TWI738435B - Pixel circuit - Google Patents

Abstract

A pixel circuit includes a driving circuit, a first switch, a second switch, a third switch, a control circuit and a light-emitting unit. The first switch connects to the driving circuit and is controlled by a first activating signal. The first switch outputs a first current based on a first duty cycle of the first activating signal. The second switch connects to the driving circuit and is controlled by a second activating signal. The second switch outputs a second current based on a second duty cycle of the second activating signal. The second duty cycle is different from the first duty cycle. The third switch connects to the second switch and receives the second current. The control circuit connects to the third switch and transmits a control signal to the third switch. The third switch outputs a third current based on the control signal and the second current. The light-emitting unit connects to the third switch and the first switch and the light-emitting unit is lightened up by the first current or the third current.

Description

Pixel circuit

The present invention relates to a pixel circuit using a first switch, a second switch and a third switch to adjust the light-emitting time of a driving current flowing through a light-emitting unit.

Organic light-emitting diodes have the advantages of self-luminescence, high brightness, high contrast, simple manufacturing process, etc., and have been gradually applied to various types of displays. The organic light-emitting diode itself is a current drive element, which controls the brightness (also known as gray scale value) of the organic light-emitting diode by giving different data voltages to the pixel circuit to generate different driving currents; however, the display requires multiple different gray scales When the number of gray levels required is greater than the number of data voltages that the data driving circuit can provide, a pixel circuit with a data voltage corresponding to a gray level value is not sufficient.

In summary, the inventor of the present invention thought about and designed a pixel circuit in order to improve the lack of conventional technology, thereby enhancing the industrial application.

In view of the above-mentioned conventional problems, the purpose of the present invention is to provide a pixel circuit to solve the problems faced by the conventional technology.

Based on the above objective, the present invention provides a pixel circuit, which includes a driving circuit, a first switch, a second switch, a third switch, a control circuit, and a light-emitting unit. The first switch is connected to the driving circuit and is controlled by a first activation signal. The first switch outputs a first current according to a first duty cycle of the first activation signal. The second switch is connected to the driving circuit and is controlled by the second activation signal. The second switch outputs a second current according to a second duty cycle of the second activation signal. The second duty cycle is different from the first duty cycle. The third switch is connected to the second switch and receives the second current. The control circuit is connected to the third switch and sends a control signal to the third switch. The third switch outputs a third current according to the control signal and the second current. The light emitting unit is connected to the third switch and the first switch, and the light emitting unit emits light according to the first current or the third current.

In the embodiment of the present invention, when the first switch, the second switch, and the third switch are turned on, the light-emitting unit is driven by the first current and the third current to emit light.

In the embodiment of the present invention, when the first switch and the second switch are turned on and the third switch is turned off, the light-emitting unit is driven by the first current to emit light.

In the embodiment of the present invention, the frequencies of the first activation signal and the second activation signal are different from each other.

In the embodiment of the present invention, the first activation signal and the second activation signal enable the first switch and the second switch to be turned on alternately.

In the embodiment of the present invention, the first switch and the second switch are triggered by a negative edge.

In the embodiment of the present invention, the driving circuit is a current source circuit.

In the embodiment of the present invention, the control circuit includes a transistor and a capacitor, the first end of the transistor is connected to the control end of the third switch, and the capacitor is arranged between the transistor and the third switch.

In the embodiment of the present invention, the third switch is triggered by a negative edge.

In the embodiment of the present invention, when the driving circuit is in the first mode, the light-emitting unit has a first brightness, and when the driving circuit is in the second mode, the light-emitting unit has a second brightness, and the second brightness is higher than the first brightness.

As mentioned above, the pixel circuit of the present invention enables the light-emitting unit to have different brightness through the manipulation of the first switch, the second switch, and the third switch.

10: Drive circuit

20: First switch

30: second switch

40: third switch

50: control circuit

60: light-emitting unit

C1, C2: Capacitance

CM: Current mirror circuit

Data: data line

Duty1: First duty cycle

Duty2: second duty cycle

EM1: First activation signal

EM2: Second activation signal

I1: first current

I2: second current

I3: third current

I _OLED : current

A1, A2: Signal

Scan: scan line

S1: first end

D1: second end

G1: Control terminal

T, T1, T2, T3, T41, T42, T5, T6, T7: Transistor

T1, T2, T11, T12, T13, T14: point in time

V _A , V _B , V _C , V _REF , V _DATA , V _DD : voltage

V _TH6 : critical voltage

VGL: first voltage

VGH: second voltage

Fig. 1 is a configuration diagram of the first embodiment of the pixel circuit of the present invention.

