CN113487994B - Pixel circuit, display device and pixel compensation method - Google Patents

Abstract

The invention discloses a pixel circuit, display equipment and a pixel compensation method, relates to the technical field of display circuits, and is used for solving the problem that in the prior art, in a PAM + PWM combined driving mode for mu LED high-gray-scale display, a PWM part can only realize positive threshold compensation. The pixel circuit includes: the circuit comprises a first switch circuit, a second switch circuit, a first capacitor, a comparison circuit, a driving circuit and a light-emitting device. The second end of the first switch circuit is electrically connected with the first end of the first capacitor and the control end of the comparison circuit. The second end of the first capacitor is electrically connected with the second end of the comparison circuit. The second end of the second switch circuit is electrically connected with the first end of the comparison circuit and the control end of the driving circuit. The second end of the driving circuit is electrically connected with the light emitting device. The display device comprises the pixel circuit. The pixel compensation method applies the pixel compensation circuit.

Description

A pixel circuit, display device and pixel compensation method

technical field

The present invention relates to the technical field of display circuits, and in particular, to a pixel circuit, a display device and a pixel compensation method.

Background technique

Compared with AMOLED (English full name: Active-matrix organic light-emitting diode, Chinese full name: Active-matrix organic light-emitting diode or active-matrix organic light-emitting diode), μLED has smaller size, faster response, and luminous efficiency. Higher, more stable and longer service life. Therefore, the display application field based on μLED has been developed rapidly. In this field, the oxide thin film transistor (English full name: oxidethin-film transistor, English abbreviation: TFT) represented by amorphous indium gallium zinc oxide (English full name: Amorphous indiumgallium zinc oxide, English abbreviation: a-IGZO) Materials have become important materials for large-size active μLED displays due to the advantages of low leakage, low fabrication temperature and low cost.

In the prior art PAM+PWM (analog voltage modulation+digital pulse width modulation) driving mode for μLED high grayscale display, the comparison transistor in the PWM part is compensated by diode connection, and this compensation method can only achieve a positive threshold value. Compensation has greater limitations.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a pixel circuit, a display device and a pixel compensation method, which are used to solve the problem that in the prior art, in the PAM+PWM combination driving mode for μLED high grayscale display, the PWM part can only realize positive threshold compensation The problem.

In a first aspect, the present invention provides a pixel circuit, including: a first switch circuit, a second switch circuit, a first capacitor, a comparison circuit, a drive circuit, and a light-emitting device. The second end of the first switch circuit is electrically connected to the first end of the first capacitor and the control end of the comparison circuit. The second end of the first capacitor is electrically connected to the second end of the comparison circuit. The second end of the second switch circuit is electrically connected to the first end of the comparison circuit and the control end of the driving circuit. The second end of the driving circuit is electrically connected with the light emitting device.

In the threshold value compensation stage, the first switch circuit and the second switch circuit are turned on, and the first switch circuit is used for providing a control voltage to the control terminal of the comparison circuit, so as to make the comparison circuit turn on. The second switch circuit is used to provide the first voltage to the comparison circuit, and adjust the potential of the second end of the comparison circuit through the first voltage, so as to realize positive threshold voltage compensation or negative threshold voltage compensation for the comparison circuit, so that the light-emitting device remains in the light-emitting stage Stablize.

Compared with the prior art, in the pixel circuit provided by the present invention, in the threshold compensation stage, after the first switch circuit is turned on, a control voltage is provided to the comparison circuit, so that the comparison circuit is in the conduction state. At the same time, the second switch circuit is turned on, and the second switch circuit provides the first voltage to the comparison circuit to adjust the potential of the second end of the comparison circuit. At this time, the first capacitor can keep the potential of the control terminal of the comparison circuit unchanged. Therefore, when the potential of the second terminal of the comparison circuit is smaller than the potential of the control terminal of the comparison circuit, the positive threshold voltage compensation of the comparison circuit can be realized; when When the potential of the second terminal of the comparison circuit is greater than the potential of the control terminal of the comparison circuit, the negative threshold voltage compensation of the comparison circuit can be realized. Based on this, in the comparative light-emitting stage, precise control of the light-emitting duration of the light-emitting device is achieved, so that the light-emitting device has a higher light-emitting precision, thereby achieving a more stable light-emitting device in the light-emitting stage.

In a second aspect, the present invention further provides a display device, including the pixel circuit described in the first aspect.

Compared with the prior art, the beneficial effects of the display device provided by the present invention are the same as the beneficial effects of the pixel circuit described in the first aspect, which will not be repeated here.

