Touch detection circuit, touch chip and electronic equipment

Abstract

The invention provides a touch control detection circuit, a touch control chip and electronic equipment, the touch control detection circuit comprises a charging and discharging circuit, a programmable gain amplifier, an analog-to-digital converter and a reference voltage generation circuit, a charge integrator in a traditional touch control detection circuit is omitted, the chip area can be greatly reduced, the cost is reduced, and the reliability of the touch control detection circuit is improved. The reference voltage generation circuit generates the reference voltage related to the voltages of the plurality of sensing channels, so that the programmable gain amplifier can subtract the reference voltage from the sensing voltage on each sensing channel, the influence of cathode noise on touch detection of the touch screen can be further inhibited, and the touch sensitivity and reliability are improved. Furthermore, the reference voltage can control the charging and discharging circuit to charge and discharge the sensing channel, so that the charging and discharging degree of the charging and discharging circuit to the sensing channel is controllable.

Description

Technical Field

[0001] The present invention relates to the field of touch control technology, and in particular to a touch control detection circuit, a touch control chip and an electronic device. Background Art

[0002] Capacitive touch screens are widely used in various electronic devices at present, which usually use capacitive sensors to realize touch detection. When a conductor such as a finger, nail, pen or other object is touching or approaching the touch screen, a corresponding touch event occurs, and the capacitance near the location of the touch event will change. By detecting the change in capacitance, the location of the touch event and the user's touch operation can be determined.

[0003] The detection of the touch screen will be affected by noise, which will seriously interfere with the circuit's recognition of touch and even cause the electronic device to not work properly. Therefore, how to reduce the impact of noise on the capacitance detection of the touch screen has become an urgent problem to be solved in this field. Summary of the invention

[0004] The object of the present invention is to provide a touch detection circuit, a touch chip and an electronic device, which can suppress the influence of cathode noise on the touch detection of a touch screen and improve the touch sensitivity and reliability.

[0005] To achieve the above object, the present invention provides a touch detection circuit, which includes:

[0006] A charge and discharge circuit is coupled to the corresponding sensing channel of the touch screen and is used to charge or discharge the sensing channel during a scanning cycle to convert the sensing signal on the sensing channel into a sensing voltage;

[0007] A reference voltage generating circuit, coupled to a plurality of sensing channels on the touch screen, and used to generate a reference voltage related to the voltages of the plurality of sensing channels;

[0008] A programmable gain amplifier, having a first input terminal coupled to the output terminal of the charge-discharge circuit, a second input terminal coupled to the output terminal of the reference voltage generating circuit, and used to amplify the difference between the sensing voltage and the reference voltage;

[0009] The analog-to-digital converter is coupled to the programmable gain amplifier and is used for quantizing the difference amplified by the programmable gain amplifier.

[0010] Optionally, the reference voltage generating circuit includes an operational amplifier having a first input terminal and multiple second input terminals, each second input terminal of the operational amplifier is respectively coupled to a corresponding one of the multiple sensing channels, the first input terminal of the operational amplifier is coupled to the output terminal of the operational amplifier, and the operational amplifier is used to output an average value of the voltages of the multiple sensing channels as the reference voltage.

[0011] Optionally, the multiple sensing channels are n sensing channels, n is an integer and n≥2, the operational amplifier includes a first input tube, n identical second input tubes and an operational amplifier circuit, the gate of the first input tube is coupled to the output end of the operational amplifier circuit, the drain of the first input tube is coupled to the first input end of the operational amplifier circuit, the source of the first input tube and the sources of the n second input tubes are both coupled to a first current source, the drains of the n second input tubes are all coupled to the second input end of the operational amplifier circuit, and the gates of the n second input tubes are respectively coupled to different sensing channels among the n sensing channels.

[0012] Optionally, the charge and discharge circuit includes a charge and discharge branch, and the charge and discharge branch includes a first switch, a second switch and a second current source, the control end of the first switch receives a first control signal, and the control end of the second switch receives a second control signal different from the first control signal; in a mutual capacitance scanning mode, one end of the second current source is connected to the first power supply voltage, and the other end is coupled to one end of the second switch, the other end of the second switch is coupled to one end of the first switch, the sensing channel and the first input end of the programmable gain amplifier, and the other end of the first switch is connected to a common reference voltage; or, in a self-capacitance scanning mode, one end of the second current source is connected to a corresponding second power supply voltage, and the other end is coupled to one end of the second switch, the other end of the second switch is coupled to one end of the first switch, the sensing channel and the first input end of the programmable gain amplifier, and the other end of the first switch is connected to the first power supply voltage.

[0013] Optionally, the output end of the reference voltage generating circuit is also coupled to the control end of the second switch, and the reference voltage generating circuit is further used to control the charge and discharge circuit to charge or discharge the sensing channel through the reference voltage.

[0014] Optionally, the charge and discharge circuit also includes an OR logic circuit and a comparator, the second input terminal of the comparator is coupled to a reference voltage, the first input terminal of the comparator is coupled to the output terminal of the reference voltage generating circuit, the output terminal of the comparator is coupled to the first input terminal of the OR logic circuit, the second input terminal of the OR logic circuit receives the first control signal, and the output terminal of the OR logic circuit outputs the second control signal.

[0015] Optionally, the charge and discharge circuit also includes a trigger and a delay device, the first input end of the trigger is coupled to the output end of the comparator, the second input end of the trigger is coupled to the output end of the delay device, the output end of the trigger is coupled to the first input end of the OR logic circuit, and the delay device is used to delay the first control signal and input it to the trigger.

[0016] Optionally, the touch detection circuit also includes a digital-to-analog converter, and the two differential output terminals of the digital-to-analog converter are respectively coupled to the first input terminal and the second input terminal of the programmable gain amplifier. The digital-to-analog converter is used to provide two differential voltages to the programmable gain amplifier, and the difference between the two differential voltages is adjustable and used to subtract non-ideal factors of the front stage of the programmable gain amplifier.

[0017] Optionally, the programmable gain amplifier includes an operational transconductance amplifier, a first input circuit and a second input circuit; one end of the first input circuit serves as the first input end of the programmable gain amplifier, and is coupled to a differential output end of the digital-to-analog converter and the output end of the charge and discharge circuit to receive one path of the differential voltage and the sensing voltage, and the other end of the first input circuit is coupled to the first input end of the operational transconductance amplifier; one end of the second input circuit serves as the second input end of the programmable gain amplifier, and is coupled to another differential output end of the digital-to-analog converter and the output end of the reference voltage generating circuit to receive another path of the differential voltage and the reference reference voltage, and the other end of the second input circuit is coupled to the second input end of the operational transconductance amplifier; the output end of the operational transconductance amplifier is coupled to the analog-to-digital converter.

[0018] Optionally, the first input circuit includes a first sampling capacitor, a first amplifying switch and a first sampling switch, one end of the first sampling capacitor is coupled to the first input end of the operational transconductance amplifier, the other end of the first sampling capacitor is coupled to one end of the first amplifying switch and one end of the first sampling switch, the other end of the first sampling switch is coupled to the output end of the charge and discharge circuit, and the other end of the first amplifying switch is coupled to a differential output end of the digital-to-analog converter; or, the second input circuit includes a second sampling capacitor, a second amplifying switch and a second sampling switch, one end of the second sampling capacitor is coupled to the second input end of the operational transconductance amplifier, the other end of the second sampling capacitor is coupled to one end of the second amplifying switch and one end of the second sampling switch, the other end of the second sampling switch is coupled to the output end of the reference voltage generating circuit, and the other end of the second amplifying switch is coupled to the other differential output end of the digital-to-analog converter; wherein both the first amplifying switch and the second amplifying switch are turned on during the amplifying phase of the programmable gain amplifier, and both the first sampling switch and the second sampling switch are turned on during the sampling phase of the programmable gain amplifier.

