charged to the voltage of the charging potential end, and the voltage difference between the charging potential end and the power supply is slightly smaller than the minimum light-emitting voltage of the light-emitting diode.

2. The micro light emitting diode display panel according to claim 1, characterized in that: The charging circuit includes a first switch, wherein a first end of the first switch is coupled to the first node, and a second end of the first switch is coupled to a charging potential end.

3. The micro light emitting diode display panel according to claim 2, characterized in that: The conduction enable signal of the first switch and the enable signal of the light-emitting driving module are in a logical negation relationship.

4. The micro light emitting diode display panel according to claim 2 or 3, characterized in that: The first switch includes a first MOS tube, one end of the source and drain of the first MOS tube is coupled to the charging potential end, the other end of the source and drain of the first MOS tube is coupled to the first node, and the gate of the first MOS tube receives a conduction enable signal.

5. The micro light emitting diode display panel according to claim 2, characterized in that: The gating switch includes a second MOS transistor, 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 coupled to the first node, and the gate of the gating switch receives the first control signal.

6. The micro light emitting diode display panel according to claim 2, characterized in that: The current source comprises a third MOS tube, wherein one end of the source and drain of the third MOS tube is coupled to the ground, the other end of the source and drain of the third MOS tube is coupled to the gate switch, and the gate of the third MOS tube receives the bias voltage.

7. The micro light emitting diode display panel according to claim 6, characterized in that: The current source further includes a fourth MOS tube, wherein one end of the source and drain of the fourth MOS tube is coupled to one end of the source and drain of the third MOS tube, the other end of the source and drain of the fourth MOS tube is coupled to the ground, and the gate of the fourth MOS tube receives the bias voltage.

8. The micro light emitting diode display panel according to claim 1, characterized in that: The pixel driving circuit further includes a capacitor, one end of which is coupled to the control end of the current source, and the other end of which is coupled to the ground.

9. The micro light emitting diode display panel according to claim 1, characterized in that: The first control signal is a pulse width modulation (PWM) signal.

10. A pixel driving circuit, characterized in that: include: A light-emitting driving module cascaded between the cathode of the light-emitting diode and the ground, the light-emitting driving module comprising a gate switch and a current source, the control end of the gate switch receives a first control signal, the control end of the current source receives a bias voltage, and the anode of the light-emitting diode is coupled to a power supply; as well as a charging circuit coupled between a charging potential terminal and a first node, wherein the first node is a coupling point between the light emitting driving module and a cathode of the light emitting diode; The charging circuit is configured to charge the first node through the charging potential terminal when the light driving module stops driving the light emitting diode to emit light, the voltage difference between the charging potential terminal and the power supply 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; Furthermore, the charging circuit is further configured to stop charging the first node when the light-emitting driving module drives the light-emitting diode to emit light; and when charging the first node is stopped, the voltage of the first node is charged to the voltage of the charging potential end, and the voltage difference between the charging potential end and the power supply is slightly smaller than the minimum light-emitting voltage of the light-emitting diode.

11. The pixel driving circuit according to claim 10, characterized in that: The charging circuit includes a first switch, wherein a first end of the first switch is coupled to the cathode of the light emitting diode, and a second end of the first switch is coupled to a charging potential end.

12. The pixel driving circuit according to claim 11, characterized in that: The conduction enable signal of the first switch and the enable signal of the light-emitting driving module are in a logical negation relationship.

13. The pixel driving circuit according to claim 11 or 12, characterized in that: The first switch includes a first MOS tube, one end of the source and drain of the first MOS tube is coupled to the charging potential end, the other end of the source and drain of the first MOS tube is coupled to the first node, and the gate of the first MOS tube receives a conduction enable signal.

14. A terminal device, characterized in that: It comprises a rear shell, a middle frame, and the micro-light emitting diode display panel as described in any one of claims 1 to 9, wherein the rear shell and the micro-light emitting diode display panel are arranged opposite to each other and connected through the middle frame.

Images