Pixel driving circuit and its control method applied to display panels; display panels

Abstract

This invention provides a pixel driving circuit and its control method for a display panel. The pixel driving circuit includes a driving transistor, a light-emitting device, and a pulse width modulation module. The pulse width modulation module includes a discharge transistor, a first switch, an initial voltage transmission module, and a pulse width modulation voltage transmission module. The discharge transistor is electrically connected between the control terminal of the driving transistor and the first switch. The input terminal of the discharge transistor is connected to the output terminal of the initial voltage transmission module, and the control terminal of the discharge transistor is connected to the output terminal of the pulse width modulation voltage transmission module. The first switch is configured to disconnect or connect the output terminal of the discharge transistor to a third voltage terminal according to an external control signal. The display panel also includes an external detection module connected to the pixel driving circuit. The external detection module is configured to detect the potential of the output terminal of the discharge transistor, improving the problem of no detection of the threshold voltage of the discharge transistor and no basis for threshold voltage compensation of the discharge transistor.

Description

Technical Field

[0001] This invention relates to the field of display technology, and more specifically to a pixel driving circuit and its control method for a display panel, and a display panel. Background Technology

[0002] Existing pulse width modulation drive circuits are divided into two types, such as Figures 1A-1B As shown, one type of circuit is the subfield segmentation circuit, which divides a frame into multiple subfields to achieve a linear increase in brightness with increasing grayscale during pulse width modulation (PWM) driving. Another type controls the emission time of the light-emitting device by using a sweep frequency control signal in conjunction with the data voltage applied to the gate of transistor T4 during the initial stage. Both types of circuits can achieve PWM driving, but they can only provide external compensation for the driving transistor T2, and do not detect the threshold voltage of the discharge transistor T4. Consequently, they cannot compensate for the discharge transistor T4 through external compensation, resulting in different conduction durations of the driving transistors T2 for each sub-pixel in the display panel, leading to uneven display. Summary of the Invention

[0003] This invention provides a pixel driving circuit and its control method for a display panel, which can improve the problem that existing pixel driving circuits do not detect the threshold voltage of the discharge transistor, resulting in no basis for compensation of the threshold voltage of the discharge transistor and uneven brightness.

[0004] This invention provides a pixel driving circuit for a display panel, comprising a driving transistor, a light-emitting device, and a pulse width modulation module. The input and output terminals of the driving transistor are electrically connected between a first voltage terminal and a second voltage terminal, and the light-emitting device is electrically connected between the input terminal of the driving transistor and the first voltage terminal. The pulse width modulation module includes a discharge transistor, a first switch, an initial voltage transmission module, and a pulse width modulation voltage transmission module. The discharge transistor is electrically connected between the control terminal of the driving transistor and the first switch. The first switch is configured to disconnect or connect the output terminal of the discharge transistor to a third voltage terminal based on an external control signal. The input terminal of the discharge transistor is connected to the output terminal of the initial voltage transmission module, and the control terminal of the discharge transistor is connected to the output terminal of the pulse width modulation voltage transmission module. The display panel also includes an external detection module connected to the pixel driving circuit, configured to detect the potential of the output terminal of the discharge transistor.

[0005] The present invention also provides a control method for a pixel driving circuit, configured to control any of the above-mentioned pixel driving circuits, comprising: a first switch disconnecting the electrical connection between the output terminal of the discharge transistor and the third voltage terminal according to the external control signal; the discharge transistor being turned on according to the pulse width modulation voltage output by the pulse width modulation voltage transmission module, thereby electrically connecting the output terminal of the initial voltage transmission module with the output terminal of the discharge transistor; and the external detection module detecting the potential of the output terminal of the discharge transistor.

[0006] The present invention also provides a display panel, including any of the above-described pixel driving circuits and an external detection module. The external detection module is electrically connected to the output terminal of the discharge transistor, and the external detection module is configured to output the external control signal and detect the potential of the output terminal of the discharge transistor.

