TWI653616B - Pixel circuit - Google Patents

Abstract

The pixel circuit includes a driving transistor, a light emitting control circuit, a first switch, a second switch, a compensation circuit, and an organic light emitting diode. The driving transistor has a first terminal, a second terminal and a control terminal. The light-emitting control circuit is coupled to the first terminal of the driving transistor and is used for receiving a system high voltage. The first switch has a first terminal, a second terminal, and a control terminal. The control terminal is used to receive a first control signal, the first terminal is used to receive a data voltage, and the second terminal is coupled to the light-emitting control circuit. The second switch has a first terminal, a second terminal, and a control terminal. The control terminal is used to receive a first control signal, the first terminal is used to receive a first reference voltage, and the second terminal is coupled to the driving transistor. First end. The compensation circuit is coupled to the light-emitting control circuit, the control terminal and the second terminal of the driving transistor, and is used for receiving a second control signal and a second reference voltage. The organic light emitting diode is coupled to the driving transistor.

Description

Pixel circuit

The present disclosure relates to a pixel circuit, and more particularly to an organic light-emitting diode pixel circuit capable of compensating for variations in threshold voltage and power supply voltage.

Compared with traditional liquid crystal displays, organic light-emitting diode displays have many advantages such as self-emission, wide viewing angle, high contrast, low power consumption, and high response rate.

The organic light emitting diode pixel circuit usually has a driving transistor for providing a driving current required for the organic light emitting diode to emit light. However, if the driving transistor is a low temperature poly-silicon thin-film transistor, the driving transistor often has variations due to the manufacturing process. For example, when using the Excimer-Laser Annealing (ELA) method to make low-temperature polycrystalline silicon thin-film transistors, the threshold voltage (threshold voltage) of the driving transistors between different pixels will be endless due to inconsistent laser power. the same. In addition, if the driving transistor is an amorphous silicon thin-film transistor, after a long period of use, the driving transistor will increase the threshold voltage due to the aging of the material. For the above related reasons, when receiving the same data voltage Next, the driving currents provided to the organic light emitting diodes by the driving transistors located in different pixels will be different, thereby making the light emitting brightness of the organic light emitting diode display uneven.

In addition, the conventional organic light-emitting diode display may experience a drop in power supply voltage, and the power supply voltage in different locations may drop to different degrees. Therefore, the inconsistency of the power supply voltage is also one of the factors causing the uneven brightness of the organic light emitting diode display.

The pixel circuit includes a driving transistor, a first light-emitting switch, a second light-emitting switch, a first switch, a second switch, a first compensation switch, a second compensation switch, a storage capacitor, and an organic light-emitting diode. The driving transistor has a first terminal, a second terminal and a control terminal. The first light-emitting switch has a first terminal, a second terminal, and a control terminal, wherein the control terminal is used to receive a light-emitting control signal, the first terminal is used to receive a system high voltage, and the second terminal is coupled to At a write node. The second light-emitting switch has a first terminal, a second terminal, and a control terminal, wherein the control terminal is used to receive the light-emitting control signal, the first terminal is used to receive the high voltage of the system, and the second terminal is coupled At the first end of the driving transistor. The first switch has a first terminal, a second terminal, and a control terminal, wherein the control terminal is used to receive a first control signal, the first terminal is used to receive a data voltage, and the second terminal is coupled to To the write node. The second switch has a first terminal, a second terminal, and a control terminal, wherein the control terminal is used to receive the first control signal, the first terminal is used to receive a first reference voltage, and the second terminal Coupled to the first terminal of the driving transistor. The first compensation switch has A first terminal, a second terminal, and a control terminal, wherein the control terminal is used to receive the first control signal, the first terminal is coupled to the second terminal of the driving transistor, and the second terminal is coupled At the control terminal of the driving transistor. The second compensation switch has a first terminal, a second terminal, and a control terminal, wherein the control terminal is used to receive the second control signal, and the first terminal is coupled to the control terminal of the driving transistor, The second terminal is used to receive a second reference voltage. The storage capacitor has a first terminal and a second terminal, wherein the first terminal is coupled to the write node, and the second terminal is coupled to the control terminal of the driving transistor. The organic light emitting diode is coupled to the driving transistor.

The pixel circuit includes a driving transistor, a first light-emitting switch, a second light-emitting switch, a first switch, a second switch, a first compensation switch, a second compensation switch, a storage capacitor, and an organic light-emitting diode. The driving transistor has a first terminal, a second terminal and a control terminal. The first light-emitting switch has a first terminal, a second terminal, and a control terminal, wherein the control terminal is used to receive a light-emitting control signal, the first terminal is used to receive a system high voltage, and the second terminal is coupled At a write node. The second light-emitting switch has a first terminal, a second terminal, and a control terminal, wherein the control terminal is used to receive the light-emitting control signal, the first terminal is used to receive the high voltage of the system, and the second terminal is coupled At the first end of the driving transistor. The first switch has a first terminal, a second terminal, and a control terminal, wherein the control terminal is used to receive a first control signal, the first terminal is used to receive a data voltage, and the second terminal is coupled to The write node. The second switch has a first terminal, a second terminal, and a control terminal, wherein the control terminal is used to receive the first control signal, the first terminal is used to receive a first reference voltage, and the second terminal is coupled Connected to the first terminal of the driving transistor. The first compensation switch has a A first terminal, a second terminal, and a control terminal, wherein the control terminal is used to receive the first control signal, the first terminal is coupled to the second terminal of the driving transistor, and the second terminal is coupled to The control terminal of the driving transistor. The second compensation switch has a first terminal, a second terminal, and a control terminal, wherein the control terminal is used to receive the second control signal, and the first terminal is coupled to the second terminal of the driving transistor, The second terminal is used to receive a second reference voltage. The storage capacitor has a first terminal and a second terminal, wherein the first terminal is coupled to the write node, and the second terminal is coupled to the control terminal of the driving transistor. The organic light emitting diode is coupled to the driving transistor.

