TWI584254B - Drive signal generation circuit - Google Patents

Description

Drive signal generation circuit

The invention relates to a signal generating circuit, in particular to a driving signal generating circuit applied to a touch panel sensing chip.

The Integrated Touch and Driver (ITD) is a new touch display technology that integrates the display driver circuit and the touch detection circuit into one chip. The display driving circuit comprises a thin film transistor circuit composed of a plurality of display units arranged in a matrix. As shown in FIG. 1, each display unit 10 includes a thin film transistor T, and one end thereof and the thin film transistor T. The pole D is electrically connected, and the other end is connected to a liquid crystal capacitor Clc of a common electrode Vcom, wherein the common electrode Vcom is divided into two separate and adjacent blocks of the electrically connectable transmitting portion TX and the receiving portion RX. The touch detection circuit includes a transmitter 11 electrically connected to the transmitting portion TX, and a receiver 12 electrically connected to the receiving portion RX.

The display driving circuit conducts the transmitting portion TX of the common electrode Vcom and the receiving portion RX during a positive half cycle of scanning, and outputs a high voltage VGH to the gate G of the thin film transistor T to turn on the thin film transistor T. Simultaneously outputting a data signal Vs to the source S of the thin film transistor T to charge the liquid crystal capacitor Cla to control the liquid crystal molecules to be twisted Turning to the display function; then, as shown in FIG. 2, the display driving circuit does not conduct the transfer portion TX of the common electrode Vcom and the receiving portion RX during a negative half cycle of scanning, and outputs a low voltage VGL to the film. The gate of the transistor T turns off the thin film transistor T. At the same time, during the negative half cycle, the transmitter 11 outputs a pulse signal Vstim for detecting the touch to the transmitting portion TX of the common electrode Vcom, so that the pulse signal Vstim is formed between the transmitting portion TX and the receiving portion RX. The capacitor Cm is transmitted to the receiving portion RX and received by the receiver 12. Therefore, when a finger h touches a glass g on the surface of the display, a capacitor C1, C2 is formed between the finger h and the transmitting portion TX and the receiving portion RX of the common electrode Vcom, respectively, and the transmitting portion TX and the receiving portion RX are changed. The capacitance value between the capacitors Cm causes the pulse signal strength received by the receiver 12 to change. Thereby, the receiver 12 can determine whether there is a finger touching the glass and the touched position according to the received pulse wave signal.

However, as shown in FIG. 2, since a parasitic capacitance Cgd exists between the gate G and the drain D of the thin film transistor T, and at this time, the gate G of the thin film transistor T is supplied with a low voltage VGL, so that the pulse wave signal Vstim will charge the liquid crystal capacitor Clc and the parasitic capacitor Cgd, causing the pulse signal Vstim received by the receiver 12 to be weakened to affect the judgment result of the touch detection. Therefore, if the pulse signal Vstim can be prevented from charging the liquid crystal capacitor Clc and the parasitic capacitor Cgd, the above problem can be effectively solved.

Therefore, the object of the present invention is to provide a driving signal generating circuit for a touch panel sensing chip, which can avoid the gate of the thin film transistor in the display. The effect of the parasitic capacitance between the pole and the drain on detecting the pulse signal of the touch.

Therefore, the driving signal generating circuit of the present invention is applied to a touch panel sensing chip. The touch panel sensing chip integrates a display driving circuit and a touch detecting circuit. The display driving circuit includes a plurality of display units, each of which The display unit comprises a thin film transistor and a liquid crystal capacitor, one end of which is electrically connected to the drain of the thin film transistor, and the other end is connected to a common electrode, and the common electrode has a separated and adjacent transmitting portion and a receiving portion; The driving signal generating circuit supplies a high voltage and a low voltage to the display driving circuit during a discharge period to output the high voltage or the low voltage to the gate of the thin film transistor; the touch detecting circuit includes a a transmitter electrically connected to the transmitting portion and a receiver electrically connected to the receiving portion, and the transmitter outputs a pulse signal for detecting touch to the transmitting portion during a charging cycle of the driving signal generating circuit The driving signal generating circuit includes: a first capacitor having a first end and a second end; a first charge pump during the discharging period and the first The first end of the capacitor is electrically coupled to charge the first capacitor, so that the first terminal provides the high voltage, and is not electrically coupled to the first end of the first capacitor during the charging period; The second capacitor has a third end and a fourth end, and the fourth end is electrically coupled to the second end of the first capacitor at a contact; a second charge pump during the discharge period Electrically coupling with the third end of the second capacitor to charge the second capacitor to provide the third terminal with the low voltage, and not to be electrically connected to the third terminal of the second capacitor during a charging cycle Coupling; and a control circuit electrically coupled to the transmitter and the contact and during the discharge cycle The grounding is performed, and the pulse signal is outputted to the contact during the charging period, so that the first end of the first capacitor provides the high voltage and the pulse signal, and the third capacitor The terminal provides the low voltage and the pulse signal.

