TWI420374B - Sensing circuit for capacitive touch panel and electronic device using the same - Google Patents

Description

Sensing circuit for a capacitive touch panel, and applying the foregoing sensing circuit Electronic device

The invention relates to a sensing circuit, in particular to a sensing circuit for a capacitive touch panel.

At present, the application of the touch panel is very extensive, such as a mobile phone, a screen for providing information inquiry in public places, an automatic teller machine, etc., and its intuitive operation replaces the functions of the keyboard and the mouse, and is quite convenient to use.

Please refer to FIG. 1 and FIG. 2 , which are schematic diagrams showing the sensing positions of the two capacitive touch panels 150 and 250 . In FIG. 1 , the capacitive touch panel 150 includes sensing lines in the X direction and the Y direction, that is, the sensing line X ₁ to the sensing line X ₄ and the sensing line Y ₁ to the sensing line Y ₄ , and each sensing line has a plurality of sensing lines respectively. Sensing electrodes (not shown), the sensing capacitance values of the sensing electrodes are represented by the sensing capacitance C _sense . When no touch event occurs, the value of the sense capacitor C _sense is zero, and when a touch event occurs, the value of the sense capacitor C _sense is not equal to zero. The capacitive touch panel 150 of FIG. 1 senses the touched position by sequentially scanning each scanning line. As shown in FIG. 1, the scanning order from the sensing lines Y ₁ to scan the sensing line Y _4, then X ₄ X ₁ from the sensing line to the sense line scanning. For example, when the intersection of the sensing line X ₄ and the sensing line Y ₁ is touched, the touched position is known by sensing the change in the capacitance value of the capacitance C _sense .

Another sensing method scans only the scanning lines in a single direction, and the unscanning direction inputs a Stimulating Signal. As shown in FIG. 2, the capacitive touch panel 250 also includes sensing lines in the X direction and the Y direction. That is, the sensing line X ₁ to the sensing line X ₄ and the sensing line Y ₁ to the sensing line Y ₄ , the scanning order is scanned from the sensing line X ₁ to the sensing line X ₄ , and the sensing line Y ₁ to the sensing line Y ₄ directly input the excitation signal. That is, the sensing line Y ₁ inputs the excitation signal, sequentially scans the sensing line X ₁ to the sensing line X ₄ , and then the sensing line Y ₂ inputs the excitation signal, and then sequentially scans the sensing line X ₁ to the sensing line X ₄ , and so on. The sensing capacitance C _trans represents the coupling capacitance value between the sensing line X ₁ and the sensing line Y ₁ . When the sensing line X ₁ and the sensing line Y ₁ are touched and untouched, the sensing capacitance C is sensed. _Trans has different values. As in Fig. 1, the position of the touched position is known by checking where the capacitance value of the sensing capacitor C _trans changes.

Referring to FIG. 3, a block diagram of the sensing circuit 100 in the prior art is schematically illustrated. The sensing circuit 100 includes a sensing unit 102 (sensing electrode), a sensing signal generating unit 104, and an integrator 106. The sensing unit 102 has the sensing capacitance C _{sense of} FIG. 1 or the capacitance value indicated by the sensing capacitance C _trans of FIG. 2 for indicating the presence or absence of a touch, when the capacitive touch panel 150 of FIG. 1 or When the capacitive touch panel 250 of FIG. 2 is touched, the capacitance value of the sensing unit 102 is changed, and the sensing signal generating unit 104 generates a sensing signal according to the change of the capacitance value, and the sensing signal is a voltage signal, and the input signal is a voltage signal. The integration is performed to the integrator 106, and the integration result is output to determine the position to be touched.

However, whether it is the capacitive touch panel 150 of FIG. 1 or the capacitive touch panel 250 of FIG. 2, there is a problem that noise affects the sensing signal. As is well known in the art, the sensing unit 102 is fabricated on a sensing electrode substrate (not shown), and the sensing signal generating unit 104 and the integrator 106 are fabricated on an Array substrate of the liquid crystal panel ( Not shown). A common voltage electrode (not shown) is provided between the sensing electrode substrate and the array substrate of the liquid crystal panel to provide a voltage level required for the operation of the liquid crystal panel. When the liquid crystal panel is operated, a common voltage signal provided by the common voltage electrode is not clean, that is, contains noise, for example, pre-charging of the source bus (not shown) when driving the liquid crystal panel (Pre-Charge) As well as the on and off actions of the switch, etc., noise will be generated, and the noise will enter the sensing circuit 100 of FIG. 3, which may easily cause the sensing circuit 100 to fail to sense the touched position or the problem of sensing errors. .