The pixel circuit includes a driving transistor, a light emitting control circuit, a first switch, a second switch, a compensation circuit, and an organic light emitting diode. The driving transistor has a first terminal, a second terminal and a control terminal. The light emitting control circuit is coupled to the first terminal of the driving transistor and is used for receiving a system high voltage. The first switch has a first terminal, a second terminal, and a control terminal, wherein the control terminal is used to receive a first control signal, the first terminal is used to receive a data voltage, and the second terminal is coupled to The light emission control circuit. The second switch has a first terminal, a second terminal, and a control terminal, wherein the control terminal is used to receive the first control signal, the first terminal is used to receive a first reference voltage, and the second terminal is coupled Connected to the first terminal of the driving transistor. The compensation circuit is coupled to the light-emitting control circuit, the control terminal of the driving transistor, and the second terminal of the driving transistor, and is configured to receive a second control signal and a second reference voltage. The organic light emitting diode is coupled to the driving transistor.

The pixel circuit includes a driving transistor, a light emitting control circuit, a first switch, a second switch, a compensation circuit, and an organic light emitting diode. The drive electric The crystal has a first terminal, a second terminal and a control terminal. The light emitting control circuit is coupled to the first terminal of the driving transistor and is used for receiving a system high voltage. The first switch has a first terminal, a second terminal, and a control terminal, wherein the control terminal is used to receive a first control signal, the first terminal is used to receive a data voltage, and the second terminal is coupled to The light emission control circuit. The second switch has a first terminal, a second terminal, and a control terminal, wherein the first terminal is used to receive a first reference voltage, and the second terminal is coupled to the first terminal of the driving transistor. The compensation circuit is coupled to the light-emitting control circuit, the control terminal of the driving transistor, and the second terminal of the driving transistor, and is configured to receive a second control signal and a second reference voltage. The organic light emitting diode is coupled to the driving transistor. The control terminal of the second switch is used to receive a third control signal.

100, 700, 800, 1000‧‧‧ pixel circuits

110‧‧‧Drive transistor

120, 820‧‧‧light control circuit

130‧‧‧The first switch

140‧‧‧Second switch

150, 750‧‧‧ compensation circuit

160‧‧‧Organic light emitting diode

222, 822‧‧‧The first illuminated switch

224, 824‧‧‧Second light switch

252, 752‧‧‧The first compensation switch

254, 754‧‧‧Second compensation switch

256, 756‧‧‧Storage capacitors

Idri‧‧‧Drive current

Nw‧‧‧ write node

EM‧‧‧lighting control signal

OVDD‧‧‧System high voltage

OVSS‧‧‧System Low Voltage

S1‧‧‧first control signal

S2‧‧‧Second control signal

Vdata‧‧‧Data voltage

Vg‧‧‧Gate signal

Vref1‧‧‧first reference voltage

Vref2‧‧‧second reference voltage

Vth‧‧‧ critical voltage

VL‧‧‧ preset low voltage

VH‧‧‧ preset high voltage

T1‧‧‧ Reset Phase

T2‧‧‧Compensation stage

T3‧‧‧light-emitting stage

In order to make the above and other purposes, features, advantages, and embodiments of the disclosure document more comprehensible, the description of the drawings is as follows: FIG. 1 is a simplified functional block of a pixel circuit according to an embodiment of the disclosure Illustration.

FIG. 2 is a simplified circuit diagram of an embodiment of the pixel circuit according to FIG. 1.

FIG. 3 is a simplified timing change diagram of an embodiment of the pixel circuit according to FIG. 2.

FIG. 4 is an equivalent circuit diagram of the pixel circuit of FIG. 1 in a reset phase.

Fig. 5 is an equivalent circuit diagram of the pixel circuit of Fig. 1 in the compensation stage.

Fig. 6 is an equivalent circuit diagram of the pixel circuit of Fig. 1 at the light emitting stage.

FIG. 7 is a simplified functional block diagram of a pixel circuit according to another embodiment of the present disclosure.

FIG. 8 is a simplified functional block diagram of a pixel circuit according to another embodiment of the present disclosure.

FIG. 9 is a simplified timing change diagram of an embodiment of the pixel circuit according to FIG. 8.

FIG. 10 is a simplified functional block diagram of a pixel circuit according to another embodiment of the present disclosure.

Hereinafter, embodiments of the present invention will be described with reference to related drawings. In the drawings, the same reference numerals represent the same or similar elements or method flows.

FIG. 1 is a simplified functional block diagram of the pixel circuit 100 according to an embodiment of the present disclosure. The pixel circuit 100 includes a driving transistor 110, a light emitting control circuit 120, a first switch 130, a second switch 140, a compensation circuit 150, and an organic light emitting diode 160. The pixel circuit 100 is configured to control the light emitting brightness of the organic light emitting diode 160 according to the received data voltage Vdata.