In a third aspect, the present invention further provides a pixel compensation method for a pixel circuit, using the pixel circuit described in the first aspect. The pixel compensation method includes:

In the threshold value compensation stage, the first switch circuit and the second switch circuit are controlled to be turned on, and the first switch circuit is used for providing a control voltage to the control terminal of the comparison circuit, so that the comparison circuit is turned on.

The second switch circuit is controlled to provide the first voltage to the comparison circuit, and the first voltage is used to adjust the potential of the second terminal of the comparison circuit to realize positive threshold compensation or negative threshold compensation for the comparison circuit, so that the light emitting device is stable in the light emitting stage.

Compared with the prior art, the beneficial effects of the pixel compensation method provided by the present invention are the same as those of the above-mentioned first aspect

The beneficial effects of the pixel circuit are the same, which will not be repeated here.

Description of drawings

The accompanying drawings described herein are used to provide further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the attached image:

Fig. 1 is the current-voltage transfer curve of μLED in the prior art;

2 is a timing diagram of a PWM driving method for high grayscale display of μLEDs in the prior art;

3 is a circuit structure diagram of a PWM+PAM driving method for high grayscale display of μLEDs in the prior art;

FIG. 4 is a structural diagram 1 of a pixel circuit provided by an embodiment of the present invention;

5 is a timing diagram of a control signal of a pixel circuit according to an embodiment of the present invention;

6 is a state diagram of a pixel circuit in an initialization stage provided by an embodiment of the present invention;

7 is a state diagram of a pixel circuit in a threshold compensation stage provided by an embodiment of the present invention;

FIG. 8 is a second structural diagram of a pixel circuit provided by an embodiment of the present invention;

9 is a state diagram of a pixel circuit provided in an embodiment of the present invention in a data input stage;

FIG. 10 is a state diagram of a pixel circuit according to an embodiment of the present invention in a comparative light-emitting stage.

Detailed ways

In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, but not to limit the present invention.

It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element.

In addition, the terms "first" and "second" are only used for descriptive purposes, and should not be construed as indicating or implying relative importance or implying the number of indicated technical features. Thus, a feature defined as "first" or "second" may expressly or implicitly include one or more of that feature. In the description of the present invention, "plurality" means two or more, unless otherwise expressly and specifically defined. "Several" means one or more than one, unless expressly specifically defined otherwise.

In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "upper", "lower", "front", "rear", "left", "right", etc. are based on those shown in the accompanying drawings The orientation or positional relationship is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the indicated device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

In the description of the present invention, it should be noted that the terms "installed", "connected" and "connected" should be understood in a broad sense, unless otherwise expressly specified and limited, for example, it may be a fixed connection or a detachable connection Connection, or integral connection; may be mechanical connection or electrical connection; may be direct connection or indirect connection through an intermediate medium, may be internal communication between two elements or an interaction relationship between the two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

FIG. 1 illustrates the current-voltage transfer curve of a μLED in the prior art. Referring to Figure 1, since the IV characteristic curve of the light-emitting device μLED is very steep, that is, the change of the voltage between the two poles corresponding to the light-emitting device μLED from a low gray-scale current to a high gray-scale current is extremely small, which makes it difficult for the gray scale to be driven by traditional analog voltages ( PAM) way to expand.

The limitation of the PAM driving method makes the digital pulse-width modulation (PWM) driving method receive extensive attention. PWM driving is to control the brightness sensed by the human eye by controlling the light-emitting time of the light-emitting device μLED. Under the condition of the same drive current and the same refresh frequency, the greater the proportion of the light-emitting device μLED light-emitting time to the total refresh time, the higher the brightness sensed by the human eye. In this way, precise control of gray-scale brightness can be achieved.

FIG. 2 illustrates a timing diagram of a PWM driving manner for high gray-scale display of a light-emitting device μLED in the prior art. Referring to FIG. 2 , in a PWM driving manner, a driving control signal can be generated by using an on-plane driving circuit (GOA circuit). The PWM drive method divides the display time of each frame into n sub-frames in equal proportions, each pixel unit needs to be turned on once in each sub-frame time, and the data voltage input by the IC (full name: Integrated Circuit) each time determines the corresponding sub-frame. Whether the light-emitting device μLED emits light within a period of time.