[0019] Optionally, the programmable gain amplifier also includes a first feedback circuit and a second feedback circuit; one end of the first feedback circuit is coupled to the output end of the operational transconductance amplifier, the other end of the first feedback circuit is coupled to the first input end of the operational transconductance amplifier, one end of the second feedback circuit is coupled to the output end of the operational transconductance amplifier, and the other end of the second feedback circuit is coupled to the second input end of the operational transconductance amplifier.

[0020] Optionally, the first feedback circuit includes a first feedback capacitor and a first feedback switch, one end of the first feedback capacitor is coupled to the first sampling capacitor and the first input end of the operational transconductance amplifier, the other end of the first feedback capacitor is coupled to one end of the first feedback switch, and the other end of the first feedback switch is coupled to the output end of the operational transconductance amplifier; or, the second feedback circuit includes a second feedback capacitor and a second feedback switch, one end of the second feedback capacitor is coupled to the second input end of the operational transconductance amplifier, the other end of the second feedback capacitor is coupled to one end of the second feedback switch, and the other end of the second feedback switch is coupled to the output end of the operational transconductance amplifier; the first amplification switch and the second amplification switch are both turned on during the amplification phase of the programmable gain amplifier.

[0021] Optionally, the programmable gain amplifier also includes first to fourth reset switches, one end of the first to fourth reset switches are respectively connected to the common reference voltage, the other end of the first reset switch is coupled to the first input end of the operational transconductance amplifier, the other end of the second reset switch is coupled to the connection node between the first feedback capacitor and the first feedback switch, the other end of the third reset switch is coupled to the connection node between the second feedback capacitor and the second feedback switch, and the other end of the fourth reset switch is coupled to the second input end of the operational transconductance amplifier; the first to fourth reset switches are all turned on during the sampling phase of the programmable gain amplifier.

[0022] Optionally, in the touch detection circuit, at least the digital-to-analog converter or the reference voltage generating circuit is shared by a plurality of the sensing channels.

[0023] Based on the same inventive concept, the present invention further provides a touch control chip, which includes the touch control detection circuit as described in the present invention.

[0024] Based on the same inventive concept, the present invention further provides an electronic device, which includes a touch screen and a touch chip as described in the present invention, wherein the touch screen has a plurality of sensing channels, and the touch chip is coupled to each of the sensing channels.

[0025] Compared with the prior art, the technical solution of the present invention has at least one of the following beneficial effects:

[0026] 1. Generate a reference voltage through the voltages of multiple sensing channels, so that the programmable gain amplifier can subtract the reference voltage from the sensing voltage on each sensing channel, thereby suppressing the influence of cathode noise on the touch detection of the touch screen and improving touch sensitivity and reliability.

[0027] 2. The charge integrator (including the integrating amplifier and integrating capacitor) in the traditional touch detection circuit is eliminated, which can greatly reduce the chip area and reduce the cost.

[0028] 3. The charging and discharging of the sensing channel by the charging and discharging circuit is controlled by a reference voltage, so that the charging and discharging degree of the sensing channel by the charging and discharging circuit is controllable.

[0029] 4. A digital-to-analog converter is set to provide two differential voltages to the programmable gain amplifier, and the difference between the two differential voltages is adjustable, so that some non-ideal factors of the front stage of the programmable gain amplifier (such as unequal parasitic capacitance Cb of each sensing channel, charging current mismatch, etc.) can be eliminated by the difference between the two differential voltages, further improving the circuit reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Those skilled in the art will appreciate that the accompanying drawings are provided for a better understanding of the present invention and do not constitute any limitation on the scope of the present invention.

[0031] Figure 1 This is a schematic diagram of the working principle of an existing touch chip.

[0032] Figure 2 It is a structural schematic diagram of a touch detection circuit in an existing touch chip.

[0033] Figure 3 FIG. 1 is a schematic diagram of the working principle of the touch detection circuit according to the first embodiment of the present invention.

[0034] Figure 4A FIG. 4 is a schematic diagram of an exemplary structure of a touch detection circuit according to the first embodiment of the present invention.

[0035] Figure 4B yes Figure 4A An exemplary schematic diagram of the architecture of a charging and discharging circuit in a touch detection circuit is shown.

[0036] Figure 5A FIG. 4 is another exemplary structural diagram of the touch detection circuit according to the first embodiment of the present invention.

[0037] Figure 5B yes Figure 5A Another exemplary architecture diagram of a charging and discharging circuit in a touch detection circuit is shown.

[0038] Figure 6 4 is a schematic diagram of an exemplary structure of a reference voltage generating circuit in a touch detection circuit according to the first embodiment of the present invention.

[0039] Figure 7 FIG. 4 is a schematic diagram of an exemplary structure of a touch detection circuit according to a second embodiment of the present invention.

[0040] Fig. 8A and Figure 8B 2 are two exemplary structural diagrams of a touch detection circuit according to a second embodiment of the present invention.

[0041] Fig. 9 FIG. 4 is a schematic diagram of the structure of a touch detection circuit according to a third embodiment of the present invention.

[0042] Fig.10 FIG. 4 is a schematic diagram of an exemplary structure of a touch detection circuit according to a third embodiment of the present invention.

[0043] Fig.11 FIG. 4 is a schematic diagram of the working timing of the touch detection circuit according to the third embodiment of the present invention. DETAILED DESCRIPTION

[0044] In the following description, a large number of specific details are given in order to provide a more thorough understanding of the present invention. However, it is obvious to those skilled in the art that the present invention can be implemented without one or more of these details. In other examples, in order to avoid confusion with the present invention, some technical features known in the art are not described. It should be understood that the present invention can be implemented in different forms and should not be interpreted as being limited to the embodiments proposed here. On the contrary, providing these embodiments will make the disclosure thorough and complete, and the scope of the present invention will be fully conveyed to those skilled in the art. The same reference numerals represent the same elements from beginning to end. It should be understood that when an element is referred to as "connected to", "coupled" other elements, it can be directly connected to other elements, or there can be intervening elements. On the contrary, when an element is referred to as "directly connected to" other elements, there is no intervening element. When used here, the singular forms of "one", "an" and "said / the" are also intended to include plural forms, unless the context clearly indicates another way. It should also be understood that the term "comprising" is used to identify the presence of features, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, steps, operations, elements, components and / or groups. When used herein, the term "and / or" includes any and all combinations of the relevant listed items.

[0045] The principle of an existing touch chip used in an OLED (Organic Light-Emitting Diode) touch screen is as follows: Figure 1 As shown. The OLED touch screen 10 generally has a plurality of longitudinally extending transmission channels TX (also called transmission lines) and a plurality of transversely extending sensing channels RX (also called sensing lines), and the intersection of each transmission channel TX and each sensing channel RX is a sensing node. The touch chip generally includes a driving circuit 11 coupled to the transmission channel TX and a touch detection circuit 12 coupled to the sensing channel RX. According to the size and shape of the OLED touch screen 10, there will be different numbers of transmission channels TX and sensing channels RX. Figure 1 In the OLED touch screen 10 shown in FIG. 1 , the number of sensing channels RX is n, and the number of sending channels TX is m. The OLED touch screen 10 has n sensing channels RX (ie, RX <1> ~RX <n>), m transmission channels TX (ie TX <1> ~TX <m>) screen model.