In this embodiment, the driving transistor 110 has a first terminal, a second terminal, and a control terminal. The first terminal is coupled to the light-emitting control circuit 120, and the control terminal and the second terminal are coupled to the compensation circuit 150. . The first switch 130 has a first terminal, a second terminal, and a control terminal. The first terminal is used to receive the data voltage Vdata, the second terminal is coupled to the write node Nw, and the control terminal is used to receive the first control signal S1. The second switch 140 has a first terminal, a second terminal and The control terminal, wherein the first terminal is used to receive the first reference voltage Vref1, the second terminal is coupled to the first terminal of the driving transistor 110, and the control terminal is used to receive the first control signal S1. The anode terminal of the organic light emitting diode 160 is coupled to the compensation circuit 150, and the cathode terminal is used to receive the system low voltage OVSS.

In FIG. 1, the light emitting control circuit 120 is configured to receive the system high voltage OVDD and is used to provide the system high voltage OVDD to the first terminal of the driving transistor 110 and the write node Nw according to the light emitting control signal EM. The compensation circuit 150 is configured to receive the second reference voltage Vref2 and to provide the gate signal Vg to the driver according to the first control signal S1, the second control signal S2, the first reference voltage Vref1, the second reference voltage Vref2, and the data voltage Vdata. Control terminal of the transistor 110.

In this embodiment, when the light-emitting control circuit 120 provides the system high voltage OVDD to the first terminal of the driving transistor 110, the driving transistor 110 generates a driving current Idri according to the gate signal Vg and the system high voltage OVDD. At this time, the anode terminal of the organic light emitting diode 160 will receive the driving current Idri through the compensation circuit 150, thereby generating a specific light emission brightness.

In practice, the driving transistor 110 can be implemented by using various suitable P-type transistors. For example, P-type low temperature polycrystalline silicon thin film transistors.

In the embodiment of FIG. 1, the compensation circuit 150 adaptively adjusts the voltage level of the gate signal Vg according to the change of the threshold voltage Vth of the driving transistor 110 and the system high voltage OVDD. Therefore, even if the threshold voltage Vth of the driving transistor 110 varies between different pixels due to process factors, or the system high voltage OVDD is disturbed or decreased, the driving current Idri of the pixel circuit 100 and the data voltage Vdata will still be maintained. Same correspondence System, so as to maintain the same correspondence relationship between the light emitting brightness of the organic light emitting diode 160 and the data voltage Vdata.

The operation of the pixel circuit 100 will be further described below with reference to FIGS. 2 and 3. Referring to FIG. 2, the light emitting control circuit 120 includes a first light emitting switch 222 and a second light emitting switch 224. The first light-emitting switch 222 has a first terminal, a second terminal, and a control terminal. The control terminal is used to receive the light-emitting control signal EM, the first terminal is used to receive the system high voltage OVDD, and the second terminal is coupled to the write node Nw. . The second light-emitting switch 224 has a first terminal, a second terminal, and a control terminal. The control terminal is used to receive the light-emitting control signal EM, the first terminal is used to receive the system high voltage OVDD, and the second terminal is coupled to the driving transistor 110. First end.

The compensation circuit 150 includes a first compensation switch 252, a second compensation switch 254, and a storage capacitor 256. The first compensation switch 252 has a first terminal, a second terminal, and a control terminal, wherein the control terminal is used to receive the first control signal S1, the first terminal is coupled to the second terminal of the driving transistor 110, and the second terminal is coupled At the control terminal of the driving transistor 110. The second compensation switch 254 has a first terminal, a second terminal, and a control terminal. The control terminal is used to receive the second control signal S2, the first terminal is coupled to the control terminal of the driving transistor 110, and the second terminal is used to receive The second reference voltage Vref2. The storage capacitor 256 has a first terminal and a second terminal, wherein the first terminal is coupled to the write node Nw, and the second terminal is coupled to the control terminal of the driving transistor 110.

In practice, the first switch 130, the second switch 140, the first light-emitting switch 222, the second light-emitting switch 224, the first compensation switch 252, and the second compensation switch 254 can be implemented with various suitable P-type transistors. For example, P Type low temperature polycrystalline silicon thin film transistor.

FIG. 3 is a simplified timing variation diagram of an embodiment of the pixel circuit 100 according to FIG. 2. Please refer to FIG. 2 and FIG. 3 at the same time. An operation cycle of the pixel circuit 100 includes a reset phase T1, a compensation phase T2, and a light-emitting phase T3 in this order.

In the reset phase T1, the first control signal S1 and the second control signal S2 are at a preset low voltage VL, and the light emission control signal EM is at a preset high voltage VH. Therefore, the first switch 130, the second switch 140, the first compensation switch 252, and the second compensation switch 254 are in an on state, and the first light-emitting switch 222 and the second light-emitting switch 224 are in an off state.

Please refer to the equivalent circuit diagram of the pixel circuit 100 shown in FIG. 4 during the reset phase T1. The data voltage Vdata is transmitted to the write node Nw through the first switch 130, and the first reference voltage Vref1 is transmitted to the first terminal of the driving transistor 110 through the second switch 140. The second reference voltage Vref2 is transmitted to the second terminal of the storage capacitor 256 through the second compensation switch 254, so that the voltage level of the gate signal Vg provided by the compensation circuit 150 is similar to the second reference voltage Vref2.

