TWI706305B - Driving method for touch display panel and driving circuit for touch display panel - Google Patents

Abstract

A driving method for a touch display panel and a driving circuit for a touch display panel are provided in the present invention. When the driving circuit enters a touch mode, the clock signal is suspended and the first scan control signal and the second scan control signal are set to gate high voltage to reduce the leakage current.

Description

Driving method of touch display panel and driving circuit of touch display panel

The present invention relates to an embedded touch panel technology. Furthermore, the present invention relates to a driving method of a touch display panel and a driving circuit of the touch display panel.

In the embedded touch panel (In-Cell Touch Panel) architecture, the display driver and touch scanning are often shared hardware, time division multiplexing (Time Division Multiplexing), and display driving time (Display Term) and touch Touch Term separates time-sharing work. When the driver data is displayed, the touch scan stops or only the touch scan data is processed. When touch scanning, the display drive stops. In order to avoid noise in the embedded touch panel, reduce the scanning signal to noise ratio (S/N) value or affect the surface content value to cause false alarm points. There are three common time-sharing multiplexing modes. They are shown as Figure 1A, Figure 1B, and Figure 1C, respectively.

Figure 1A shows the prior art embedded touch A schematic diagram of the panel performing vertical blanking touch sensing (V-blanking TP term). Please refer to Figure 1A, where TP represents the touch sensing period, and DSP represents the display period. In this example, the entire touch sensing task (Touch Sensing Task) is arranged between the display frame and the frame, that is, the vertical synchronization period (V-banking).

FIG. 1B is a schematic diagram of a prior art embedded touch panel performing H-blanking TP term. Please refer to Figure 1B. In this example, one or several touch-sensing tasks are arranged between the Display Line and the line. Generally speaking, the touch-sensing tasks will be arranged in During the horizontal synchronization (H-blanking).

FIG. 1C is a schematic diagram of a prior art embedded touch panel for hybrid touch sensing. Please refer to Figure 1C. In this example, one or more touch sensing tasks are arranged between the display scan line and the line and between the display frame and the frame. In other words, it is a combination of the above two.

Generally using embedded touch architecture, the GOA (Gate on Array, gate drive circuit board) circuit is triggered by the start pulse, and it is transmitted down through the shift register S/R circuit. During the touch sensing period, TP The internal behavior will affect the image quality of the display and whether the touch sensing operation is normal, especially when the panel is at a high temperature, if the gate high voltage VGH and gate low voltage VGL are both at The behavior of high-impedance floating voltage (Hi-z floating) will cause abnormal display of the panel due to the leakage of GOA circuit.

An object of the present invention is to provide a driving circuit and a driving method for a touch display panel, which can reduce leakage current by controlling the power supply voltage to the shift register, thereby improving the abnormal display of the panel.

In view of this, the present invention provides a driving circuit for a touch display panel. The driving circuit of the touch display panel includes a gate very high voltage power supply, a gate low voltage power supply, and a gate driving circuit. The extremely high voltage power supply is used to output an extremely high voltage. The gate low voltage power supply is used to output a gate low voltage. The gate drive circuit includes N shift registers, and each shift register includes a first scan direction control node, a second scan direction control node, a clock node, an energy storage node, and an output node. The first scanning direction control node receives a first scanning direction control signal. The second scanning direction control node receives a second scanning direction control signal. The clock node is used to receive a clock signal. The energy storage node is electrically connected to the first scan direction control node through at least one transistor, and is electrically connected to the second scan direction control node through at least one transistor. The Kth output node outputs the Kth scan signal.

When the first scanning direction control signal is the gate high voltage, and the second scanning direction control signal is the gate low voltage, the gate driving circuit sequentially outputs the scanning signals from the first shift register; when the first scanning When the direction control signal is the gate low voltage and the second scanning direction control signal is the gate high voltage, the gate drive circuit is sequentially output from the Nth shift register Scan the signal. When entering the touch mode, the clock signal is suspended, and at the same time, the first scan control signal and the second scan control signal are set to a high gate voltage at the same time, so as to reduce the effect of the energy storage node on the first scan direction control node and The above-mentioned second scan direction controls the leakage current of the node.