[0046] Since the human body is a conductor and is connected to the ground, the self-capacitance and mutual capacitance of the channel touched or approached by the finger will change. Therefore, the touch chip can use self-capacitance and mutual capacitance, two capacitance detection methods, to detect the change of self-capacitance or mutual capacitance on the OLED touch screen 10, and then calculate the touch position of the finger according to the change of self-capacitance or mutual capacitance, so as to realize touch recognition on the OLED touch screen 10. Exemplarily, when performing self-capacitance detection, the touch chip scans the change of self-capacitance of each transmitting channel and sensing channel to the ground. When the finger approaches or touches, the self-capacitance on the transmitting channel TX and the sensing channel RX near the finger will increase. When performing mutual capacitance detection, the touch chip detects the change of mutual capacitance between the transmitting channel TX and the sensing channel RX. Among them, Figure 1 In FIG. 1 , Cm is a parasitic capacitance between a transmission channel TX and a sensing channel RX, and Cb is a parasitic capacitance between a cathode of the OLED touch screen 10 and the sensing channel RX.

[0047] The existing touch detection circuit 12 generally includes an analog front-end circuit AFE (Analog Front-end) and an analog-to-digital converter circuit ADC (Analog-to-Digital Converter).

[0048] Taking self-capacitance detection as an example, the principle of an analog front-end circuit AFE in a conventional touch detection circuit 12 applied to an OLED touch chip is as follows: Figure 2 The analog front-end circuit AFE includes a charge-discharge circuit 120, a charge integrator CA and a programmable gain amplifier PGA. The charge integrator CA includes a charge amplifier CA_OP, an integration switch M0 and an integration capacitor Cfb. Figure 2 In the figure, Cathode is the cathode of the OLED touch screen, Csig represents the capacitance generated between the finger touching the OLED touch screen and the sensing channel RX (i.e., the capacitance component generated between the finger and the touch screen), and Cb represents the parasitic capacitance between the cathode and the sensing channel RX, which is usually a large capacitance of up to several hundred pF. When the noise of the cathode Cathode is not considered, Cb can be considered as the parasitic capacitance between the sensing channel RX and the ground AVSS.

[0049] The working principle of the touch chip is to generate Csig when a finger touches the screen, and Csig disappears when the finger leaves the screen. By scanning the changes in the self-capacitance of each sending channel and sensing channel to the ground (i.e., whether there is Csig), it can determine whether the OLED touch screen 10 is touched and the touched position.

[0050] Please combine Figure 2 and Figure 3 When the touch chip is scanned for the first time (the finger is not placed on the OLED touch screen at this time), the charge and discharge circuit 120 first pulls the sensing channel RX to the ground potential and resets the charge amplifier CA_OP; then, the charge and discharge circuit 120 charges the sensing channel RX until the potential VRX of the sensing channel RX is equal to the common reference voltage VCOM. In this process, the charge amount Q charged by the charge and discharge circuit 120 to the sensing channel RX is Q = VCOM*Cb. When a finger touches, the above scanning process is repeated.

[0051] At this time, before and after the charge-discharge circuit 120 provides the output to the charge integrator CA, Q+(VCOM-VOUT)*Cfb=VCOM*(Cb+Csig). Thus, VOUT=VCOM-VCOM*Csig / Cfb.

[0052] Programmable gain amplifier PGA is generally designed in coherent double sampling mode. In a scanning cycle, the first sampling VOUT is defined as VOUT1, and the second sampling VOUT is defined as VOUT2. If there is no finger touch, Csig = 0, then the voltage difference between the two sampling VOUTs ⊿VOUT = VOUT2-VOUT1 = 0. If there is a finger touch, Csig≠0, then the voltage difference between the two sampling VOUTs ⊿VOUT = VOUT2-VOUT1 = -VCOM*Csig / Cfb.

[0053] The ⊿VOUT is amplified by the PGA and provided to the ADC for quantization. Based on the quantization result, it can be determined whether the touch screen is touched and the touch position.

[0054] The above touch detection circuit has the following defects:

[0055] 1. In the above analysis, it is assumed that the cathode Cathode is a quiet (noise-free) ground potential, and the potential of the finger is also equivalent to the ground. But in fact, the cathode Cathode is a potential that is easy to introduce noise. For example, when the OLED touch screen displays white and black images alternately, it will cause the cathode to generate a peak-to-peak noise of about 1V. Moreover, Cb is generally much larger than Csig, which causes the cathode Cathode noise (a common mode noise) to seriously interfere with the touch detection circuit 12's recognition of touch, and even cause the touch chip and the electronic equipment with the touch chip to not work properly at all.

[0056] 2. Since CA_OP and Cfb are required in the charge integrator CA, the circuit occupies chip area and has high cost.

[0057] Based on this, the present invention provides a touch detection circuit, a touch chip and an electronic device, which generate an average value through the sensing signals of multiple sensing channels RX as the voltage of one input end of the PGA, and the sensing signal of each sensing channel RX is used as the voltage of the other input end of the PGA, so that the signal of each sensing channel RX can be subtracted from the average value through the PGA, so that the interference caused by the cathode noise is the same for all sensing channels RX, and the voltage difference obtained by the PGA will no longer be interfered by the cathode noise, thereby eliminating the noise introduced on the cathode, and at the same time, the charge integrator CA in the traditional touch detection circuit can be omitted (especially the integrating amplifier CA_OP and the feedback capacitor Cfb are omitted), which can greatly reduce the chip area and reduce the cost.

[0058] The following is combined with Figures 3 to 11 The technical solution proposed by the present invention is further described in detail with specific embodiments. The advantages and features of the present invention will become clearer according to the following description. It should be noted that the drawings are all in a very simplified form and are not in precise proportions, and are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention.

[0059] First embodiment

[0060] Please refer to Figure 3 The present embodiment provides a touch detection circuit 12, which is coupled to the touch screen 10 and is used to detect the capacitance change on the touch screen 10. The detection result of the touch detection circuit 12 can be used to identify the location of the touch event on the touch screen 10 and determine the user's touch operation.

[0061] The touch screen 10 may be any touch screen such as an OLED touch screen, and has m longitudinally extending transmission channels TX (ie, TX <1> ~TX <m>) and n transversely extending sensing channels RX (ie, RX <1> ~RX <n>), the intersection of each transmission channel TX and each sensing channel RX is a sensing node, and the values ​​of m and n depend on the size and shape of the touch screen 10.

[0062] In this embodiment, the touch detection circuit 12 has a plurality of touch detection branches (not shown in FIG. Figure 3 The number of touch detection branches is the same as the number of sensing channels RX. The touch detection branches are coupled to the sensing channels RX in a one-to-one correspondence, and each touch detection branch includes a charge-discharge circuit 120, a programmable gain amplifier PGA, and an analog-to-digital converter ADC coupled in sequence. The touch detection circuit 12 also has a reference voltage generating circuit 121 coupled to the charge-discharge circuit 120 of each touch detection branch.

[0063] The charge and discharge circuit 121 is used to charge or discharge the sensing channel RX during the scanning cycle to convert the sensing signal on the sensing channel RX into a sensing voltage VRX. The reference voltage generation circuit 121 is coupled to the j sensing channels RX on the touch screen 10, and is used to generate a reference reference voltage VRXM related to the voltages of the j sensing channels RX, where j is an integer and 2≤j≤n. The programmable gain amplifier PGA is used to amplify the difference between the sensing voltage VRX and the reference reference voltage VRXM. The analog-to-digital converter ADC is used to quantize the difference amplified by the programmable gain amplifier PGA.