FIG. 2A is a schematic diagram of the first aspect of the first embodiment of the pixel circuit of the present invention.

FIG. 2B is a waveform diagram of the first aspect of the first embodiment of the pixel circuit of the present invention.

FIG. 3A is a schematic diagram of the second aspect of the first embodiment of the pixel circuit of the present invention.

FIG. 3B is a waveform diagram of the second aspect of the first embodiment of the pixel circuit of the present invention.

Fig. 4 is a brightness diagram of the first embodiment of the pixel circuit of the present invention in a normal state.

FIG. 5 is a brightness diagram of the first embodiment of the pixel circuit of the present invention in a high-brightness state.

FIG. 6A is a schematic diagram of the first aspect of the second embodiment of the pixel circuit of the present invention.

Fig. 6B is a waveform diagram of the first aspect of the second embodiment of the pixel circuit of the present invention.

FIG. 6C is a schematic diagram of the second aspect of the second embodiment of the pixel circuit of the present invention.

Fig. 6D is a waveform diagram of the second aspect of the second embodiment of the pixel circuit of the present invention.

FIG. 6E is a schematic diagram of the third aspect of the second embodiment of the pixel circuit of the present invention.

Fig. 6F is a waveform diagram of the third aspect of the second embodiment of the pixel circuit of the present invention.

Fig. 6G is a schematic diagram of the fourth aspect of the second embodiment of the pixel circuit of the present invention.

Fig. 6H is a waveform diagram of the fourth aspect of the second embodiment of the pixel circuit of the present invention.

Fig. 7 is a configuration diagram of the third embodiment of the pixel circuit of the present invention.

The advantages, features, and technical methods of the present invention will be described in more detail with reference to exemplary embodiments and the accompanying drawings to make it easier to understand, and the present invention can be implemented in different forms, so it should not be understood to be limited to what is here. The stated embodiments, on the contrary, for those with ordinary knowledge in the technical field, the provided embodiments will make this disclosure more thorough, comprehensive and complete to convey the scope of the present invention, and the present invention will only be additional Defined by the scope of the patent application.

It should be understood that although the terms "first", "second", etc. may be used in the present invention to describe various elements, components, regions, layers and/or parts, these elements, components, regions, layers and/or parts Should not be restricted by these terms. These terms are only used to distinguish one element, component, region, layer and/or section from another element, component, region, layer and/or section. Therefore, the "first element", "first part", "first area", "first layer" and/or "first part" discussed below can be referred to as "second element", "second part" , "Second Area", "Second Layer" and/or "Second Part" without departing from the spirit and teachings of the present invention.

In addition, the terms "including" and/or "including" refer to the existence of the features, regions, wholes, steps, operations, elements, and/or components, but do not exclude one or more other features, regions, wholes, steps, operations , The presence or addition of elements, components, and/or combinations thereof.

Unless otherwise defined, all terms (including technical and scientific terms) used in the present invention have the same meanings as commonly understood by those of ordinary skill in the technical field to which the present invention belongs. It will be further understood that terms such as those defined in commonly used dictionaries should be interpreted as having the The related technology and the meaning in the context of the present invention are defined consistent with the meaning, and will not be construed as an idealized or excessively formal meaning unless explicitly defined as such in this document.

Please refer to FIG. 1, which is a configuration diagram of the first embodiment of the pixel circuit of the present invention. As shown in FIG. 1, the pixel circuit of the present invention includes a driving circuit 10, a first switch 20, a second switch 30, a third switch 40, a control circuit 50, and a light emitting unit 60. The first switch 20 is connected to the driving circuit 10 and is controlled by the first activation signal EM1. The first switch 20 outputs the first current I1 according to the first duty cycle Duty1 of the first activation signal EM1. The second switch 30 is connected to the driving circuit 10 and controlled by the second activation signal EM2. The second switch 30 outputs the second current I2 according to the second duty cycle Duty2 of the second activation signal EM2, the second duty cycle Duty2 and the first duty cycle Duty1 Different. The third switch 40 is connected to the second switch 30 and receives the second current I2. The control circuit 50 is connected to the third switch 40 and sends a control signal to the third switch 40, and the third switch 40 outputs a third current I3 according to the control signal and the second current. The light emitting unit 60 is connected to the third switch 40 and the first switch 20, and the light emitting unit 60 emits light according to the first current I1 or the third current I3.