Therefore, a method is needed to solve the above problem that the noise affects the sensing signal.

An object of the present invention is to provide a sensing circuit for a capacitive touch panel, which can greatly reduce noise by adding a path for noise to pass through, so that noise is differentially processed through two paths having the same electrical condition. The size of the noise allows the sensing signal to be sensed correctly.

A sensing circuit for a capacitive touch panel according to the present invention includes a sensing signal portion, a reference signal portion, and an integrator. The sensing signal portion is configured to generate a sensing signal based on the capacitance value of the capacitive touch panel and receive a noise, and the capacitance value of the capacitive touch panel is touched and untouched. different. The reference signal portion is configured to receive the noise and output a reference signal and has the same electrical condition as the sensing signal portion. The integrator is configured to receive the sensing signal and the reference signal, subtract the sensing signal and the reference signal, and generate an output signal.

A sensing circuit for a capacitive touch panel according to the present invention includes a sensing signal path, a reference signal path, and a first differential amplifier. The sensing signal path is used to generate a sensing signal based on the capacitance value of the capacitive touch panel and receiving one of the noises, and the capacitance value of the capacitive touch panel is touched and untouched. different. The reference signal path is for receiving the noise and outputting a reference signal and having the same electrical condition as the sensing signal path. The first differential amplifier is configured to receive the sensing signal and the reference signal, subtract the sensing signal and the reference signal, and generate an output signal.

The technical contents of the present invention will be described in detail below with reference to the accompanying drawings.

Referring to Figure 4, a block diagram of a sensing circuit 400 in accordance with the present invention is shown. The sensing circuit 400 can reduce the influence of the noise S _noise generated by the common voltage electrode 440 in the capacitive touch panel (not shown). The sensing circuit 400 basically includes a sensing signal portion 411, a reference signal portion 421, and an integrator 406. The sensing signal portion 411 is configured to generate a sensing signal S _t based on the capacitance value of the capacitive touch panel and the received noise S _noise . The capacitance value of the capacitive touch panel is different when it is touched and not touched. The reference signal unit 421 is configured to receive the noise S _noise and output a reference signal S _noise '. The reference signal unit 421 is an analog sensing signal unit 411 and has the same electrical conditions as the sensing signal unit 411. The integrator 406 is configured to receive the sensing signal S _t and the reference signal S _noise ', and the characteristic is to integrate the difference between the two inputs, so the integrator 406 subtracts the sensing signal S _t and the reference signal S _noise ' And generate an output signal S _out .

The reference signal portion 421 has a capacitance value which is substantially equal to the capacitance value when the sensing signal portion 411 is not touched. The same electrical conditions of the sensing signal portion 411 and the reference signal portion 421 refer to the electronic components of the reference signal portion 421 and the equivalent circuits of the analog sensing signal portion 411 for the impedance and capacitance values of the two. The electrical characteristics are as uniform as possible, and the purpose is to make the noise S _noise pass through the same circuit, and ensure that the noise S _noise passes through the sensing signal portion 411 and the reference signal portion 421 and enters the integrator 406 as much as possible.

In order to make the present invention easier to understand, the differences between the prior art and the present invention will be described below. Referring to Fig. 5, there is shown a circuit diagram of a first embodiment according to Fig. 4. This embodiment is a sensing circuit 500 in a capacitive touch panel for scanning one direction and then scanning another direction. The sensing signal unit 511 includes a sensing unit 512 and a sensing signal generating unit 514. The reference signal portion 521 includes a reference unit 522 and a reference signal generating unit 524.

The sensing unit 512 has a sensing capacitance value, that is, the capacitance value is represented by the sensing capacitance C _sense . When the capacitive touch panel is not touched, the capacitance of the sensing capacitor C _sense of the sensing unit 512 is zero. When the capacitive touch panel is touched, the capacitance of the sensing capacitor C _sense is not zero. . In addition, the sensing unit 512 also has a parasitic capacitance value, which is an equivalent capacitance value between the common voltage electrode 540 and the sensing electrode substrate, and is represented by a parasitic capacitance C _par1 . The noise S _noise of the common voltage electrode 540 is coupled to the sensing unit 512 via the parasitic capacitance C _par1 .