[0007] Embodiments of the present invention provide a pixel driving circuit and control method for a display panel, and a display panel thereof. By including a pulse width modulation module including a discharge transistor and a first switch, the first switch can disconnect the electrical connection between the output terminal of the discharge transistor and the third voltage terminal according to an external control signal. When the control terminal of the discharge transistor receives the pulse width modulation voltage output by the pulse width modulation voltage transmission module and is turned on, the input terminal of the discharge transistor receives the initial voltage transmitted by the initial voltage transmission module to charge the output terminal of the discharge transistor. Then, the potential of the output terminal of the discharge transistor is detected by an external detection module to obtain the threshold voltage of the discharge transistor. This realizes the detection of the threshold voltage of the discharge transistor, improving the problem that existing pixel driving circuits do not detect the threshold voltage of the discharge transistor, resulting in the display panel using the pixel driving circuit having no basis for compensation of the threshold voltage of the discharge transistor and the problem of uneven brightness. Attached Figure Description

[0008] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0009] Figures 1A-1B This is a schematic diagram of the structure of a pixel driving circuit in the prior art;

[0010] Figure 2 This is a schematic diagram of a display panel provided in an embodiment of the present invention;

[0011] Figures 3A-3C This is a schematic diagram of the pixel driving circuit provided in an embodiment of the present invention;

[0012] Figure 4This is a flowchart of the pixel driving circuit provided in an embodiment of the present invention;

[0013] Figures 5A-5B This is a timing diagram of the pixel driving circuit provided in an embodiment of the present invention. Detailed Implementation

[0014] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Furthermore, it should be understood that the specific embodiments described herein are only configured to illustrate and explain the present invention, and are not configured to limit the present invention. In the present invention, unless otherwise stated, directional terms such as "upper" and "lower" generally refer to the upper and lower positions of the device in actual use or operation, specifically the drawing directions in the accompanying drawings; while "inner" and "outer" refer to the outline of the device.

[0015] Specifically, such as Figures 1A-1B This is a schematic diagram of the structure of a pixel driving circuit in the prior art, where DL represents the data line, SL represents the scan line, DiL represents the discharge control line, VDD represents the first voltage terminal, VSS represents the second voltage terminal, Vne represents the discharge voltage terminal, Vref represents the third voltage terminal, T1 to T5 represent transistors, and C1 to C3 represent capacitors.

[0016] like Figure 2 This is a schematic diagram of a display panel provided in an embodiment of the present invention. The present invention provides a display panel including a plurality of sub-pixels Pi and an external detection module 100.

[0017] Optionally, the display panel includes a self-emissive display panel.

[0018] Optionally, the sub-pixel Pi includes the pixel driving circuit. For example... Figures 3A-3C This is a schematic diagram of the pixel driving circuit provided in an embodiment of the present invention. The pixel driving circuit is applied in the display panel and includes a driving transistor Tdr, a light-emitting device Di, and a pulse width modulation module 200.

[0019] The input and output terminals of the driving transistor Tdr are electrically connected between the first voltage terminal VDD and the second voltage terminal VSS. The driving transistor Tdr is configured to generate a driving current to drive the light-emitting device Di to emit light.

[0020] Optionally, the light-emitting device Di is electrically connected between the input terminal of the driving transistor Tdr and the first voltage terminal VDD. Optionally, the light-emitting device Di includes organic light-emitting diodes, sub-millimeter light-emitting diodes, and micro light-emitting diodes, etc.

[0021] The pulse width modulation module 200 is electrically connected to the driving transistor Tdr, and the pulse width modulation module 200 is configured to control the duration for which the driving transistor Tdr drives the light-emitting device Di to emit light according to the sweep frequency signal Swe.

[0022] The pulse width modulation module 200 includes a discharge transistor Tdc and a first switch Swi. The discharge transistor Tdc is electrically connected between the control terminal of the driving transistor Tdr and the first switch Swi. The first switch Swi is electrically connected between the discharge transistor Tdc and the third voltage terminal Vref.

[0023] Wherein, the first switch Swi is configured to disconnect the electrical connection between the output terminal of the discharge transistor Tdc and the third voltage terminal Vref according to the external control signal EC, or to connect the output terminal of the discharge transistor Tdc and the third voltage terminal Vref. The input terminal of the discharge transistor Tdc is configured to receive an initial voltage Vi. The control terminal of the discharge transistor Tdc is configured to receive a pulse width modulation voltage Vpwm to turn on the discharge transistor Tdc. The potential of the output terminal of the discharge transistor Tdc is configured to be detected by the external detection module 100.

