TWI707325B - Light emitting diode driving circuit - Google Patents

Abstract

A light emitting diode driving circuit is disclosed. The light emitting diode driving circuit includes a first transistor, a capacitor, a driving transistor, a light emitting diode and a switch transistor. The first transistor and the switch transistor are connected to the control gate of the driving transistor. When the light emitting diode driving circuit is in a first mode, the first transistor is turned on and the switch transistor is turned off. The dimming of the light emitting diode is based on a gray scale writing signal through the first transistor. When the light emitting diode driving circuit is in a second mode, the switch transistor is turned on and the first transistor is turned off. The VGS is pulled up by the Gate off signal through the switch transistor, so as to achieve the power saving effect.

Description

Light-emitting diode drive circuit

The present invention relates to a light emitting diode (Light Emitting Diode, LED) drive circuit, in particular to a light emitting diode drive circuit in a display with high contrast display effect.

Active light-emitting diodes can be used as backlight modules of display devices, and display devices made by them can be widely used in display screens of mobile phones, televisions, car monitors, notebook computers, etc. As far as the operating principle of the light-emitting diode is concerned, as the bias voltage increases, the driving current can increase the brightness of the light-emitting diode. In order to increase the current, it is necessary to increase the voltage difference between the gate and source of the driving transistor or the voltage difference between the two ends. However, this method makes the power consumption of the transistor account for a considerable proportion. With the current demand for power saving in electronic devices, it is difficult to choose between increasing the drive current and reducing power consumption.

In the prior art, although the voltage difference can be increased by compensating the working voltage, it still does not solve the main purpose of saving power consumption. The control and driving of the light-emitting diode still consumes a considerable proportion of the driving transistor on.

In summary, the conventional light-emitting diode drive circuit still has considerable defects in use. Therefore, the present invention designs a light-emitting diode drive circuit with switching modes, To improve the lack of the existing technology, to ensure that the brightness of the light-emitting diode can be maintained and reduce the power consumption of the power line, thereby enhancing the implementation and utilization in the industry.

In view of the above-mentioned problems of the prior art, the purpose of the present invention is to provide a light-emitting diode drive circuit, which has a high-contrast display mode and a normal state display mode, and by switching between different states to solve the driving circuit Among them, thin film transistors consume too much power.

According to the above objective, an embodiment of the present invention provides a light-emitting diode driving circuit, which includes a first transistor, a capacitor, a driving transistor, a light-emitting diode, and a switching transistor. Wherein, the first transistor has a first end, a second end and a control end, and the first end is connected to the data line. The capacitor has a first end and a second end, and the first end is connected to the second end of the first transistor. The driving transistor has a first terminal, a second terminal and a control terminal. The first terminal is connected to the first voltage source and receives the first working voltage (VDD), the second terminal is connected to the second terminal of the capacitor, and the control terminal is connected to the first transistor The second end. The light emitting diode has a first end and a second end, the first end is connected to the second end of the driving transistor, and the second end is connected to the second voltage source. The switching transistor has a first end, a second end and a control end. The first end is connected to the control line, and the second end is connected to the control end of the driving transistor. When the light-emitting diode driving circuit is in the first mode, the first transistor is turned on and the switching transistor is off; when the light-emitting diode driving circuit is in the second mode, the switching transistor is turned on and the first transistor is turned off.

According to the above objective, another embodiment of the present invention provides a light-emitting diode driving circuit, which includes a first transistor, a second transistor, a third transistor, a light-emitting diode, a switching transistor, and a fourth transistor. Wherein, the first transistor has a first end, a second end and a control end, and the first end is connected to the data line. The second transistor has a first end, a second end and a control end. The first end is connected to the first The second terminal of the crystal is used for receiving the reference voltage, and the control terminal and the second terminal of the first transistor are connected to the first node. The third transistor has a first end, a second end and a control end, and the control end is connected to the first node. The light emitting diode has a first end and a second end. The first end is connected to a first voltage source and receives a first working voltage (VDD), and the second end is connected to the first end of the third transistor. The switching transistor has a first end, a second end and a control end, and the first end is connected to the control line. The fourth transistor has a first end, a second end, and a control end. The first end is connected to the second end of the switching transistor, the second end is connected to the second end of the third transistor, and the control end is connected to the switching transistor. The second end is connected to the second node. When the light emitting diode driving circuit is in the first mode, the first transistor is turned on and the switching transistor is turned off, and the first transistor, the second transistor, the third transistor and the light emitting diode form a first current mirror circuit; When the light-emitting diode driving circuit is in the second mode, the switching transistor is turned on and the first transistor is off, and the switching transistor, the fourth transistor, the third transistor and the light-emitting diode form a second current mirror circuit.