[0064] Exemplarily, the charge and discharge circuit 120 <1> The output terminal of the sensing channel RX <1> and programmable gain amplifier PGA <1> The first input terminal is coupled to a programmable gain amplifier PGA <1> The output terminal and analog-to-digital converter ADC <1> The input terminal is coupled; the charge and discharge circuit 120 <2> The output terminal of the sensing channel RX <2> and programmable gain amplifier PGA <2> The first input terminal is coupled to a programmable gain amplifier PGA <2> The output terminal and analog-to-digital converter ADC <2> The input terminal is coupled; the charge and discharge circuit 120 <3> The output terminal of the sensing channel RX <3> and programmable gain amplifier PGA <3> The first input terminal is coupled to a programmable gain amplifier PGA <3> The output terminal and analog-to-digital converter ADC <3> Similarly, the charge and discharge circuit 120 <n-1>The output terminal of the sensing channel RX <n-1>and programmable gain amplifier PGA <n-1>The first input terminal is coupled to a programmable gain amplifier PGA <n-1>The output terminal and analog-to-digital converter ADC <n-1>The input terminal is coupled; the charge and discharge circuit 120 <n>The output terminal of the sensing channel RX <n>and programmable gain amplifier PGA <n>The first input terminal is coupled to a programmable gain amplifier PGA <n>The output terminal and analog-to-digital converter ADC <n>The reference voltage generating circuit 121 is coupled to the input terminal of the programmable gain amplifier PGA. <1> ~PGA <n>The second input terminals of are coupled.

[0065] It should be understood that in this embodiment, each touch detection branch is coupled to a sensing channel RX in a one-to-one correspondence, but the technical solution of the present invention is not limited thereto. In other embodiments of the present invention, at least part of the circuit in a touch detection branch can be shared by multiple sensing channels RX at the same time, for example, multiple PGAs are coupled to the same ADC, and for another example, a charge and discharge circuit 120 is coupled to multiple PGAs at the same time. And no matter what specific circuit design is adopted, as long as the functions of the charge and discharge circuit 120, the programmable gain amplifier PGA, the analog-to-digital converter ADC and the reference voltage generating circuit 121 can be realized. Therefore, the charge and discharge circuit 120, the reference voltage generating circuit 121, the programmable gain amplifier PGA and the analog-to-digital converter ADC in this embodiment can be implemented by any suitable circuit design.

[0066] As an example, see Figure 4A and Figure 4B The charge and discharge circuit 120 is applied in the mutual capacitance scanning mode and includes a charge and discharge branch 120a, and the charge and discharge branch 120a includes a first switch Q0, a second switch MP1 and a current source I0. Among them, the first switch Q0 and the second switch MP1 can adopt any suitable three-terminal switch elements, such as MOS tubes, triodes, etc. The control end of the first switch Q0 receives the first control signal S1, and the control end of the second switch MP1 (for example, the gate of the PMOS tube) receives the second control signal S2 different from the first control signal S1. One end of the current source I0 is connected to the first power supply voltage AVSS (the voltage AVSS is an internal ground voltage, which can be different from the external ground voltage or 0V voltage), and the other end is coupled to one end of the second switch MP1 (for example, the source of the PMOS tube), and the other end of the second switch MP1 (for example, the drain of the PMOS tube) is coupled to one end of the first switch Q0, the sensing channel RX and the first input end of the programmable gain amplifier PGA. The other end of the first switch Q0 is connected to the common reference voltage VCOM.

[0067] When a touch event occurs when a conductor such as a finger approaches or contacts the touch screen 10, Csig (i.e., the capacitance component generated between the finger and the touch screen) is generated, and the mutual capacitance between the transmission channel TX and the sensing channel RX at the touch event location changes from the original Cm to Cm-Csig (i.e., the equivalent parasitic capacitance between the transmission channel TX and the sensing channel RX changes), and the corresponding touch detection branch in the touch detection circuit 12 can detect Csig; and when the conductor such as a finger is away from the screen (i.e., when no touch event occurs or after the touch event is canceled), Csig disappears. Therefore, by combining the detection results of all touch detection branches in the touch detection circuit 12 coupled to the touch screen 10, it is possible to determine whether Csig exists on the entire screen of the touch screen 10, determine whether a touch event occurs on the entire screen of the touch screen 10, and determine the location of the touch event.

[0068] The working process of the charge and discharge branch 120a is as follows: First, the S1 signal jumps high and controls Q0 to be closed and turned on, the touch detection branch is reset, and the potential of the sensing channel RX is pulled to VCOM. After the reset is completed, the S1 signal jumps low and controls Q0 to be disconnected, and when the waiting transmission channel TX jumps high (that is, jumps from a low level to a high level), the S2 signal jumps high and controls MP1 to be closed and turned on, and the second current source I0 in the charge and discharge branch 120a charges or discharges the sensing channel RX, and subtracts the reference, thereby converting the capacitance variable Csig into a sensing voltage VRX containing touch information. The sensing voltage VRX is different when there is a finger touch or not. By quantifying this "difference", the size of Csig can be determined, and thus it can be determined whether there is a touch on the touch screen 10.

[0069] As another example, see Figure 5A and Figure 5B The charge and discharge circuit 120 is applied in the self-capacitance scanning mode and includes a charge and discharge branch 120a, which includes a first switch Q0, a second switch MP1 and a second current source I0. The control end of the first switch Q0 receives the first control signal S1, the control end of the second switch MP1 (for example, the gate of the PMOS tube) receives the second control signal S2 different from the first control signal S1, one end of the second current source I0 is connected to the corresponding second power supply voltage AVDD (the voltage may be the system operating voltage), the other end of the second current source I0 is coupled to one end of the second switch MP1 (for example, the source of the PMOS tube), the other end of the second switch MP1 (for example, the drain of the PMOS tube) is coupled to one end of the first switch Q0, the sensing channel RX and the first input end of the programmable gain amplifier PGA, and the other end of the first switch Q0 is connected to the first power supply voltage AVSS.

[0070] When a finger or other conductor approaches or contacts the touch screen 10, a touch event occurs, and the self-capacitance of the sensing channel RX at the touch event location changes, that is, Csig (i.e., the capacitance component generated between the finger and the touch screen) is generated, and the corresponding touch detection branch in the touch detection circuit 12 can detect Csig; and when the finger or other conductor is away from the screen (i.e., when no touch event occurs or after the touch event is cancelled), Csig disappears. Therefore, by combining the detection results of all touch detection branches in the touch detection circuit 12 coupled to the touch screen 10, it is possible to determine whether Csig exists on the entire screen of the touch screen 10, determine whether a touch event occurs on the entire screen of the touch screen 10, and determine the location of the touch event.

[0071] The working process of the charge-discharge branch 120a includes: first, the S1 signal jumps high to control Q0 to close and turn on, and the touch detection branch is reset. During the reset period, the charge-discharge branch 120a discharges the sensing channel RX until the potential of the sensing channel RX is pulled down to AVSS. After the reset is completed, the S2 signal immediately jumps high and controls MP1 to close, and the charge-discharge branch 120a charges the sensing channel RX. The charging time is the width of the S2 high level, thereby converting the self-capacitance change Csig into a sensing voltage VRXg containing finger information.

