TW201027413A - Switched-capacitor circuit of capacitive touch panel and detection method thereof - Google Patents

Abstract

The invention provides a switched-capacitor circuit of capacitive touch panel and detection method thereof. By means of sensing the variation of the capacitance value of the side capacitance at the intersection point of the X-axis sensing line and the Y-axis sensing line, it is able to determine whether the object touches the intersection point of the X-axis sensing line and the Y-axis sensing line. Thus, the correct position of all fingers in the multiple-finger application can be recognized.

Description

201027413 VI. Description of the Invention: [Technical Leadership of the Invention] + The present invention relates to a capacitive touch panel', particularly to a switched capacitor circuit and a method for picking up a capacitive touch panel. [Prior Art] A capacitive touch panel is an input device that allows a finger to slide on a smooth panel to control the movement of the cursor. Because of its small size, low cost, low power consumption, and long service life, it is therefore It is widely used as an input device in various electronic products. The current capacitive touch panel is positioned by scanning the X-axis and the Y-axis or directly detecting the X-axis and Y-axis positions to create an anchor point at the intersection of the X-axis and the γ-axis. 1 shows a conventional capacitive touch panel 1A including a plurality of X-axis sensing lines TX1 to TX8 and a plurality of Y-axis sensing lines TY1 to TY6' when the finger 12 touches the capacitive touch panel 1 When 〇, if the capacitance value on the sensing lines TX8 and TY3 is detected to change, it can be judged that the finger is at the intersection of the sensing lines τ χ 8 and ΤΥ 3 . However, such a positioning method does not have a correct method for finger position in multi-finger applications. Figure 2 shows the situation when two fingers touch the capacitive touch panel. When the fingers 20 and 22 touch the capacitive touch panel, the sensing lines τχ2, ΤΧ4 'ΤΥ2 and ΤΥ4 are detected. The capacitance value changes, so in addition to the positions of the fingers 2〇 and 22 (ΤΧ2, ΤΥ4) and (TX4JY2), two ghost points 24 and 26 will appear at the positions (ΤΧ2, ΤΥ2) and (TX4JY4). This makes it impossible for the capacitive touch panel 10 to correctly judge the positions of the fingers 2 and 22. Therefore, one application can be achieved in a multi-specified position of the capacitive touch panel. SUMMARY OF THE INVENTION The purpose of the present invention is to propose a switching capacitor circuit and a fine method for achieving a plurality of designated bits in a capacitive touch panel. According to the present invention, the "switching capacitor circuit of the capacitive touch panel and the detecting method" generates an electrical valley value of the side-by-side electrical connection at the intersection of the 应$cord line and the second sensing line. It is judged whether there is something touching the point and the point. The switched capacitor circuit includes a first switching circuit connected to the first sensing line for connecting the first sensing line to a -first voltage terminal or a second voltage terminal, an operational amplifier '-second input terminal and An output end, the first wheel end of the operational amplifier is connected to the second voltage end, and a second switching circuit is connected to the second sensing line, the second wire is connected to the scale voltage terminal or the operational amplifier The second input end, the switching capacitor has a first end and a second end, and the first end of the switching capacitor is connected to the operation A _ the second input end is a third cut _ the circuit is connected to the operational amplifier Between the second input end and the round output end, the output end of the operational amplifier is connected to the second input end of the operational amplifier, and the fourth switching circuit is connected to the second end of the switching capacitor for The switching capacitor 'two ends are connected to the second terminal or the output terminal of the operational amplifier. 1 The detecting method includes first connecting the first sensing line and the second sensing line to a -first voltage terminal and a second power to accumulate a charge on the side capacitor. Then, the first sensing line Switching to the second voltage terminal and switching the second sensing line to the second input end of the operational amplifier, while switching the second 4 201027413 end of the switching capacitor to the output of the operational amplifier, followed by the side capacitor The charge is transferred to the switching capacitor to determine the voltage at the output of the operational amplifier, and finally, based on the voltage at the output of the operational amplifier, it is determined whether an object touches the intersection. [Embodiment] FIG. 3 shows two sensing lines τ χ and τ γ on a capacitive touch panel, and a side capacitor 30 is generated at the intersection of the sensing lines ΤΧ and ΤΥ, which has a capacitance value Cxy, when the finger touches the sensing When the intersection of the lines TX and TY is again, the capacitance value of the side capacitor 30 will change. 4 shows an embodiment of the switched capacitor circuit 4A of the present invention, wherein the inductor 50 is an equivalent circuit of the sensing lines TX and TY, and the capacitor 5002 is a sensing capacitor of the sensing line TX, which has a capacitance value (^, the capacitance 5004 is an induction The sensing capacitor of the line TY has a capacitance value Cy. In the switched capacitor circuit 40, the switching circuit 4002 has a switch SW1 connected between the voltage terminal Vc and the sensing line TX and a switch SW2 connected between the sensing line τχ and the voltage terminal Vcom. The φ switches SW1 and SW2 are respectively controlled by the clocks ρ! and p2, and the switching circuit 4004 has the switch SW3 connected between the sensing line TY and the voltage terminal Vcom and the switch SW4 connected to the sensing line TY and the input terminal 4012 of the operational amplifier 4010. The switches SW3 and SW4 are controlled by the clocks pi and P2, respectively. The operational amplifier 4010 has an input terminal 4014 and an output terminal 4016 in addition to the input terminal 4012. The input terminal 4014 of the operational amplifier 4010 is connected to the voltage terminal Vcom, and the switching capacitor is switched. The CF has a first end 4018 and a second end 4020, wherein the first end 4018 of the switching capacitor CF is connected to the input terminal 4012 of the operational amplifier 4010. The switching circuit 4006 has a switch SW5 connected to the operational amplifier 40. The input terminal 4012 between 201027413 and the output terminal 4016 is controlled by the clock ρι, and the switching circuit 4〇〇8 has a switch SW6 connected between the second terminal 4〇2〇 of the switching capacitor CF and the voltage terminal Vcom. And the switch SW7 is connected between the second end 4020 of the switching capacitor CF and the output terminal 4016 of the operational amplifier 4010, and the switches SW6 and SW7 are respectively controlled by the clocks P1 and P2. Figure 5 shows when the finger touches the sensor 5〇 In the case, when the finger touches the intersection of the sensing line τχ and TY, the sensing capacitances 5〇〇2 ❹ and 5004 of the sensing ^χ&τγ have capacitance increments Δ(:χ and ACy, respectively, while the side capacitor 30 There is also a capacitor increment ACxy. Figure 6 shows the switching capacitor circuit 4 in Figure 5 when the clock ρι turns on the switch. Figure 7 shows the switching capacitor circuit 4 in Figure 5 when the clock P2 turns on the switch Referring to FIG. 6, the clock ρι opens the switches SW1, SW3, SW5, and SW6, and the clock I»2 is turned off (touching the switch SW2, SW4, and SW7', so the sensing line TX is connected to the power terminal %, and the sensing line τ γ is connected to the voltage. At the terminal Vcom, the second end of the switching capacitor CF is connected to the voltage terminal ν·, the operational amplifier 4010 The output terminal 4016 is connected to its input terminal 4〇12. Since the sensing capacitor 5〇〇2 of the sensing reference line TX has a capacitance increment ACx, its charge