At present, the driving method combining PWM and PAM has gradually become an important method to solve the μLED display of active light-emitting devices. FIG. 3 illustrates the circuit structure diagram of the PWM+PAM driving method for high gray scale display of the light-emitting device μLED in the prior art. Referring to FIG. 3 , the PWM driving method can achieve higher gray scale, but the driving speed of the GOA circuit is limited. , when the resolution is high, turning it on multiple times results in a long part of the time that cannot be used for light emission, thus limiting the improvement of the number of gray scales. However, the comparison transistor 332 in the PWM part of the existing PAM+PWM driving method adopts a diode connection method for compensation, and this compensation method can only realize the compensation for the positive threshold voltage of the comparison transistor 332, but cannot compensate for the depletion IGZO TFT. (Thin film transistors) realize threshold compensation, which has great limitations.

In view of the above technical problems, an embodiment of the present invention provides a pixel circuit, which is driven by a combined driving method of PAM+PWM. FIG. 4 illustrates a first structural diagram of a pixel circuit provided by an embodiment of the present invention. 4 , a pixel circuit provided by an embodiment of the present invention includes: a first switch circuit, a second switch circuit, a first capacitor C2, a comparison circuit, a drive circuit, and a light-emitting device μLED. The second end of the first switch circuit is electrically connected to the first end of the first capacitor C2 and the control end of the comparison circuit. The second end of the first capacitor C2 is electrically connected to the second end of the comparison circuit. The second end of the second switch circuit is electrically connected to the first end of the comparison circuit and the control end of the driving circuit. The second end of the driving circuit is electrically connected to the light emitting device μLED.

In the threshold value compensation stage, the first switch circuit and the second switch circuit are turned on, and the first switch circuit is used for providing a control voltage to the control terminal of the comparison circuit, so as to make the comparison circuit turn on. The second switch circuit is used to provide the first voltage to the comparison circuit, and adjust the potential of the second end of the comparison circuit through the first voltage, so as to realize positive threshold voltage compensation or negative threshold voltage compensation for the comparison circuit, so that the light-emitting device remains in the light-emitting stage Stablize.

Compared with the prior art, in the pixel circuit provided by the present invention, in the threshold compensation stage, after the first switch circuit is turned on, a control voltage is provided to the comparison circuit, so that the comparison circuit is in the conduction state. At the same time, the second switch circuit is turned on, and the second switch circuit provides the first voltage to the comparison circuit to adjust the potential of the second end of the comparison circuit. At this time, the first capacitor can keep the potential of the control terminal of the comparison circuit unchanged. Therefore, when the potential of the second terminal of the comparison circuit is smaller than the potential of the control terminal of the comparison circuit, the positive threshold voltage compensation of the comparison circuit can be realized; when When the potential of the second terminal of the comparison circuit is greater than the potential of the control terminal of the comparison circuit, the negative threshold voltage compensation of the comparison circuit can be realized. Based on this, in the comparative light-emitting stage, precise control of the light-emitting duration of the light-emitting device is achieved, so that the light-emitting device has a higher light-emitting precision, thereby achieving a more stable light-emitting device in the light-emitting stage.

In a possible implementation manner, referring to FIG. 2 , the above-mentioned pixel circuit may further include a third switch circuit. The third switch circuit is electrically connected between the second end of the first capacitor and the second end of the comparison circuit. The control terminals of the first switch circuit, the second switch circuit and the third switch circuit are all electrically connected to the first control signal terminal, the first terminal of the first switch circuit is electrically connected to the reference power terminal, and the second switch circuit The first end of the is electrically connected to the first level signal end;

In the threshold compensation stage, the first control signal terminal is used to provide the first control signal to the control terminals of the first switch circuit, the second switch circuit and the third switch circuit, so that the first switch circuit, the second switch circuit and the third switch circuit The switch circuit is turned on.

In a possible implementation manner, referring to FIG. 4 , the above-mentioned pixel circuit further includes a reset circuit. The control terminal of the reset circuit is electrically connected to the second control signal terminal, the first terminal of the reset circuit is electrically connected to the second level signal terminal, and the second terminal of the reset circuit is electrically connected to the second terminal of the first capacitor.

In the initialization stage, the first control signal terminal controls the third switch circuit to be turned off, and the second control signal terminal controls the reset circuit to be turned on, so as to initialize the first capacitor C2. Based on the initialization of the first capacitor C2, the compensation effect on the comparison circuit can be guaranteed in the threshold compensation stage.

In a possible implementation manner, referring to FIG. 4 , the above pixel circuit further includes: a first input circuit, a second input circuit and a second capacitor C3.

