TW201533632A - Photo sensing circuit and touch display panel - Google Patents

Abstract

A photo sensing circuit and a touch display panel thereof are provided. The photo sensing circuit includes a switch transistor, a photo sensing unit, a transformation transistor, a voltage compensation unit. The switch transistor transmits a touch voltage to a read data line according to a first gate signal. The photo sensing unit receives a first system voltage and a second gate signal to output a photo sensing voltage. The transformation transistor receives a second system and provides the touch voltage according to the photo sensing voltage. The voltage compensation unit electronically connects the photo sensing unit and the transformation transistor and compensates the photo sensing voltage according to a third gate signal.

Description

Light sensing circuit and touch display panel thereof

The present invention relates to a sensing circuit, and more particularly to a light sensing circuit and a touch display panel thereof.

With the rapid development and application of information technology, wireless mobile communication and information appliances, in order to achieve more convenient carrying, lighter weight and more user-friendly operation, many electronic devices have been input devices such as traditional keyboards or mice. Switching to using a touch panel as an input device. Among them, the combination of the display panel and the touch panel makes the design of the human interface more convenient.

When the touch panel is combined with the display panel in a built-in manner, it helps to reduce the volume of the electronic device and achieve the demand for volume thinning. Therefore, the technology of the touch panel built in the display panel has been gradually paid attention to, and the optical touch module is directly built into the display panel to form an optical touch display panel (optical touch display panel). The technology is gradually maturing and stable.

In general, an optical touch panel built in a display panel has a plurality of photo sensing circuits arranged in a matrix form. Check if a touch event occurs. The light sensing circuit senses the intensity of the incident light through a photoelectric element (such as a photodiode or a photoelectric crystal), and converts it into a voltage signal through a Thin Film Transistor (TFT) to determine whether the optical touch panel is A touch event occurs. However, in the case where a bias voltage is applied to the thin film transistor, there is a deterioration phenomenon, so that the threshold voltage of the thin film transistor changes. In the case of a change in the threshold voltage, the judgment of the touch event is affected, so how to make the thin film transistor operate normally becomes an important point in designing the light sensing circuit.

The invention provides a light sensing circuit and a touch display panel thereof, which can avoid abnormal operation of the light sensing circuit due to the drift of the threshold voltage of the transistor.

The light sensing circuit of the present invention comprises a switching transistor, a photosensitive unit, a conversion transistor and a voltage compensation unit. The switch transistor has a first end, a second end and a control end, wherein the first end of the switch transistor electrically receives a touch voltage, and the second end of the switch transistor is electrically connected to the read data line. The control terminal of the switching transistor receives a first gate signal. The photosensitive unit receives a first system voltage and a second gate signal, and outputs a light sensing voltage according to the second gate signal. The conversion transistor has a first end, a second end and a control end, wherein the first end of the conversion transistor receives a second system voltage, the second end of the conversion transistor provides a touch voltage, and the control of the conversion transistor The terminal receives the light sensing voltage. The voltage compensation unit receives a third gate signal, and is electrically connected to the photosensitive unit and the second end of the conversion transistor for The light sensing voltage is compensated according to the third gate signal.

The touch display panel of the present invention includes a plurality of scan lines, a plurality of data lines, a plurality of pixels, a plurality of read data lines, and a plurality of light sensing circuits as described above. The pixels are electrically connected to the corresponding scan lines and corresponding data lines. The light sensing circuit electrically connects the corresponding scan line and the corresponding read data line to output a corresponding touch voltage.

In an embodiment of the invention, a first enable period of the first gate signal is earlier than a second enable period of the second gate signal, and a second enable period of the second gate signal is earlier than the second A third enablement period of the three-gate signal.

In an embodiment of the invention, the compensated photo-sensing voltage is equal to a threshold voltage of the switching transistor.

In an embodiment of the invention, the voltage compensation unit includes an adjustment transistor having a first end, a second end, and a control end, wherein the first end of the adjustment transistor receives the photo sensing voltage and adjusts the transistor The second end is electrically connected to the second end of the conversion transistor, and the control end of the adjustment transistor receives the third gate signal.

In an embodiment of the invention, the light sensing circuit further includes a capacitor electrically connected between the light sensing voltage and a reference voltage.

In an embodiment of the invention, the photosensitive unit includes a first photo-sensing transistor having a first end, a second end, and a control end, wherein the first end of the first photo-sensing transistor receives the first A system voltage, the second end of the first photo-sensing transistor outputs a photo-sensing voltage, and the control end of the first photo-sensing transistor receives the second gate signal.