According to the driving circuit of the touch display panel according to the preferred embodiment of the present invention, when the touch mode is entered, the clock signal is suspended, and at the same time, the first scan control signal and the second scan control signal are simultaneously The gate voltage is set to the very high voltage, and then the gate very high voltage power supply is set to high impedance, and at the same time the gate low voltage power supply is driven to maintain the gate low voltage, so as to reduce the first scan by the energy storage node The leakage current of the direction control node and the second scanning direction control node. In addition, in a preferred embodiment, when the touch mode is entered, the clock node, the first scan direction control node, and the second scan direction control node simultaneously load a touch signal to reduce panel noise , Increase the accuracy of touch.

According to the driving circuit of the touch display panel according to the preferred embodiment of the present invention, each shift register includes a first transistor, a second transistor, a third transistor, a capacitor and a pull-down circuit . The gate of the first transistor of the Kth shift register is coupled to the output end of the K-1th shift register, and the first source drain of the first transistor of the Kth shift register Is coupled to the first scan direction control node of the Kth shift register, and the second source and drain of the first transistor of the Kth shift register is coupled to the storage of the Kth shift register Can node. The gate of the second transistor of the Kth shift register is coupled to the output terminal of the K+1th shift register, and the Kth shift register is The first source and drain of the second transistor of the register is coupled to the second scan direction control node of the Kth shift register, and the second source and drain of the second transistor of the Kth shift register The energy storage node of the Kth shift register is coupled.

The gate of the third transistor of the Kth shift register is coupled to the energy storage node of the Kth shift register, and the first source and drain of the third transistor of the Kth shift register The clock node of the Kth shift register is coupled to receive a clock signal, and the second source and drain of the third transistor of the Kth shift register is coupled to the Kth shift register The output node. The first end of the capacitor of the Kth shift register is coupled to the energy storage node of the Kth shift register, and the second end of the capacitor of the Kth shift register is coupled to the Kth shifter The output terminal of the register. The pull-down circuit of the Kth shift register is coupled to the first end of the capacitor of the Kth shift register and the second source and drain of the third transistor of the Kth shift register.

The present invention also provides a driving method of a touch display panel. The driving method of the touch display panel includes the following steps: in a scan mode, according to a voltage of a first scan direction control signal and a second scan direction control signal, Determine the scanning direction, and scan sequentially according to a clock signal; when switching from scanning mode to touch mode, the driving method of the touch display panel includes the following steps: pausing the clock signal; controlling the first scanning direction signal, and The voltage of the second scan direction control signal is set to an extremely high voltage to reduce the leakage current of the energy storage node to the first scan direction control node and the second scan direction control node.

The touch display according to the preferred embodiment of the present invention When entering the touch mode, the first scan direction control signal, the second scan direction control signal, and the stopped clock signal load a touch signal at the same time to reduce panel noise and increase touch control. Accuracy.

The spirit of the present invention is to change the first scanning direction control signal and the second scanning direction control signal to the gate voltage during the period when the gate driver stops scanning and enters touch control, thereby allowing the first scanning direction control signal and The transistor on the node coupled with the second scan direction control signal is forcibly turned off, thereby reducing the leakage current of the driving circuit of the touch display panel.

In order to make the above and other objects, features and advantages of the present invention more comprehensible, preferred embodiments and accompanying drawings are described in detail as follows.

201‧‧‧Gate extremely high voltage power supply

202‧‧‧Gate low voltage power supply

203‧‧‧Gate drive circuit

VGH‧‧‧High gate voltage

VGL‧‧‧Low gate voltage

SR‧‧‧Shift register

N31‧‧‧First scan direction control node

N32‧‧‧The second scanning direction control node

N33‧‧‧Clock Node

N34‧‧‧Energy Storage Node

N35‧‧‧Output node

301‧‧‧First Transistor

302‧‧‧Second Transistor

303‧‧‧Third Transistor

304‧‧‧Capacitor

305‧‧‧Pull-down circuit

U2D‧‧‧First scan direction control signal

D2U‧‧‧Second scan direction control signal

Gn-1‧‧‧The scanning signal of the shift register of the upper level

Gn+1‧‧‧The scanning signal of the shift register of the next level

CLK‧‧‧Clock signal

AVDD‧‧‧The positive supply voltage of the panel

AVEE‧‧‧Panel negative power supply voltage

Sx‧‧‧Touch sensor signal

S801~S804‧‧‧The steps of the driving method of the touch display panel of the embodiment of the present invention

S901~S903‧‧‧The sub-steps of step S804 of the method of driving the touch display panel of the embodiment of the present invention

FIG. 1A is a schematic diagram of a prior art embedded touch panel performing vertical blank touch sensing.