In an embodiment of the invention, the pulse wave signal is a square wave or a sine wave.

In an embodiment of the invention, the pulse signal can be positive or negative.

In an embodiment of the invention, the first charge pump has a first voltage source for generating the high voltage, and includes an electrical coupling between the first voltage source and the first end of the first capacitor. a first switch, during the discharging period, the first switch is turned on, the first voltage source is connected to the first capacitor and charged, and during the charging period, the first switch is turned off, so that the first switch The voltage source is disconnected from the first capacitor; and the second charge pump has a second voltage source that generates the low voltage, and includes a first end electrically coupled to the second voltage source and the second capacitor a second switch, during the discharging period, the second switch is turned on, the second voltage source is connected to the second capacitor and charged, and during the charging period, the second switch is turned off, so that The second voltage source is disconnected from the second capacitor.

In an embodiment of the invention, the control circuit includes a third switch for guiding the contact and the pulse signal, and a fourth switch for guiding the contact to the ground.

The effect of the invention is that the voltage signal supplied to the gate of the thin film transistor is synchronized with the pulse signal of the transmitter output to the transmitting portion of the common electrode, thereby eliminating The influence of the parasitic capacitance between the gate and the drain of the thin film transistor on the pulse signal enables the receiver to more accurately perform touch detection based on the received pulse signal.

2‧‧ ‧ gate driver

10‧‧‧Display unit

11‧‧‧transmitter

12‧‧‧ Receiver

21‧‧‧Drive signal generation circuit

22‧‧‧Drive Control Circuit

23‧‧‧Control circuit

24‧‧‧First voltage source

25‧‧‧second voltage source

T‧‧‧film transistor

D‧‧‧汲

G‧‧‧ gate

S‧‧‧ source

Vcom‧‧‧ common electrode

Clc‧‧ liquid crystal capacitor

TX‧‧‧Transportation Department

RX‧‧‧Receiving Department

VGH‧‧‧High voltage

VGL‧‧‧ low voltage

Cgd‧‧‧ parasitic capacitance

C1‧‧‧first capacitor

C2‧‧‧second capacitor

CP1‧‧‧first charge pump

CP2‧‧‧second charge pump

Vstim‧‧‧ pulse signal

P1‧‧‧ first end

P2‧‧‧ second end

P3‧‧‧ third end

P4‧‧‧ fourth end

P‧‧‧Contact

SW1‧‧‧ first switch

SW2‧‧‧second switch

SW3‧‧‧ third switch

SW4‧‧‧fourth switch

H‧‧‧ finger

G‧‧‧glass

Other features and effects of the present invention will be clearly shown in the embodiments with reference to the drawings, wherein: FIG. 1 is a schematic diagram illustrating that a display unit in a display driving circuit of a conventional touch panel sensing wafer is driven, FIG. FIG. 3 is a schematic diagram illustrating a touch detection circuit of a touch panel sensing chip for performing touch detection; FIG. 3 is a view illustrating an embodiment of a driving signal generating circuit of the present invention included in a gate driver of a touch panel sensing chip; 4 is a schematic diagram of a detailed circuit of the driving signal generating circuit of the embodiment; and FIG. 5 illustrates that the first capacitor and the second capacitor of the embodiment are respectively output during the charging period and the discharging period of the first (second) charge pump. Schematic diagram of the voltage signal.

Before the present invention is described in detail, it should be noted that in the following description, similar elements are denoted by the same reference numerals.

Referring to FIG. 3, an embodiment of the driving signal generating circuit of the present invention is applied to a touch panel inductive chip (Integrated Touch and Driver, ITD), which integrates a display driving circuit and a touch detection. Measuring electricity The display driving circuit comprises a thin film transistor circuit composed of a plurality of display units arranged in a matrix, and as shown in FIG. 1, each display unit 10 includes a thin film transistor T, and one end thereof and a thin film transistor T The drain D is electrically connected, and the other end is connected to a liquid crystal capacitor Clc of a common electrode Vcom, wherein the common electrode Vcom is divided into two separate and adjacent blocks which can be electrically connected to the transmitting portion TX and the receiving portion RX. The touch detection circuit includes a transmitter 11 electrically connected to the transmitting portion TX, and a receiver 12 electrically connected to the receiving portion RX.