[0072] From the above working process, it can be seen that when S2 is high, the second current source I0 charges the sensing channel RX. The voltage charged to the sensing channel RX when there is a finger touch is lower than the voltage charged when there is no finger touch. Therefore, the sensing voltage VRX is different when there is a finger touch or not. This difference can be used to detect the size of Csig to determine whether the touch screen 10 is touched.

[0073] As an example, see Figure 6 The reference voltage generating circuit 121 includes an operational amplifier VCM_GEM_OP having a first input terminal (+) and n second input terminals (-), each second input terminal of the operational amplifier VCM_GEM_OP being connected to n sensing channels RX <1> ~RX <n>The first input terminal of the operational amplifier VCM_GEM_OP is coupled to the output terminal of the operational amplifier VCM_GEM_OP. The operational amplifier VCM_GEM_OP is used to sense n sensing channels RX <1> ~RX <n>The average value of the voltage is calculated and used as the reference voltage VRXM, that is, VRXM = (RX <1> +RX <2> +RX <2> +……+RX <n>) / n.

[0074] The operational amplifier VCM_GEM_OP can be implemented using any suitable circuit design. As an example, please combine Figure 3 and Figure 6 The operational amplifier VCM_GEM_OP includes a first input transistor mos0, n identical second input transistors mos1 to mosn and an operational amplifier circuit 121a. The gate of the first input transistor mos0 is coupled to the output terminal of the operational amplifier circuit 121a and PGA1 <1> ~PGA1 <n>The drain of the first input tube mos0 is coupled to the first input terminal of the operational amplifier circuit 121a, the source of the first input tube mos0 and the sources of the n second input tubes mos1-mosn are coupled to a first current source I1, the drains of the n second input tubes mos1-mosn are coupled to the second input terminal of the operational amplifier circuit 121a, and the gates of the n second input tubes mos1-mosn are respectively coupled to the sensing channel RX <1> ~RX <n>, where the gate of mos1 is coupled to the sensing channel RX <1> , the gate of mos2 is coupled to the sensing channel RX <2> , and so on, the gate of the mosn is coupled to the sensing channel RX <n>.

[0075] The width-to-length ratios of the second input tubes mos1 to mosn are all equal, and the width-to-length ratio of the first input tube mos0 is n times the width-to-length ratio of the second input tube mos1. The operational amplifier VCM_GEM_OP is equivalent to splitting one end of the input pair of the conventional operational amplifier into n equal parts, and because the RX received by the second input tubes mos1 to mosn <1> To RX <n>The voltage of the operational amplifier VCM_GEM_OP is close and the variation is small. The operational amplifier VCM_GEM_OP works in the linear region, and the operational amplifier VCM_GEM_OP adopts the unity gain connection method (that is, its output terminal is connected to the gate of mos0). Therefore, the output VRXM of the operational amplifier VCM_GEM_OP is equal to all input RX <1> To RX <n>The average value of .

[0076] by Figure 3 , FIG. 5A to FIG. 5B and Figure 6 Taking the self-capacitance scanning mode shown in the figure as an example, the working process of the touch detection branch of this embodiment is as follows:

[0077] Initially, S1 jumps high to control Q0 to close, and the charge-discharge branch 120a discharges the sensing channel RX through Q0. At this time, the VRX voltage output by the charge-discharge branch 120a is low (discharged to AVSS);

[0078] When S1 jumps low to control Q0 to disconnect, S2 jumps high to control MP1 to turn on, and the second current source I0 charges the sensing channel VRX and outputs the sensing voltage VRX. <1> To RX <n>Generates a reference voltage VRXM.

[0079] Then, the PGA samples the VRX and VRXM voltages and amplifies their difference before sending it to the ADC for quantization. Moreover, on the touch screen 10, the VRX output by the sensing channel RX coupled to the charge-discharge circuit 120 that is touched is smaller than VRXM, and the VRX output by the sensing channel coupled to the charge-discharge circuit that is not touched is larger than VRXM. After the PGA amplifies this difference and then quantifies it to the ADC, it can be determined which sensing channels are touched and which are not touched.

[0080] The technical solution of this embodiment is that, firstly, the reference voltage generating circuit 121 does not need a dedicated sensing channel or other reference voltage source as the reference reference voltage VRXM, but selects all sensing channels RX <1> To RX <n>The average value of RX is used as the reference voltage VRXM, so it has a wider range of uses and greater product value. <1> To RX <n>The average value of the cathode noise is used as the reference voltage VRXM, so that the interference caused by the cathode noise is effective for all sensing channels RX <1> To RX <n>The difference between VRX and VRXM will no longer be disturbed by cathode noise (also known as common mode noise), which can suppress the influence of cathode noise on touch detection of the touch screen and improve touch sensitivity and reliability. Furthermore, the charge integrator (including integration amplifier and integration capacitor) in the traditional touch detection circuit is omitted, which can greatly reduce the chip area and cost.

[0081] Please refer to Figure 3 This embodiment further provides a touch control chip, which includes the touch control detection circuit 12 as described in this embodiment.

[0082] Optionally, the touch control chip may further include a driving circuit 11, and the driving circuit 11 is coupled to each transmission channel TX of the touch screen 10. In other embodiments of the present invention, the driving circuit 11 may be integrated into a driving chip independent of the touch control chip.

[0083] Please refer to Figure 3 This embodiment also provides an electronic device, which includes a touch screen 10 and the touch chip of this embodiment.

[0084] The touch control chip and the electronic device of the present embodiment have improved performance due to the adoption of the touch control detection circuit of the present embodiment.

[0085] It should be understood that VRXM output by the reference voltage generating circuit 121 is equal to RX <1> To RX <n>The average value is only an example, and the technical solution of the present invention is not limited to this. In other embodiments of the present invention, the VRXM output by the reference voltage generating circuit 121 can also be the same as RX <1> To RX <n>Other values ​​related to RX <1> To RX <n>The weighted values ​​obtained by performing weighted calculations with different weights, etc., as long as the VRXM output by the reference voltage generating circuit 121 is equal to the RX <1> To RX <n>If at least two of the above are correlated, the influence of cathode noise on the touch detection of the touch screen can be suppressed to a certain extent. Therefore, even if the reference voltage generating circuit 121 adopts other circuit designs, it also belongs to the technical solution of the present invention.

[0086] Second embodiment

[0087] Please combine Figure 3 , Figure 7 and FIG. 8A to FIG. 8B The present embodiment provides a touch detection circuit 12, which is coupled to the touch screen 10 and is used to detect the capacitance change on the touch screen 10. The detection result of the touch detection circuit 12 can be used to identify the location of the touch event on the touch screen 10 and determine the user's touch operation. The touch detection circuit 12 has several touch detection branches (not shown in FIG. Figure 3 The touch detection branch can be coupled to the sensing channel RX in a one-to-one correspondence, or one touch detection branch can be coupled to multiple sensing channels RX at the same time. The touch detection circuit 12 can be applied in a mutual capacitance scanning mode or a self-capacitance scanning mode, and its charge-discharge circuit 120 has a charge-discharge branch 120a coupled to the sensing channel RX.

[0088] The touch detection circuit 12 of the present embodiment is different from the touch detection circuit of the first embodiment in that the output end of the reference voltage generating circuit 121 is also coupled to the control end of the charge and discharge branch 120a in the charge and discharge circuit 120 of each touch detection branch, so that the reference voltage VRXM output by the reference voltage generating circuit 121 (as a feedback) is used to control the extent to which the charge and discharge branch 120a charges or discharges the coupled sensing channel RX (that is, the amount of charge charged or discharged by the charge and discharge branch 120a to the coupled sensing channel RX is controllable).