The first terminal of the first input circuit is electrically connected to the pulse width modulation terminal, the second terminal of the first input circuit is electrically connected to the second terminal of the first capacitor C2, and the control terminal of the first input circuit is electrically connected to the third control signal terminal. connect. The first terminal of the second input circuit is electrically connected to the analog voltage modulation terminal, the second terminal of the second input circuit is electrically connected to the control terminal of the driving circuit and the first terminal of the second capacitor C3, and the control terminal of the second input circuit is electrically connected to the control terminal of the driving circuit and the first terminal of the second capacitor C3. The third control signal terminal is electrically connected. The first terminal of the second capacitor C3 is electrically connected to the control terminal of the driving circuit, and the second terminal of the second capacitor C3 and the first terminal of the driving circuit are electrically connected to the first power terminal.

In the signal input stage, the first control signal terminal controls the first switch circuit, the second switch circuit and the third switch circuit to be turned off. The second control signal terminal controls the reset circuit to be turned off. The third control signal terminal controls the conduction of the first input circuit and the second input circuit. Under the coupling effect of the first capacitor, the voltage of the control terminal of the comparison circuit increases, so that the comparison circuit is turned off, and the first terminal of the second input circuit The voltage is stored in the second capacitor C3.

In the comparison light-emitting stage, the third control signal terminal controls the first input circuit and the second input circuit to be turned off, and the storage voltage of the second capacitor drives the driving circuit to be turned on, so that the light-emitting device emits light.

It should be understood that the second end of the second capacitor C3 can also be selected to be electrically connected to any other DC power source, and the specific selection can be made according to the actual situation.

In a possible implementation manner, referring to FIG. 4 , the above-mentioned pixel circuit may further include a third capacitor C1 and a fourth switch circuit. The first terminal of the third capacitor is electrically connected to the fourth control signal terminal, and the second terminal of the third capacitor is electrically connected to the second terminal of the first capacitor. The first terminal of the fourth switch circuit is electrically connected to the first power supply terminal, the second terminal of the fourth switch circuit is electrically connected to the second terminal of the comparison circuit, and the control terminal of the fourth switch circuit is electrically connected to the fifth control signal terminal. The first terminal of the fourth switch circuit is electrically connected to the first power supply terminal, the second terminal of the fourth switch circuit is electrically connected to the second terminal of the comparison circuit, and the control terminal of the fourth switch circuit is electrically connected to the fifth control signal terminal.

In the comparison light-emitting stage, the fourth control signal terminal provides a fourth control signal from low to high or from high to low to the first terminal of the third capacitor. Under the coupling effect of the first capacitor and the third capacitor, the first The voltage of the first terminal of the capacitor gradually increases or decreases, so that the comparison circuit is turned on, the fifth control signal terminal controls the fourth switch circuit to be turned on, and the voltage of the first terminal of the comparison circuit is set to the voltage of the first power supply terminal, so that the driving The circuit is turned off and the light-emitting device stops emitting light.

It can be known from the above circuit structure that the pixel circuit provided by the embodiment of the present invention may include a first switch circuit, a second switch circuit, a third switch circuit, a fourth switch circuit, a reset circuit, a first input circuit, a second input circuit, A comparison circuit, a driving circuit, a first capacitor, a second capacitor, a third capacitor and a light emitting device. The first switch circuit, the second switch circuit, the third switch circuit, the fourth switch circuit, the reset circuit, the first input circuit, the second input circuit, the comparison circuit and the driving circuit can all use N-type transistors, but not limited to this . For example: the reset circuit is transistor T1, the first switch circuit is transistor T2, the second switch circuit is transistor T3, the third switch circuit is transistor T4, the fourth switch circuit is transistor T8, the first input circuit is transistor T6, and the third switch circuit is transistor T8. The two input circuits are transistor T7, the comparison circuit is transistor T5, and the driving circuit is transistor T9. The light emitting device may be a μLED. The first switch circuit, the second switch circuit, the third switch circuit, the fourth switch circuit, the reset circuit, the first input circuit, the first capacitor and the third capacitor are the PWM driving parts. The second input circuit, the driving circuit and the second capacitor form the PAM driving part.

The first control signal terminal outputs the first control signal SN, the second control signal terminal outputs the second control signal RESET, the third control signal terminal outputs the third control signal SNN, the fourth control signal terminal outputs the fourth control signal SWEEP, and the third control signal terminal outputs the fourth control signal SWEEP. The fifth control signal terminal outputs the fifth control signal EM. The fourth control signal SWEEP and the fifth control signal EM may be global control signals, and the first control signal SN, the second control signal RESET and the third control signal SNN may be reusable control signals, that is: the first control signal of the current stage A control signal SN can serve as the third control signal SNN of the upper stage and the second control signal RESET of the next stage.