FIG. 1B is a schematic diagram of a prior art embedded touch panel performing horizontal synchronous touch sensing.

FIG. 1C is a schematic diagram of a prior art embedded touch panel for hybrid touch sensing.

FIG. 2 is a circuit diagram of a driving circuit of a touch display panel according to a preferred embodiment of the present invention.

Figure 3 shows the touch screen of a preferred embodiment of the present invention Circuit diagram of the shift register of the driving circuit for controlling the display panel.

FIG. 4 is an operation waveform diagram of the shift register of the driving circuit of the touch display panel in the prior art.

FIG. 5 is an operation waveform diagram of the shift register of the driving circuit of the touch display panel according to a preferred embodiment of the present invention.

FIG. 6 is an operation waveform diagram of the shift register of the driving circuit of the touch display panel according to a preferred embodiment of the present invention.

FIG. 7 is an operation waveform diagram of the shift register of the driving circuit of the touch display panel according to a preferred embodiment of the present invention.

FIG. 8 is a flowchart of a driving method of a touch display panel according to a preferred embodiment of the present invention.

FIG. 9 is a flowchart of sub-steps of step S804 of a driving method of a touch display panel according to a preferred embodiment of the present invention.

FIG. 2 is a circuit diagram of a driving circuit of a touch display panel according to a preferred embodiment of the present invention. Please refer to FIG. 2, the driving circuit of this touch display panel includes a very high voltage power supply 201, a low voltage power supply 202 and a gate driving circuit 203. The very high voltage power supply 201 is used to output a very high voltage VGH. The gate low voltage power supply 202 is used to output a gate low voltage VGL. The gate driving circuit 203 includes N shift registers SR.

FIG. 3 is a circuit diagram of a shift register of a driving circuit of a touch display panel according to a preferred embodiment of the present invention. Please refer to 3, the shift register is implemented in the form of GOA (Gate on Array, gate drive circuit substrate), so the above transistors are all thin film transistors. The shift register includes a first scan direction control node N31, a second scan direction control node N32, a clock node N33, an energy storage node N34, an output node N35, a first transistor 301, a second Two transistors 302, a third transistor 303, a capacitor 304, and a pull-down circuit 305.

The first scanning direction control node N31 is used to input the first scanning direction control signal U2D. The second scanning direction control node N32 is used to input the second scanning direction control signal D2U. The gate of the first transistor 301 receives the output signal (marked Gn-1) of the previous stage, the first source and drain is coupled to the first scan direction control node N31, and the second source and drain is coupled to the energy storage node N34. The gate of the second transistor 302 receives the output signal (marked Gn+1) of the next stage, the first source and drain is coupled to the second scan direction control node N32, and the second source and drain is coupled to the energy storage node N34. The gate of the third transistor 303 is coupled to the energy storage node N34, the first source and drain is coupled to the clock node N33, and the second source and drain is coupled to the output node N35. The capacitor 304 is coupled between the output node N35 and the energy storage node N34. The pull-down circuit 305 is coupled to the energy storage node N34 and the output node N35.

When the first scanning direction control signal U2D is the gate high voltage VGH, and the second scanning direction control signal D2U is the gate low voltage VGL, the scanning direction of the gate driving circuit is from top to bottom (G1, G2→GN) ; When the first scanning direction control signal U2D is the gate low voltage VGL, and the second scanning direction control signal D2U is the gate high voltage VGH At this time, the scanning direction of the gate drive circuit is from bottom to top (GN, GN-1→G1). The clock signal CLK is input from the clock node N33.

FIG. 4 is an operation waveform diagram of the shift register of the driving circuit of the touch display panel in the prior art. Please refer to Figure 4, where the solid line is the ideal waveform and the dashed line is the actual waveform. In this prior art, the first scanning direction control signal U2D is the gate high voltage VGH, and the second scanning direction control signal D2U is the gate low voltage VGL as an example. When the driving circuit of the touch display panel enters the touch mode from the scan mode, the clock signal CLK is suspended and maintained at a low voltage, and the gate high voltage VGH and gate low voltage VGL are both set to high Impedance (floating).