[0024] By disconnecting the output terminal of the discharge transistor Tdc from the third voltage terminal Vref according to the external control signal EC, the initial voltage Vi received at the input terminal of the discharge transistor Tdc can charge the output terminal of the discharge transistor Tdc when the control terminal of the discharge transistor Tdc receives the pulse width modulation voltage Vpwm and turns on. The initial voltage Vi stops charging the output terminal of the discharge transistor Tdc when the voltage difference between the control terminal and the output terminal of the discharge transistor Tdc equals the threshold voltage Vth of the discharge transistor Tdc. Therefore, by using the external detection module 100 to detect the potential at the output terminal of the discharge transistor Tdc, and in conjunction with the information that charging of the output terminal of the discharge transistor Tdc stops when the initial voltage Vi is equal to the voltage difference between the control terminal and the output terminal of the discharge transistor Tdc, the threshold voltage Vth of the discharge transistor Tdc can be obtained. This achieves the detection of the threshold voltage Vth of the discharge transistor Tdc, improving the existing pixel driving circuit's lack of detection of the threshold voltage Vth of the discharge transistor Tdc, which leads to the display panel using the pixel driving circuit having no basis for compensating for the threshold voltage Vth of the discharge transistor Tdc, resulting in uneven brightness.

[0025] Optionally, the first switch Swi can be configured as a transistor, that is, the first switch Swi has a control terminal, an input terminal and an output terminal. The control terminal of the first switch Swi is configured to receive the external control signal EC. The input terminal and the output terminal of the first switch Swi are electrically connected between the output terminal of the discharge transistor Tdc and the third voltage terminal Vref.

[0026] Optionally, the external detection module 100 is electrically connected to the output terminal of the discharge transistor Tdc. The external detection module 100 is configured to output the external control signal EC and detect the potential at the output terminal of the discharge transistor Tdc, so as to cooperate with the pixel driving circuit to detect and compensate the threshold voltage Vth of the discharge transistor Tdc. Optionally, the pulse width modulation module 200 further includes an initial voltage transmission module 201 and a pulse width modulation voltage transmission module 202. The input terminal of the discharge transistor Tdc is connected to the output terminal of the initial voltage transmission module 201, and the control terminal of the discharge transistor Tdc is connected to the output terminal of the pulse width modulation voltage transmission module 202. The initial voltage transmission module 201 is configured to transmit the initial voltage Vi to the control terminal of the driving transistor Tdr and the input terminal of the discharge transistor Tdc according to the detection control signal Cont. The pulse width modulation voltage transmission module 202 is configured to output the pulse width modulation voltage Vpwm to the control terminal of the discharge transistor Tdc according to the pulse width modulation signal SPWM.

[0027] Optionally, the initial voltage transmission module 201 includes an initial transistor Ti1, and the pulse width modulation voltage transmission module 202 includes a first data transistor Tda1.

[0028] The input terminal of the initial transistor Ti1 is electrically connected to the initial voltage terminal VI that transmits the initial voltage Vi. The output terminal of the initial transistor Ti1 is electrically connected to the control terminal of the driving transistor Tdr and the output terminal of the initial voltage transmission module 201. The control terminal of the initial transistor Ti1 is electrically connected to the detection control line CL that transmits the detection control signal Cont. The initial transistor Ti1 is configured to transmit the initial voltage Vi to the control terminal of the driving transistor Tdr and the input terminal of the discharge transistor Tdc according to the detection control signal Cont, so as to reset the potential of the control terminal of the driving transistor Tdr and the input terminal of the discharge transistor Tdc using the initial voltage Vi, and to charge the output terminal of the discharge transistor Tdc using the initial voltage Vi when the first switch Swi is open and the discharge transistor Tdc is turned on.

[0029] The input terminal of the first data transistor Tda1 is electrically connected to the data line DL that transmits the pulse width modulation voltage Vpwm. The output terminal of the first data transistor Tda1 is electrically connected to the control terminal of the discharge transistor Tdc. The control terminal of the first data transistor Tda1 is also electrically connected to the pulse width modulation control line WL that transmits the pulse width modulation signal SPWM. Specifically, the first data transistor Tda1 is configured to output the pulse width modulation voltage Vpwm to the control terminal of the discharge transistor Tdc according to the pulse width modulation signal SPWM, thereby controlling the discharge transistor Tdc to be turned on or off via the pulse width modulation voltage Vpwm.

[0030] Optionally, in order to enable the pulse width modulation module 200 to control the emission duration of the light-emitting device Di, the pulse width modulation module 200 further includes a potential coupling module 203, which is configured to couple the sweep frequency signal Swe to the control terminal of the discharge transistor Tdc.