In a possible implementation manner, the second control signal RESET can also be used as a global signal to control all pixels to initialize at the same time, and then perform compensation and data input line by line.

The above-mentioned first level signal terminal outputs a high-level control signal VGH, and the above-mentioned second level signal terminal outputs a low-level control signal VGL.

The above-mentioned reference power supply terminal outputs the reference voltage Verf, and the first power supply terminal outputs the low voltage VSS. The pulse width modulation terminal outputs the pulse width modulation signal PWMD, and the analog voltage modulation terminal outputs the analog voltage modulation PAMD.

In a possible implementation manner, the pulse width modulation terminal PWMD is electrically connected to the first terminal of the first input circuit through the first data signal line, and the analog voltage modulation terminal PAMD is electrically connected to the second input circuit through the first data signal line The first terminal of the PWM is electrically connected, and the pulse width modulation terminal PWMD and the analog voltage modulation terminal PAMD are used to respectively input electrical signals to the first input circuit and the second input circuit in the same period.

In a possible implementation manner, the pulse width modulation terminal PWMD is electrically connected to the first terminal of the first input circuit through a third data signal line, and is used for inputting an electrical signal to the first input circuit during the first period; analog voltage modulation The terminal PAMD is electrically connected to the first terminal of the second input circuit through the third data signal line, and is used for inputting an electrical signal to the second input circuit during the second period.

It should be noted that the relationship between the high-level control signal VGH, the low-level control signal VGL and the low voltage VSS is: VGH>VSS>VGL. The relationship between the reference voltage Verf, the high-level control signal VGH and the low voltage VSS is: VGH>Vref>VSS. The relationship between the pulse width modulation signal PWMD, the analog voltage modulation PAMD and the low voltage VSS is: PAMD>VSS>PWMD.

FIG. 5 illustrates a timing diagram of a control signal of a pixel circuit provided by an embodiment of the present invention. Referring to FIG. 5 , the working process of the pixel circuit provided by the embodiment of the present invention can be divided into an initialization phase, a threshold compensation phase, a data input phase, and a comparative light-emitting phase. The circuit states of each stage will be described one by one below.

FIG. 6 illustrates a state diagram of a pixel circuit provided in an embodiment of the present invention in an initialization stage. 5 and 6, in the initialization stage, the first control signal SN, the third control signal SNN and the fifth control signal EM all have a low level, so that the first switch circuit T2, the second switch circuit T3, the third switch The circuit T4, the fourth switch circuit T8, the first input circuit T6 and the second output circuit T7 are all turned off. At the same time, since the first switch circuit T2 is turned off, the comparison circuit T5 is turned off; since the second switch circuit T3 is turned off, the driving circuit T9 is turned off. The second control signal RESET has a high level, so that the reset circuit T1 is turned on. The fourth control signal SWEEP has a low level, the fifth control signal EM has a low level, and the light emitting device is turned off to prevent flickering. At this time, the potential of the second end of the first capacitor C2 is set to the low level control signal VGL, that is, initializing the first capacitor C2 can ensure the compensation effect of the comparison circuit in the threshold compensation stage.

It is worth noting that, when the compensation time of the threshold compensation stage is sufficient (for example, the compensation time is greater than 50 microseconds), the initialization stage can be omitted, which can be determined according to the actual situation.

FIG. 7 illustrates a state diagram of a pixel circuit provided by an embodiment of the present invention in a threshold compensation stage. 5 and 7 , in the threshold compensation stage, the first control signal SN has a high level, so that the first switch circuit T1 , the second switch circuit T3 and the third switch circuit T4 are all turned on. The first switch circuit T1 is turned on, and the reference voltage Vref has a high level, so that the comparison circuit T5 is turned on. The second control signal RESET has a low level to turn off the reset circuit. Both the third control signal SNN and the fifth control signal EM have a low level, so that the first input circuit T6 , the second input circuit T7 and the fourth switch circuit T8 are all turned off. The fourth control signal SWEEP maintains a low level. The fifth control signal EM has a low level to turn off the light emitting device. The second control signal RESET has a low level, so that the reset circuit T1 is turned off. At this time, the second switch circuit charges the second end of the comparison circuit T5 and the second end of the first capacitor C2 until the comparison circuit T5 is turned off, and finally the voltage of the second end of the comparison circuit T5 is stabilized to Vref-Vth5, The voltage across the first capacitor C2 is stabilized at Vth5. Since the present invention uses the source follower structure for compensation, the voltage of the second terminal of the comparison circuit T5 can be charged to a higher potential than the voltage of the control terminal of the comparison circuit T5, so that the negative threshold voltage of the comparison circuit can be realized. compensate. The threshold value compensation process can ensure that in the next comparison light-emitting stage, the drift of the threshold voltage of the comparison circuit T5 will not affect the switching state of the first input circuit T6.