Specifically, when the light-emitting diode drive circuit is in the first mode, the control end of the first transistor can receive a high-contrast signal to turn on the first transistor, receive the gray-scale write signal transmitted by the data line, and drive the transistor The first gate-source cross voltage (VGS) corresponds to the gray-scale write signal; when the LED driving circuit is in the second mode, the control terminal of the switching transistor can receive the gate-off (GOFF) signal to turn it on The transistor is switched to drive the first gate-source cross voltage of the transistor to be pulled up to the second gate-source cross voltage by the gate-off signal. In addition, the first operating voltage of the first voltage source can be reduced to the second operating voltage (VDD').

As mentioned above, according to the light-emitting diode driving circuit disclosed in the embodiment of the present invention, it can perform local dimming operation on the board of the light-emitting diode in the first mode, so that each partition writes Enter the corresponding gray scale to form a high-contrast display effect; in the second mode, the gate-source cross-voltage can be increased, and the working voltage can be reduced to achieve the effect of power saving.

B1, B2: Boost circuit

C: Capacitance

C1: The first storage capacitor

C2: second storage capacitor

CL: control line

DL: Data line

DT: drive transistor

GOA: Gate drive array

GOFF: gate off signal

LED: light emitting diode

M1: first mode

M2: second mode

N1: the first node

N2: second node

Qn: Drive signal

S1: the first voltage source

SL: scan line

SR_R, SR_L: scanning signal transistor

SW: switching transistor

SW1: The first switching transistor

SW2: second switching transistor

T1: first transistor

T2: second transistor

T3: third transistor

T4: The fourth transistor

V1: The first boost source

V2: second boost source

VDD: first working voltage

VDD’: Second working voltage

VSS: second voltage source

11: Pull-up control circuit

12: Pull-down control circuit

13: High drive circuit

14: pull-down circuit

15: Main pull-down circuit

16: drive circuit

17: iTP circuit

20: Pixel writing circuit

30: Low power circuit

50: LED drive transistor

In order to make the technical features, content and advantages of the present invention and the effects that can be achieved more obvious, the present invention is combined with the accompanying drawings and described in detail in the form of embodiments as follows: Figure 1 is an embodiment of the present invention Schematic diagram of the LED driving circuit.

FIG. 2 is a schematic diagram of a light-emitting diode driving circuit according to another embodiment of the invention.

FIG. 3A is a schematic diagram of a boost circuit according to an embodiment of the invention.

Figure 3B is a waveform diagram of the boost circuit of the embodiment of the present invention.

FIG. 4A is a schematic diagram of a boost circuit according to another embodiment of the invention.

Figure 4B is a waveform diagram of a boost circuit according to another embodiment of the invention.

FIG. 5 is a block diagram of a light-emitting diode driving circuit according to an embodiment of the present invention.

In order to understand the technical features, content and advantages of the present invention and its achievable effects, the present invention is described in detail in the form of embodiments with accompanying drawings as follows. The figures used therein are only For the purpose of illustrating and supplementing the description, it may not be the true proportions and precise configuration after the implementation of the present invention. Therefore, the proportions and configuration relationships of the attached drawings should not be interpreted or limited to the scope of rights of the present invention in actual implementation. Narrate.