[0089] As an example, see Fig. 8A , the charge-discharge circuit 120 has a charge-discharge branch 120a, an OR logic circuit OR and a comparator COMP. The charge-discharge branch 120a includes a first switch Q0, a second switch MP1 and a second current source I0. The second input terminal (-) of the comparator COMP is coupled to a reference voltage VR1, the first input terminal (+) of the comparator COMP is coupled to the output terminal of the reference voltage generating circuit 121 to access the reference reference voltage VRXM, the output terminal of the comparator COMP is coupled to the first input terminal of the OR logic circuit OR, the second input terminal of the OR logic circuit OR receives the first control signal S1, and the output terminal of the OR logic circuit OR is coupled to the control terminal of the second switch MP1 to output the second control signal S2 to the second switch MP1. The first control signal S1 is also input to the control terminal of the first switch Q0.

[0090] The connection relationship between the first switch Q0, the second switch MP1 and the second current source I0 in the charge-discharge branch 120a and the connection relationship between the charge-discharge branch 120a, the sensing channel RX and the programmable gain amplifier PGA are the same as those in the first embodiment and are not described again.

[0091] In this example, taking the mutual capacitance scanning mode as an example, initially, S1 jumps high and controls Q0 to be closed, and the charge-discharge branch 120a discharges the sensing channel RX through Q0, pulling the VRX voltage down to AVSS, and the VO output by the comparator COMP is also low. When S1 jumps low and controls Q0 to be disconnected, S2 jumps high to control MP1 to be closed and turned on, and the second current source I0 charges the sensing channel RX. When VRXM is equal to the reference voltage VR1, the VO output by the comparator COMP jumps high and stops charging. Subsequently, the PGA samples the VRX and VRXM voltages and amplifies their difference and passes it to the ADC for quantization.

[0092] As an example, see Figure 8B The charge and discharge circuit 120 has a charge and discharge branch 120a, an OR logic circuit OR, a trigger SR_latch, a delay device delay and a comparator COMP. The charge and discharge branch 120a includes a first switch Q0, a second switch MP1 and a second current source I0. The second input terminal (-) of the comparator COMP is coupled to a reference voltage VR1, the first input terminal (+) of the comparator COMP is coupled to the output terminal of the reference voltage generating circuit 121 to access the reference reference voltage VRXM, the output terminal of the comparator COMP is coupled to the first input terminal S of the trigger SR_latch, the input terminal of the delay device delay, the control terminal of the first switch Q0 and the second input terminal of the OR logic circuit OR all receive the first control signal S1, the output terminal of the delay device delay is coupled to the first input terminal R of the trigger SR_latch, the output terminal of the trigger SR_latch is coupled to the first input terminal of the OR logic circuit OR, and the output terminal of the OR logic circuit OR is coupled to the control terminal of the second switch MP1 to output the second control signal S2 to the second switch MP1.

[0093] The connection relationship between the first switch Q0, the second switch MP1 and the second current source I0 in the charge-discharge branch 120a and the connection relationship between the charge-discharge branch 120a, the sensing channel RX and the programmable gain amplifier PGA are the same as those in the first embodiment and are not described again.

[0094] In this example, taking the mutual capacitance scanning mode as an example, initially, S1 jumps high and controls Q0 to be closed, and the charge-discharge branch 120a discharges the sensing channel RX through Q0, pulling the VRX voltage down to AVSS, and the S output by the comparator COMP is also low. When S1 jumps low and controls Q0 to be disconnected, S2 jumps high to control MP1 to be closed and turned on, and the second current source I0 charges the sensing channel RX. When VRXM is equal to the reference voltage VR1, the S output by the comparator COMP jumps high and stops charging. Subsequently, the PGA samples the VRX and VRXM voltages and amplifies their difference and passes it to the ADC for quantization.

[0095] In this example, on the one hand, the setting of the trigger SR_latch can avoid the phenomenon that the output S of the comparator COMP jumps high and then jumps low again due to circuit interference; on the other hand, the delay device delay can generate R after S1 is relatively delayed a little, thereby avoiding the problem that the first input terminal and the second input terminal of the trigger SR_latch are simultaneously valid, which leads to the problem of competition risk in the trigger SR_latch. In summary, the technical solution of this example is relatively Fig. 8A The example shown has higher reliability.

[0096] Please refer to Figure 3 This embodiment further provides a touch control chip, which includes the touch control detection circuit 12 as described in this embodiment.

[0097] Please refer to Figure 3 This embodiment also provides an electronic device, which includes a touch screen 10 and the touch chip of this embodiment.

[0098] The touch control chip and the electronic device of the present embodiment have improved performance due to the adoption of the touch control detection circuit of the present embodiment.

[0099] In summary, the touch detection circuit, touch chip and electronic device of this embodiment have higher performance than those of the first embodiment.

[0100] Third embodiment

[0101] Please combine Figure 3 , Fig. 9 and Fig.10 The present embodiment provides a touch detection circuit 12, which is coupled to the touch screen 10 and is used to detect the capacitance change on the touch screen 10. The detection result of the touch detection circuit 12 can be used to identify the location of the touch event on the touch screen 10 and determine the user's touch operation. The touch detection circuit 12 has several touch detection branches (not shown in FIG. Figure 3 The touch detection branch can be coupled to the sensing channel RX in a one-to-one correspondence, or one touch detection branch can be coupled to multiple sensing channels RX at the same time. The touch detection circuit 12 can be applied in a mutual capacitance scanning mode or a self-capacitance scanning mode, and its charge-discharge circuit 120 has a charge-discharge branch 120a coupled to the sensing channel RX.

[0102] The touch detection circuit 12 of this embodiment is different from the touch detection circuit of the second embodiment in that it further includes a digital-to-analog converter DAC, and the two differential output terminals of the digital-to-analog converter DAC are respectively coupled to the first input terminal and the second input terminal of the programmable gain amplifier PGA. The digital-to-analog converter DAC is used to provide two differential voltages VDACP and VDANC to the programmable gain amplifier PGA, and the difference between the two differential voltages VDACP and VDANC VDACP-VDANC is adjustable and used to subtract the non-ideal factors of the front stage of the programmable gain amplifier PGA.

[0103] It should be understood that the DAC can be designed to be shared. In this case, in the touch detection circuit 12, the DAC and the reference voltage generation circuit 121 are shared by multiple sensing channels, that is, multiple PGAs share one DAC. Of course, one PGA can also use one DAC. According to the number of bits of the DAC, the DAC can output many voltages (for example, 8 bits have 256 voltages). The DAC can be further coupled to the output end of the ADC, so as to control which voltage it outputs as the two differential voltages VDACP and VDANC required by the corresponding PGA according to the digital signal output by the ADC. Of course, the DAC can further use the digital signal provided by other digital circuits to control which voltage it outputs as the two differential voltages VDACP and VDANC required by the corresponding PGA.

[0104] As an example, see Fig.10 The PGA includes an operational transconductance amplifier PGA_OP, a first input circuit and a second input circuit. The first input circuit includes a first sampling capacitor CS1, a first amplifying switch Q1 and a first sampling switch Q2, and the second input circuit includes a second sampling capacitor CS2, a second amplifying switch Q4 and a second sampling switch Q3.

[0105] Optionally, the PGA of this example further includes a first feedback circuit and a second feedback circuit, wherein the first feedback circuit includes a first feedback capacitor CF1 and a first feedback switch Q7, and the second feedback circuit includes a second feedback capacitor CF2 and a second feedback switch Q8.