[0031] Optionally, the potential coupling module 203 includes a first capacitor C1. The first terminal of the first capacitor C1 is electrically connected to the control terminal of the discharge transistor Tdc, and the second terminal of the first capacitor C1 is electrically connected to the sweep frequency control line SwL that transmits the sweep frequency signal Swe. The sweep frequency signal Swe is coupled to the control terminal of the discharge transistor Tdc via the first capacitor C1, so that when the discharge transistor Tdc is turned on, the third voltage terminal Vref is electrically connected to the control terminal of the driving transistor Tdr, thereby controlling the driving transistor Tdr to turn off. This prevents any driving current from flowing between the first voltage terminal VDD and the second voltage terminal VSS through the light-emitting device Di, thus controlling the light-emitting device Di to stop emitting light.

[0032] Alternatively, please continue reading Figures 3A-3C The pixel driving circuit further includes a pulse amplitude modulation module 300, which is electrically connected to the driving transistor Tdr. The pulse amplitude modulation module 300 is configured to couple a pulse amplitude modulation voltage Vpam to the control terminal of the driving transistor Tdr according to the pulse amplitude modulation signal SPAM, so as to control the amplitude of the driving current generated by the driving transistor Tdr.

[0033] Optionally, the pulse amplitude modulation module 300 includes a compensation transistor Tc, a second data transistor Tda2, a second capacitor C2, and a third capacitor C3.

[0034] The control terminal of the compensation transistor Tc is electrically connected to the compensation control line BL, the input terminal of the compensation transistor Tc is electrically connected to the input terminal of the driving transistor Tdr, and the output terminal of the compensation transistor Tc is electrically connected to the control terminal of the driving transistor Tdr. The compensation transistor Tc is configured to make the driving transistor Tdr form a diode connection according to the compensation control signal Comp transmitted by the compensation control line BL.

[0035] The input terminal of the second data transistor Tda2 is electrically connected to the data line DL that transmits the amplitude modulation voltage Vpam. The output terminal of the second data transistor Tda2 is electrically connected to the control terminal of the driving transistor Tdr. The control terminal of the second data transistor Tda2 is electrically connected to the amplitude modulation control line AL that transmits the amplitude modulation signal SPAM. The second data transistor Tda2 is configured to output the amplitude modulation voltage Vpam to the second capacitor C2 according to the amplitude modulation signal SPAM, so as to couple the potential of the control terminal of the driving transistor Tdr through the second capacitor C2.

[0036] The first terminal of the second capacitor C2 is electrically connected to the output terminal of the second data transistor Tda2, and the second terminal of the second capacitor C2 is electrically connected to the control terminal of the driving transistor Tdr; the first terminal of the third capacitor C3 is electrically connected to the control terminal of the driving transistor Tdr, and the second terminal of the second capacitor C2 is electrically connected to the second voltage terminal VSS.

[0037] Optionally, the pulse amplitude modulation module 300 further includes a reset transistor Ti2. The input terminal of the reset transistor Ti2 is electrically connected to the data line DL, the output terminal of the reset transistor Ti2 is electrically connected to the first terminal of the second capacitor C2, and the control terminal of the reset transistor Ti2 is electrically connected to the reset control line ReL. The reset transistor Ti2 is configured to transmit the reset signal transmitted by the data line DL to the first terminal of the second capacitor C2 according to the reset control signal Res transmitted by the reset control line ReL, so as to cooperate with the initial transistor Ti1 to reset the potential across the second capacitor C2.

[0038] Optionally, to prevent the light-emitting device Di from emitting light erroneously, the first voltage terminal VDD transmits a first voltage value V1 and a second voltage value V2, wherein the second voltage value V2 is greater than the first voltage value V1; the voltage value transmitted at the second voltage terminal VSS is less than the second voltage value V2 but greater than or equal to the first voltage value V1. Specifically, the first voltage terminal VDD has the second voltage value V2 when the driving transistor Tdr controls the light-emitting device Di to emit light.

[0039] Optionally, the first voltage value V1 can be 0V, and the second voltage value V2 can be 12V. The voltage supplied by the third voltage terminal can be equal to the voltage supplied by the second voltage terminal.

[0040] Figure 4 This is a flowchart of a pixel driving circuit provided in an embodiment of the present invention; the present invention also provides a control method for a pixel driving circuit, configured to control any of the above-mentioned pixel driving circuits, the control method for the pixel driving circuit comprising:

[0041] The first switch Swi disconnects the electrical connection between the output terminal of the discharge transistor Tdc and the third voltage terminal Vref according to the external control signal EC;

[0042] The discharge transistor Tdc is turned on according to the pulse width modulation voltage Vpwm output by the pulse width modulation voltage transmission module 202, electrically connecting the output terminal of the initial voltage transmission module 201 to the output terminal of the discharge transistor Tdc. The external detection module 100 detects the potential of the output terminal of the discharge transistor Tdc. That is, the control terminal of the discharge transistor Tdc receives the pulse width modulation voltage Vpwm to turn on the discharge transistor Tdc, and the input terminal of the discharge transistor Tdc receives the initial voltage Vi, causing the initial voltage Vi to be output to the output terminal of the discharge transistor Tdc, so that the potential of the output terminal of the discharge transistor Tdc can be detected by the external detection module 100.