The photosensitive unit includes a second light sensing transistor and a third light sensing transistor. The second light sensing transistor has a first end, a second end, and a control end, The first end of the second photo-sensing transistor receives the first system voltage, and the control end of the second photo-sensing transistor receives the second gate signal. The third photo-sensing transistor has a first end, a second end, and a control end, wherein the first end of the third photo-sensing transistor is electrically connected to the second end of the second photo-sensing transistor, The second end of the third photo-sensing transistor outputs a photo-sensing voltage, and the control end of the third photo-sensing transistor receives the second gate signal.

In an embodiment of the invention, the photosensitive unit includes a fourth light sensing transistor and a fifth light sensing transistor. The fourth photo-sensing transistor has a first end, a second end and a control end, wherein the first end of the fourth photo-sensing transistor receives the first system voltage, and the control end of the fourth photo-sensing transistor Receive light sensing voltage. The fifth photo-sensing transistor has a first end, a second end, and a control end, wherein the first end of the fifth photo-sensing transistor is electrically connected to the second end of the fourth photo-sensing transistor, The second end of the fifth photo-sensing transistor outputs a photo-sensing voltage, and the control end of the fifth photo-sensing transistor receives the second gate signal.

The first system voltage is a system high voltage and the second system voltage is a system low voltage.

Based on the above, the light sensing circuit and the touch display panel of the embodiment of the present invention, the voltage compensation unit can adjust the light sensing voltage according to the third gate signal, thereby compensating for the drift light of the threshold voltage of the switching transistor, so that The sensing circuit can still normally detect the touch of the light touch pen. Thereby, the operation abnormality of the photo sensing circuit due to the drift of the threshold voltage of the transistor can be avoided.

The above described features and advantages of the invention will be apparent from the following description.

100‧‧‧Touch display panel

111‧‧‧ scan line

120‧‧‧Information line

130‧‧‧ pixels

140‧‧‧Read data line

150, 200, 300, 400, 500‧‧‧ light sensing circuits

1511, 151a~151c‧‧‧Photosensitive unit

153, 153a‧‧‧ voltage compensation unit

CA‧‧‧ capacitor

CLC‧‧‧Liquid Crystal Capacitor

CST‧‧‧ storage capacitor

F_n~F_n+1‧‧‧Screen period

G_n~G_n+2‧‧‧gate signal

OT1~OT5‧‧‧Light Sense Transistor

PS1~PS6‧‧‧ Pulse

TA‧‧‧Switching electric crystal

TB‧‧‧Transition transistor

TC‧‧‧Adjusting the crystal

TD‧‧‧ data transistor

Vcom‧‧‧Common voltage

VH‧‧‧ system high voltage

VL‧‧‧ system low voltage

VOP‧‧‧Light sensing voltage

VR‧‧‧reference voltage

Vt‧‧‧ touch voltage

FIG. 1A is a schematic diagram of a system of a touch display panel according to an embodiment of the invention.

FIG. 1B is a schematic diagram showing operational waveforms of a light sensing circuit according to an embodiment of the invention.

2 is a circuit diagram of a light sensing circuit in accordance with an embodiment of the present invention.

3 is a circuit diagram of a light sensing circuit in accordance with an embodiment of the present invention.

4 is a circuit diagram of a light sensing circuit in accordance with an embodiment of the present invention.

FIG. 5 is a circuit diagram of a light sensing circuit according to an embodiment of the invention.

FIG. 1A is a schematic diagram of a system of a touch display panel according to an embodiment of the invention. Referring to FIG. 1A , in the embodiment, the touch display panel 100 includes a plurality of scan lines 111 , a plurality of data lines 120 , a plurality of pixels 130 , and a plurality of read data lines 140 (only a single one is shown here). An example) and a plurality of light sensing circuits 150. The scan lines 111 respectively receive a gate signal (eg, G_n~G_n+2, n is a positive integer). The embodiment of the present invention is not limited thereto. The configuration and the proportion of the pixel 130 and the light sensing circuit 150 are used for the description.

The pixel 130 is electrically connected to the corresponding scan line 110 and the corresponding data line 120, and has a data transistor TD, a storage capacitor CST, and a liquid crystal capacitor CLC. Wherein, the first end of the data transistor TD is electrically connected to the corresponding data line 120, and the data The control terminal of the transistor TD is electrically connected to the corresponding scan line 110. The storage capacitor CST and the liquid crystal capacitor CLC are electrically connected between the second end of the data transistor TD and the common voltage Vcom.