FIG. 8 illustrates a second structural diagram of a pixel circuit provided by an embodiment of the present invention. In a possible implementation, referring to FIG. 8 , in the threshold compensation stage, in order to make the potential of the control terminal of the comparison circuit more stable and achieve a better threshold voltage compensation effect, the pixel circuit may further include a fourth capacitor C4 and a Five switch circuit T10. The fourth capacitor C4 is electrically connected between the first capacitor C2 and the third switch circuit. The first terminal of the fifth switch circuit is electrically connected to the first terminal of the first switch circuit, the second terminal of the fifth switch circuit T10 is electrically connected to the second terminal of the first capacitor C2, and the control terminal of the fifth switch circuit is electrically connected to the second terminal of the first capacitor C2. Five control signals are electrically connected.

FIG. 9 illustrates a state diagram of a pixel circuit provided in an embodiment of the present invention in a data input stage. Referring to FIG. 5 and FIG. 9 , in the data input stage, the first control signal SN has a low level, so that the first switch circuit T2 , the second switch circuit T3 and the third switch circuit T4 are turned off. The third control signal SNN has a high level, so that the first input circuit T6 and the second input circuit T7 are turned on. At this time, the voltage of the second terminal of the first capacitor C2 is set to PWMD from Vref-Vth5, and the voltage of the first terminal of the first capacitor C2 becomes PWMD+Vth5 due to the coupling effect of the first capacitor C2. Since PWMD<VSS<Vref, the comparison circuit T5 is turned off. At this time, the voltage of the first terminal of the comparison circuit is set to PAMD and stored on the second capacitor C3.

FIG. 10 illustrates a state diagram of a pixel circuit provided by an embodiment of the present invention in a comparative light-emitting stage. Referring to FIG. 5 and FIG. 10 , in the comparison light-emitting stage, the third control signal SNN has a low level, so that the first input circuit T6 and the second input circuit T7 are turned off. The fifth control signal EM has a high level, so that the fourth switch circuit T8 is turned on, the voltage of the second end of the comparison circuit is set to VSS, and at the same time, the fifth control signal EM can set the anode of the light-emitting device μLED to a high level level. At this time, the second capacitor C3 keeps the voltage of the first terminal of the comparison circuit T5 at PAWD. The size of the PAWD can control the driving current of the driving circuit T9, that is, control the brightness of the light-emitting device μLED. According to the transistor's saturation current formula:

It can be obtained that in the comparative light-emitting stage, the current of the light-emitting device μLED is:

分别表示驱动电路T9的迁移率、单位面积栅介质电容和沟道宽长比。where μ, C _ox and

Respectively represent the mobility of the driving circuit T9, the gate dielectric capacitance per unit area and the channel width to length ratio.

10 , when the fourth control signal SWEEP gradually changes linearly from low level to high level, the voltage of the control terminal of the comparison circuit T5 gradually increases linearly through the capacitive coupling effect of the first capacitor C2 and the third capacitor C1 . At this time, the voltage of the control terminal of the comparison circuit T5 can be expressed as:

V _A =PWMD+Vth5+ΔSWEEP.

At this time, the voltage of the second terminal of the comparison circuit T5 is VSS. At the beginning of the comparison light _- emitting stage, VA is smaller than VSS, so the comparison circuit T5 is turned off, the first terminal of the comparison circuit T5 is kept as VA ₌ PAMD, and the current of the light-emitting device μLED remains unchanged. As the fourth control signal SWEEP further increases, the voltage VA of the control terminal of the comparison circuit T5 is gradually larger than VSS+ _Vth5 , that is, PWMD+ΔSWEEP>VSS, the comparison circuit T5 is turned on, and the low voltage VSS of the first power supply terminal is transmitted to the comparison The first end point D of the circuit T5 turns off the driving circuit T9. At this time, the light emitting device μLED stops emitting light.

In the comparison process, due to the threshold voltage compensation, the comparison result will not be affected by the change of the threshold voltage of the comparison circuit T5, which greatly improves the stability and reliability of the comparison result.

It should be understood that "x" in Fig. 6 to Fig. 10 indicates that the circuit is in an off state.