[0106] Further optionally, the PGA of this example further includes first to fourth reset switches Q5 , Q6 , Q9 and Q10 .

[0107] Among them, one end of the first sampling capacitor CS1 is coupled to one end of the first feedback capacitor CF1, one end of the first reset switch Q5 and the first input end VIP_OP of the operational transconductance amplifier PGA_OP, the other end of the first sampling capacitor CS1 is coupled to one end of the first amplifying switch Q1 and one end of the first sampling switch Q2, the other end of the first sampling switch Q2 is coupled to the output end of the charge-discharge branch 120a to access the sensing voltage VRX, the other end of the first amplifying switch Q1 is coupled to a differential voltage VDACP output by the digital-to-analog converter DAC, the other end of the first feedback capacitor CF1 is coupled to one end of the first feedback switch Q7 and one end of the second reset switch Q6, and the other end of the first feedback switch Q7 is coupled to an output end VON of the operational transconductance amplifier PGA_OP and an input end of the analog-to-digital converter ADC.

[0108] One end of the second sampling capacitor CS2 is coupled to one end of the second feedback capacitor CF2, one end of the fourth switch Q10, and the second input end VIN_OP of the operational transconductance amplifier PGA_OP. The other end of the second sampling capacitor CS2 is coupled to one end of the second amplifying switch Q4 and one end of the second sampling switch Q3. The other end of the second sampling switch Q3 is coupled to the output end of the reference voltage generating circuit 121 to access the reference reference voltage VRXM. The other end of the second amplifying switch Q4 is coupled to another differential voltage VDACN output by the digital-to-analog converter DAC. The other end of the second feedback capacitor CF2 is coupled to one end of the second feedback switch Q8 and one end of the third switch Q9. The other end of the second feedback switch Q8 is coupled to the other output end VOP of the operational transconductance amplifier PGA_OP and the other input end of the analog-to-digital converter ADC.

[0109] The other end of the first reset switch Q5 , the other end of the second reset switch Q6 , the other end of the third reset switch Q9 and the other end of the fourth reset switch Q10 all receive a common mode voltage VCM, which is, for example, AVDD / 2.

[0110] The control ends of Q2, Q3, Q5, Q6, Q9 and Q10 all receive the sampling clock signal CLKS of the programmable gain amplifier PGA, and the control ends of Q1, Q4, Q7 and Q8 all receive the amplified phase signal AMP of the programmable gain amplifier PGA. Among them, CS1 and CS2 have the same size and the capacitance value CS is adjustable, CF1 and CF2 have the same size and the capacitance value C FB All adjustable.

[0111] Please refer to Fig.11 The working timing of the touch detection circuit of this embodiment is as follows:

[0112] Initially, S1 is high and controls Q0 to be closed, and the charge-discharge circuit 120 discharges the sensing channel RX through Q0. At this time, the VRX voltage is pulled down to AVSS, the S output of the comparator COMP is also low, and the R output of the delay device delay is high.

[0113] When S1 jumps low and controls Q0 to be disconnected, R output by the delay device jumps low, S2 jumps high and controls MP1 to be turned on, and the second current source I0 charges the sensing channel RX and provides the sensing voltage VRX to the PGA.

[0114] When the reference voltage VRXM is equal to the reference voltage VR1, S output by the comparator COMP jumps high, S2 jumps low and the control MP1 is turned off, and the second current source I0 stops charging the sensing channel RX.

[0115] Subsequently, the sampling clock signal CLKS of the PGA jumps high, Q2, Q3, Q5, Q6, Q9, and Q10 are all closed and turned on, the first sampling capacitor CS1 is connected to VRX, and the second sampling capacitor CS2 is connected to VRXM, so that the PGA samples the voltages of VRX and VRXM. The VRX on the touched sensing channel RX is smaller than VRXM, and the VRX on the untouched sensing channel RX is larger than VRXM.

[0116] After that, the sampling clock signal CLKS jumps low, Q2, Q3, Q5, Q6, Q9, and Q10 are all disconnected, the amplified phase signal AMP jumps high, Q1, Q4, Q7, and Q8 are all closed and turned on, the first sampling capacitor CS1 is connected to VDACP, and the second sampling capacitor CS2 is connected to VDACN. Therefore, the PGA uses the difference VDACP-VDACN to subtract the influence of some non-ideal factors of the previous stage (such as unequal Cb of each sensing channel RX, charging current mismatch, etc.) on the sampling result, and amplifies the corresponding processing structure and hands it over to the ADC for quantization. Therefore, based on the overall detection results of the touch detection circuit 12 on the touch screen 10, it is possible to determine which channels are touched and which channels are not touched.

[0117] Among them, the output result of PGA is:

[0118]

[0119] It can be seen from the above formula that by adjusting the difference (VDACP-VDACN), the non-ideal factors of the previous stage can be reduced to the greatest extent. As an example, in order to cover the worst case of channel mismatch, a 7-9 bit adjustable differential DAC can be designed as the DAC required for this example. Moreover, the first input circuit and the first feedback circuit cooperate with each other, and the second input circuit and the second feedback circuit cooperate with each other, so that the output of the PGA is only related to the difference (VDACP-VDACN), the difference (VRX-VRXM) and the capacitance ratio CS / CFB. When the difference (VDACP-VDACN) remains unchanged, the capacitance ratio CS / CFB can be adjusted and controlled to adjust and control the gain coefficient of the operational transconductance amplifier PGA_OP, thereby increasing the dynamic range of the programmable gain amplifier PGA and improving the touch detection accuracy.

[0120] Please refer to Figure 3 This embodiment further provides a touch control chip, which includes the touch control detection circuit 12 as described in this embodiment.

[0121] Please refer to Figure 3 This embodiment also provides an electronic device, which includes a touch screen 10 and the touch chip of this embodiment.

[0122] The touch control chip and the electronic device of the present embodiment have improved performance due to the adoption of the touch control detection circuit of the present embodiment.

[0123] In summary, the touch detection circuit, touch chip and electronic device of this embodiment have higher performance than those of the second embodiment.

[0124] The above description is only a description of the preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. Any changes or modifications made by a person skilled in the art in the field of the present invention based on the above disclosure shall fall within the scope of protection of the technical solution of the present invention.< / n> < / n> < / n> < / n> < / n> < / n> < / n> < / n> < / n> < / n> < / n> < / n> < / n> < / n> < / n> < / n> < / n> < / n> < / n> < / n> < / n> < / n> < / n> < / m> < / m> < / n>

Claims

1. A touch detection circuit, characterized in that: include: A charge and discharge circuit is coupled to the corresponding sensing channel of the touch screen and is used to charge or discharge the sensing channel during a scanning cycle to convert the sensing signal on the sensing channel into a sensing voltage; A reference voltage generating circuit, coupled to a plurality of sensing channels on the touch screen, and used to generate a reference voltage related to the voltages of the plurality of sensing channels; A programmable gain amplifier, having a first input terminal coupled to the output terminal of the charge-discharge circuit, a second input terminal coupled to the output terminal of the reference voltage generating circuit, and used to amplify the difference between the sensing voltage and the reference voltage; The analog-to-digital converter is coupled to the programmable gain amplifier and is used for quantizing the difference amplified by the programmable gain amplifier.

2. The touch detection circuit according to claim 1, characterized in that: The reference voltage generating circuit includes an operational amplifier having a first input terminal and multiple second input terminals, each second input terminal of the operational amplifier is respectively coupled to a corresponding one of the multiple sensing channels, the first input terminal of the operational amplifier is coupled to the output terminal of the operational amplifier, and the operational amplifier is used to output the average value of the voltages of the multiple sensing channels as the reference voltage.