The duty cycles of the first activation signal EM1 and the second activation signal EM2 are different from each other. The first activation signal EM1 and the second activation signal EM2 enable the first switch 20 and the second switch 30 to be turned on alternately, that is, the first switch 20 and the second switch 30 are not turned on at the same time. The first switch 20, the second switch 30, and the third switch 40 are all triggered by negative edges. The first switch 20 and the second switch 30 are turned on when receiving the negative edges of the first activation signal EM1 and the second activation signal EM2. The switch 20 and the second switch 30 are closed when receiving the positive edges of the first activation signal EM1 and the second activation signal EM2.

In other words, the control circuit 50 includes a transistor T and a capacitor C1. The first terminal S1 of the transistor T is connected to the control terminal (that is, the gate) of the third switch 40, and the capacitor C is disposed between the transistor T and the third switch 40. In between, the second terminal D1 of the transistor T receives the first voltage VGL and the second voltage VGH, the control terminal G1 of the transistor T turns on the transistor T, and the transistor T receives the first voltage according to the second terminal D1. VGL and the second voltage VGH output the first voltage VGL and the second voltage VGH at the first terminal S1, and the second voltage VGH is higher than the first voltage VGL. The light-emitting unit 60 can be a horizontal light-emitting diode, a flip-chip light-emitting diode, a vertical light-emitting diode or other electronic components, and is not limited to the scope of the present invention.

Please refer to FIGS. 2A to 3B, which are schematic diagrams of the first aspect of the first embodiment of the pixel circuit of the present invention, and the waveforms of the first aspect of the first embodiment of the pixel circuit of the present invention. Figure. A schematic diagram of the first aspect of the second embodiment of the pixel circuit of the present invention, and a waveform diagram of the first aspect of the second embodiment of the pixel circuit of the present invention. As shown in FIGS. 2A to 3B, the operation of the pixel circuit of the present invention is described in detail as follows: (1) As shown in FIGS. 2A and 2B, during the time point T1, the first switch 20 and the second switch 20 The switch 30 receives the first activation signal EM1 and the second activation signal EM2 and turns on alternately. The control terminal G1 of the transistor T turns on the transistor T, and the transistor T turns on the first voltage VGL according to the first voltage VGL received by the second terminal D1. The terminal S1 outputs the first voltage VGL and transmits a control signal to the third switch 40 to turn it on. The first switch 20 outputs the first current I1 to the light-emitting unit 60, and the second switch 30 outputs the second current I2 to the third switch 40 The third switch 40 outputs a third current I3 to the light-emitting unit 60 according to the control signal and the second current I2, and the light-emitting unit 60 emits light according to the first current I1 and the third current I3. For example, the time that the first current I1 flows through the light-emitting unit 60 accounts for 40% of a screen time, and the time that the third current I3 flows through the light-emitting unit 60 accounts for 60% of a screen time. The foregoing is only an example. The time ratio of the current I1 and the third current I3 flowing through the light-emitting unit 60 can be adjusted according to requirements, and is not limited to the scope of the present invention.

(2) As shown in FIGS. 3A and 3B, during the time point T2, the first switch 20 receives the first activation signal EM1 and is turned on, and the second switch 30 receives the second activation signal EM2 but is not turned on, and the transistor T The control terminal G1 turns on the transistor T, and the transistor T receives according to the second terminal D1 The second voltage VGH outputs the second voltage VGH at the first terminal S1, so that the third switch 40 is turned off, and the light-emitting unit 60 emits light according to the first current I1.

In summary, the first voltage VGL and the second voltage VGH are used to control the conduction condition of the third switch 40, so that the light-emitting unit 60 receives two currents (the first current I1 or the first current I1 and the third current I1 during the time point T1). The current I3) has two kinds of brightness, thereby reducing the complexity of the pixel circuit.

Please refer to FIGS. 4 and 5, which are the brightness diagrams of the first embodiment of the pixel circuit of the present invention in the normal state and the brightness diagrams of the first embodiment of the pixel circuit of the present invention in the high-brightness state. As shown in Figure 4, in the normal state of the pixel circuit of the present invention, when the driving circuit 10 is in the first mode (for example, L168), the light-emitting unit 60 has the first brightness (which may be, for example, 140nit), and the light-emitting unit 60 The current of the unit 60 is the first current I1 (as shown in Fig. 3A); when the driving circuit is in the second mode (for example, L255), the light-emitting unit 60 has a second brightness (which can be, for example, 350 nit) and flows through the light-emitting unit The current of 60 is the first current I1 and the third current I3 (as shown in Figure 2A), and the second brightness is higher than the first brightness.