The sensing unit 512 receives the noise S _noise via the parasitic capacitance C _par1 and has a first equivalent capacitance value or a second equivalent capacitance value. The first equivalent capacitance value is a capacitance value when the capacitive touch panel is touched (ie, a capacitance value of the sensing capacitor C _sense ) and an equivalent capacitance value of a capacitance value of the parasitic capacitance C _par1 , and a second equivalent capacitance value The capacitance value of the capacitive touch panel when it is not touched (that is, the capacitance value of the sensing capacitor C _sense is zero) and the equivalent capacitance value of the capacitance value of the parasitic capacitance C _par1 . The sensing signal generating unit 514 is coupled to the sensing unit 512 to generate the sensing signal S _t according to the first equivalent capacitance value and the noise S _noise or according to the second equivalent capacitance value and the noise S _noise .

The signal of node 1 in Fig. 5 includes the portion generated by the control signal V _Toggle (such as a square wave) and the portion generated by the noise S _noise . The control signal V _Toggle is an additional signal for reflecting the occurrence of a touch event (ie, the value of the _sense capacitor C _sense ), that is, the control signal V _{Toggle is} used to set the first equivalent capacitance value or the second equivalent capacitance. The value is converted to a change in the signal to indicate the presence or absence of a touch event, wherein the control signal V _{Toggle is} coupled to the sense signal generating unit 514 through a first coupling capacitor C _c1 . As for the noise S _noise coupled through the parasitic capacitance C _par1 , the portion S _1noise generated at the node 1 can be obtained by the following formula (1):

S _noise noise in addition to the establishment of the present invention, another path portion through the outer sensing signal 511, the voltage for the common electrode 540 S _noise by the noise. The reference unit 522 receives the noise S _noise and has a third equivalent capacitance value. The third equivalent capacitance value is an equivalent capacitance value of the capacitance value of the analog capacitive touch panel when not touched and the capacitance value of the parasitic capacitance C _par1 , that is, having the same second equivalent capacitance value as the sensing unit 512 The value. Therefore, the reference unit 522 has a capacitance C _par2 for simulating the parasitic capacitance C _par1 . The noise S _{noise is} coupled to the reference unit 522 through the capacitor C _par 2 . As described above, the parasitic capacitance C _par1 is an equivalent capacitance between the common voltage electrode 540 and the sensing electrode substrate, which can be obtained by measurement, and the capacitor C _par2 is an additional capacitor having a substantial parasitic capacitance C _par1 Equal capacitance values.

The circuit of the reference signal generating unit 524 is the same as the circuit of the sensing signal generating unit 514, and outputs the reference signal S _noise ' according to the third equivalent capacitance value of the reference unit 522 and the noise S _noise . The reference signal generating unit 524 has an additional second coupling capacitor C _c2 , so that the electrical condition of the reference signal portion 521 is the same as the electrical condition of the sensing signal portion 511 , and the control signal V _{Toggle is} coupled to the first coupling capacitor C _c1 as Similarly, the sensing signal generating unit 514 is coupled to the reference signal generating unit 524 through the second coupling capacitor C _c2 so that the electrical condition of the noise S _noise passing through the reference signal portion 521 is the same as the electrical condition passing through the sensing signal portion 511. The capacitance value of the second coupling capacitor C _c2 is substantially equal to the capacitance value of the first coupling capacitor C _c1 . Therefore, the noise signal S _2noise of node 2 is:

Since the capacitance value of the capacitor C _par2 is substantially equal to the capacitance value of the parasitic capacitance C _par1 , and the capacitance value of the second coupling capacitor C _c2 is substantially equal to the capacitance value of the first coupling capacitor C _c1 , therefore:

The noise difference between the two inputs of the input integrator 506 is:

Comparing the noise S _{1noise of the prior} art of the formula (1) with the noise (S _1noise -S _2noise ) of the first embodiment of the formula (2), the size of the noise of the formula (2) is compared. The size of the noise of the equation (1) is reduced The signal integrated by the integrator 506 can eliminate the noise S _noise and increase the sensitivity of the sensing circuit 500.