In the drawings, the thickness or width of layers, films, panels, regions, light guides, etc., are exaggerated for clarity. Throughout the specification, the same reference numerals denote the same elements. It should be understood that when an element such as a layer, film, region, or substrate is referred to as being "on" or "connected" to another element, it can be directly on or connected to the other element, or Intermediate elements can Also exists. Conversely, when an element is referred to as being "directly on" or "directly connected to" another element, there are no intervening elements. As used herein, "connection" can refer to a physical and/or electrical connection. Furthermore, "electrically connected" or "coupled" may mean that there are other elements between two elements. In addition, it should be understood that although the terms “first”, “second”, and “third” may be used herein to describe various elements, components, regions, layers and/or parts, they are used to refer to an element, component , Region, layer and/or part are distinguished from another element, component, region, layer and/or part. Therefore, it is only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or its sequence relationship.

Unless otherwise defined, all terms (including technical and scientific terms) used herein have meanings commonly understood by those skilled in the art 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 meanings consistent with their meanings in the context of related technologies and the present invention, and will not be interpreted as idealized or excessive The formal meaning, unless explicitly defined as such in this article.

Please refer to FIG. 1, which is a schematic diagram of a light-emitting diode driving circuit according to an embodiment of the present invention. As shown in the figure, the light emitting diode driving circuit includes a first transistor T1, a capacitor C, a driving transistor DT, a light emitting diode LED, and a switching transistor SW. The first transistor T1 has a first terminal, a second terminal and a control terminal. The first terminal is connected to the data line DL, the second terminal is connected to the control terminal of the driving transistor DT, and the control terminal is connected to the scan line SL. The capacitor C has a first end and a second end, the first end is connected to the second end of the first transistor T1, and the second end is connected between the driving transistor DT and the light emitting diode LED. The driving transistor DT has a first terminal, a second terminal and a control terminal. The first terminal is connected to the first voltage source S1 and receives the first working voltage VDD, the second terminal is connected to the second terminal of the capacitor C, and the control terminal is connected to the first power source S1. The second end of crystal T1. The light emitting diode LED has a first end and a second end, the first end is connected to the second end of the driving transistor DT, and the second end is connected to the second voltage source VSS. The switching transistor SW has a first end, a second end and a control end, the first end is connected to Connected to the control line CL, the second end is connected to the control end of the driving transistor DT, and the control end is connected between the first end and the control line CL.

The driving circuit defined in this embodiment is formed in a plurality of pixel arrays interlaced by a plurality of data lines DL and scan lines SL, and the first transistor T1 in each pixel area can receive the data signal of the data line DL and cooperate with the scan The scan signal provided by the line SL writes the grayscale value of the corresponding pixel area to control the dimming degree of the light-emitting diode LED. The sub-millimeter light-emitting diode (Mini LED) display device formed by the pixel array can be Achieve high contrast display effect. In this embodiment, when the light-emitting diode driving circuit is in the first mode M1, the first transistor T1 receives the high-contrast signal from the scan line SL to turn on the first transistor T1, and receives the gray level of the data line DL Write the signal. The capacitor C in the driving circuit stores the voltage of the gray-scale write signal, so that the driving transistor DT determines the first gate-source voltage (VGS) of the driving transistor DT according to the stored voltage, and further generates a driving current to control the light-emitting second The brightness of the polar body LED. At this time, the switching transistor SW is in the off state and disconnected from the control terminal of the driving transistor DT. Although each of the above-mentioned pixel regions can be controlled by the corresponding first transistor T1 to control the dimming degree of the region, the above-mentioned high-contrast display state control method requires a large amount of power to be consumed on the first transistor T1. The power consumption of the display device is reduced. When the display device does not require a high-contrast display effect, for example, when performing a general paper operation or displaying a menu screen, the light-emitting diode driving circuit is switched to the second mode M2.