From the working process of the above-mentioned pixel circuit in four stages, it can be known that the turn-on time of the comparison circuit T5 can be controlled by controlling the size of the pulse width modulation signal PWMD at the pulse width modulation end, and the turn-on time of the comparison circuit T5 can control the first end D of the comparison circuit. The level of the dot is high and low, so as to control the turn-on time of the driving circuit T9, and finally realize the control of the light-emitting time of the light-emitting device μLED. Based on this, the purpose of controlling the light-emitting time of the light-emitting device μLED by the pulse width modulation signal PWM can be achieved. For example, the larger the value of the pulse width modulation signal PWMD, the longer the turn-on time of the comparison circuit T5, the shorter the time that the voltage at the first terminal D of the comparison circuit remains at the pulse width modulation signal PAMD, the longer the turn-on time of the driving circuit T9. Shorter, the shorter the light-emitting time of the light-emitting device μLED. Therefore, the pixel circuit successfully combines the PAM driving method with the PWM driving method, and converts the analog voltage to the digital pulse width inside the pixel circuit. The IC is compatible with the design of the traditional analog voltage driving circuit, and the complexity is low, which greatly reduces the cost. The PWM part can realize positive and negative threshold compensation for the comparison circuit T5, which greatly enhances the stability and reliability of the comparison result.

To sum up, in the pixel circuit provided by the embodiment of the present invention, the connection mode of the second switch circuit T3, the comparison circuit T5, the third switch circuit T4 and the first capacitor C2 constitutes a source follower structure, so that in the threshold compensation stage, The voltage of the control terminal A of the comparison circuit T5 can be fixed, and the second terminal B or C of the comparison circuit T5 is charged by the high voltage of the first terminal D of the comparison circuit T5. Based on this, it is not affected by the positive or negative value of the threshold voltage of the comparison circuit, and the threshold voltage of the comparison circuit T5 can be detected to ensure that in the comparison light-emitting stage, the light-emitting brightness and light-emitting time of the light-emitting device are not affected by the threshold voltage of the comparison circuit T5. Therefore, factors such as gate bias voltage and ambient temperature will not affect the threshold voltage of the comparison circuit T5, so that the comparison result will drift.

An embodiment of the present invention also provides a display device, including the pixel circuit described in the above technical solution.

Compared with the prior art, the beneficial effects of the display device provided by the present invention are the same as those of the pixel circuit described in the above technical solutions, which will not be repeated here.

Embodiments of the present invention also provide a pixel compensation method for a pixel circuit, using the pixel circuit described in the above technical solution. The pixel compensation method includes:

Step S100 : in the threshold compensation stage, control the first switch circuit and the second switch circuit to be turned on, and the first switch circuit is used for providing a control voltage to the control terminal of the comparison circuit to turn on the comparison circuit.

Step S200: Control the second switch circuit to provide the first voltage to the comparison circuit, and the first voltage is used to adjust the potential of the second end of the comparison circuit, so as to realize positive threshold compensation or negative threshold compensation for the comparison circuit, so that the light-emitting device is in the light-emitting stage keep it steady.

Compared with the prior art, the beneficial effects of the pixel compensation method provided by the present invention are the same as the beneficial effects of the pixel circuit described in the first aspect, and are not repeated here.

The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention. should be included within the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims (9)

1. A pixel circuit, comprising: the circuit comprises a first switch circuit, a second switch circuit, a first capacitor, a comparison circuit, a drive circuit, a light-emitting device and a third switch circuit;

the control ends of the first switch circuit, the second switch circuit and the third switch circuit are all electrically connected with a first control signal end; the first end of the first switch circuit is electrically connected with a reference power supply end, and the second end of the first switch circuit is electrically connected with the first end of the first capacitor and the control end of the comparison circuit; a second end of the first capacitor is electrically connected with a second end of the comparison circuit through the third switch circuit; the first end of the second switch circuit is electrically connected with the first level signal end, the second end of the second switch circuit is electrically connected with the first end of the comparison circuit and the control end of the drive circuit, and the second end of the drive circuit is electrically connected with the light-emitting device;

in the threshold compensation stage, the first control signal terminal is configured to provide a first control signal to control terminals of the first switch circuit, the second switch circuit, and the third switch circuit to turn on the first switch circuit, the second switch circuit, and the third switch circuit, the first switch circuit is configured to provide a control voltage to a control terminal of the comparison circuit to turn on the comparison circuit, the second switch circuit is configured to provide a first voltage to the comparison circuit, and a potential of a second terminal of the comparison circuit is adjusted by the first voltage to implement positive threshold voltage compensation or negative threshold voltage compensation on the comparison circuit, so that the light emitting device is stable in the light emitting stage.