The sensing signal portion 511 preferably includes a first filter 518 coupled between the sensing signal generating unit 514 and the integrator 506 for filtering the sensing signal S _t generated by the sensing signal generating unit 514. The high frequency part. The reference signal portion 521 preferably includes a second filter 528 coupled between the reference signal generating unit 524 and the integrator 506, and the circuit of the second filter 528 and the first filter 518. The circuit is the same to filter out the high frequency portion of the reference signal S _noise '.

In this embodiment, the first filter 518 includes a third resistor R ₃ coupled between the sensing signal generating unit 514 and the integrator 506; and a third capacitor C ₃ coupled to the integrator 506 and a ground. Between the ends. The second filter 528 includes a fourth resistor R ₄ coupled between the reference signal generating unit 524 and the integrator 506; and a fourth capacitor C ₄ coupled between the integrator 506 and a ground. In order to make the circuit of the first filter 518 and the circuit of the second filter 528 the same, the resistance value of the third resistor R ₃ is substantially equal to the resistance value of the fourth resistor R ₄ , and the capacitance value of the third capacitor C ₃ is the same. The capacitance values of the four capacitors C _{4 are} substantially equal.

The integrator 506 includes a first differential amplifier 532, a first resistor R ₁ and a first capacitor C ₁ . The first differential amplifier 532 has an inverting input (-), a non-inverting input (+), and an output node 4. The first resistor R _{1 is} coupled between the sensing signal portion 511 and the inverting input terminal (-). The first capacitor C _{1 is} coupled between the inverting input terminal (-) and the output node 4. In order for the noise S _noise to pass through the same path before entering the two input terminals of the first differential amplifier 532, the integrator 506 further has a ground matching unit 536 for non-inverting the input first differential amplifier 532. The circuit of the input terminal (+) is the same as the circuit of the inverting input terminal (-) of the first differential amplifier 532. The grounding matching unit 536 includes a second resistor R ₂ and a second capacitor C ₂ , and the value of the second resistor R ₂ must be equal to the value of the first resistor R _{1 , and} the value of the second capacitor C ₂ must be the same as the first The values of the capacitors C ₁ are equal. The second resistor R _{2 is} coupled between the reference signal portion 521 and the non-inverting input terminal (+) of the first differential amplifier 532, and the second capacitor C ₂ is coupled to the non-inverting phase of the first differential amplifier 532. Between the input (+) and a ground.

The sensing signal portion 511 and the first resistor R ₁ and the first capacitor C ₁ in the integrator 506 form a complete path through which the sensing signal S _t generated according to the presence or absence of the touch and the noise S _noise can be regarded as a sense. Signal path 510. The reference signal portion 521 and the second resistor R ₂ and the second capacitor C ₂ of the integrator 506 form a path through which the noise S _noise passes, which can be regarded as the reference signal path 520. The reference signal path 520 is an analog sense signal path 510 such that the electrical conditions of the two paths are the same.

The output of the integrator 506 is further coupled to an amplifying unit 530 for amplifying the output signal S _out generated by the integrator 506. The amplifying unit 530 includes a second differential amplifier 534, a fifth resistor R ₅ and a sixth resistor R ₆ . The second differential amplifier 534 has an inverting input (-), a non-inverting input (+), and an output node 3, and the non-inverting input (+) is coupled to the output node 4 of the integrator 506. The fifth resistor R _{5 is} coupled between the inverting input terminal (-) and a ground terminal. The sixth resistor R _{6 is} coupled between the inverting input terminal (-) and the output node 3.

Sense signal generation unit 514 of the switch SW ₁ is switched to different scan lines, each scan line comprising a plurality of sensing unit 512, the rest of the element comprises an integrator 506, a first filter 518, the reference unit 522, the reference signal The generating unit 524, the ground matching unit 536, the second filter 528, and the amplifying unit 530 are portions shared by all the scanning lines.

In the actual circuit layout, the sensing signal generating unit 514, the first filter 518, the reference signal portion 521, the integrator 506, and the amplifying unit 530 are generally integrated on the array substrate of the liquid crystal panel, or are formed independently of the array substrate. As described above, each sensing unit 512 is a sensing electrode in the capacitive touch panel and is fabricated on the sensing electrode substrate.