Also referring to Figure 1, in this embodiment, when the LED driving circuit is in the second mode M2, the first transistor T1 is turned off to stop the grayscale writing function, and the control terminal of the switching transistor SW receives control The gate off (GOFF) signal transmitted by the line CL turns on the switching transistor SW. The second terminal of the switching transistor SW is connected to the control terminal of the driving transistor DT. When it is turned on, the gate off (GOFF) signal can turn on the driving power. The first gate-source voltage (VGS) of the crystal DT is pulled up to the first gate-source voltage (VGS'). In this embodiment, the gate off (GOFF) signal can be a high level voltage (VGH), for example, The 6V of the original data line is pulled up to greater than 10V. In one embodiment, the voltage level of the gate-off (GOFF) signal is greater than the maximum value of the data voltage transmitted by the data line DL. By pulling the gate source of the driving transistor DT high across the voltage, the voltage difference (VDS) between the first terminal and the second terminal is reduced, thus achieving the effect of power saving. In addition, all pixel areas are controlled by a gate off (GOFF) signal to drive the transistor DT, so that the current driving the light-emitting diode LED is consistent, and the pixel area used as the backlight unit in the display device is provided with uniform brightness.

Following the above embodiment, when switching to the second mode M2, the display device can further reduce the operating voltage of the first voltage source S1 through the control circuit or the control chip, for example, reduce the first operating voltage VDD to the second operating voltage VDD ', so that the driving current can maintain the brightness of the driving light emitting diode LED, while reducing the power consumption of the power line.

Please refer to FIG. 2, which is a schematic diagram of a light-emitting diode driving circuit according to another embodiment of the present invention. As shown in the figure, the light-emitting diode driving circuit includes a first transistor T1, a second transistor T2, a third transistor T3, a light-emitting diode LED, a switching transistor SW, and a fourth transistor T4. The first transistor T1 has a first terminal, a second terminal and a control terminal. The first terminal is connected to the data line DL, the second terminal is connected to the first terminal of the second transistor T2, and the control terminal is connected to the scan line SL. The second transistor T2 has a first terminal, a second terminal and a control terminal. The first terminal is connected to the second terminal of the first transistor T1. The second terminal is used to receive a reference voltage, such as the ground voltage shown in the figure. The control terminal and the second terminal of the first transistor T1 are connected to the first node N1. The third transistor has a first end, a second end and a control end. The first end is connected to the second end of the light emitting diode LED, the second end is connected to the second end of the fourth transistor T4, and the control end is connected to The first node N1. The light emitting diode LED has a first terminal and a second terminal. The first terminal is connected to the first voltage source S1 and receives the first working voltage VDD, and the second terminal is connected to the first terminal of the third transistor T3. The switching transistor SW has a first end, a second end and a control end. The first end is connected to the control line CL, and the second end is connected to the fourth transistor T4. One end, the control end is connected to the control line CL. The fourth transistor T4 has a first end, a second end and a control end. The first end is connected to the second end of the switching transistor SW, and the second end is connected to the second end of the third transistor T3. The control end is connected to the switching The second end of the transistor SW is connected to the second node N2.

The driving circuit defined in this embodiment is a current mirror circuit. When the light-emitting diode driving circuit is in the first mode M1, the first transistor T1, the second transistor T2, and the third transistor T3 are turned on, and the fourth transistor Transistor T4 and switching transistor SW are turned off. The first transistor T1, the second transistor T2, the third transistor T3 and the light emitting diode LED form a first current mirror circuit, that is, the first current mirror circuit flows through the first transistor T1. The current mirror shoots to the light-emitting diode LED and drives the light-emitting diode LED to emit light. Similar to the previous embodiment, the first transistor T1 receives the high-contrast signal from the scan line SL to turn on the first transistor T1, and receives the gray-scale write signal from the data line DL. The current of T1 is the driving current mirrored to the light-emitting diode LED, so the dimming of the light-emitting diode LED can be controlled by the gray-scale write signal to achieve a high-contrast display effect.