[0043] Optionally, when the pixel driving circuit is applied to the display panel, the first switch Swi can disconnect the electrical connection between the output terminal of the discharge transistor Tdc and the third voltage terminal Vref according to the external control signal EC when the display panel is powered on, so as to detect the threshold voltage Vth of the discharge transistor Tdc and store the detected threshold voltage Vth of the discharge transistor Tdc in the external detection module 100, so as to compensate the threshold voltage Vth of the discharge transistor Tdc according to the data stored in the external detection module 100 when the light-emitting device Di emits light. By detecting the threshold voltage Vth of the discharge transistor Tdc only once when the display panel is powered on, the threshold voltage Vth information detected at power-on can be used for compensation during the multiple display stages of the light-emitting device Di, which helps to reduce power consumption. Moreover, the detection of the threshold voltage Vth of the discharge transistor Tdc no longer occupies the time for light emission or threshold voltage Vth compensation. This can improve the reduction of the duty cycle of the pulse width modulation signal SPWM caused by the occupancy of the internal compensation threshold voltage Vth or light emission time due to the detection of the threshold voltage Vth of the discharge transistor Tdc. This would further reduce the duty cycle of the pulse width modulation signal SPWM in low grayscale display, which may cause display problems such as flickering that can be observed by the human eye.

[0044] Optionally, the pixel driving circuit further includes a pulse amplitude modulation module 300 electrically connected to the driving transistor Tdr. Accordingly, please continue reading... Figure 4 After the discharge transistor Tdc is turned on according to the pulse width modulation voltage Vpwm output by the pulse width modulation voltage transmission module 202, electrically connecting the output terminal of the initial voltage transmission module 201 to the output terminal of the discharge transistor Tdc, and the external detection module 100 detects the potential of the output terminal of the discharge transistor Tdc, the method further includes:

[0045] The pulse amplitude modulation module 300 receives the pulse amplitude modulation signal SPAM and couples the pulse amplitude modulation voltage Vpam to the control terminal of the driving transistor Tdr, so that the driving transistor Tdr controls the amplitude of the driving current according to the pulse amplitude modulation voltage Vpam.

[0046] The pulse width modulation module 200 receives the sweep frequency signal Swe and couples the potential of the control terminal of the discharge transistor Tdc to electrically connect the third voltage terminal Vref to the control terminal of the driving transistor Tdr when the discharge transistor Tdc is turned on, thereby controlling the driving transistor Tdr to stop driving the light-emitting device Di to emit light.

[0047] Optionally, the pulse width modulation module 300 includes a first capacitor C1. A first terminal of the first capacitor C1 is electrically connected to the control terminal of the discharge transistor Tdc, and a second terminal of the first capacitor C1 is electrically connected to the sweep frequency control line SwL that transmits the sweep frequency signal Swe. The sweep frequency signal Swe is coupled to the potential of the control terminal of the discharge transistor Tdc via the first capacitor C1, so that the pulse width modulation module 200 is coupled to the potential of the control terminal of the discharge transistor Tdc through the first capacitor C1.

[0048] like Figures 5A-5B This is a timing diagram of a pixel driving circuit provided in an embodiment of the present invention. Taking an example where each transistor in the pixel driving circuit is an N-type transistor, the control method of the pixel driving circuit is described. Figure 5A The timing diagram shows the detection of the discharge transistor Tdc threshold voltage Vth in the pixel driving circuit. Figure 5B The timing diagram for implementing the control of the light-emitting device Di in the pixel driving circuit is shown; Data represents the signal transmitted by the data line DL.

[0049] Please continue reading. Figures 3A-3C and Figure 5A The threshold voltage Vth of the discharge transistor Tdc is detected through an initialization phase ta1 and a detection phase ta2.

