Amplification circuit and touch device
By designing operational amplifiers and compensation circuits in touch devices, the voltage signal amplitude of the charge amplifier output is reduced, the problem of oversaturation of the analog-to-digital converter is solved, and the accuracy and working efficiency of touch position recognition are improved.
Patent Information
- Application Number
- CN202411105332.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-08-12
- Publication Date
- 2024-12-31
AI Technical Summary
In touch devices, the voltage signal amplitude output by the charge amplifier may exceed the maximum input amplitude of the analog-to-digital converter, resulting in the output signal of the analog-to-digital converter being oversaturated and the touch position cannot be accurately determined.
An amplifier circuit is designed, including an operational amplifier, feedback loop and compensation circuit. The compensation current is output through the compensation circuit, which reduces the amplitude of the output voltage signal of the operational amplifier and avoids oversaturation of the analog-to-digital converter. The compensation circuit can reduce the voltage signal amplitude of the charge amplifier output by adjusting the compensation resistance value or using a phase shift circuit, an analog-to-digital converter, and a current digital-to-analog converter to adjust the phase and compensation current.
It effectively reduces the risk of oversaturation of the output signal of the analog-to-digital converter, improves the accuracy and working efficiency of touch position recognition, and avoids the reduction of signal-to-noise ratio.
Smart Images
Figure CN119232160A_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the field of touch control technology, and in particular to an amplifier circuit and a touch control device. Background Art
[0002] A touch device generally includes a touch panel, a charge amplifier and an analog-to-digital converter. The touch panel is provided with touch electrodes. The charge amplifier converts the output signal of the touch electrode into a voltage signal, which is then converted into a digital signal by the analog-to-digital converter to detect the touch position. However, the amplitude of the voltage signal output by the charge amplifier may exceed the maximum input amplitude of the analog-to-digital converter, causing the output signal of the analog-to-digital converter to be oversaturated, and thus the touch position cannot be determined based on the output signal of the analog-to-digital converter. Summary of the invention
[0003] In view of the above problems, the present application provides an amplifier circuit and a touch control device, which can reduce the amplitude of the voltage signal output by the charge amplifier, thereby reducing the risk of oversaturation of the output signal of the analog-to-digital converter.
[0004] In a first aspect, the present application provides an amplifier circuit, which includes: an operational amplifier, which includes an operational amplifier and a feedback loop, wherein the non-inverting input terminal of the operational amplifier receives a scanning signal of a touch electrode, the inverting input terminal of the operational amplifier receives an output signal of the touch electrode, and is electrically connected to the output terminal of the operational amplifier through the feedback loop; a compensation circuit, which is electrically connected to the inverting input terminal of the operational amplifier, and is used to output a compensation current to reduce the output voltage of the operational amplifier.
[0005] In a possible implementation, the compensation circuit includes a compensation resistor, one end of the compensation resistor receives the scanning signal, and the other end of the resistor is electrically connected to the inverting input end of the operational amplifier.
[0006] In a possible implementation manner, the resistance value of the compensation resistor is determined according to the output voltage of the operational amplifier.
[0007] In one possible implementation, the compensation circuit includes a phase shifting circuit, an analog-to-digital converter and a current digital-to-analog converter. The phase shifting circuit is used to receive a scanning signal and to adjust the phase of the scanning signal to a target phase; the analog-to-digital converter is electrically connected to the phase shifting circuit to generate a digital signal according to the target phase; the current digital-to-analog converter is electrically connected to the phase shifting circuit to generate a compensation current according to the digital signal.
[0008] In a possible implementation manner, the target phase is determined according to an output voltage of the operational amplifier.
[0009] In a possible implementation, the touch electrode is electrically connected to one end of a parasitic capacitor and one end of an input resistor, the other end of the parasitic capacitor receives a scan signal, and the other end of the input resistor is electrically connected to an inverting input end of an operational amplifier.
[0010] In a possible implementation, the feedback loop includes a feedback resistor and a feedback capacitor, and both ends of the feedback resistor and both ends of the feedback capacitor are electrically connected to the inverting input terminal and the output terminal of the operational amplifier, respectively.
[0011] In a second aspect, the present application provides a touch device, including a touch panel and an amplifier circuit provided by any possible implementation of the first aspect, wherein a touch electrode is disposed on the touch panel.