When the display device does not require a high-contrast display effect, the light-emitting diode driving circuit switches to the second mode M2. The first transistor T1 is turned off to stop the grayscale writing function, and the control terminal of the switching transistor SW and the first terminal receive the gate off (GOFF) signal transmitted by the control circuit CL to turn on the switching transistor SW, so that the switching transistor SW SW is connected to the fourth transistor T4, the switching transistor SW, the fourth transistor T4, the third transistor T3 and the light-emitting diode LED form a second current mirror circuit, which is mirrored by the current flowing through the switching transistor SW The light-emitting diode LED drives the light-emitting diode LED to emit light. The switching transistor SW pulls up the gate-source cross voltage (VGS) through the gate-off (GOFF) signal, so that the voltage difference (VDS) between the first terminal and the second terminal is reduced, achieving the effect of saving power while maintaining Uniform brightness.

Similar to the foregoing embodiments, the display device can further reduce the operating voltage of the first voltage source S1 through the control circuit or the control chip, for example, reduce the first operating voltage VDD to the second operating voltage VDD' enables the driving current to maintain the brightness of the driving light-emitting diode LED while reducing the power consumption on the power line.

Please refer to FIG. 3A, which is a schematic diagram of a boost circuit according to an embodiment of the present invention. As shown in the figure, the light-emitting diode driving circuit includes scanning signal transistors SR_R, SR_L, capacitor C, driving transistor DT, light-emitting diode LED, and switching transistor SW. In the light-emitting diode driving circuit of this embodiment, the components and structures that are the same as those in the embodiment in FIG. 1 please refer to the foregoing example, and the description will not be repeated. However, the difference from the previous embodiment is that the light-emitting diode driving circuit may include scan signal transistors SR_R and SR_L, the control terminals of which are respectively connected to the scan lines SL. In this embodiment, different scan lines SL can be used. Send the start signal and end signal of scanning, and then adjust the dimming state of the light-emitting diode LED in accordance with the gray-scale write signal of the data line. In the first mode, the switching transistor SW is turned off, and the light-emitting diode driving circuit writes grayscale data by scanning the signal transistors SR_R and SR_L, so that the display device can present a high-contrast effect.

In this embodiment, the main difference from the previous embodiment is that the light emitting diode drive circuit further includes a boost circuit B1, and the boost circuit B1 includes a first boost source V1 and a first storage capacitor C1. The first storage capacitor C1 includes a first end and a second end. The first end is connected to the second end of the switching transistor SW, the second end is connected to the first boost source V1, and the first storage capacitor C1 stores the first boost When the switching transistor SW is turned on, the voltage provided by the boost pulse signal of the source V1 further raises the level of the driving signal Qn provided to the driving transistor DT. Please refer to FIG. 3B, which is a waveform diagram of the boost circuit B1 of the embodiment of the present invention. As shown in the figure, when the display device is switched from the first mode to the second mode, the switching transistor SW receives the gate-off (GOFF) signal transmitted by the control circuit CL to turn on the switching transistor SW, and at the same time, the switching transistor SW is turned off (GOFF). ) The signal pulls up the level of the driving signal Qn, when the boost circuit B1 uses the first boost source After V1 provides the boost pulse signal, it can not only raise the level of the driving signal Qn, but also reduce the voltage of the gate-off (GOFF) signal to save power.

Please refer to FIG. 4A, which is a schematic diagram of a boost circuit according to another embodiment of the present invention. As shown in the figure, the light emitting diode driving circuit includes scanning signal transistors SR_R, SR_L, capacitor C, driving transistor DT, light emitting diode LED, first switching transistor SW1 and second switching transistor SW2. In the light-emitting diode driving circuit of this embodiment, the components and structures that are the same as those in the embodiment in FIG. 3A, please refer to the foregoing example, and the description will not be repeated. In this embodiment, the main difference from the embodiment in FIG. 3A is that the boost circuit B2 includes a first boost source V1, a second boost source V2, a first storage capacitor C1, and a second storage capacitor C2. In order to cooperate with two different boost sources, two switching transistors are provided correspondingly. In the first mode, the first switching transistor SW2 is turned off, and the light-emitting diode drive circuit is written by scanning signal transistors SR_R and SR_L The grayscale data enables the display device to present a high-contrast effect.