Referring to Figure 6, there is shown a circuit diagram of a second embodiment according to Figure 4. This embodiment is an embodiment of the sensing circuit 600 in a capacitive touch panel for scanning only one direction and inputting an excitation signal in the other direction. The sensing signal unit 611 includes a sensing unit 612 and a sensing signal generating unit 614. The reference signal portion 621 includes a reference unit 622 and a reference signal generating unit 624.

When the capacitive touch panel is touched, the sensing unit 612 has a sensing capacitance value, that is, a capacitance value represented by the sensing capacitance C _trans . The capacitance value when the capacitive touch panel is not touched, that is, the capacitance value of the capacitance C _trans ' when the reference unit 622 simulates that the capacitive touch panel is not touched. In addition, the sensing unit 612 and having a parasitic capacitance, to the parasitic capacitance and the parasitic capacitance C _par3 C _par5 common voltage is represented as the equivalent capacitance value between the sensing electrode 640 and the electrode substrate. The noise S _noise of the common voltage electrode 640 is coupled to the sensing unit 612 via the parasitic capacitance C _par3 .

The sensing unit 612 receives the noise S _noise via the parasitic capacitance C _par3 and has a first equivalent capacitance value or a second equivalent capacitance value. A first capacitance value of the equivalent capacitance value of the capacitive touch panel is touched when the (sensing capacitor of capacitance value C _trans) and the parasitic capacitance C _par3, the equivalent capacitance value of C _par5, the second, etc. capacitance C _trans' when the effect of the capacitance value of the capacitive touch panel is untouched and the parasitic capacitance capacitance value C _par3, the equivalent capacitance value of C _par5. The sensing signal generating unit 614 is coupled to the sensing unit 612, and generates the sensing signal S _t according to the first equivalent capacitance value and the noise S _noise or according to the second equivalent capacitance value and the noise S _noise .

The signal of node 5 in Fig. 6 includes the portion generated by the control signal V _Toggle (such as a square wave) and the portion generated by the noise S _noise . The control signal V _Toggle is an additional signal for reflecting the occurrence of a touch event (ie, the value of the sensing capacitor C _trans ), that is, the control signal V _{Toggle is} used to use the first equivalent capacitance value or the second equivalent capacitance. The value is converted to a change in the signal to indicate the presence or absence of a touch event, wherein the control signal V _{Toggle is} directly applied to the sensing unit 612 and the sensing signal generating unit 614. As _par3 noise S _noise coupling through the parasitic capacitance generated in the node C _S 5noise 5 may be part of the following (3) formula:

S _noise noise in addition to the establishment of the present invention, another path through the outer portion 611 sensing signal, S _noise for noise passed through the common electrode 640 voltage. The reference unit 622 receives the noise S _noise and has a third equivalent capacitance value. The third capacitance value of the equivalent capacitance C _trans analog capacitive touch panel when the untouched 'and the capacitance value of the parasitic capacitance C _par3, the equivalent capacitance value of C _par5, i.e. having the sensing unit The second equivalent capacitance value of 612 is the same value. Thus the reference unit 622, and a capacitor having a capacitance _C par4 _C par6 represent the analog parasitic capacitance C _par3, C _par5. The noise S _{noise is} coupled to the reference unit 622 through the capacitor C _par4 . As with the first embodiment of FIG fifth example, the capacitance _C par4 and the capacitance of the capacitor _C par6 is applied, each having a substantially equal capacitance value of the parasitic capacitance and the capacitance C _par3 C _par5.

The circuit of the reference signal generating unit 624 is the same as the circuit of the sensing signal generating unit 614, and outputs the reference signal S _noise ' according to the third equivalent capacitance value of the reference unit 622 and the noise S _noise . In order to make the electrical condition of the reference signal portion 621 and the electrical condition of the sensing signal portion 611 the same, the control signal V _{Toggle is} directly applied to the reference unit 622 and the reference signal generated as applied to the sensing unit 612 and the sensing signal generating unit 614. The unit 624 is such that the electrical condition of the noise S _noise passing through the reference signal portion 621 is the same as the electrical condition passing through the sensing signal portion 611. Therefore, the noise S _6noise of node 6 is:

Since the capacitance value of the capacitance of the parasitic capacitance _C par4 C _par3 the capacitance value is substantially equal, thus:

The noise difference between the two inputs of the input integrator 606 is:

Comparing the noise S _{5noise of the prior} art of the formula (3) with the noise (S _5noise -S _6noise ) of the second embodiment of the formula (4), the size of the noise of the equation (4) is compared. The size of the noise of the equation (3) is reduced The signal integrated by the integrator 606 can eliminate the noise S _noise and increase the sensitivity of the sensing circuit 600.