[0012] In a possible implementation, a touch analog-to-digital converter is further included. The touch analog-to-digital converter is electrically connected to the output end of the operational amplifier, and the touch analog-to-digital converter is used to convert the output voltage of the operational amplifier into a digital touch signal.
[0013] In a possible implementation, a position detection circuit is further included. The position detection circuit is electrically connected to the touch analog-to-digital converter and is used to obtain the touch position of the touch electrode according to the digital touch signal. BRIEF DESCRIPTION OF THE DRAWINGS
[0014] Figure 1 A schematic diagram of a touch device provided in this application.
[0015] Figure 2 A circuit diagram of a charge amplifier provided in this application.
[0016] Figure 3 Another circuit diagram of the charge amplifier provided in this application.
[0017] Figure 4 A schematic diagram of the waveforms of the input signal and the output signal of the charge amplifier provided in this application. DETAILED DESCRIPTION
[0018] The technical solutions in the embodiments of the present application will be clearly described below in conjunction with the drawings in the embodiments of the present application.
[0019] It is understandable that the connection relationship described in this application refers to direct or indirect connection. For example, the connection between A and B can be either a direct connection between A and B or an indirect connection between A and B through one or more other electrical components. For example, A and C can be directly connected, and C and B can be directly connected, so that A and B are connected through C. It is also understandable that the "A connects B" described in this application can be a direct connection between A and B, or an indirect connection between A and B through one or more other electrical components.
[0020] In the description of this application, unless otherwise specified, " / " means "or", for example, A / B can mean A or B. "And / or" in this article is only a way to describe the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone.
[0021] In the description of this application, words such as "first" and "second" are only used to distinguish different objects, and do not limit the quantity and execution order, and words such as "first" and "second" do not necessarily limit differences. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions.
[0022] A touch device generally includes a touch panel, a charge amplifier and an analog-to-digital converter. The touch panel is provided with touch electrodes. The charge amplifier converts the output signal of the touch electrode into a voltage signal, which is then converted into a digital signal by the analog-to-digital converter to detect the touch position. However, the amplitude of the voltage signal output by the charge amplifier may exceed the maximum input amplitude of the analog-to-digital converter, causing the output signal of the analog-to-digital converter to be oversaturated, and thus the touch position cannot be determined based on the output signal of the analog-to-digital converter.
[0023] Therefore, the present application provides an amplifier circuit and a touch control device, which can reduce the amplitude of the voltage signal output by the charge amplifier, thereby reducing the risk of oversaturation of the output signal of the analog-to-digital converter.
[0024] Specifically, see Figure 1 , Figure 1 FIG. 1 is a schematic diagram of a touch control device 10 provided in the present application. The touch control device 10 includes a touch control panel 11 and a processing circuit 12 .
[0025] A plurality of touch electrodes 111 are provided on the touch panel 11, and each touch electrode 111 is connected to an input source 112. The input source 112 is used to provide a scanning signal of a specific frequency to the touch electrode 111. The specific frequency can be preset according to actual conditions, for example, the specific frequency can be 100 kHz. The scanning signal can be a sinusoidal signal.
[0026] The touch electrodes 111 are electrically connected to the processing circuit 12. The processing circuit 12 is used to receive output signals of the touch electrodes 111 and determine whether the touch electrodes 111 are touched and the specific touch positions according to the output signals of the touch electrodes 111.
[0027] In some embodiments, the plurality of touch electrodes 111 may be electrically connected to the processing circuit 12 via a multiplexer, and the multiplexer may select an output signal of at least one row / column of touch electrodes from the plurality of touch electrodes 111 and transmit the output signal to the processing circuit 12. After the processing circuit 12 processes and analyzes the output signal of the multiplexer, a specific touch position on the touch panel 11 may be obtained.
[0028] Specifically, the processing circuit 12 includes a charge amplifier 121 and a touch analog-to-digital converter 122. The charge amplifier 121 is electrically connected to the plurality of touch electrodes 111, and is used to receive the output signals of the plurality of touch electrodes 111, and convert the output signals of the plurality of touch electrodes 111 into voltage signals. Specifically, the charge amplifier 121 receives the amount of charge output by the plurality of touch electrodes 111, and amplifies the amount of charge output by the plurality of touch electrodes 111 into a voltage signal. When the touch electrode 111 is touched, for example, when the user's finger or stylus performs operations such as clicking, pressing, and sliding on the touch panel 11, the capacitance of the touch electrode 111 changes, and therefore the output signal of the touch electrode 111 also changes accordingly, that is, the amount of charge output by the touch electrode 111 changes. At this time, the output signal of the charge amplifier 121 will also change, that is, the output voltage of the charge amplifier 121 will change.