In this embodiment, the system low voltage OVSS is greater than the first reference voltage Vref1, and the first reference voltage Vref1 is greater than the second reference voltage Vref2. In detail, the first reference voltage Vref1 can be set to be less than the sum of the system low voltage OVSS and a turn-on voltage of the organic light emitting diode 160. The second reference voltage Vref2 may be set to be smaller than the difference between the first reference voltage Vref1 and the absolute value of the threshold voltage Vth of the driving transistor 110. Therefore, in the reset phase T1, the driving transistor 110 will be in a conducting state, and the organic The light emitting diode 160 is in an off state.

In this way, in the reset phase T1, the pixel circuit 100 not only resets the voltage levels of the first terminal, the second terminal, and the control terminal of the driving transistor, but also prevents the organic light emitting diode 160 from emitting light by mistake.

In the compensation phase T2, the first control signal S1 is at a preset low voltage VL, and the second control signal S2 and the lighting control signal EM are at a preset high voltage VH. Therefore, the first switch 130, the second switch 140, and the first compensation switch 252 are in an on state, and the first light-emitting switch 222, the second light-emitting switch 224, and the second compensation switch 254 are in an off state.

Please refer to the equivalent circuit diagram of the pixel circuit 100 shown in FIG. 5 during the compensation phase T2. Since the first switch 130 is turned on, the write node Nw is maintained at the data voltage Vdata. The first reference voltage Vref1 is transmitted to the second terminal of the storage capacitor 256 through the second switch 140, the driving transistor 110, and the first compensation switch 252. Therefore, the voltage level of the gate signal Vg provided by the compensation circuit 150 will gradually rise from approximately the second reference voltage Vref2 until the voltage level of the gate signal Vg approaches the first reference voltage Vref1 and the voltage of the driving transistor 110. The difference in the absolute value of the threshold voltage Vth causes the driving transistor 110 to switch to the off state.

In other words, at the end of the compensation phase T2, the voltage level of the gate signal Vg can be represented by the following "Formula 1": Vg = Vref1- | Vth | "Formula 1"

In this embodiment, the first reference voltage Vref1 is less than the sum of the system low voltage OVSS and the turn-on voltage of the organic light emitting diode 160. Therefore, during the entire compensation phase, the second terminal of the driving transistor 110 (that is, The voltage of the anode terminal of the organic light emitting diode 160) will be less than the sum of the system low voltage OVSS and the on-voltage of the organic light emitting diode 160, so that the organic light emitting diode 160 is maintained in an off state to avoid false light emission.

In addition, it can be known from the above “Formula 1” that at the end of each compensation phase, the anode terminal of the organic light emitting diode 160 is reset to a fixed voltage that is not affected by different data voltages Vdata (ie, the first The difference between the absolute value of the reference voltage Vref1 and the threshold voltage Vth).

In the light-emitting phase T3, the first control signal S1 and the second control signal S2 are at a preset high voltage VH, and the light-emitting control signal EM is at a preset low voltage VL. Therefore, the first switch 130, the second switch 140, the first compensation switch 252, and the second compensation switch 254 are in an off state, and the first light-emitting switch 222 and the second light-emitting switch 224 are in an on state.

Please refer to the equivalent circuit diagram of the pixel circuit 100 shown in FIG. 6 at the light emitting stage T3. The system high voltage OVDD is transmitted to the write node Nw via the first light-emitting switch 222, so that the voltage of the write node Nw is changed from the data voltage Vdata to the system high voltage OVDD. Therefore, the voltage change amount ΔVnw of the write node Nw can be expressed by the following “Formula 2”: △ Vnw = OVDD-Vdata “Formula 2”

Since the control terminal of the driving transistor 110 is in a floating state, the voltage change amount ΔVnw of the write node Nw will be transmitted to the control of the driving transistor 110 through the capacity coupling effect of the storage capacitor 256. end.

That is, in the light-emitting phase T3, the voltage change amount ΔVg of the gate signal Vg is approximately and positively related to the voltage change amount of the write node Nw. △ Vnw. Therefore, the voltage level of the gate signal Vg can be expressed by the following “Formula 3”: Vg = Vref1- | Vth | + △ Vg = Vref1- | Vth | + △ Vnw = Vref1- | Vth | + OVDD-Vdata 3》

In addition, the system high voltage OVDD is also transmitted to the first terminal of the driving transistor 110 through the second light-emitting switch 224, so that the driving transistor 110 operates in a saturation region. Therefore, the driving transistor 110 generates a driving current Idri according to the voltage difference between the first terminal and the control terminal of the driving transistor 110, and the driving current Idri can be expressed by the following “Formula 4”:

In “Formula 4”, k represents the product of the carrier mobility of the driving transistor 110, the unit capacitance of the gate oxide layer, and the gate width-to-length ratio.

It can be known from the above-mentioned "Formula 3" and "Formula 4" that when the data voltage Vdata is the same, the value of the driving current Idri is independent of the threshold voltage Vth of the driving transistor 110 and the system high voltage OVDD. Therefore, the pixel circuit 100 can effectively eliminate the problem of uneven brightness of the organic light emitting diode panel caused by the threshold voltage variation or the decrease in the power supply voltage.

In addition, at the light-emitting stage T3, when the control terminal of the driving transistor 110 is in a floating state, if the system high voltage OVDD has a voltage disturbance, In some cases, the voltage change amount is transmitted to the control terminal of the driving transistor 110 through the capacitive coupling effect of the storage capacitor 256, so that the voltage change amount of the gate signal Vg is positively related to the voltage change amount of the system high voltage OVDD. Therefore, the voltage difference between the first terminal and the control terminal of the driving transistor 110 is still maintained at a fixed value, so that the magnitude of the driving current Idri is maintained, and the stability of the light emitting brightness of the organic light emitting diode is maintained in the light emitting stage T3. .