As shown in Fig. 5, when the pixel circuit of the present invention is in a high-brightness state, when the driving circuit 10 is in the first mode (for example, L168), the light-emitting unit 60 has the first brightness (which may be, for example, 400nit), and flows through The current of the light-emitting unit 60 is the first current I1 (as shown in Figure 3A); when the driving circuit is in the second mode (for example, L255), the light-emitting unit 60 has a second brightness (which may be, for example, 1000 nit), and flows through the light The current of the unit 60 is the first current I1 and the third current I3 (as shown in FIG. 2A), and the second brightness is higher than the first brightness. It should be noted that the current of the driving circuit 10 in the normal state and the high-brightness state is not the same. For example, the current flowing through the driving circuit 10 in the normal state is 3A, and the driving circuit 10 is in the high-brightness state. The current flowing through is 5A. The current flowing through the driving circuit 10 in the high-brightness state is higher than the current flowing in the normal state. The current value of the driving circuit 10 in the high-brightness state and in the normal state can be Adjusted according to actual conditions, it is not limited to the scope of the present invention.

Please refer to FIGS. 6A to 6H, which are the schematic diagrams of the first aspect of the second embodiment of the pixel circuit of the present invention, and the waveforms of the first aspect of the second embodiment of the pixel circuit of the present invention. Figure. Schematic diagram of the second aspect of the second embodiment of the pixel circuit of the present invention, the waveform diagram of the second aspect of the second embodiment of the pixel circuit of the present invention, and the second aspect of the pixel circuit of the present invention The schematic diagram of the third aspect of the embodiment, the waveform diagram of the third aspect of the second embodiment of the pixel circuit of the present invention, the schematic diagram of the fourth aspect of the second embodiment of the pixel circuit of the present invention, the present invention Waveform diagram of the fourth aspect of the second embodiment of the pixel circuit of the invention. As shown in FIGS. 6A to 6H, the driving circuit 10 of the second embodiment of the present invention is composed of a plurality of transistors T1 to T6. The transistor T1 and the first switch 20 are controlled by the first start signal EM1. T2 is controlled by the second switch 30 and the second activation signal EM2.

Here, the operation of the second embodiment of the present invention is described in detail as follows: (1) As shown in FIG. 6A and FIG. 6B, during the time point T11, the first switch 20 and the transistor T1 are activated by the first activation signal EM1. The second switch 30 and the transistor T2 are closed due to the positive edge of the second enable signal EM2, the transistor T5 is turned on due to the negative edge of the signal A1, and the transistors T41 and T3 are turned off due to the negative edge of the signal A2. Turn on, the control terminal G1 of the transistor T makes the transistor T non-conductive (as shown in Figure 1), the voltage V _A at point A is approximately the voltage V _REF , the voltage V _B at point B is approximately the voltage V _DATA , the light-emitting unit 60 does not emit light.

(2) As shown in Figures 6C and 6D, during the time point T12, the first switch 20 and the transistor T1 are closed due to the positive edge of the first start signal EM1, and the second switch 30 and the transistor T2 are closed due to the first start signal EM1. 2. The positive edge of the start signal EM2 is turned off, the transistor T5 is turned off due to the positive edge of the signal A1, the transistors T41, T42 and T3 are turned on due to the negative edge of the signal A2, and the control terminal G1 of the transistor T turns on the transistor T (As shown in Figure 1), the transistor T outputs the first voltage VGL or the second voltage VGH at the first terminal S1 according to the first voltage VGL or the second voltage VGH received by the second terminal D1 to charge the capacitor C1, The voltage V A at point _A is approximately the difference between the voltage V _{DD and the threshold voltage V TH6} of the transistor T6, the voltage V B at point _B is approximately the voltage V _DATA , and the light-emitting unit 60 does not emit light.

k(V _DATA -V _REF )²，k為電晶體T9的製程參數，發光單元60發光。 (3) As shown in Figures 6E and 6F, during the time point T13, the first switch 20 and the transistor T1 are turned on due to the negative edge of the first start signal EM1, and the second switch 30 and the transistor T2 are turned on due to the first start signal EM1. 2. The positive edge of the start signal EM2 is turned off, the transistor T5 is turned off due to the positive edge of the signal A1, the transistors T41, T42 and T3 are turned off due to the positive edge of the signal A2, and the control terminal G1 of the transistor T makes the transistor T not Turn on (as shown in Figure 1), the voltage V _A at point A is V _DD -|V _TH6 |+(V _REF -V _DATA ), the voltage V _B at point B is approximately the voltage V _REF , the current of the light-emitting unit 60 I _OLED is

k ( V _DATA - V _REF ) ² , k is a process parameter of the transistor T9, and the light-emitting unit 60 emits light.