[0050] Please continue reading. Figure 3B and Figure 5A In the initialization phase ta1: the first switch Swi is closed according to the external control signal EC; the detection control signal Cont and the pulse width modulation signal SPWM are at high level, so that the initial transistor Ti1 is turned on according to the detection control signal Cont, the first data transistor Tda1 is turned on according to the pulse width modulation signal SPWM, the initial voltage Vi is transmitted to the input terminal of the discharge transistor Tdc through the initial transistor Ti1, and the pulse width modulation voltage Vpwm transmitted by the data line DL is transmitted to the control terminal of the discharge transistor Tdc.

[0051] Please continue reading. Figure 3C and Figure 5A In the detection phase ta2: the first switch Swi, according to the external control signal EC, disconnects the electrical connection between the output terminal of the discharge transistor Tdc and the third voltage terminal Vref at the boundary between the initialization phase ta1 and the detection phase ta2. The discharge transistor Tdc remains on, and the initial voltage Vi is transmitted through the input terminal of the discharge transistor Tdc to the output terminal of the discharge transistor Tdc to charge the output terminal of the discharge transistor Tdc until the voltage difference Vgs between the control terminal and the output terminal of the discharge transistor Tdc is equal to the threshold voltage Vth of the discharge transistor Tdc (i.e., Vgs = Vth). The initial voltage Vi stops charging the output terminal of the discharge transistor Tdc. The external detection module 100 detects the potential of the output terminal of the discharge transistor Tdc and obtains the threshold voltage Vth of the discharge transistor Tdc based on the fact that the voltage difference between the control terminal and the output terminal of the discharge transistor Tdc is equal to the threshold voltage Vth of the discharge transistor Tdc.

[0052] In the initialization phase ta1 and the detection phase ta2, the compensation transistor Tc is turned off according to the compensation control signal Comp, the second data transistor Tda2 is turned off according to the pulse amplitude modulation signal SPAM, and the reset transistor Ti2 is turned off according to the reset control signal Res.

[0053] Please continue reading. Figures 3A-3C and Figure 5B The control of the light-emitting device Di goes through a reset stage t1, a compensation stage t2, a data writing stage t3, and a light-emitting stage t4. In the control stage of the light-emitting device Di, the first switch Swi is closed according to the external control signal EC so that the output terminal of the discharge transistor Tdc is electrically connected to the third voltage terminal Vref.

[0054] During the reset phase t1: the reset control signal Res and the detection control signal Cont are at high levels; the reset transistor Ti2 is turned on according to the reset control signal Res; the initial transistor Ti1 is turned on according to the detection control signal Cont; the initial voltage Vi is transmitted to the control terminal of the driving transistor Tdr; the reset signal transmitted by the data line DL is transmitted to the first terminal of the second capacitor C2; the potential across the third capacitor C3 is initialized using the initial voltage Vi and the voltage provided by the third voltage terminal Vref; and the potential across the second capacitor C2 is initialized using the initial voltage Vi and the voltage corresponding to the reset signal.

[0055] During the compensation phase t2: the compensation control signal Comp is high, the compensation transistor Tc is turned on, causing the driving transistor Tdr to be connected in a diode configuration. The control terminal potential of the driving transistor Tdr is pulled down by the third voltage terminal Vref until the difference between the voltage at the control terminal of the driving transistor Tdr and the voltage provided by the third voltage terminal Vref is equal to the threshold voltage Vth_T2 of the driving transistor Tdr. At this point, the third voltage terminal Vref stops pulling down the control terminal potential of the driving transistor Tdr, so that the control terminal voltage Vg_T2 of the driving transistor Tdr is the sum of the voltage provided by the third voltage terminal Vref and the threshold voltage Vth_T2 of the driving transistor Tdr (i.e., Vg_T2 = Vref + Vth_T2). The threshold voltage Vth_T2 of the driving transistor Tdr is stored at the second terminal of the second capacitor C2 to achieve internal compensation of the threshold voltage Vth_T2 of the driving transistor Tdr.

[0056] During the data writing phase t3: the pulse width modulation signal SPWM is high, the first data transistor Tda1 is turned on, and the pulse width modulation voltage Vpwm transmitted by the data line DL is transmitted to the control terminal of the discharge transistor Tdc via the first data transistor Tda1, making the voltage at the control terminal of the discharge transistor Tdc equal to the pulse width modulation voltage Vpwm. Afterwards, the sweep frequency signal Swe changes from a high level to a low level. The change in the sweep frequency signal Swe is coupled to the control terminal of the discharge transistor Tdc via the first capacitor C1, causing the potential at the control terminal of the discharge transistor Tdc to be pulled low, and the discharge transistor Tdc to be turned off. Subsequently, the amplitude modulation signal SPAM is at a high level, the second data transistor Tda2 is turned on, and the amplitude modulation voltage Vpam is transmitted to the first terminal of the second capacitor C2 through the second data transistor Tda2, and coupled to the control terminal of the driving transistor Tdr through the second capacitor C2. This causes the voltage at the control terminal of the driving transistor Tdr to change from the sum of the voltage provided by the third voltage terminal Vref and the threshold voltage Vth of the driving transistor Tdr to the sum of the voltage provided by the third voltage terminal Vref, the threshold voltage Vth of the driving transistor Tdr, and the amplitude modulation voltage Vpam (i.e., Vg_T2 = Vref + Vth_T2 + Vpam).