As shown in FIG. 3, the display driving circuit further includes a gate driver 2 including the driving signal generating circuit 21 and a driving control circuit 22 of the embodiment. As shown in FIG. 4, the driving signal generating circuit 21 includes a first capacitor C1, a first charge pump CP1, a second capacitor C2, a second charge pump CP2, and a control circuit 23. The first capacitor C1 has a first terminal P1 and a second terminal P2. The first terminal P1 is electrically connected to the driving control circuit 22; the first charge pump CP1 has a first voltage source 24 that generates a high voltage VGH. The first voltage source 20 is electrically connected to the first capacitor C1 via a first switch SW1, and the first charge pump CP1 controls the first switch SW1 to conduct the first capacitor C1 and the first voltage source 24 during a discharge period. The output high voltage VGH charges the first capacitor C1, causes the first capacitor C1 to supply the high voltage VGH to the drive control circuit 22, and controls the first switch SW1 to open the first end P1 of the first capacitor C1 during a charging cycle. A voltage source 24 causes the first terminal P1 to assume a high impedance state.

The second capacitor C2 has a third terminal P3 and a fourth terminal P4. The third terminal P3 is electrically connected to the driving control circuit 22, and the fourth terminal P4 and the second terminal P2 of the first capacitor C1 are electrically connected to a contact P. The second charge pump CP2 has a second voltage source 25 that generates a low voltage VGL, and the second charge pump CP2 controls the second switch SW2 and the third terminal P3 of the second capacitor C2 to be electrically coupled during the discharge period. In order to charge the second capacitor C2, the second capacitor C2 supplies the low voltage VGL to the drive control circuit 22, and controls the second switch SW2 to open the third end P3 and the second of the second capacitor C2 during the charging period. The voltage source 25 causes the third terminal P3 to assume a high impedance state.

The control circuit 23 is electrically coupled to the transmitter 12 and the contact P to receive the pulse signal Vstim (for example, a square wave or a sine wave) provided by the transmitter 12, and includes a guiding contact P and a pulse signal Vstim. The third switch SW3, and a fourth switch SW4 that connects the contact P to the ground (GND). As shown in FIG. 4 and FIG. 5, during the discharge period, the control circuit 23 controls the third switch SW3 to ground the contact P to make the first end P1 of the first capacitor C1 and the third end P3 of the second capacitor C2. The high voltage VGH and the low voltage VGL are respectively output to the driving control circuit 22, and during the charging period, the control circuit 23 controls the fourth switch SW4 to conduct the pulse signal Vstim to the contact P, at which time the first capacitor C1 is The first end P1 and the third end P3 of the second capacitor C2 are in a high impedance state, so the voltage supplied to the drive control circuit 22 by the first end P1 of the first capacitor C1 will become the high voltage VGH plus the pulse signal Vstim, so that The voltage difference across the first capacitor C1 still maintains a high voltage VGH level, and at the same time, the second capacitor C2 The voltage supplied to the drive control circuit 22 by the third terminal P3 will become the low voltage VGL plus the pulse signal Vstim, so that the voltage difference across the second capacitor C2 remains at the low voltage VGL level. It is worth mentioning that the pulse signal Vstim can be positive (as shown by the solid line waveform in the figure) or negative (as indicated by the dotted waveform in the figure).

Therefore, as shown in FIG. 1, FIG. 3 and FIG. 5, during the positive half cycle of the scan signal of the drive control circuit 22 (corresponding to the discharge period of the first (second) charge pump CP1 (CP2)), the drive control The circuit 22 outputs a high voltage VGH to the gate of the thin film transistor T to turn on the thin film transistor T, and during the negative half cycle (corresponding to the discharge period of the first (second) charge pump CP1 (CP2)), As shown in FIG. 3, the drive control circuit 22 outputs a low voltage VGL plus a pulse signal Vstim to the gate G of the thin film transistor T to turn off the thin film transistor T. At the same time, during the negative half cycle, the transmitter 11 also synchronously outputs the pulse signal Vstim to the transmitting portion TX of the common electrode Vcom, and transmits the pulse signal Vstim to the receiving portion via the capacitor Cm formed between the transmitting portion TX and the receiving portion RX. RX is received by receiver 12. Further, since the pulse signal Vstim included in the voltage supplied to the gate G of the thin film transistor T is exactly the same as and synchronized with the pulse signal Vstim transmitted to the receiving portion RX, the pulse signal Vstim transmitted to the receiving portion RX is transmitted. The liquid crystal capacitor Clc and the parasitic capacitor Cgd are not charged, and the influence of the liquid crystal capacitor Clc and the parasitic capacitance Cgd on the pulse signal Vstim is eliminated.