Since the scan signal Gn-1 is the gate low voltage VGL at this time, and the second scan direction control signal D2U is also the gate low voltage VGL, theoretically, the second transistor 302 should not be turned on. In fact, since the gate low voltage VGL is originally a negative voltage, when the gate low voltage VGL floats, the current tends to charge with a higher ground voltage. In addition, the discharge speed of the first source and drain of the second transistor 302 (the end point receiving the second scan direction control signal D2U) and the gate of the second transistor 302 may be different, which often results in the second transistor 302 being slightly When turned on, the charge stored in the capacitor 304 coupled to the energy storage node N34 is discharged by the second transistor 302. This also causes that when the driving circuit of the touch display panel returns from the touch mode to the scan mode, the gate driving voltage is insufficient, resulting in abnormal display of the panel.

FIG. 5 is an operation waveform diagram of the shift register of the driving circuit of the touch display panel according to a preferred embodiment of the present invention. Please refer Referring to FIG. 5, in this embodiment, the first scanning direction control signal U2D is the gate high voltage VGH, and the second scanning direction control signal D2U is the gate low voltage VGL as an example. When the driving circuit of the touch display panel enters the touch mode from the scan mode, the clock signal CLK is suspended and maintained at a low voltage. In this embodiment, when the driving circuit of the touch display panel enters the touch mode from the scan mode, the second scan direction control signal D2U is deliberately converted from the gate low voltage VGL to the gate high voltage VGH, thereby allowing The voltage between the gate of the second transistor 302 and the first source and drain is less than the threshold voltage of the second transistor 302, so that the second transistor 302 maintains a cut-off state. Therefore, even if the gate high voltage VGH and the gate low voltage VGL are both set to high impedance (floating), the discharge effect on the path of the second transistor 302 can be reduced.

FIG. 6 is an operation waveform diagram of the shift register of the driving circuit of the touch display panel according to a preferred embodiment of the present invention. Please refer to Fig. 6, in this embodiment, similarly, when the driving circuit of the touch display panel enters the touch mode from the scan mode, the second scan direction control signal D2U is deliberately converted from the gate low voltage VGL to the gate Very high voltage VGH. However, only the gate high voltage VGH is set to high impedance (floating), and the gate low voltage VGL is maintained. In this way, the gate of the second transistor 302 will continue to be maintained at the low gate voltage VGL (negative voltage), and therefore, the second transistor 302 is forced to be maintained in a cut-off state. Therefore, in this embodiment, the discharge effect on the path of the second transistor 302 can be reduced.

Figure 7 shows the touch screen of a preferred embodiment of the present invention The operation waveform diagram of the shift register of the driving circuit of the control display panel. Please refer to Figure 7. In this embodiment, in addition to maintaining the operations in Figures 5 and 6, the first scan direction control node N31, the second scan direction control node N32, and the clock node N33 are deliberately loaded with touch Sense the signal. Since the touch sensing signal in the embedded touch panel is given to each ground electrode (VCOM) of the panel, when the voltage of the ground electrode changes, the voltage between the liquid crystal panel and the ground electrode will interfere with the accuracy of touch. In order to eliminate this type of interference, touch sensing signals are deliberately added to the gate drive part so that the voltage of the panel also floats with the touch sensing signals, thereby enhancing the accuracy of touch sensing.

In the above embodiments, only the gate low voltage VGL is also maintained, and the gate high voltage is set to high impedance. In this way, with the loading of touch sensing signals, the benefits of power saving can be achieved. For example, the positive power supply voltage (AVDD) and negative power supply voltage (AVEE) of the panel are 6V and -6V, respectively; the swing of the touch sensing signal Sx is assumed to be 4V, and the gate voltage VGH is 12V; The gate low voltage VGL is -12V. If the gate voltage VGH is not set to high impedance, and 12V is given in a full drive mode, since the touch sensing signal Sx is also loaded, the true voltage must be supplemented by the positive power supply voltage of the panel (Charge Pump) can only support 16V swing when the voltage is increased to 3 times. This design has many disadvantages: for example, the power consumption of the integrated circuit is significantly increased, the number of external flying capacitors of the integrated circuit is large, and the power supply design of the integrated circuit is more complicated.