To sum up, even if the threshold voltages Vth of the driving transistors 110 of each pixel circuit are different from each other, or affected by the power supply voltage disturbance or drop, the corresponding relationship between the driving current Idri and the data voltage Vdata of each pixel circuit is still Will be consistent.

FIG. 7 is a simplified functional block diagram of the pixel circuit 700 according to an embodiment of the present disclosure. The pixel circuit 700 is similar to the pixel circuit 100 except that the pixel circuit 700 replaces the compensation circuit 150 of the pixel circuit 100 with a compensation circuit 750. The compensation circuit 750 includes a first compensation switch 752, a second compensation switch 754, and a storage capacitor 756.

In this embodiment, the first compensation switch 752 has a first terminal, a second terminal, and a control terminal. The control terminal is used to receive the first control signal S1, and the first terminal is coupled to the second terminal of the driving transistor 110. The second terminal is coupled to the control terminal of the driving transistor 110. The second compensation switch 754 has a first terminal, a second terminal, and a control terminal. The control terminal is used to receive the second control signal S2, the first terminal is coupled to the second terminal of the driving transistor 110, and the second terminal is used to Receive the second reference voltage Vref2. The storage capacitor 756 has a first terminal and a second terminal, wherein the first terminal is coupled to the second terminal of the first switch 130 and the second terminal is coupled to the control terminal of the driving transistor 110.

In practice, the first compensation switch 752 and the second compensation switch 754 can be implemented by using various suitable P-type transistors. For example, P-type low temperature polycrystalline silicon thin film transistors. The other switches in Figure 7 can also be implemented with various suitable P-type transistors.

In the reset phase T1, the second reference voltage Vref2 is transmitted to the second terminal of the storage capacitor 756 through the first compensation switch 752 and the second compensation switch 754, so that the voltage level provided by the compensation circuit 750 is similar to that of the second reference voltage Vref2. The gate signal Vg is sent to a control terminal of the driving transistor 110.

In the compensation phase T2, the first compensation switch 752 is in an on state and the second compensation switch 754 is in an off state. Therefore, the voltage level of the gate signal Vg is increased from the approximate value of the second reference voltage Vref2 to the difference between the absolute value of the first reference voltage Vref1 and the threshold voltage Vth, as shown in the above “Formula 1”.

During the light-emitting phase T3, the first compensation switch 752 and the second compensation switch 754 are both in an off state. Therefore, the voltage level of the gate signal Vg is as shown in the above “Formula 3”. In addition, the driving transistor 110 generates a driving current Idri as shown in the above “Formula 4”.

The circuit structure, operation mode, and advantages of many functional blocks of the pixel circuit 700 are similar to those of the pixel circuit 100. For the sake of brevity, details are not repeated here.

FIG. 8 is a simplified functional block diagram of the pixel circuit 800 according to an embodiment of the present disclosure. The pixel circuit 800 is similar to the pixel circuit 100, except that the pixel circuit 800 replaces the light emission control circuit 120 of the pixel circuit 100 with a light emission control circuit 820. The light emission control circuit 820 includes a first light emission The switch 822 and the second light-emitting switch 824.

In this embodiment, the first light-emitting switch 822 has a first terminal, a second terminal, and a control terminal, where the control terminal is used to receive the first control signal S1, the first terminal is used to receive the system high voltage OVDD, and the second terminal is coupled Connected to the second terminal of the first switch 130. The second light-emitting switch 824 has a first terminal, a second terminal, and a control terminal. The control terminal is used to receive the first control signal S1, the first terminal is used to receive the system high voltage OVDD, and the second terminal is coupled to the driving transistor 110 First end.

In practice, the first light-emitting switch 822 and the second light-emitting switch 824 may be implemented by using various suitable N-type transistors. For example, N-type low temperature polycrystalline silicon thin film transistors. The other switches in Figure 8 can be implemented with various suitable P-type transistors.

FIG. 9 is a simplified timing change diagram according to an operation embodiment of the pixel circuit 800. The operation of the pixel circuit 800 will be further described below with reference to FIGS. 8 and 9. In the reset phase T1 and the compensation phase T2, the first control signal S1 is at a preset low voltage VL, so that the first light-emitting switch 822 and the second light-emitting switch 824 are in an off state. Therefore, during the reset phase T1 and the compensation phase T2, the system high voltage OVDD is not transferred to the write node Nw and the first terminal of the driving transistor 110.

In the light-emitting phase T3, the first control signal S1 is at a preset high voltage VH, so that the first light-emitting switch 822 and the second light-emitting switch 824 are in an on state. Therefore, the system high voltage OVDD is transferred to the write node Nw and the first terminal of the driving transistor 110, so that the driving transistor 110 generates a driving current Idri as shown in the above-mentioned "Formula 4".

Compared with the pixel circuit 100, the pixel circuit 800 does not need to use the light emission control signal EM, so it has a simpler circuit structure and a smaller circuit area. The circuit structure, operation mode, and advantages of many functional blocks of the pixel circuit 800 are similar to the pixel circuit 100, and for the sake of brevity, they are not repeated here.