The light sensing circuit 150 is electrically connected to the corresponding scan line 110 and the corresponding read data line 140 to output a corresponding touch voltage Vt. The light sensing circuit 150 is electrically connected to the three adjacent scan lines 110. The light sensing circuit 150 includes a switching transistor TA, a switching transistor TB, a photosensitive unit 151, and a voltage compensation unit 153. The first end of the switching transistor TA receives the touch voltage Vt, and the second end of the switching transistor TA is electrically connected to the corresponding read data line 140. The control end of the switching transistor TA is electrically connected to the corresponding scan line 111 for receiving. Gate signal G_n (corresponding to the first gate signal).

The photosensitive unit 151 receives the system high voltage VH (corresponding to the first system voltage), and is electrically connected to the corresponding scan line 111 to receive the gate signal G_n+1 (corresponding to the second gate signal), wherein the photosensitive unit 151 is based on the gate signal G_n+1 outputs the photo-sensing voltage VOP, that is, the photo-sensing unit 151 determines the voltage level of the photo-sensing voltage VOP according to the gate signal G_n+1 and the intensity of the ambient light. The first end of the conversion transistor TB receives the system low voltage VL (corresponding to the second system voltage), the second end of the conversion transistor TB provides the touch voltage Vt, and the control end of the conversion transistor TB is electrically connected to the photosensitive unit 151 for receiving Light sensing voltage VOP. The system high voltage VH and the system low voltage VL are, for example, positive voltages of 30 volts and 10 volts, respectively.

The voltage compensation unit 153 receives the gate signal G_n+2 (corresponding to the third gate signal), and electrically connects the photosensitive unit 151 and the second end of the conversion transistor TB to compensate the light sensing voltage according to the gate signal G_n+2. VOP. In other words, when voltage compensation When the unit 153 is controlled by the gate signal G_n+2, the voltage compensation unit 153 adjusts the photo sensing voltage VOP by using the photo sensing voltage VOP and corresponding to the threshold voltage of the switching transistor TB, so that the transistor TB is converted. The effect of the drift of the threshold voltage caused by the degradation can be eliminated due to the compensation of the voltage. The compensated photo-sensing voltage VOP will first be substantially equal to but lower than the threshold voltage of the switching transistor TB, but may attenuate a fixed voltage difference with time.

FIG. 1B is a schematic diagram showing operational waveforms of a light sensing circuit according to an embodiment of the invention. Referring to FIG. 1A and FIG. 1B, during each picture period (eg, F_n~F_n+1), the period during which the gate signal G_n forms a pulse wave (eg, PS1, PS4) (corresponding to the first enable period) is, for example, earlier than the gate. The period during which the signal G_n+1 forms a pulse wave (such as PS2, PS5) (corresponding to the second enable period), and the period during which the gate signal G_n+1 forms a pulse wave (such as PS2, PS5) is, for example, earlier than the gate signal G_n+ 2 A period during which pulse waves (such as PS3, PS6) are formed (corresponding to the third enable period). In the picture period F_n, it is assumed that the light sensing circuit 150 does not detect the touch of the light touch pen, that is, the rising amplitude of the light sensing voltage VOP is small, so that the light sensing voltage VOP does not exceed the conversion power. The threshold voltage Vth1 of the crystal TB.

In the picture period F_n+1, the light sensing circuit 150 outputs the touch voltage Vt according to the pulse wave PS1 of the gate signal G_n. Moreover, since the photo sensing voltage VOP does not exceed the threshold voltage Vth1 of the switching transistor TB, the touch voltage Vt outputted by the photo sensing circuit 150 does not form a pulse wave (representing that the photo sensing circuit 150 does not detect light) Touch the touch of the pen). Then, the sensing unit 151 of the photo sensing circuit 150 is turned on according to the pulse wave PS2 of the gate signal G_n+1, so that the photo sensing voltage VOP will wait. The system is at high voltage VH (ie, resets the sensing result). After the gate signal G_n+2 forms the pulse wave PS3, the voltage compensation unit 153 is turned on, so that the photo sensing voltage VOP is adjusted by the touch voltage Vt. Since the touch voltage Vt is voltage 0 at this time, the light sensing voltage VOP is not adjusted.