In an embodiment of the circuit, the actual circuits of the first filter 618, the second filter 628, the integrator 606, the ground matching unit 636, and the amplifying unit 630 are as described in the first embodiment of FIG. 5 above, and thus are no longer Narration.

As FIG. 5, the sensing signal 611 plus integrator portion 606 of the seventh resistor R ₇ and the seventh capacitor C ₇ according to a complete absence of the sense of touch, and the generated noise signal S _t S _noise as measured by the The path can be regarded as the sensing signal path 610. The reference signal portion 621 and the eighth resistor R ₈ and the eighth capacitor C ₈ of the integrator 606 form a path through which the noise S _noise passes, which can be regarded as the reference signal path 620. The reference signal path 620 is an analog sense signal path 610 such that the electrical conditions of the two paths are the same.

The invention increases the reference signal path for the noise to pass, so that the noise passes through the sensing signal path and the reference signal path with the same electrical condition, and then outputs to the two input ends of the differential amplifier, and the two paths are transmitted through the differential amplifier. After the noise is subtracted, the size of the noise in the sensing signal is greatly reduced, so that the output of the differential amplifier can only be correctly sensed by the signal generated by the sensing component, thereby increasing the sensitivity and correctness of the sensing circuit. .

FIG. 7 illustrates an electronic device 700 including a capacitive touch panel 750, wherein the capacitive touch panel 750 includes one of the sensing circuits 400, 500, and 600 in accordance with the present invention. The capacitive touch panel 750 including one of the sensing circuits 400, 500, and 600 as shown in FIGS. 4 through 6 may be part of the electronic device 700. The electronic device 700 includes a capacitive touch panel 750 and a power supply 740 coupled to the capacitive touch panel 750 for supplying power to the capacitive touch panel 750. The electronic device 700 can be a mobile phone, a digital camera, a personal digital assistant, a notebook computer, a desktop computer, a television, a satellite navigation, an on-board display, an aviation display, or a portable digital video disc (DVD). Video camera, etc.

The present invention has been described above with respect to the preferred embodiments, but the description is merely illustrative and not intended to limit the invention. The scope of the present invention is defined by the scope of the appended claims, and should not be construed as being limited by the scope of the invention. Specific forms.

1-6. . . node

100, 400, 500, 600. . . Sense circuit

102, 512, 612. . . Sensing unit

104, 514, 614. . . Sense signal generating unit

106, 406, 506, 606. . . Integrator

150, 250, 750. . . Capacitive touch panel

411, 511, 611. . . Sense signal department

421, 521, 621. . . Reference signal department

440, 540, 640. . . Common voltage electrode

510, 610. . . Sense signal path

518, 618. . . First filter

520, 620. . . Reference signal path

522, 622. . . Reference unit

524, 624. . . Reference signal generation unit

528, 628. . . Second filter

530, 630. . . Amplification unit

532. . . First differential amplifier

534. . . Second differential amplifier

536, 636. . . Ground matching unit

700. . . Electronic device

740. . . Power Supplier

R ₁ -R ₈ . . . First resistance - eighth resistance

C ₁ -C4. . . First capacitor - fourth capacitor

_{C par, C par1, C par3} , C par5. . . Parasitic capacitance

C _par2 , C _par4 , C _par6 . . . capacitance

C _sense , C _trans . . . Sense capacitance

C _trans '. . . Capacitance when the sensing unit is not touched

C _c1 . . . First coupling capacitor

C _c2 . . . Second coupling capacitor

SW ₁ . . . switch

S _t . . . Sense signal

S _noise . . . Noise

S _noise '. . . Reference signal

S _out . . . Output signal

X ₁ -X ₄ , Y ₁ -Y ₄ . . . Sensing line

FIG. 1 and FIG. 2 are schematic diagrams showing two capacitive touch panels sensing a touched position;

Figure 3 is a block diagram showing the sensing circuit in the prior art;

Figure 4 is a block diagram showing a sensing circuit in accordance with the present invention;

Figure 5 is a circuit diagram showing a first embodiment according to Figure 4;

Figure 6 is a circuit diagram showing a second embodiment according to Figure 4;

FIG. 7 illustrates an electronic device including a capacitive touch panel, wherein the capacitive touch panel includes a sensing circuit in accordance with the present invention.