3. The touch detection circuit according to claim 2, characterized in that: The multiple sensing channels are n sensing channels, n is an integer and n≥2, the operational amplifier includes a first input tube, n identical second input tubes and an operational amplifier circuit, the gate of the first input tube is coupled to the output end of the operational amplifier circuit, the drain of the first input tube is coupled to the first input end of the operational amplifier circuit, the source of the first input tube and the sources of the n second input tubes are both coupled to a first current source, the drains of the n second input tubes are all coupled to the second input end of the operational amplifier circuit, and the gates of the n second input tubes are respectively coupled to different sensing channels among the n sensing channels.

4. The touch detection circuit according to claim 1, characterized in that: The charge and discharge circuit includes a charge and discharge branch, and the charge and discharge branch includes a first switch, a second switch and a second current source, the control end of the first switch receives a first control signal, and the control end of the second switch receives a second control signal different from the first control signal; in a mutual capacitance scanning mode, one end of the second current source is connected to the first power supply voltage, and the other end is coupled to one end of the second switch, the other end of the second switch is coupled to one end of the first switch, the sensing channel and the first input end of the programmable gain amplifier, and the other end of the first switch is connected to a common reference voltage; or, in a self-capacitance scanning mode, one end of the second current source is connected to the corresponding second power supply voltage, and the other end is coupled to one end of the second switch, the other end of the second switch is coupled to one end of the first switch, the sensing channel and the first input end of the programmable gain amplifier, and the other end of the first switch is connected to the first power supply voltage.

5. The touch detection circuit according to claim 4, characterized in that: The output end of the reference voltage generating circuit is also coupled to the control end of the second switch, and the reference voltage generating circuit is also used to control the charge and discharge circuit to charge or discharge the sensing channel through the reference voltage.

6. The touch detection circuit according to claim 5, characterized in that: The charge and discharge circuit also includes an OR logic circuit and a comparator, the second input terminal of the comparator is coupled to a reference voltage, the first input terminal of the comparator is coupled to the output terminal of the reference voltage generating circuit, the output terminal of the comparator is coupled to the first input terminal of the OR logic circuit, the second input terminal of the OR logic circuit receives the first control signal, and the output terminal of the OR logic circuit outputs the second control signal.

7. The touch detection circuit according to claim 6, characterized in that: The charge and discharge circuit also includes a trigger and a delay device, wherein the first input terminal of the trigger is coupled to the output terminal of the comparator, the second input terminal of the trigger is coupled to the output terminal of the delay device, the output terminal of the trigger is coupled to the first input terminal of the OR logic circuit, and the delay device is used to delay the first control signal and input it to the trigger.

8. The touch detection circuit according to any one of claims 1 to 7, characterized in that: It also includes a digital-to-analog converter, wherein two differential output terminals of the digital-to-analog converter are respectively coupled to the first input terminal and the second input terminal of the programmable gain amplifier, and the digital-to-analog converter is used to provide two differential voltages to the programmable gain amplifier, and the difference between the two differential voltages is adjustable and used to subtract the non-ideal factors of the front stage of the programmable gain amplifier.

9. The touch detection circuit according to claim 8, characterized in that: The programmable gain amplifier comprises an operational transconductance amplifier, a first input circuit and a second input circuit; one end of the first input circuit serves as a first input end of the programmable gain amplifier and is coupled to a differential output end of the digital-to-analog converter and an output end of the charge-discharge circuit to receive one path of the differential voltage and the sensing voltage, and the other end of the first input circuit is coupled to the first input end of the operational transconductance amplifier; One end of the second input circuit serves as the second input end of the programmable gain amplifier, coupled to another differential output end of the digital-to-analog converter and the output end of the reference voltage generating circuit to receive another differential voltage and the reference reference voltage, and the other end of the second input circuit is coupled to the second input end of the operational transconductance amplifier; the output end of the operational transconductance amplifier is coupled to the analog-to-digital converter.

10. The touch detection circuit according to claim 9, characterized in that: The first input circuit includes a first sampling capacitor, a first amplifying switch and a first sampling switch, one end of the first sampling capacitor is coupled to the first input end of the operational transconductance amplifier, the other end of the first sampling capacitor is coupled to one end of the first amplifying switch and one end of the first sampling switch, the other end of the first sampling switch is coupled to the output end of the charge-discharge circuit, and the other end of the first amplifying switch is coupled to a differential output end of the digital-to-analog converter; Alternatively, the second input circuit includes a second sampling capacitor, a second amplifying switch and a second sampling switch, one end of the second sampling capacitor is coupled to the second input end of the operational transconductance amplifier, the other end of the second sampling capacitor is coupled to one end of the second amplifying switch and one end of the second sampling switch, the other end of the second sampling switch is coupled to the output end of the reference voltage generating circuit, and the other end of the second amplifying switch is coupled to the other differential output end of the digital-to-analog converter; wherein the first amplifying switch and the second amplifying switch are both turned on during the amplifying phase of the programmable gain amplifier, and the first sampling switch and the second sampling switch are both turned on during the sampling phase of the programmable gain amplifier.

11. The touch detection circuit according to claim 9, characterized in that: The programmable gain amplifier also includes a first feedback circuit and a second feedback circuit; one end of the first feedback circuit is coupled to the output end of the operational transconductance amplifier, the other end of the first feedback circuit is coupled to the first input end of the operational transconductance amplifier, one end of the second feedback circuit is coupled to the output end of the operational transconductance amplifier, and the other end of the second feedback circuit is coupled to the second input end of the operational transconductance amplifier.

12. The touch detection circuit according to claim 11, characterized in that: The first feedback circuit includes a first feedback capacitor and a first feedback switch, one end of the first feedback capacitor is coupled to the first sampling capacitor and the first input end of the operational transconductance amplifier, the other end of the first feedback capacitor is coupled to one end of the first feedback switch, and the other end of the first feedback switch is coupled to the output end of the operational transconductance amplifier; or, the second feedback circuit includes a second feedback capacitor and a second feedback switch, one end of the second feedback capacitor is coupled to the second input end of the operational transconductance amplifier, the other end of the second feedback capacitor is coupled to one end of the second feedback switch, and the other end of the second feedback switch is coupled to the output end of the operational transconductance amplifier; the first amplification switch and the second amplification switch are both turned on during the amplification phase of the programmable gain amplifier.

13. The touch detection circuit according to claim 11, characterized in that: The programmable gain amplifier also includes first to fourth reset switches, one end of the first to fourth reset switches are respectively connected to the common reference voltage, the other end of the first reset switch is coupled to the first input end of the operational transconductance amplifier, the other end of the second reset switch is coupled to the connection node of the first feedback capacitor and the first feedback switch, the other end of the third reset switch is coupled to the connection node of the second feedback capacitor and the second feedback switch, and the other end of the fourth reset switch is coupled to the second input end of the operational transconductance amplifier; the first to fourth reset switches are all turned on during the sampling phase of the programmable gain amplifier.

14. The touch detection circuit according to claim 8, characterized in that: In the touch detection circuit, at least the digital-to-analog converter or the reference voltage generating circuit is shared by a plurality of the sensing channels.

15. A touch chip, characterized in that: The method comprises a touch detection circuit as claimed in any one of claims 1 to 14.

16. An electronic device, characterized in that: The invention comprises a touch screen and a touch chip as claimed in claim 15, wherein the touch screen has a plurality of sensing channels, and the touch chip is coupled to each of the sensing channels.

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