The first storage capacitor C1 includes a first end and a second end. The first end is connected to the second end of the first switching transistor SW1. The second end is connected to the first boost source V1. The first storage capacitor C1 stores the first The voltage provided by the boost pulse signal of the boost source V1. The second storage capacitor C2 includes a first terminal and a second terminal. The first terminal is connected to the second terminal of the second switching transistor SW2, the second terminal is connected to the second boost source V2, and the second storage capacitor C2 stores the second terminal. The voltage provided by the boost pulse signal of the boost source V2. Please refer to FIG. 4B, which is a waveform diagram of the boost circuit B2 according to another embodiment of the present invention. As shown in the figure, when the display device is switched from the first mode to the second mode, the first switching transistor SW1 and the second switching transistor SW2 receive the gate off (GOFF) signal transmitted by the control line CL to turn on the first switch Transistor SW1 and second switching transistor SW2 simultaneously pull up the level of driving signal Qn through the gate-off (GOFF) signal. When the boost circuit B2 provides a boost pulse signal through the first boost source V1, The level of the driving signal Qn can be raised, After the second boost source V2 provides the boost pulse signal, the level of the driving signal Qn can be raised again, so that the voltage of the gate off (GOFF) signal can be reduced in this embodiment to achieve the effect of power saving.

Please refer to FIG. 5, which is a block diagram of a light emitting diode driving circuit according to an embodiment of the present invention. As shown in the figure, the structure of the light emitting diode driving circuit includes a gate driving array GOA, a pixel writing circuit 20, a low power consumption circuit 30, and an LED driving transistor 50. The gate drive array GOA includes a pull-up control circuit 11, a pull-down control circuit 12, a high drive circuit 13, a pull-down circuit 14, a main pull-down circuit 15, a drive circuit 16, and an iTP circuit 17, which are respectively connected to the power supply lines (VSS~VGH) . When it is the turn to drive at this stage, the ST signal uses the pull-up control circuit 11 to pull up the Q(n) point to the first stage (usually the level is VGH), and then through the high drive circuit 13 to further pull Q(n) When it reaches the second stage (usually the level is 1.5~2.0VGH), the driving circuit 16 will start to charge G(n), and further turn on the pixel writing circuit 20. After this level of driving is completed, the pull-down control circuit 12 is activated, and the pull-down circuit 14 and the main pull-down circuit 15 are used to pull down the Q(n) point and the G(n) point to a low level (usually the level is VGL). In the second mode, the iTP circuit 17 will be activated to control the G(n) point at a low level.

The pixel writing circuit 20 is connected to the driving circuit 16, and the gray scale value of each pixel area is transmitted to the LED driving transistor 50 through the 8Bit control signal, that is, in the first mode, the gray scale writing signal is transmitted through the data line To the first transistor, the first transistor controls the gate source cross voltage of the LED driving transistor 50 to match the working voltage VDD and the second voltage provided by the first voltage source connected to the two ends of the LED driving transistor 50 The ground terminal voltage VSS provided by the source generates a driving current for driving the light emitting diode.

When the light-emitting diode drive circuit detects the mode switch, that is, when the user switches from the high-contrast display state to the power-saving mode of the general display state, the iTP circuit 17 will receive the gate off (GOFF) signal, and It is converted into a control signal, and the pixel writing circuit 20 is turned off. At the same time, the gate off (GOFF) signal is also sent to the low-power circuit 30, and the low-power circuit 30 sends a 1Bit control signal. The LED drives the transistor 50. In other words, when the first mode is converted to the second mode, the low-power circuit 30 turns on the switching transistor by the gate off (GOFF) signal, and the gate of the LED driving transistor 50 is pulled up by the gate off (GOFF) signal. The pole source cross-voltage, thus reducing the voltage difference required to drive the light-emitting diode, thereby achieving the effect of power saving.

The above description is only 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 attached patent application.