[0029] The touch analog-to-digital converter 122 is electrically connected to the charge amplifier 121, and is used to generate a digital voltage signal according to the output voltage of the charge amplifier 121. In some embodiments, the touch analog-to-digital converter 122 is also electrically connected to a processor, and the processor is used to obtain touch information of the touch electrode 111 according to the digital voltage signal, wherein the touch information includes whether the touch electrode 111 is touched and the specific touch position.
[0030] See also Figure 2 , Figure 2 The circuit diagram of the charge amplifier 121 provided in the present application. The charge amplifier 121 includes an operational amplifier 1211 and a feedback loop 1212. The feedback loop 1212 includes a feedback capacitor CF and a feedback resistor RF, and both ends of the feedback capacitor CF and both ends of the feedback resistor RF are electrically connected to the inverting input terminal and the output terminal of the operational amplifier 1211, respectively. The non-inverting input terminal of the operational amplifier 1211 receives the scanning signal Vi. The inverting input terminal of the operational amplifier 1211 is also electrically connected to the touch electrode 111 through the input resistor RL, and the touch electrode 111 is also electrically connected to the input source 112 through the parasitic capacitor CL to receive the scanning signal Vi.
[0031] According to the virtual short and virtual open principle of the operational amplifier 1211, the voltage signal Vout output by the operational amplifier 1211 and the scanning signal Vi received by the inverting input terminal of the operational amplifier 1211 satisfy the following formula (1):
[0032]
[0033] Wherein, A is the gain coefficient of the operational amplifier 1211, Z2 is the total impedance of the feedback loop 1212, and Z1 is the equivalent total impedance of the inverting input terminal of the operational amplifier 1211. Z2 and Z1 satisfy the following formula (2) and formula (3) respectively.
[0034]
[0035]
[0036] Substituting formula (2) and formula (3) into formula (1), we can obtain:
[0037] According to formula (4), the amplitude of the voltage signal output by the operational amplifier 1211 should be smaller than the voltage amplitude of the scanning signal. However, since the leakage current and bias current of the operational amplifier 1211 affect the amplitude of the voltage signal output by the operational amplifier 1211, the amplitude of the voltage signal output by the operational amplifier 1211 may be larger than the voltage amplitude of the scanning signal. As a result, the voltage amplitude received by the touch analog-to-digital converter 122 may exceed its maximum input voltage amplitude, causing the output signal of the touch analog-to-digital converter 122 to be oversaturated and unable to generate the corresponding digital voltage signal normally, thereby reducing the touch position recognition accuracy and work efficiency of the touch device 10. If this problem is improved by reducing the voltage amplitude of the output signal of the touch electrode 111, the signal-to-noise ratio of the touch device 10 will be reduced, which will also reduce the touch position recognition accuracy and work efficiency of the touch device 10.
[0038] Therefore, the present application compensates for the input signal of the charge amplifier 121, so that the amplitude of the voltage signal output by the charge amplifier 121 can be reduced without reducing the voltage amplitude of the output signal of the touch electrode 111, thereby reducing the risk of over-saturation of the output signal of the touch analog-to-digital converter 122.
[0039] For details, please refer again to Figure 1 and Figure 2 The touch control device 10 further includes a compensation circuit 13. The compensation circuit 13 is electrically connected to the inverting input terminal of the operational amplifier 1211 and is used to output a compensation current to reduce the voltage amplitude of the output signal of the operational amplifier 1211. Figure 2As shown, in this embodiment, the compensation circuit 13 includes a compensation resistor R1, one end of the compensation resistor R1 receives the scan signal Vi, and the other end of the compensation resistor R1 is electrically connected to the inverting input end of the operational amplifier 1211 and one end of the input resistor RL.