[0057] During the light-emitting stage t4, the driving transistor Tdr is turned on, and the driving current Ids flowing through the light-emitting device Di to emit light is equal to K*(Vgs_T2-Vth_T2). 2 =K*(Vpam+Vref+Vth_T2-VSS-Vth_T2) 2 =K*(SPAM_data+Vref-VSS) 2 Therefore, the driving current flowing through the light-emitting device Di is no longer affected by the threshold voltage Vth_T2 of the driving transistor Tdr. Where K = (C ox μ n W) / 2L;C ox μ n W and L represent the channel capacitance per unit area, channel mobility, channel width, and channel length, respectively.

[0058] Optionally, the voltage value corresponding to the sweep frequency signal Swe can be gradually increased during the light emission stage to couple the control terminal potential of the discharge transistor Tdc through the first capacitor C1 until the discharge transistor Tdc is turned on. The voltage provided by the third voltage terminal Vref is transmitted to the control terminal of the driving transistor Tdr through the discharge transistor Tdc, so that the driving transistor Tdr is turned off, thereby controlling the light-emitting device Di to stop emitting light and realizing the control of the light emission duration of the light-emitting device Di.

[0059] Optionally, different pulse width modulation voltages Vpwm can be transmitted to the control terminal of the discharge transistor Tdc during the data writing stage t3 to control the turn-on time of the discharge transistor Tdc, thereby controlling the light emission duration of the light-emitting device Di at different gray levels.

[0060] Optionally, the external detection module 100 is configured to detect the threshold voltage Vth of the discharge transistor Tdc when the display panel is powered on, in order to reduce power consumption and improve issues such as flicker.

[0061] Optionally, the external detection module 100 may also be configured to be used during the stage when the display panel controls the sub-pixel Pi to be displayed (i.e., corresponding to...). Figure 5B During the t1 to t4 stages shown, the threshold voltage Vth of the detected and stored discharge transistor Tdc is superimposed on the signal Data transmitted by the data line DL to achieve a compensation effect on the threshold voltage Vth of the discharge transistor Tdc and improve the display quality of the display panel.

[0062] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only configured to help understand the method and core ideas of the present invention. At the same time, those skilled in the art will recognize that there will be changes in the specific implementation methods and application scope based on the ideas of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A pixel driving circuit for use in a display panel, characterized in that, The pixel driving circuit includes: A driving transistor, wherein the input and output terminals of the driving transistor are electrically connected between a first voltage terminal and a second voltage terminal; A light-emitting device is electrically connected between the input terminal of the driving transistor and the first voltage terminal; A pulse width modulation module includes a discharge transistor, a first switch, an initial voltage transmission module, and a pulse width modulation voltage transmission module. The discharge transistor is electrically connected between the control terminal of the driving transistor and the first switch. The first switch is configured to open or close the output terminal of the discharge transistor and a third voltage terminal according to an external control signal. The input terminal of the discharge transistor is connected to the output terminal of the initial voltage transmission module to receive the initial voltage transmitted by the initial voltage transmission module. The control terminal of the discharge transistor is connected to the output terminal of the pulse width modulation voltage transmission module. The display panel further includes an external detection module connected to the pixel driving circuit, the external detection module being configured to detect the potential at the output terminal of the discharge transistor; Specifically, the first switch disconnects the electrical connection between the output terminal of the discharge transistor and the third voltage terminal according to the external control signal. When the control terminal of the discharge transistor is turned on by receiving the pulse width modulation voltage output by the pulse width modulation voltage transmission module, the initial voltage received at the input terminal of the discharge transistor charges the output terminal of the discharge transistor until the voltage difference between the control terminal and the output terminal of the discharge transistor is equal to the threshold voltage of the discharge transistor. At this point, the initial voltage stops charging the output terminal of the discharge transistor, and the external detection module detects the potential at the output terminal of the discharge transistor.