C: Capacitance

CL: control line

DL: Data line

DT: drive transistor

LED: light emitting diode

M1: first mode

M2: second mode

S1: the first voltage source

SL: scan line

SW: switching transistor

T1: first transistor

VDD: first working voltage

VDD’: Second working voltage

VSS: second voltage source

Claims (9)

A light-emitting diode drive circuit, comprising: a first transistor having a first end, a second end and a control end, the first end is connected to a data line; a capacitor having a first end And a second end, the first end is connected to the second end of the first transistor; a driving transistor has a first end, a second end and a control end, the first end is used to receive A first operating voltage, the second terminal is connected to the second terminal of the capacitor, and the control terminal is connected to the second terminal of the first transistor; a light emitting diode having a first terminal and a second terminal , The first terminal is connected to the second terminal of the driving transistor, the second terminal is connected to a second voltage source; and a switching transistor having a first terminal, a second terminal and a control terminal, the first terminal One end is connected to a control line, and the second end is connected to the control end of the drive transistor; wherein, when the light-emitting diode drive circuit is in a first mode, the first transistor is turned on and the switching transistor Off; when the light-emitting diode drive circuit is in a second mode, the switching transistor is turned on and the first transistor is turned off. The light-emitting diode drive circuit of claim 1, wherein when the light-emitting diode drive circuit is in the first mode, the control terminal of the first transistor receives a high-contrast signal to turn on the first circuit The crystal receives a gray-scale write signal sent by the data line, and a first gate-source cross voltage of the drive transistor corresponds to the gray-scale write signal; when the light-emitting diode drive circuit is the second In the mode, the control terminal of the switching transistor receives a gate-off signal to turn on the switching transistor, and the first gate-source cross voltage of the driving transistor is pulled by the gate-off signal Up to a second gate source cross voltage. The light-emitting diode driving circuit according to claim 2, wherein when the light-emitting diode driving circuit is in the second mode, the first operating voltage is reduced to a second operating voltage. The light-emitting diode drive circuit of claim 2, wherein the second end of the switching transistor is connected to a boost circuit, and the boost circuit provides a boost pulse signal to raise the second gate Source cross voltage. The light emitting diode drive circuit according to claim 4, wherein the boost circuit includes at least one storage capacitor. The light emitting diode driving circuit according to claim 2, wherein the gate off signal is a high-level voltage. A light-emitting diode drive circuit, comprising: a first transistor having a first end, a second end and a control end, the first end is connected to a data line; a second transistor having a A first terminal, a second terminal and a control terminal, the first terminal is connected to the second terminal of the first transistor, the second terminal is used to receive a reference voltage, the control terminal and the first transistor The second end is connected to a first node; a third transistor has a first end, a second end and a control end, and the control end is connected to the first node; a light-emitting diode having A first terminal and a second terminal, the first terminal is used for receiving a first working voltage, and the second terminal is connected to the first terminal of the third transistor; A switching transistor has a first end, a second end and a control end, the first end is connected to a control line; and a fourth transistor has a first end, a second end and a control end Terminal, the first terminal is connected to the second terminal of the switching transistor, the second terminal is connected to the second terminal of the third transistor, and the control terminal and the second terminal of the switching transistor are connected to A second node; wherein, when the light-emitting diode drive circuit is in a first mode, the first transistor is turned on and the switching transistor is turned off, the first transistor, the second transistor, and the third The transistor and the light emitting diode form a first current mirror circuit; when the light emitting diode drive circuit is in a second mode, the switching transistor is turned on and the first transistor is turned off, the switching transistor, the The fourth transistor, the third transistor and the light emitting diode form a second current mirror circuit. According to the light-emitting diode driving circuit of claim 7, when the light-emitting diode driving circuit is in the first mode, the control terminal of the first transistor receives a high contrast signal to turn on the first transistor , Receiving a gray-scale write signal sent by the data line, a driving current of the light-emitting diode corresponding to the gray-scale write signal; when the light-emitting diode driving circuit is in the second mode, the switching circuit The control terminal of the crystal receives a gate-off signal to turn on the switching transistor, and the drive current corresponds to the gate-off signal. The light emitting diode drive circuit according to claim 8, wherein when the light emitting diode drive circuit is in the second mode, the first operating voltage is reduced to a second operating voltage.

Images