It is assumed that the light sensing circuit 150 detects the touch of the light touch pen during the picture period F_n+1, so that the light sensing voltage VOP exceeds the threshold voltage Vth1 of the switching transistor TB. During the picture period F_n+2, the light sensing circuit 150 outputs a touch voltage Vt forming a pulse wave according to the pulse wave PS4 of the gate signal G_n (indicating that the light sensing circuit 150 detects the touch of the light touch pen) At this time, the switching transistor TB is turned on by the photo sensing voltage VOP. Then, the sensing unit 151 of the photo sensing circuit 150 is also turned on according to the pulse wave PS5 of the gate signal G_n+1, so that the photo sensing voltage VOP is again equal to the system high voltage VH (ie, the reset sensing result is reset). ). After the gate signal G_n+2 forms the pulse wave PS6, the voltage compensation unit 153 is turned on, so that the photo sensing voltage VOP is adjusted according to the touch voltage Vt. Since the touch voltage Vt is the system low voltage VL at this time, the light sensing voltage VOP is turned down to correspond to the drift of the threshold voltage generated by the switching transistor TB receiving the high voltage (for example, drifting to the threshold voltage Vth2. The light sensing circuit 150 still detects the touch of the light touch pen during the picture period F_n+2, so that the light sensing voltage VOP exceeds the threshold voltage Vth2 of the conversion transistor TB.

According to the above, since the light sensing voltage VOP can be adjusted according to the drift of the threshold voltage of the switching transistor TB, the light sensing circuit 150 can still normally detect the touch of the light touch pen. Thereby, the transistor of the light sensing circuit 100 can be avoided. The drift of the threshold voltage of TB causes an abnormal operation.

2 is a circuit diagram of a light sensing circuit in accordance with an embodiment of the present invention. 1A and 2, wherein the same or similar elements are given the same or similar reference numerals. In this embodiment, the light sensing circuit 200 is substantially the same as the light sensing circuit 150, but the light sensing circuit 200 further includes a capacitor CA electrically connected between the light sensing voltage VOP and the reference voltage VR, wherein the reference voltage VR can be any DC voltage.

3 is a circuit diagram of a light sensing circuit in accordance with an embodiment of the present invention. 1A and 3, wherein the same or similar elements are designated by the same or similar reference numerals. In the present embodiment, the light sensing circuit 300 is substantially the same as the light sensing circuit 150, and is different in the photosensitive unit 151a and the voltage compensation unit 153a.

The photosensitive unit 151a includes a light sensing transistor OT1 (corresponding to a first light sensing transistor). The first end of the photo-sensing transistor OT1 receives the system high voltage VH, the second end of the photo-sensing transistor OT1 outputs the photo-sensing voltage VOP, and the control end of the photo-sensing transistor OT1 receives the gate signal G_n+1. The voltage compensation unit 153a includes an adjustment transistor TC. The first end of the adjustment transistor TC receives the photo-sensing voltage VOP, and the second end of the adjustment transistor TC is electrically connected to the second end of the conversion transistor TB, and the control terminal of the adjustment transistor TC receives the gate signal G_n+2.

4 is a circuit diagram of a light sensing circuit in accordance with an embodiment of the present invention.

1A, 3, and 4, wherein the same or similar elements are given the same or similar reference numerals. In the present embodiment, the light sensing circuit 400 is substantially the same as the light sensing circuit 300, which differs in the photosensitive unit 151b. The photosensitive unit 151b includes a light sensing transistor OT2 (corresponding to a second light sensing transistor) and an OT3 (corresponding to the third Light sensing transistor). The first end of the photo-sensing transistor OT2 receives the system high voltage VH, and the control end of the photo-sensing transistor OT2 receives the gate signal G_n+1. The first end of the photo-sensing transistor OT3 is electrically connected to the second end of the light-receiving transistor OT2, and the second end of the photo-sensing transistor OT3 outputs the photo-sensing voltage VOP, and the control of the photo-sensing transistor OT3 The terminal receives the gate signal G_n+1.

FIG. 5 is a circuit diagram of a light sensing circuit according to an embodiment of the invention. Please refer to FIG. 1A, FIG. 3 and FIG. 5, wherein the same or similar elements are given the same or similar reference numerals. In the present embodiment, the light sensing circuit 500 is substantially the same as the light sensing circuit 300, which differs in the photosensitive unit 151c. The photosensitive unit 151c includes a photo sensing transistor OT4 (corresponding to a fourth photo sensing transistor) and OT5 (corresponding to a fifth photo sensing transistor). The first end of the photo-sensing transistor OT4 receives the system high voltage VH, and the control end of the photo-sensing transistor OT4 receives the photo-sensing voltage VOP. The first end of the photo-sensing transistor OT5 is electrically connected to the second end of the light-receiving transistor OT4, and the second end of the photo-sensing transistor OT5 outputs a photo-sensing voltage VOP, and the photo-sensing transistor OT5 is controlled. The terminal receives the gate signal G_n+1.