2. The pixel driving circuit according to claim 1, characterized in that, The initial voltage transmission module includes an initial transistor, the input terminal of which is electrically connected to an initial voltage terminal, the output terminal of which is electrically connected to the control terminal of the driving transistor and the output terminal of the initial voltage transmission module, and the control terminal of the initial transistor is electrically connected to a detection control line. The pulse width modulation voltage transmission module includes a first data transistor, the input terminal of which is electrically connected to a data line, the output terminal of which is electrically connected to the output terminal of the pulse width modulation voltage transmission module, and the control terminal of which is electrically connected to a pulse width modulation control line.

3. The pixel driving circuit according to claim 2, characterized in that, The pulse width modulation module further includes: A first capacitor, the first terminal of which is electrically connected to the control terminal of the discharge transistor, and the second terminal of which is electrically connected to the sweep frequency control line.

4. The pixel driving circuit according to claim 1, characterized in that, It also includes a pulse amplitude modulation module, which comprises: A compensation transistor, wherein the control terminal of the compensation transistor is electrically connected to the compensation control line, the input terminal of the compensation transistor is electrically connected to the input terminal of the driving transistor, and the output terminal of the compensation transistor is electrically connected to the control terminal of the driving transistor; The second data transistor has its input terminal electrically connected to the data line, its output terminal electrically connected to the control terminal of the driving transistor, and its control terminal electrically connected to the pulse amplitude modulation control line. A second capacitor, the first terminal of which is electrically connected to the output terminal of the second data transistor, and the second terminal of which is electrically connected to the control terminal of the driving transistor; and The third capacitor has its first terminal electrically connected to the control terminal of the driving transistor, and its second terminal electrically connected to the second voltage terminal.

5. The pixel driving circuit according to claim 4, characterized in that, The pulse amplitude modulation module further includes: A reset transistor, wherein the input terminal of the reset transistor is electrically connected to the data line, the output terminal of the reset transistor is electrically connected to the first terminal of the second capacitor, and the control terminal of the reset transistor is electrically connected to the reset control line.

6. The pixel driving circuit according to claim 1, characterized in that, The first voltage transmitted at the first voltage terminal has a first voltage value and a second voltage value, wherein the second voltage value is greater than the first voltage value. The voltage value transmitted at the second voltage terminal is less than the second voltage value but greater than or equal to the first voltage value; The first voltage terminal has the second voltage value when the driving transistor controls the light-emitting device to emit light.

7. A control method for a pixel driving circuit, characterized in that, Configured to control the pixel driving circuit as described in any one of claims 1 to 6, comprising: The first switch disconnects the electrical connection between the output terminal of the discharge transistor and the third voltage terminal according to the external control signal; The discharge transistor is turned on according to the pulse width modulation voltage output by the pulse width modulation voltage transmission module, so that the output terminal of the initial voltage transmission module is electrically connected to the output terminal of the discharge transistor, and the external detection module detects the potential of the output terminal of the discharge transistor.

8. The control method for the pixel driving circuit according to claim 7, characterized in that, The pixel driving circuit further includes a pulse amplitude modulation module electrically connected to the driving transistor; The method further includes, after the step of the discharge transistor being turned on according to the pulse width modulation voltage output by the pulse width modulation voltage transmission module, electrically connecting the output terminal of the initial voltage transmission module to the output terminal of the discharge transistor, and the external detection module detecting the potential of the output terminal of the discharge transistor, the method further includes: The pulse amplitude modulation module couples the pulse amplitude modulation voltage to the control terminal of the driving transistor, so that the driving transistor controls the amplitude of the driving current according to the pulse amplitude modulation voltage. The discharge transistor control terminal potential is coupled through the pulse width modulation module to electrically connect the third voltage terminal to the control terminal of the driving transistor when the discharge transistor is turned on, thereby controlling the driving transistor to stop driving the light-emitting device to emit light.

9. The control method for the pixel driving circuit according to claim 8, characterized in that, The pulse width modulation module includes a first capacitor, the first terminal of which is electrically connected to the control terminal of the discharge transistor, and the second terminal of which is electrically connected to the sweep frequency control line. The pulse width modulation module is coupled to the potential of the discharge transistor control terminal through the first capacitor.

10. A display panel, characterized in that, include: The pixel driving circuit as described in any one of claims 1 to 6; as well as An external detection module is electrically connected to the output terminal of the discharge transistor. The external detection module is configured to output the external control signal and detect the potential at the output terminal of the discharge transistor.

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