[0040] When the compensation circuit 13 is electrically connected to the inverting input terminal of the operational amplifier 1211, the equivalent total impedance Z3 of the inverting input terminal of the operational amplifier 1211 satisfies the following formula (5):
[0041]
[0042] From formula (5), we can see that Z3 is obviously smaller than Z1. Therefore, from formula (1), we can get Reduce, that is, the compensation circuit 13 can reduce the voltage signal Vout output by the operational amplifier 1211 , thereby reducing the risk of over-saturation of the output signal of the touch analog-to-digital converter 122 .
[0043] On the other hand, since the scanning signal Vi passes through the parasitic capacitor C1 and the input resistor RL, there is a phase difference between the voltage signal at the inverting input terminal of the operational amplifier 1211 and the scanning signal Vi. As a result, there is a voltage difference between the two ends of the compensation resistor R1, so that a current flows through the compensation resistor R1, that is, the compensation resistor R1 outputs a compensation current.
[0044] According to the virtual short and virtual open principle of the operational amplifier 1211, the voltage signal Vout output by the operational amplifier 1211 and the scanning signal Vi also satisfy the following formula (6):
[0045] Vout=Vi-*ZZ3-*Z1(6)
[0046] Wherein, I is the current at the output end of the operational amplifier 1211. According to the virtual disconnection principle of the operational amplifier 1211, the operational amplifier 1211 works in the amplification region, and its inverting input end is deemed to have no current flowing in, so the current output by the input source 112 flows through the feedback loop 1212 to the output end of the operational amplifier 1211. When the compensation circuit 13 is electrically connected to the inverting input end of the operational amplifier 1211, the compensation circuit 13 provides an additional compensation current, thereby increasing I. As can be seen from formula (6), Vout decreases. In this way, the compensation current can reduce the voltage signal Vout output by the operational amplifier 1211.
[0047] In some embodiments, the resistance value of the compensation resistor R1 can be determined according to the amplitude of the voltage signal output by the operational amplifier 1211. That is, the resistance value of the compensation resistor R1 can be adaptively adjusted according to the amplitude of the voltage signal output by the operational amplifier 1211. By adjusting the resistance value of the compensation resistor R1, the equivalent total impedance Z3 of the inverting input terminal of the operational amplifier 1211 can be adjusted, thereby reducing the amplitude of the voltage signal output by the operational amplifier 1211. On the other hand, by adjusting the resistance value of the compensation resistor R1, the current value of the compensation current can be adjusted, thereby reducing the amplitude of the voltage signal output by the operational amplifier 1211.
[0048] See also Figure 3 In another embodiment, the compensation circuit 13 includes a phase shift circuit 131, an analog-to-digital converter 132, and a current digital-to-analog converter 133. The input end of the phase shift circuit 131 receives the scanning signal Vi, is used to adjust the phase of the scanning signal Vi, and outputs the second scanning signal Vii after the phase is adjusted. The input end of the analog-to-digital converter 132 receives the second scanning signal Vii after the phase is adjusted, and is used to output a digital signal according to the phase difference between the second scanning signal Vii and the scanning signal Vi. The input end of the current digital-to-analog converter 133 receives the digital signal, and generates a corresponding compensation current according to the digital signal.
[0049] The phase shift circuit 131 may include electronic components with phase shift function such as capacitors, inductors, and all-pass filters. The phase shift adjustment amount of the phase shift circuit 131 for the scanning signal Vi can be determined according to the amplitude of the voltage signal output by the operational amplifier 1211. That is, the phase shift adjustment amount of the phase shift circuit 131 for the scanning signal Vi can be adaptively adjusted according to the amplitude of the voltage signal output by the operational amplifier 1211. By adjusting the phase shift adjustment amount of the scanning signal Vi by the phase shift circuit 131, that is, changing the phase of the second scanning signal Vii, the digital signal output by the analog-to-digital converter 132 can be changed, thereby changing the magnitude of the compensation current. As can be seen from formula (6), the current value of the compensation current is related to the voltage signal Vout output by the operational amplifier 1211, so adjusting the current value of the compensation current can correspondingly reduce the voltage signal Vout output by the operational amplifier 1211.
[0050] See also Figure 4 , Figure 4 Schematic diagram of the waveform of the input signal and output signal of the charge amplifier 121 provided in the present application. Curve L1 is the input signal of the charge amplifier 121, and curve L2 and curve L3 are the output signals of the charge amplifier 121 in the scenario where the compensation circuit 13 is not electrically connected and in the scenario where the compensation circuit 13 is electrically connected, respectively.