Therefore, as shown in FIG. 3, when a finger h touches a glass g on the surface of the display, and at the transmitting portion TX and the receiver R of the finger h and the common electrode Vcom When the capacitors C1 and C2 are respectively formed, and the capacitance value between the transmitting portion TX and the receiving portion RX is changed, the pulse signal Vstim received by the receiver 12 is no longer affected by the parasitic capacitance Cgd, that is, the receiver 12 receives. The strength change of the pulse signal Vstim is only related to the capacitors C1 and C2, so the receiver 12 can more accurately determine whether there is a finger touching the glass g and the touched position according to the strength of the pulse signal Vstim.

In summary, the above embodiment eliminates the thin film transistor T by synchronizing the voltage signal supplied to the gate G of the thin film transistor T with the pulse signal Vstim output from the transmitter 11 to the transmitting portion TX of the common electrode Vcom. The influence of the parasitic capacitance Cgd between the gate G and the drain D on the pulse signal Vstim enables the receiver 12 to perform touch detection more accurately according to the received pulse signal Vstim, which truly achieves the effect of the present invention. purpose.

However, the above is only the embodiment of the present invention, and the scope of the invention is not limited thereto, and all the equivalent equivalent changes and modifications according to the scope of the patent application and the patent specification of the present invention are still The scope of the invention is covered.

11‧‧‧transmitter

21‧‧‧Drive signal generation circuit

23‧‧‧Control circuit

24‧‧‧First voltage source

25‧‧‧second voltage source

VGH‧‧‧High voltage

VGL‧‧‧ low voltage

C1‧‧‧first capacitor

C2‧‧‧second capacitor

CP1‧‧‧first charge pump

CP2‧‧‧second charge pump

Vstim‧‧‧ pulse signal

P1‧‧‧ first end

P2‧‧‧ second end

P3‧‧‧ third end

P4‧‧‧ fourth end

P‧‧‧Contact

SW1‧‧‧ first switch

SW2‧‧‧second switch

SW3‧‧‧ third switch

SW4‧‧‧fourth switch

Claims (5)

A driving signal generating circuit is applied to a touch panel sensing chip. The touch panel sensing chip integrates a display driving circuit and a touch detecting circuit. The display driving circuit includes a plurality of display units, and each display unit includes a display unit. a thin film transistor and a liquid crystal capacitor, one end of which is electrically connected to the drain of the thin film transistor, and the other end of which is connected to a common electrode, and the common electrode has a separated and adjacent transmitting portion and a receiving portion; the driving signal is generated The circuit provides a high voltage and a low voltage to the display driving circuit during a discharge period to output the high voltage or the low voltage to the gate of the thin film transistor; the touch detecting circuit includes a transmitting portion An electrically connected transmitter and a receiver electrically connected to the receiving portion, and the transmitter outputs a pulse signal for detecting touch to the transmitting portion during a charging cycle of the driving signal generating circuit; the driving signal The generating circuit includes: a first capacitor having a first end and a second end; a first charge pump during the discharging period and the first capacitor The second terminal is electrically coupled to charge the first capacitor to provide the high voltage to the first terminal, and is not electrically coupled to the first end of the first capacitor during the charging period; a third end and a fourth end, and the fourth end is electrically coupled to the second end of the first capacitor at a contact; a second charge pump during the discharge period and the second capacitor The third end is electrically coupled to charge the second capacitor to provide the low voltage to the third terminal, and is not electrically coupled to the third end of the second capacitor during a charging cycle; and a control circuit electrically coupled to the transmitter and the contact, and grounding the contact during the discharge period, and outputting the pulse signal to the contact during the charging period to make the first capacitor The first end provides the high voltage and the pulse signal, and the third end of the second capacitor provides the low voltage and the pulse signal. The driving signal generating circuit of claim 1, wherein the pulse wave signal is a square wave or a sine wave. The driving signal generating circuit of claim 1, wherein the pulse signal can be positive or negative. The driving signal generating circuit of claim 1, wherein the first charge pump has a first voltage source for generating the high voltage, and includes a first one electrically coupled to the first voltage source and the first capacitor a first switch between the terminals, during the discharging period, the first switch is turned on, the first voltage source is connected to the first capacitor and charged, and during the charging period, the first switch is turned off, Disconnecting the first voltage source from the first capacitor; and the second charge pump has a second voltage source that generates the low voltage, and includes a second voltage source and the second capacitor a second switch between the first ends, during the discharging period, the second switch is turned on, the second voltage source is electrically connected to the second capacitor and charged, and during the charging period, the second switch Turning off, disconnecting the second voltage source from the second capacitor. The driving signal generating circuit of claim 1, wherein the control circuit comprises a third switch for guiding the contact and the pulse signal, and a fourth switch for guiding the contact to the ground. .