400. . . Sense circuit

406. . . Integrator

411. . . Sense signal department

421. . . Reference signal department

440. . . Common voltage electrode

S _t . . . Sense signal

S _noise . . . Noise

S _noise '. . . Reference signal

S _out . . . Output signal

Claims (17)

A sensing circuit for a capacitive touch panel includes: a sensing signal portion for generating a sensing signal based on a capacitance value of the capacitive touch panel and receiving a noise signal, the capacitive type The capacitance value of the touch panel is different when it is touched and not touched; a reference signal portion is configured to receive the noise and output a reference signal, and the reference signal portion has the same as the sensing signal portion. And an integrator for receiving the sensing signal and the reference signal, subtracting the sensing signal and the reference signal, and generating an output signal, wherein: the sensing signal portion comprises: a sense The measuring unit receives the noise via a parasitic capacitance, the sensing unit has a first equivalent capacitance value or a second equivalent capacitance value, and the first equivalent capacitance value is that the capacitive touch panel is touched The capacitance value of the time and the equivalent capacitance value of the capacitance value of the parasitic capacitance, the second equivalent capacitance value is a capacitance value of the capacitive touch panel when not touched and an equivalent capacitance of the capacitance value of the parasitic capacitance Value; and one The signal generating unit is coupled to the sensing unit, and generates the sensing signal according to the first equivalent capacitance value and the noise, or according to the second equivalent capacitance value and the noise; and the reference signal portion The method includes: a reference unit receiving the noise and having a third equivalent capacitance value, wherein the third equivalent capacitance value is a capacitance value when the capacitive touch panel is not touched and the An equivalent capacitance value of the capacitance value of the parasitic capacitance; and a reference signal generating unit coupled to the reference unit, and outputting the reference signal according to the third equivalent capacitance value and the noise, wherein the reference unit has the sense The circuit of the same unit is measured, and the reference signal generating unit has the same circuit as the sensing signal generating unit. The sensing circuit of claim 1, wherein the reference signal portion has a capacitance value that is substantially equal to a capacitance value when the sensing signal portion is not touched. The sensing circuit of claim 1, wherein the reference signal portion has electronic components connected to simulate an equivalent circuit of the sensing signal portion. The sensing circuit of claim 1, wherein the integrator comprises: a first differential amplifier having an inverting input terminal, a non-inverting input terminal, and an output node; a first resistor, A first end is coupled to the sensing signal portion, and a second end is coupled to the inverting input terminal; and a first capacitor having a first end coupled to the inverting input end, and a first end The second end is coupled to the output node. The sensing circuit of claim 4, wherein the integrator further comprises a grounding matching unit, the grounding matching unit comprising: a second resistor having a first end coupled to the reference signal portion, and One The second end is coupled to the non-inverting input terminal; and the second capacitor has a first end coupled to the non-inverting input end, and a second end coupled to a ground end, wherein the second resistor has a resistance The value is substantially equal to the resistance of the first resistor, and the capacitance of the second capacitor is substantially equal to the capacitance of the first capacitor. The sensing circuit of claim 5, wherein the sensing signal portion further includes a first filter coupled between the sensing signal generating unit and the integrator for filtering The high frequency portion of the sensing signal generated by the sensing signal generating unit; and the reference signal portion further includes a second filter coupled between the reference signal generating unit and the integrator, and the second filtering The circuit of the device is the same as the circuit of the first filter for filtering the high frequency portion of the reference signal. The sensing circuit of claim 5, comprising: a first coupling capacitor, a control signal coupled to the sensing signal generating unit via the first coupling capacitor; and a second coupling capacitor, the control The signal is coupled to the reference signal generating unit via the second coupling capacitor, wherein a capacitance value of the first coupling capacitor is substantially equal to a capacitance value of the second coupling capacitor. The sensing circuit of claim 5, wherein the reference unit comprises a capacitor, the capacitance value of the capacitor is substantially equal to a capacitance value of the parasitic capacitor, and the noise is coupled to the capacitor through the capacitor Reference unit. The sensing circuit described in claim 1 of the patent application further