[0051] like Figure 4As shown, when the compensation circuit 13 is not electrically connected to the inverting input terminal of the operational amplifier 1211, the voltage amplitude of the output signal of the charge amplifier 121 is greater than the voltage amplitude of the output signal of the touch electrode 111, so that the voltage amplitude received by the touch analog-to-digital converter 122 may exceed its maximum input voltage amplitude, causing the output signal of the touch analog-to-digital converter 122 to be oversaturated and unable to generate the corresponding digital voltage signal normally, thereby reducing the touch position recognition accuracy and working efficiency of the touch device 10.
[0052] When the compensation circuit 13 is electrically connected to the inverting input terminal of the operational amplifier 1211, the voltage amplitude of the output signal of the charge amplifier 121 is greater than the voltage amplitude of the output signal of the touch electrode 111, thereby reducing the risk of oversaturation of the output signal of the touch analog-to-digital converter 122 and improving the touch position recognition accuracy and working efficiency of the touch device 10.
[0053] Therefore, the present application provides an amplifier circuit and a touch control device, which can reduce the amplitude of the voltage signal output by the charge amplifier, thereby reducing the risk of oversaturation of the output signal of the analog-to-digital converter.
[0054] Those skilled in the art should recognize that the above embodiments are only used to illustrate the present application and are not intended to be limiting of the present application. As long as they are within the spirit and scope of the present application, appropriate changes and modifications to the above embodiments are within the scope of protection claimed in the present application.
Claims
1. An amplifier circuit, characterized in that: The amplifying circuit comprises: An operational amplifier, the operational amplifier comprising an operational amplifier and a feedback loop, wherein a non-inverting input terminal of the operational amplifier receives a scanning signal of a touch electrode, an inverting input terminal of the operational amplifier receives an output signal of the touch electrode, and is electrically connected to an output terminal of the operational amplifier through the feedback loop; A compensation circuit is electrically connected to the inverting input terminal of the operational amplifier, and is used to output a compensation current to reduce an output voltage of the operational amplifier.
2. The amplifier circuit according to claim 1, characterized in that: The compensation circuit includes a compensation resistor, one end of which receives the scanning signal, and the other end of which is electrically connected to the inverting input end of the operational amplifier.
3. The amplifier circuit according to claim 2, characterized in that: The resistance value of the compensation resistor is determined according to the output voltage of the operational amplifier.
4. The amplifier circuit according to claim 1, characterized in that: The compensation circuit includes a phase shift circuit, an analog-to-digital converter and a current digital-to-analog converter, wherein the phase shift circuit is used to receive the scanning signal and to adjust the phase of the scanning signal to a target phase; The analog-to-digital converter is electrically connected to the phase shift circuit, and is used to generate a digital signal according to the target phase; The current digital-to-analog converter is electrically connected to the phase shift circuit, and is used to generate the compensation current according to the digital signal.
5. The amplifier circuit according to claim 4, characterized in that: The target phase is determined according to an output voltage of the operational amplifier.
6. The amplifier circuit according to any one of claims 1 to 5, characterized in that: The touch electrode is electrically connected to one end of a parasitic capacitor and one end of an input resistor. The other end of the parasitic capacitor receives a scan signal. The other end of the input resistor is electrically connected to the inverting input end of the operational amplifier.
7. The amplifier circuit according to any one of claims 1 to 5, characterized in that: The feedback loop includes a feedback resistor and a feedback capacitor, and both ends of the feedback resistor and the feedback capacitor are electrically connected to the inverting input terminal and the output terminal of the operational amplifier respectively.
8. A touch device, characterized in that: The invention comprises a touch panel and the amplifying circuit according to any one of claims 1 to 7, wherein the touch panel is provided with the touch electrode.
9. The touch control device according to claim 8, wherein: It also includes a touch analog-to-digital converter, which is electrically connected to the output end of the operational amplifier and is used to convert the output voltage of the operational amplifier into a digital touch signal.
10. The touch control device according to claim 9, characterized in that: The system further comprises a processor, which is electrically connected to the touch analog-to-digital converter and is used to obtain the touch position of the touch electrode according to the digital touch signal.