Qcx=Vcx(Cx+ACx), 弋 1 Equation 2 The sensing capacitor 5004 of the sensing line TY has a capacitance increment, so its charge Qcy=Vcomx (Cy+ACy) Similarly, the charge of the side capacitor 30 201027413

Qcxy=(Vc-Vc〇m)x(Cxy+ACxy) Equation 3 Due to the virtual grounding principle, the voltage at the input terminal 4012 of the operational amplifier 4010 is equal to the voltage ycom at the input terminal 4014, so the switching capacitors CF are terminated at 4018 and 4020. The voltage on the voltage is equal 'so the charge on the switching capacitor CF is 〇, at which time the voltage Vo on the wheel-out terminal 4016 of the operational amplifier is V=Vcom. φ Then, referring to FIG. 7, the clock P1 turns off the switches SW1, SW3, SW5 and SW6 and the clock P2 turns on the switches SW2, SW4 and SW7, so that the sensing line XX is connected to the voltage terminal Vcom' the sensing line TY is connected to the wheel of the operational amplifier 4010. The terminal 4012, the second end of the switching capacitor CF is connected to the wheel terminal 4016 of the operational amplifier 4010. The output of the sensing capacitor 5002 of the sensing line TX is turned off between the output terminal 4016 and the input terminal 4012 of the operational amplifier 4010.