k(V _DATA -V _REF )²，k為電晶體T9的製程參數，發光單元60發光。 As shown in Figures 6G and 6H, during the time point T14, the first switch 20 and the transistor T1 are closed due to the positive edge of the first activation signal EM1, and the second switch 30 and the transistor T2 are closed due to the second activation signal. The negative edge of EM2 is turned on, the transistor T5 is turned off due to the positive edge of the signal A1, the transistors T41, T42, and T3 are turned off due to the positive edge of the signal A2, and the control terminal G1 of the transistor T makes the transistor T non-conductive (e.g. As shown in Figure 1), the voltage V _A at point A is V _DD -|V _TH6 |+(V _REF -V _DATA ), the voltage V _B at point B is approximately the voltage V _REF , and the voltage V _C at point C is the first A voltage VGL, the current I _OLED of the light-emitting unit 60 is

k ( V _DATA - V _REF ) ² , k is a process parameter of the transistor T9, and the light-emitting unit 60 emits light.

Please refer to FIG. 7, which is a configuration diagram of the third embodiment of the pixel circuit of the present invention. As shown in Figure 7, the driving circuit 10 of the third embodiment of the present invention is composed of two transistors T1~T2 and a capacitor C2. The transistor T1 is connected to the scan line Scan and the data line Data, and the transistor T2 is connected to the voltage V _DD , the drive circuit 10 can also be other control structures. The drive circuit can be, for example, a current mirror circuit, a 3T1C architecture, a 3T2C architecture, a 4T1C architecture, a 4T2C architecture, a 5T1C architecture, a 5T2C architecture, a 6T1C architecture, and 6T2C. The structure and so on are not limited to the scope of the present invention.

As mentioned above, the pixel circuit of the present invention, through the control of the first switch 20, the second switch 30, and the third switch 40, enables the light-emitting unit 60 to have different brightness and reduces the complexity of the circuit.

The above descriptions are merely illustrative and not restrictive. Any equivalent modifications or alterations that do not depart from the spirit and scope of the present invention should be included in the scope of the appended patent application.

10: Drive circuit

20: First switch

30: second switch

40: third switch

50: control circuit

60: light-emitting unit

C1: Capacitance

EM1: First activation signal

EM2: Second activation signal

T: Transistor

VGL: first voltage

VGH: second voltage

V _REF , V _SS : voltage

Claims (10)

A pixel circuit comprising: a driving circuit; a first switch connected to the driving circuit and controlled by a first activation signal, the first switch outputting a first operation period according to a first duty cycle of the first activation signal Current; a second switch, connected to the drive circuit and controlled by a second start signal, the second switch outputs a second current according to a second work cycle of the second start signal, the second work cycle and the first A duty cycle is different; a third switch is connected to the second switch and receives the second current; a control circuit is connected to the third switch and sends a control signal to the third switch, and the third switch is controlled according to the The signal and the second current output a third current; and a light-emitting unit connected to the third switch and the first switch, and the light-emitting unit emits light according to the first current or the third current. According to the pixel circuit of claim 1, when the first switch, the second switch, and the third switch are turned on, the light-emitting unit is driven by the first current and the third current to emit light during the time point . In the pixel circuit of claim 1, when the first switch and the second switch are turned on and the third switch is turned off, the light-emitting unit is driven by the first current to emit light during the time point. In the pixel circuit described in claim 1, the frequencies of the first activation signal and the second activation signal are different from each other. In the pixel circuit according to claim 1, the first activation signal and the second activation signal enable the first switch and the second switch to be turned on alternately. The pixel circuit according to claim 1, wherein the first switch and the second switch are triggered by a negative edge. The pixel circuit according to claim 1, wherein the driving circuit includes a current source circuit. The pixel circuit according to claim 1, wherein the control circuit includes a transistor and a capacitor, the first terminal of the transistor is connected to the control terminal of the third switch, and the capacitor is disposed between the transistor and the third switch. Between switches. The pixel circuit according to claim 8, wherein the third switch is triggered by a negative edge. For the pixel circuit of claim 1, when the driving circuit is in a first mode, the light-emitting unit has a first brightness, and when the driving circuit is in a second mode, the light-emitting unit has a second brightness, the The second brightness is higher than the first brightness.

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