2. The pixel circuit according to claim 1, further comprising: a reset circuit;

the control end of the reset circuit is electrically connected with the second control signal end; the first end of the reset circuit is electrically connected with the second level signal end, and the second end of the reset circuit is electrically connected with the second end of the first capacitor;

in an initialization stage, the first control signal terminal controls the third switch circuit to be turned off, and the second control signal terminal controls the reset circuit to be turned on, so that the first capacitor is initialized.

3. The pixel circuit according to any one of claims 1 to 2, further comprising: the first input circuit, the second input circuit and the second capacitor;

the first end of the first input circuit is electrically connected with the pulse width modulation end, the second end of the first input circuit is electrically connected with the second end of the first capacitor, and the control end of the first input circuit is electrically connected with the third control signal end;

the first end of the second input circuit is electrically connected with the analog voltage modulation end, the second end of the second input circuit is electrically connected with the control end of the driving circuit and the first end of the second capacitor, and the control end of the second input circuit is electrically connected with the third control signal end;

the first end of the second capacitor is electrically connected with the control end of the driving circuit, and the second end of the second capacitor and the first end of the driving circuit are electrically connected with a first power supply end;

in a signal input stage, the third control signal end controls the first input circuit and the second input circuit to be conducted, under the coupling effect of the first capacitor, the control end voltage of the comparison circuit is increased, the comparison circuit is turned off, and the voltage of the first end of the second input circuit is stored in the second capacitor.

4. The pixel circuit according to claim 3, wherein the pulse width modulation terminal is electrically connected to the first terminal of the first input circuit through a first data signal line, the analog voltage modulation terminal is electrically connected to the first terminal of the second input circuit through a first data signal line, and the pulse width modulation terminal and the analog voltage modulation terminal are configured to input an electrical signal to the first input circuit and the second input circuit, respectively, at the same time period;

and/or the pulse width modulation end is electrically connected with the first end of the first input circuit through a third data signal line and is used for inputting an electric signal to the first input circuit in a first period; the analog voltage modulation terminal is electrically connected with the first terminal of the second input circuit through a third data signal line and is used for inputting an electric signal to the second input circuit in a second period.

5. The pixel circuit according to claim 3, wherein during a comparative light emitting period, the third control signal terminal controls the first input circuit and the second input circuit to turn off, and the storage voltage of the second capacitor drives the driving circuit to turn on, so as to make the light emitting device emit light.

6. The pixel circuit according to claim 1, further comprising a third capacitor and a fourth switch circuit, wherein a first terminal of the third capacitor is electrically connected to a fourth control signal terminal, and a second terminal of the third capacitor is electrically connected to a second terminal of the first capacitor;

a first end of the fourth switching circuit is electrically connected with a first power supply end, a second end of the fourth switching circuit is electrically connected with a second end of the comparison circuit, and a control end of the fourth switching circuit is electrically connected with a fifth control signal end;

in a comparative light-emitting stage, the fourth control signal terminal provides a fourth control signal from low to high or from high to low to the first terminal of the third capacitor, under the coupling effect of the first capacitor and the third capacitor, the voltage of the first terminal of the first capacitor gradually increases or decreases to enable the comparison circuit to be switched on, the fifth control signal terminal controls the fourth switch circuit to be switched on, the voltage of the first terminal of the comparison circuit is set to the voltage of the first power supply terminal to enable the driving circuit to be switched off, and the light-emitting device stops emitting light.

7. The pixel circuit according to claim 1, further comprising a fourth capacitor and a fifth switch circuit;

the fourth capacitor is electrically connected between the first capacitor and the third switch circuit, the first end of the fifth switch circuit is electrically connected with the first end of the first switch circuit, the second end of the fifth switch circuit is electrically connected with the second end of the first capacitor, and the control end of the fifth switch circuit is electrically connected with a fifth control signal.

8. A display device comprising the pixel circuit according to any one of claims 1 to 7.

9. A pixel compensation method of a pixel circuit, characterized in that the pixel circuit of any one of claims 1 to 7 is applied; the pixel compensation method of the pixel circuit comprises the following steps:

in a threshold compensation stage, controlling a first switch circuit, a second switch circuit and a third switch circuit to be opened, wherein the first switch circuit is used for providing a control voltage to a control end of the comparison circuit so as to enable the comparison circuit to be opened;

and controlling the second switch circuit to provide a first voltage to the comparison circuit, wherein the first voltage is used for adjusting the potential of the second end of the comparison circuit so as to realize positive threshold compensation or negative threshold compensation on the comparison circuit and keep the light-emitting device stable in a light-emitting stage.

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