Qcx=Vcomx(Cx+ACx) The charge of the sense capacitor 5004 of the sense line TY

Qcy=Vcomx(Cy+ACy) Equation 5 and the charge on the side capacitor 30 is all transferred to the switching capacitor CF'. Therefore, the charge on the side capacitor 30 is 〇, and the charge on the switching power gCF can be known from Equation 3.

Qcf=(Vb-Vcom)xCF=(Vc-Vcom)x(Cxy+ACxy) Equation 6 7 201027413 According to Equation 6, the voltage at the output of the operational amplifier 4016 can be further obtained.

Vo=[(Cxy+ACxy)/CF]x(Vc-Vcom)+Vcom Equation 7 In the switched capacitor circuit 40, the change in the capacitance values of the sensing capacitors 5002 and 5004 of the sensing lines TX and TY does not affect the switched capacitor circuit. The output v〇 causes a shadow Φ. FIG. 8 shows a case where no finger touches the sensor 50, wherein the sensing capacitors 5002 and 5004 of the sensing lines TX and TY have capacitance increments acx and ACy, respectively, but since the finger does not touch the intersection of the sensing line TX and TY, Therefore, the side capacitor 30 has no capacitance increment. Fig. 9 shows the case where the switching capacitor circuit 40 of Fig. 8 is turned on when the clock P1 is turned on. Fig. 1 is a view showing the case where the switching capacitor circuit 4 in Fig. 8 is turned on when the clock P2 is turned on. Referring to FIG. 9, the clock pi turns on the switches SW, SW3, SW5, and SW6, and the clock P2 turns off the switches SW2, ©SW4, and SW7. Therefore, the sensing line TX is connected to the voltage terminal Vc, and the sensing line TY is connected to the voltage terminal Vcom'. The second end of the switching capacitor CF is connected to the voltage terminal vcom, and the output terminal 4016 of the operational amplifier 4010 is connected to the input terminal 4012. Since the sensing capacitor 5002 of the sensing line XX has a capacitance increment ACx, the charge is as shown in the formula 1 The sensing capacitor 5004 of the 有 has a capacitance increment ACy, so its charge is as shown in Equation 2, and the charge of the side capacitor 30

Qcxy=(Vc-Vcom)xCxy Equation 8 201027413 Due to the virtual grounding principle, the voltage on the input terminal 4012 of the operational amplifier 4010 is equal to the voltage Vcom on the input terminal 4014, so the voltages across the terminals 4018 and 4020 of the switching capacitor CF are equal, The charge on the switching capacitor CF is zero, at which time the voltage on the output terminal 4016 of the operational amplifier is V 〇 = Vcom. Then, referring to FIG. 10, the clock Pi turns off the switches SWh SW3, SW5 and SW6 and the clock P2 turns on the switches SW2, SW4 and SW7. Therefore, the sensing line TX is connected to the voltage terminal Vcom' the sensing line τγ is connected to the input terminal 4012 of the operational amplifier 4010. The second end of the switching capacitor CF is connected to the output terminal 4016 of the operational amplifier 4010, and the output terminal 4016 of the operational amplifier 4〇1〇 and the input terminal 4012 are disconnected. At this time, the charge of the sensing capacitor 5002 of the sensing line TX is as In Equation 4, the charge of the sense capacitor 5〇〇4 of the sense line TY is as shown in Equation 5, and the charge on the side capacitor 30 is all transferred to the switching capacitor CF, so the charge on the side valley 30 is 〇. 'The § can be used to know the charge on the switching capacitor

Qcf=(V〇-Yc〇m) xCF=(Vc-Vcom)xCxy Equation 9 Φ According to Equation 9, the voltage on the output terminal of the operational amplifier 4010 can be further determined.