In summary, in the light sensing circuit and the touch display panel of the embodiment of the invention, the voltage compensation unit can adjust the light sensing voltage according to the drift of the threshold voltage of the switching transistor, so the light sensing circuit can still detect normally. The touch of the light touched pen was detected. Thereby, the operation abnormality of the photo sensing circuit due to the drift of the threshold voltage of the transistor can be avoided.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the invention, and any one of ordinary skill in the art without departing from the invention. In the spirit and scope, the scope of protection of the present invention is subject to the definition of the appended patent application.

100‧‧‧Touch display panel

110‧‧‧ scan line

120‧‧‧Information line

130‧‧‧ pixels

140‧‧‧Read data line

150‧‧‧Light sensing circuit

151‧‧‧Photosensitive unit

153‧‧‧Voltage compensation unit

CLC‧‧‧Liquid Crystal Capacitor

CST‧‧‧ storage capacitor

G_n~G_n+2‧‧‧gate signal

TA‧‧‧Switching electric crystal

TB‧‧‧Transition transistor

TD‧‧‧ data transistor

Vcom‧‧‧Common voltage

VH‧‧‧ system high voltage

VL‧‧‧ system low voltage

VOP‧‧‧Light sensing voltage

Vt‧‧‧ touch voltage

Claims (10)

A light sensing circuit includes: a switching transistor having a first end, a second end, and a control end, the first end of the switch transistor electrically receiving a touch voltage, the switch transistor The second end is electrically connected to a read data line, the control end of the switch transistor receives a first gate signal, and a photosensitive unit receives a first system voltage and a second gate signal, and according to the The second gate signal outputs a light sensing voltage; a switching transistor has a first end, a second end and a control end, and the first end of the switching transistor receives a second system voltage, the conversion The second end of the transistor provides the touch voltage, the control terminal of the conversion transistor receives the light sensing voltage, and a voltage compensation unit receives a third gate signal and is electrically connected to the photosensitive unit and The second end of the conversion transistor is configured to compensate the photo sensing voltage according to the third gate signal. The optical sensing circuit of claim 1, wherein a first enabling period of the first gate signal is earlier than a second enabling period of the second gate signal, the second gate The second enable period of the signal is earlier than a third enable period of the third gate signal. The light sensing circuit of claim 1, wherein the compensated light sensing voltage is equal to a threshold voltage of the switching transistor. The optical sensing circuit of claim 1, wherein the voltage is supplemented The compensation unit includes: an adjustment transistor having a first end, a second end, and a control end, the first end of the adjustment transistor receiving the photo sensing voltage, the second end of the adjustment transistor being electrically The second end of the switching transistor is connected to the second transistor. The control terminal of the adjusting transistor receives the third gate signal. The optical sensing circuit of claim 1, further comprising: a capacitor electrically connected between the photo sensing voltage and a reference voltage. The light sensing circuit of claim 1, wherein the photosensitive unit comprises: a first light sensing transistor having a first end, a second end, and a control end, the first light sensation Receiving the first system voltage, the second end of the first photo-sensing transistor outputs the photo-sensing voltage, and the control end of the first photo-sensing transistor receives the first Two gate signals. The photo sensing circuit of claim 1, wherein the photosensitive unit comprises: a second photo-sensing transistor having a first end, a second end, and a control end, the second light sensation The first end of the test crystal receives the first system voltage, the control end of the second photo-sensing transistor receives the second gate signal; and a third photo-sensing transistor has a first end a second end and a control end, the first end of the third photo-sensing transistor is electrically connected to the second end of the second photo-sensing transistor, and the third photo-sensing transistor The second end outputs the photo sensing voltage, and the control end of the third photo sensing transistor receives the second gate signal. The light sensing circuit of claim 1, wherein the photosensitive unit comprises: a fourth light sensing transistor having a first end, a second end, and a control end, the fourth light sensation The first end of the photo-electric crystal receives the first system voltage, the control end of the fourth photo-sensing transistor receives the photo-sensing voltage, and a fifth photo-sensing transistor has a first end, a second end and a control end, the first end of the fifth photo-sensing transistor is electrically connected to the second end of the fourth photo-sensing transistor, the fifth photo-sensing transistor The second end outputs the photo sensing voltage, and the control end of the fifth photo sensing transistor receives the second gate signal. The optical sensing circuit of claim 1, wherein the first system voltage is a system high voltage and the second system voltage is a system low voltage. A touch display panel includes: a plurality of scan lines; a plurality of data lines; a plurality of pixels, electrically connecting corresponding scan lines and corresponding data lines; a plurality of read data lines; and a plurality of patent applications The optical sensing circuit of item 1 is electrically connected to the corresponding scan line and the corresponding read data line to output a corresponding touch voltage.