FIG. 10 is a simplified functional block diagram of the pixel circuit 1000 according to an embodiment of the present disclosure. The pixel circuit 1000 is similar to the pixel circuit 800, except that the pixel circuit 1000 replaces the compensation circuit 150 of the pixel circuit 800 with a compensation circuit 750.

The circuit structure, operation mode, and advantages of many functional blocks of the pixel circuit 1000 are similar to those of the pixel circuit 800. For the sake of brevity, details are not repeated here.

According to the above “Formula 4”, even if the threshold voltage Vth of the driving transistor 110 varies and the system high voltage OVDD decreases due to the internal resistance of the wire, the pixel circuits 100, 700, 800 and 1000 can still maintain the driving current Idri and the data voltage Vdata The correspondence relationship between the constants is unchanged, and the correspondence relationship between the light emitting brightness of the organic light emitting diode 160 and the data voltage Vdata is maintained.

In addition, it is also known from the above “Formula 4” that before each entering the light-emitting stage T3, the anode terminal of the organic light-emitting diode 160 will be reset to a fixed voltage that is not affected by different data voltages Vdata (ie, The difference between the absolute value of the first reference voltage Vref1 and the threshold voltage Vth). During the light-emitting phase T3, any disturbance of the system high voltage OVDD can be transmitted to the gate terminal of the driving transistor 110 through the capacitive coupling effect of the storage capacitors 256 and 756, so as to fix the first terminal of the driving transistor 110 and the control terminal. Voltage difference, And stabilize the light emitting brightness of the organic light emitting diode 160.

In some embodiments, the control terminal of the second switch 140 of the pixel circuit 100, 700, 800, or 1000 may instead receive a third control signal (not shown in the figure) instead of receiving the first control signal S1. . The third control signal is at a preset high voltage VH during the reset phase T1 and the light emitting phase T3, and is at a preset low voltage VL during the compensation phase T2. Therefore, the second switch 140 is turned off during the reset phase T1 and the light emitting phase T3, and is turned on during the compensation phase T2.

The control terminal of the second switch 140 is changed to operate the pixel circuits 100, 700, 800, and 1000 that receive the third control signal, which are similar to the pixel circuit that receives the first control signal S1 from the control terminal of the second switch 140, respectively. How 100, 700, 800, and 1000 work.

That is, in some embodiments where the control terminal of the second switch 140 of the pixel circuit 100, 700, 800, or 1000 is changed to receive the third control signal, in the reset phase T1, the compensation circuits 150 and 750 provide The voltage level of the gate signal Vg is equal to the second reference voltage Vref2, instead of being close to the second reference voltage Vref2. In the compensation phase T2, the voltage level of the gate signal Vg provided by the compensation circuits 150 and 750 is as shown in the above “Formula 1”, and will rise from the second reference voltage Vref2 to approach the first reference voltage Vref1 and the threshold voltage Vth. The absolute value of the difference. At the light-emitting stage T3, the voltage level of the gate signal Vg provided by the compensation circuits 150 and 750 is as shown in the above “Formula 3”, and the voltage change amount of the gate signal Vg is positively related to the voltage change amount of the write node Nw .

It is worth mentioning that since the second switch 140 is in the reset stage T1 is in the off state, so current does not flow from the first terminal of the second switch 140 to the second terminal of the second compensation switch 254 or 754. Therefore, by changing the control end of the second switch 140 to certain embodiments in which the third control signal is received, power consumption can be further saved.

In other embodiments, in addition to changing the control terminal of the second switch of the pixel circuits 100 and 700 to receive the third control signal, the first switch and the first compensation switch may also be changed to N-type transistors. It is implemented, and the control terminal of the first switch and the first compensation switch is changed to receive the light emitting control signal EM.

In this way, in addition to preventing current from flowing from the first terminal of the second switch 140 to the second terminal of the second compensation switch 254 or 754 during the reset phase T1, the first control signal S1 can be further omitted to reduce the circuit area. .

In still other embodiments, the first switch, the second switch, and the first compensation switch of the pixel circuits 100 and 700 may be implemented as N-type transistors, and the first switch, the second switch, and the first switch may be implemented. The control end of the compensation switch and the receiving switch receives the light-emitting control signal EM instead. In this way, the first control signal S1 can be omitted to reduce the circuit area.

Certain terms are used in the description and the scope of patent applications to refer to specific elements. However, it should be understood by those with ordinary knowledge in the technical field that the same elements may be referred to by different names. The scope of the specification and patent application does not take the difference in names as a way to distinguish components, but rather uses the difference in functions of components as a basis for distinguishing. "Inclusion" mentioned in the specification and the scope of patent application is an open-ended term, so it should be interpreted as "including but not limited to". In addition, "coupling" is included in this package Contains any direct and indirect means of connection. Therefore, if the first element is described as being coupled to the second element, it means that the first element can be directly connected to the second element through electrical connection or signal connection methods such as wireless transmission or optical transmission, or through other elements or connections. Means are indirectly electrically or signally connected to the second element.

The above are only preferred embodiments of the present invention, and any equivalent changes and modifications made according to the claims of the present invention shall fall within the scope of the present invention.