However, if only the drive gate low voltage VGL is -12V, let the gate extremely high voltage VGH float, then the positive power supply voltage of the panel only needs to be increased to twice the voltage by the charge pump to meet the needs of the LCD panel.

Although the above embodiment takes the first scanning direction control signal U2D as the gate high voltage VGH, and the second scanning direction control signal D2U as the gate low voltage VGL as an example, those with ordinary knowledge in the technical field should know that the first The scanning direction control signal U2D is the gate low voltage VGL, and the second scanning direction control signal D2U is the gate high voltage VGH. The operation principle is the same. Therefore, the present invention is not limited to this.

FIG. 8 is a flowchart of a driving method of a touch display panel according to a preferred embodiment of the present invention. Please refer to Figure 8. The driving method of this touch display panel includes the following steps:

Step S800: start.

Step S801: Determine the scanning direction according to the voltage of a first scanning direction control signal and a second scanning direction control signal, and scan sequentially according to a clock signal.

Step S802: Determine whether to enter the touch mode. If the judgment is no, then continue to step S801, and if the judgment is yes, then go to step S803.

Step S803: Pause the clock signal.

Step S804: Set the voltages of the first scan direction control signal and the second scan direction control signal to an extremely high voltage to reduce the difference between the energy storage node and the first scan direction control node and the second scan direction control node. Leakage current.

FIG. 9 is a flowchart of sub-steps of step S804 of a driving method of a touch display panel according to a preferred embodiment of the present invention. Step S804 also includes:

Step S901: Set the gate voltage to high impedance.

Step S902: Maintain a low gate voltage.

Step S903: Load a touch signal on the clock node, the first scan direction control node, and the second scan direction control node at the same time.

In this way, in addition to increasing the accuracy of touch sensing, power consumption and circuit design complexity can be further reduced.

To sum up, the spirit of the present invention is to change the first scan direction control signal and the second scan direction control signal to the gate high voltage during the period when the gate driver stops scanning and enters touch control. The transistors on the nodes to which the scan direction control signal and the second scan direction control signal are coupled are forcibly turned off, thereby reducing the leakage current of the driving circuit of the touch display panel.

In a further embodiment of the present invention, a low-voltage power supply for driving the gate is added to maintain the low-voltage potential of the gate, and the high-voltage power supply for the gate is turned off, thereby not only reducing power consumption, but also reducing the touch display panel The leakage current of the drive circuit.

The specific embodiments proposed in the detailed description of the preferred embodiments are only used to facilitate the description of the technical content of the present invention, instead of restricting the present invention to the above-mentioned embodiments in a narrow sense, and do not exceed the spirit of the present invention and apply for patents below. The scope of the situation, the implementation of various changes, all belong to The scope of the invention. Therefore, the protection scope of the present invention shall be subject to those defined by the attached patent application scope.

S801~S804‧‧‧The steps of the driving method of the touch display panel of the embodiment of the present invention

Claims (7)