Vo=(Cxy/CF)x(Vc-Vcom)+Vcom Equation 10 From Equation 7 and Equation 10, when the finger touches the sensor 5〇, the side capacitor 3〇 will change, and the op amp side will be changed. The voltage on the output terminal 4〇16 changes, and the sense capacitances of the sense lines τχ and τγ are 5〇〇2 and 5〇〇4. The change of the capacitance value does not affect the output terminal ν〇 of the switched capacitor circuit. The multi-finger application can correctly position the finger. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a conventional capacitive touch panel; FIG. 2 shows a case where two fingers touch the capacitive touch panel of FIG. 1; FIG. 3 shows two sensings of the capacitive touch panel. Lines τ χ and τ γ ; _ Figure 4 shows an embodiment of the switched capacitor circuit of the present invention; Figure 5 shows the situation when the finger touches the inductor of Figure 4; Figure 6 shows the switched capacitor circuit of Figure 5 when the clock ρ opens the switch Figure 7 shows the switching capacitor circuit of Figure 5 when the clock P2 opens the switch; Figure 8 shows the situation when no finger touches the sensor in Figure 4; Figure 9 shows the switching capacitor circuit of Figure 8 at the time of the pulse The case when the switch is turned on; and, FIG. 10 shows the case where the switching capacitor circuit of FIG. 8 is turned on when the clock P2 is turned on. ® [Main component symbol description] 10 Capacitive touch panel 12 Finger 20 Finger 22 Finger 24 Ghost point 26 Ghost point 30 Side capacitor 201027413 40 Switching capacitor circuit 4002 Switching circuit 4004 Switching circuit 4006 Switching circuit 4008 Switching circuit 4010 Operational amplifier 4012 The input terminal 4014 of the operational amplifier 3010 The input terminal 4016 of the operational amplifier 3010 The output terminal 4018 of the operational amplifier 3010 The first end 4020 of the switching capacitor CF 40 The second end of the switching capacitor CF 50 The sensor 5002 The sensing line of the sensing line TX 5004 The sensing line TY Inductive capacitance

Claims (1)

201027413 VII. Patent application scope: i A switched capacitive circuit of a capacitive touch panel, the capacitive touch panel having a first sensing line and a second sensing line, wherein the first sensing line and the second sensing line The switching capacitor circuit includes: a first switching circuit connected to the first sensing line for connecting the first sensing line to a first voltage terminal or a second voltage terminal An operational amplifier having a first input terminal, a second input terminal, and a round output terminal. The first input terminal of the operational amplifier is connected to the second voltage terminal, and a second switching circuit v is connected to the second sensing line. The second sensing line is connected to the second voltage terminal or the second input end of the operational amplifier; the switching capacitor has a first end and a second end, and the first end of the switching capacitor is connected to the operational amplifier a second input terminal; a third switching circuit coupled between the second input terminal and the output terminal of the operational amplifier for connecting the output terminal of the operational amplifier to the operational amplifier a second input terminal; and a fourth switching circuit connected to the second end of the switching capacitor for connecting the second end of the switching capacitor to the second voltage terminal or the output end of the operational amplifier; wherein, when the object When the intersection is touched, the capacitance of the side capacitor changes, which in turn causes the voltage at the output of the operational amplifier to change. The switching capacitor circuit of claim 1, wherein the first switching circuit comprises: 12 201027413 a first switch 'connected between the first sensing line and the first voltage terminal; and a second switch connected to Between the first sensing line and the second voltage terminal. 3. The switched capacitor circuit of claim 1, wherein the second switching circuit comprises: a first switch coupled between the second sensing line and the second voltage terminal; A first switch ' is coupled between the second sense line and the second input of the operational amplifier. 4. The switched capacitor circuit of claim 1, wherein the third switching circuit includes a switch coupled between the second input and the output of the operational amplifier. 5. The switched capacitor circuit of claim 1, wherein the fourth switching circuit comprises: a first switch connected between the second end of the switching capacitor and the second voltage terminal; and a second switch 'connected to Between the second end of the switching capacitor and the output of the operational amplifier. 6. A method for detecting a capacitive touch panel, the capacitive touch panel having a first sensing line and a second sensing line, generating a side at an intersection of the first and second sensing lines Capacitor, the detecting method comprises the steps of: connecting the first sensing line and the second sensing line to a first voltage terminal and a second voltage terminal respectively to accumulate charges on the side capacitor; and detecting the The charge of the side capacitor is used to determine whether the capacitance value of the side capacitor changes "to determine whether an object touches the intersection. 7. The method of claim 6, wherein the step of detecting the charge of the side capacitor to determine whether the capacitance of the side capacitor changes comprises: 13 201027413 respectively respectively, the first sensing line and the second sensing line Switching to the second voltage terminal and the first input end of an operational amplifier to transfer the charge of the side capacitor to a switching capacitor, wherein the second input end of the operational amplifier is connected to the second voltage terminal, and the switching capacitor Connected between the first input end and the output end of the operational amplifier; and determine whether the capacitance value of the side capacitance changes according to the voltage on the output end of the operational amplifier. 14