Claims (12)

A pixel circuit includes: a driving transistor having a first terminal, a second terminal, and a control terminal; a first light-emitting switch having a first terminal, a second terminal, and a control terminal, wherein: The control terminal is used to receive a light-emitting control signal, the first terminal is used to receive a system high voltage, the second terminal is coupled to a write node, and a second light-emitting switch has a first terminal and a second terminal And a control terminal, wherein the control terminal is used to receive the light emitting control signal, the first terminal is used to receive the high voltage of the system, the second terminal is coupled to the first terminal of the driving transistor; a first switch Has a first terminal, a second terminal, and a control terminal, wherein the control terminal is used to receive a first control signal, the first terminal is used to receive a data voltage, and the second terminal is coupled to the write Node; a second switch having a first terminal, a second terminal, and a control terminal, wherein the control terminal is used to receive the first control signal, the first terminal is used to receive a first reference voltage, and the first Two terminals are coupled to the first terminal of the driving transistor; a first compensation switch There is a first terminal, a second terminal and a control terminal, wherein the control terminal is used for receiving the first control signal, the first terminal is coupled to the second terminal of the driving transistor, and the second terminal is coupled The control terminal connected to the driving transistor; a second compensation switch having a first terminal, a second terminal and a control terminal, wherein the control terminal is used for receiving a second control signal, and the first terminal is coupled Connected to the control terminal of the driving transistor, the second terminal is used to receive a second reference voltage; a storage capacitor has a first terminal and a second terminal, wherein the first terminal is coupled to the write Node, the second terminal is coupled to the control terminal of the driving transistor; and an organic light emitting diode is coupled to the driving transistor; wherein, in a reset stage, the first switch, the second The switch, the first compensation switch, and the second compensation switch are in an on state. During a compensation phase, the first switch, the second switch, and the first compensation switch are in an on state, and the second compensation switch is in an off state. State, in a light-emitting stage, the first switch, the Second switch, the first compensation and the second compensation switching switch is in the OFF state. A pixel circuit includes: a driving transistor having a first terminal, a second terminal, and a control terminal; a first light-emitting switch having a first terminal, a second terminal, and a control terminal, wherein: The control terminal is used to receive a light-emitting control signal, the first terminal is used to receive a system high voltage, the second terminal is coupled to a write node, and a second light-emitting switch has a first terminal and a second terminal And a control terminal, wherein the control terminal is used to receive the light emitting control signal, the first terminal is used to receive the system high voltage, the second terminal is coupled to the first terminal of the driving transistor; a first switch Has a first terminal, a second terminal, and a control terminal, wherein the control terminal is used to receive a first control signal, the first terminal is used to receive a data voltage, and the second terminal is coupled to the write Node; a second switch having a first terminal, a second terminal, and a control terminal, wherein the control terminal is used to receive the first control signal, the first terminal is used to receive a first reference voltage, and the first Two terminals are coupled to the first terminal of the driving transistor; a first compensation switch There is a first terminal, a second terminal, and a control terminal, wherein the control terminal is used to receive the first control signal, the first terminal is coupled to the second terminal of the driving transistor, and the second terminal is coupled Connected to the control terminal of the driving transistor; a second compensation switch having a first terminal, a second terminal and a control terminal, wherein the control terminal is used for receiving a second control signal, and the first terminal is coupled Connected to the second terminal of the driving transistor, the second terminal is used to receive a second reference voltage; a storage capacitor has a first terminal and a second terminal, wherein the first terminal is coupled to the write terminal An input node, the second terminal is coupled to the control terminal of the driving transistor; and an organic light emitting diode is coupled to the driving transistor; wherein, in a reset stage, the first switch, the first The two switches, the first compensation switch, and the second compensation switch are in an on state. In a compensation stage, the first switch, the second switch, and the first compensation switch are in an on state, and the second compensation switch is in an off state. Off state, in a light-emitting stage, the first switch, the Second switch, the first compensation and the second compensation switching switch is in the OFF state. A pixel circuit includes: a driving transistor having a first terminal, a second terminal and a control terminal; a light-emitting control circuit coupled to the first terminal of the driving transistor for receiving a system voltage Voltage; a first switch having a first terminal, a second terminal, and a control terminal, wherein the control terminal is used to receive a first control signal, the first terminal is used to receive a data voltage, and the second terminal A second switch having a first terminal, a second terminal, and a control terminal, wherein the control terminal is used for receiving the first control signal, and the first terminal is used for receiving a first A reference voltage, the second terminal is coupled to the first terminal of the driving transistor; a compensation circuit is coupled to the light emitting control circuit, the control terminal of the driving transistor and the second terminal of the driving transistor Terminal for receiving a second control signal and a second reference voltage; and an organic light emitting diode coupled to the driving transistor; wherein, in a reset stage, the first control signal and the first reference signal The two control signals are at a preset low voltage. The pixel circuit of claim 3, wherein, in a compensation stage, the first control signal is at the preset low voltage and the second control signal is at a preset high voltage. A pixel circuit includes: a driving transistor having a first terminal, a second terminal and a control terminal; a light-emitting control circuit coupled to the first terminal of the driving transistor for receiving a system voltage Voltage; a first switch having a first terminal, a second terminal, and a control terminal, wherein the control terminal is used to receive a first control signal, the first terminal is used to receive a data voltage, and the second terminal A second switch having a first terminal, a second terminal, and a control terminal, wherein the control terminal is used for receiving the first control signal, and the first terminal is used for receiving a first A reference voltage, the second terminal is coupled to the first terminal of the driving transistor; a compensation circuit is coupled to the light emitting control circuit, the