A driving circuit for a touch display panel includes: a very high voltage power supply for outputting a very high voltage; a low voltage power supply for outputting a low gate voltage; and a gate driving circuit, Including: N shift registers, each of the shift registers includes: a first scanning direction control node, receiving a first scanning direction control signal; a second scanning direction control node, receiving a second Scan direction control signal; a clock node for receiving a clock signal; an energy storage node electrically connected to the first scan direction control node through at least one transistor, and electrically connected to the second scan through at least one transistor Direction control node; and an output node, wherein the Kth output node outputs the Kth scan signal; wherein, when the first scan direction control signal is the gate high voltage, and the second scan direction control signal is the When the gate voltage is low, the gate driving circuit sequentially outputs scanning signals from the first shift register; wherein, when the first scanning direction control signal is the gate low voltage, and the second scanning direction is controlled When the signal is the very high voltage of the gate, the gate drive circuit sequentially outputs the scan signal from the Nth shift register; among them, when the touch mode is entered, the clock signal is suspended, and at the same time, the first The scan control signal and the second scan control signal are set at the same time The gate voltage is set to a very high voltage to reduce the leakage current of the energy storage node to the first scan direction control node and the second scan direction control node. For example, in the driving circuit of the touch display panel described in the first item of the scope of patent application, when the touch mode is entered, the clock node, the first scan direction control node, and the second scan direction control node simultaneously load a Touch signal. For example, the driving circuit of the touch display panel described in item 1 of the scope of patent application, wherein when entering the touch mode, the clock signal is suspended, and at the same time, the first scan control signal and the second scan control signal are simultaneously The gate voltage is set to the very high voltage, and then the gate very high voltage power supply is set to high impedance, and at the same time the gate low voltage power supply is driven to maintain the gate low voltage, so as to reduce the first scan by the energy storage node The leakage current of the direction control node and the second scanning direction control node. For the driving circuit of the touch display panel described in the first item of the patent application, each of the shift registers includes: a first transistor including a gate, a first source and drain, and a The second source drain, wherein the gate of the first transistor of the Kth shift register is coupled to the output terminal of the K-1th shift register, and the first transistor of the Kth shift register is The first source and drain of a transistor is coupled to the first scan direction control node of the Kth shift register, and the second source and drain of the first transistor of the Kth shift register is coupled to the Kth Energy storage node of a shift register; A second transistor, including a gate, a first source-drain, and a second source-drain, wherein the gate of the second transistor of the Kth shift register is coupled to the K+1th The output terminal of the shift register, the first source and drain of the second transistor of the Kth shift register is coupled to the second scan direction control node of the Kth shift register, and the Kth shift register The second source and drain of the second transistor of the bit register is coupled to the energy storage node of the Kth shift register; a third transistor includes a gate, a first source and drain, and a first Two source drains, where the gate of the third transistor of the Kth shift register is coupled to the energy storage node of the Kth shift register, and the third voltage of the Kth shift register The first source and drain of the crystal is coupled to the clock node of the Kth shift register to receive a clock signal. The second source and drain of the third transistor of the Kth shift register is coupled to the The output nodes of K shift registers; a capacitor including a first terminal and a second terminal, wherein the first terminal of the capacitor of the Kth shift register is coupled to the Kth shift register The second end of the capacitor of the Kth shift register is coupled to the output end of the Kth shift register; a pull-down circuit, where the pull-down of the Kth shift register The circuit is coupled to the first end of the capacitor of the Kth shift register and the second source and drain of the third transistor of the Kth shift register. A driving method of a touch display panel is used to drive a gate driving circuit. The gate driving circuit includes N shift registers, and each of the shift registers includes a first scanning direction A first scan direction control node of the control signal for receiving a second scan direction control A second scan direction control node of the signal, a clock node for receiving a clock signal, an energy storage node, and an output node, wherein the energy storage node is electrically connected to the first scan direction control through at least one transistor Node and electrically connected to the second scan direction control node through at least one transistor, wherein the Kth output node outputs the Kth scan signal. The driving method of the touch display panel includes: in a scan mode, according to The voltage of a first scanning direction control signal and a second scanning direction control signal determines the scanning direction and scans sequentially according to a clock signal; when the scanning mode is switched to the touch mode, the touch display panel The driving method includes the following steps: suspending the clock signal; and setting the voltages of the first scanning direction control signal and the second scanning direction control signal to an extremely high voltage, so as to reduce the energy storage node's impact on the first scanning direction. The leakage current of the control node and the above-mentioned second scan direction control node. For the driving method of the touch display panel described in item 5 of the scope of patent application, when the touch mode is entered, the clock node, the first scan direction control node, and the second scan direction control node simultaneously load a Touch signal. The method for driving a touch display panel as described in item 5 of the scope of patent application, which further includes a gate for outputting an extremely high voltage A high-voltage power supply and a gate-low-voltage power supply for outputting a gate-low-voltage, wherein when entering the touch mode, the clock signal is suspended, and at the same time, the first scan control signal and the second scan control The signal is set to the very high voltage of the gate at the same time. After that, the very high voltage power supply of the gate is set to high impedance, and the gate low-voltage power supply is driven to maintain the low voltage of the gate at the same time, so as to reduce the impact of the energy storage node on the first The leakage current of the scanning direction control node and the second scanning direction control node.

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