includes an enlarged single The element is coupled to the integrator for amplifying the output signal generated by the integrator. A sensing circuit for a capacitive touch panel includes: a sensing signal path for generating a sensing signal based on a capacitance value of the capacitive touch panel and receiving a noise signal, the capacitive type The capacitance value of the touch panel is different when it is touched and not touched; a reference signal path is used to receive the noise and output a reference signal having the same path as the sensing signal path. An electrical condition; and a first differential amplifier for receiving the sensing signal and the reference signal, subtracting the sensing signal and the reference signal, and generating an output signal, wherein: the sensing signal path includes a sensing unit receives the noise via a parasitic capacitance, the sensing unit has a first equivalent capacitance value or a second equivalent capacitance value, and the first equivalent capacitance value is the capacitive touch panel The capacitance value when being touched and the equivalent capacitance value of the capacitance value of the parasitic capacitance, the second equivalent capacitance value is a capacitance value when the capacitive touch panel is not touched and a capacitance value of the parasitic capacitance a sensing signal generating unit coupled to the sensing unit, generating the sensing signal according to the first equivalent capacitance value and the noise, or according to the second equivalent capacitance value and the noise a first resistor coupled to the sensing signal generating unit, and a second terminal coupled to the inverting input of the first differential amplifier; and a first capacitor having a first One end is coupled to the inversion of the first differential amplifier An input end and a second end are coupled to the output end of the first differential amplifier; and the reference signal path includes: a reference unit that receives the noise and has a third equivalent capacitance value, the third class The capacitance value is an equivalent capacitance value that simulates the capacitance value of the capacitive touch panel when it is not touched and the capacitance value of the parasitic capacitance; a reference signal generating unit is coupled to the reference unit, according to the third The second capacitor has a first end coupled to the reference signal generating unit, and a second end coupled to the non-inverting input of the first differential amplifier. And a second capacitor having a first end coupled to the non-inverting input of the first differential amplifier, and a second end coupled to the ground, wherein the reference unit has the sensing unit In the same circuit, the reference signal generating unit has the same circuit as the sensing signal generating unit, the resistance value of the second resistor is substantially equal to the resistance value of the first resistor, and the capacitance value of the second capacitor is substantially On and A first capacitance equal to the capacitance value. The sensing circuit of claim 10, wherein the reference signal path has a capacitance value that is substantially equal to a capacitance value when the sensing signal path is not touched. The sensing circuit of claim 10, wherein the reference signal path has electronic components connected to simulate an equivalent circuit of the sensing signal path. The sensing circuit of claim 10, wherein: The sensing signal path further includes a first filter coupled between the sensing signal generating unit and the first end of the first resistor for filtering the sense generated by the sensing signal generating unit The high frequency portion of the signal signal; and the reference signal path further includes a second filter coupled between the reference signal generating unit and the first end of the second resistor, and the circuit of the second filter The first filter has the same circuit for filtering the high frequency portion of the reference signal. The sensing circuit of claim 10, comprising: a first coupling capacitor, a control signal coupled to the sensing signal generating unit via the first coupling capacitor; and a second coupling capacitor, the control The signal is coupled to the reference signal generating unit via the second coupling capacitor, wherein a capacitance value of the first coupling capacitor is substantially equal to a capacitance value of the second coupling capacitor. The sensing circuit of claim 10, wherein the reference unit comprises a capacitor, the capacitance value of the capacitor is substantially equal to the capacitance of the parasitic capacitor, and the noise is coupled to the capacitor through the capacitor Reference unit. The sensing circuit of claim 10, further comprising an amplifying unit coupled to the first differential amplifier for amplifying the output signal generated by the first differential amplifier. An electronic device comprising: a capacitive touch panel comprising a sensing circuit according to claim 1 or 10, wherein the electronic device is a mobile phone, a digital camera, a number of assistants, and a Notebook computer, a desktop computer, a TV, a satellite guide Navigation, a car display, an aviation display or a portable digital video disc player.