control terminal of the driving transistor and the second terminal of the driving transistor Terminal for receiving a second control signal and a second reference voltage; and an organic light emitting diode coupled to the driving transistor; wherein, in a light emitting stage, the first control signal and the second The control signal is at a preset high voltage. The pixel circuit of claim 5, wherein the light-emitting control circuit includes: a first light-emitting switch having a first terminal, a second terminal, and a control terminal, wherein the control terminal is used to receive a light-emitting control signal, The first terminal is used to receive the high voltage of the system, the second terminal is coupled to the second terminal of the first switch, and a second light-emitting switch having a first terminal, a second terminal, and a control terminal. The control terminal is used to receive the light emitting control signal, the first terminal is used to receive the high voltage of the system, and the second terminal is coupled to the first terminal of the driving transistor. The pixel circuit as claimed in claim 5, wherein the light-emitting control circuit includes: a first light-emitting switch having a first terminal, a second terminal, and a control terminal, wherein the control terminal is configured to receive the first control signal The first terminal is used to receive the high voltage of the system, the second terminal is coupled to the second terminal of the first switch; and a second light-emitting switch having a first terminal, a second terminal and a control Terminal, wherein the control terminal is used to receive the first control signal, the first terminal is used to receive the system high voltage, and the second terminal is coupled to the first terminal of the driving transistor. The pixel circuit as claimed in claim 5, wherein the compensation circuit comprises: a first compensation switch having a first terminal, a second terminal and a control terminal, wherein the control terminal is configured to receive the first control signal, The first terminal is coupled to the second terminal of the driving transistor, and the second terminal is coupled to the control terminal of the driving transistor. A second compensation switch has a first terminal, a second terminal, and A control terminal, wherein the control terminal is used to receive the second control signal, the first terminal is coupled to the control terminal of the driving transistor, and the second terminal is used to receive a second reference voltage; and a storage capacitor Has a first terminal and a second terminal, wherein the first terminal is coupled to the second terminal of the first switch, and the second terminal is coupled to the control terminal of the driving transistor. The pixel circuit as claimed in claim 5, wherein the compensation circuit comprises: a first compensation switch having a first terminal, a second terminal and a control terminal, wherein the control terminal is configured to receive the first control signal, The first terminal is coupled to the second terminal of the driving transistor, and the second terminal is coupled to the control terminal of the driving transistor. A second compensation switch has a first terminal, a second terminal, and A control terminal, wherein the control terminal is used to receive the second control signal, the first terminal is coupled to the second terminal of the driving transistor, and the second terminal is used to receive the second reference voltage; and a storage The capacitor has a first terminal and a second terminal, wherein the first terminal is coupled to the second terminal of the first switch, and the second terminal is coupled to the control terminal of the driving transistor. A pixel circuit includes: a driving transistor having a first terminal, a second terminal and a control terminal; a light-emitting control circuit coupled to the first terminal of the driving transistor for receiving a system voltage Voltage; a first switch having a first terminal, a second terminal, and a control terminal, wherein the control terminal is used to receive a first control signal, the first terminal is used to receive a data voltage, and the second terminal Coupled to the light-emitting control circuit; a second switch having a first terminal, a second terminal, and a control terminal; the first terminal is used to receive a first reference voltage; the second terminal is coupled to the driver The first terminal of the transistor; a compensation circuit coupled to the light-emitting control circuit, the control terminal of the driving transistor and the second terminal of the driving transistor, and configured to receive a second control signal and a A second reference voltage; and an organic light emitting diode coupled to the driving transistor; wherein the control terminal of the second switch is used to receive a third control signal, and in a reset phase, the first control The signal and the second control signal are at a preset low voltage And the third control signal is at a predetermined high voltage. A pixel circuit includes: a driving transistor having a first terminal, a second terminal and a control terminal; a light-emitting control circuit coupled to the first terminal of the driving transistor for receiving a system voltage Voltage; a first switch having a first terminal, a second terminal, and a control terminal, wherein the control terminal is used to receive a first control signal, the first terminal is used to receive a data voltage, and the second terminal Coupled to the light-emitting control circuit; a second switch having a first terminal, a second terminal, and a control terminal; the first terminal is used to receive a first reference voltage; the second terminal is coupled to the driver The first terminal of the transistor; a compensation circuit coupled to the light-emitting control circuit, the control terminal of the driving transistor and the second terminal of the driving transistor, and configured to receive a second control signal and a A second reference voltage; and an organic light emitting diode coupled to the driving transistor; wherein the control terminal of the second switch is used to receive a third control signal, and the first control signal is in a compensation phase And the third control signal is at a preset low voltage And the second control signal is at a predetermined high voltage. A pixel circuit includes: a driving transistor having a first terminal, a second terminal and a control terminal; a light-emitting control circuit coupled to the first terminal of the driving transistor for receiving a system voltage Voltage; a first switch having a first terminal, a second terminal, and a control terminal, wherein the control terminal is used to receive a first control signal, the first terminal is used to receive a data voltage, and the second terminal Coupled to the light-emitting control circuit; a second switch having a first terminal, a second terminal, and a control terminal; the first terminal is used to receive a first reference voltage; the second terminal is coupled to the driver The first terminal of the transistor; a compensation circuit coupled to the light-emitting control circuit, the control terminal of the driving transistor and the second terminal of the driving transistor, and configured to receive a second control signal and a A second reference voltage; and an organic light emitting diode coupled to the driving transistor; wherein the control terminal of the second switch is used to receive a third control signal, and the first control signal is in a light emitting stage The second control signal and the third control signal In a predetermined high voltage.