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CN-117234349-B - Capacitance sensing device and capacitance sensing method

CN117234349BCN 117234349 BCN117234349 BCN 117234349BCN-117234349-B

Abstract

Embodiments of the present disclosure relate to a capacitive sensing apparatus and a capacitive sensing method. The capacitive sensing device includes switching circuitry, a counter circuit, a comparator circuit, an amplifier circuit including first and second inputs and an output, and a feedback capacitor. The feedback capacitor is coupled between the first input terminal and the output terminal of the amplifier circuit, and the first input terminal is coupled to the capacitor to be tested. The switching circuitry transmits the first voltage to the second input terminal and couples the first input terminal to the output terminal in the first stage, and transmits the second voltage to the second input terminal in the second stage, and adjusts the output voltage of the output terminal in the third stage. The counter circuit starts counting in a third stage and stops counting according to the control signal to generate a count value capable of reflecting the capacitance change of the capacitor to be measured. The comparator circuit generates a control signal according to the output voltage and the second reference voltage in a third stage.

Inventors

  • CAI XUMING

Assignees

  • 瑞昱半导体股份有限公司

Dates

Publication Date
20260505
Application Date
20220608

Claims (10)

  1. 1. A capacitive sensing device, comprising: An amplifier circuit, wherein a first input of the amplifier circuit is coupled to a capacitor under test; A feedback capacitor coupled between the first input and an output of the amplifier circuit; Switching circuitry to transmit a first reference voltage to a second input of the amplifier circuit in a first stage and to couple the first input to the output, and to transmit a second reference voltage to the second input in a second stage and to adjust an output voltage of the output in a third stage; a counter circuit for starting counting in the third stage and stopping counting according to a control signal to generate a count value reflecting the capacitance change of the capacitor to be tested, and And the comparator circuit is used for generating the control signal according to the output voltage and the second reference voltage in the third stage.
  2. 2. The capacitive sensing device of claim 1, wherein the first reference voltage is lower than the second reference voltage, and the switching circuitry is to transmit current to the first input to adjust the output voltage in the third phase.
  3. 3. The capacitive sensing device of claim 1, wherein the second reference voltage is lower than the first reference voltage, and the switching circuitry is to draw current from the first input to ground to adjust the output voltage in the third phase.
  4. 4. The capacitive sensing device of claim 1, wherein the switching circuitry comprises: a first switch for conducting in the first phase to transmit the first reference voltage to the second input terminal; a second switch for conducting in the first phase to couple the first input terminal to the output terminal; a third switch for conducting in the second stage to transmit the second reference voltage to the second input terminal; Current source circuit, and A fourth switch for conducting in the third stage to couple the current source circuit to the first input terminal to adjust the output voltage.
  5. 5. The capacitive sensing device of claim 4, wherein the first reference voltage is lower than the second reference voltage, and the current source circuit is configured to transmit current to the first input via the fourth switch.
  6. 6. The capacitive sensing device of claim 4, wherein the second reference voltage is lower than the first reference voltage and the current source circuit is to draw current from the first input to ground via the fourth switch.
  7. 7. The capacitance sensing device of claim 1, wherein a capacitance change of the capacitor under test is proportional to the count value.
  8. 8. The capacitance sensing device according to claim 1, wherein the count value indicates a length of time between when the counter circuit starts counting to a stage when the output voltage is less than or equal to the second reference voltage, or indicates a length of time between when the counter circuit starts counting to a stage when the output voltage is greater than or equal to the second reference voltage.
  9. 9. The capacitive sensing device of claim 1, wherein the count value is proportional to a voltage difference between the first reference voltage and the second reference voltage.
  10. 10. A capacitive sensing method, comprising: In a first stage, transmitting a first reference voltage to a first input of an amplifier circuit and coupling a second input of the amplifier circuit to an output of the amplifier circuit, wherein the second input is coupled to the output via a feedback capacitor and to ground via a capacitor under test; Transmitting a second reference voltage to the first input terminal in a second stage; in the third stage, regulating output voltage of the output terminal and generating control signal according to the output voltage and the second reference voltage, and And starting counting when entering the third stage, and stopping counting according to the control signal to generate a count value, wherein the count value is used for reflecting the capacitance change of the capacitor to be tested.

Description

Capacitance sensing device and capacitance sensing method Technical Field The present disclosure relates to a capacitive sensing device, and more particularly, to a capacitive sensing device and a capacitive sensing method capable of sensing a change in capacitance of a touch device. Background Touch devices are commonly found in electronic products for various applications. Touch input is received by using a touch element connected to a specific potential (e.g., ground) in a self-capacitive touch device. In some related art, the capacitive sensing circuit has a high circuit complexity, and the capacitive sensing circuit directly amplifies the charge variation on the touch device by using an amplifier, and directly outputs a signal generated by the amplifier as a sensing signal. However, in the above technique, the amplifier may amplify noise in the system together so that the output becomes supersaturated. Thus, the operation of the sensing circuit will fail, and it cannot be effectively identified whether the touch input is received. Disclosure of Invention In some embodiments, it is an object of the present invention (but not limited to) to provide a capacitive sensing device and a capacitive sensing method for confirming a change of capacitance by using a counter, so as to overcome the above-mentioned drawbacks of the prior art. In some embodiments, a capacitive sensing device includes an amplifier circuit, a feedback capacitor, switching circuitry, a counter circuit, and a comparator circuit. The first input of the amplifier circuit is coupled to the capacitor under test. The feedback capacitor is coupled between the first input terminal and the output terminal of the amplifier circuit. The switching circuitry is configured to transmit a first reference voltage to a second input of the amplifier circuit and couple the first input to the output in a first stage, to transmit a second reference voltage to the second input in a second stage, and to adjust an output voltage of the output in a third stage. The counter circuit is used for starting counting in a third stage and stopping counting according to the control signal to generate a count value, wherein the count value is used for reflecting the capacitance change of the capacitor to be tested. The comparator circuit is used for generating a control signal according to the output voltage and the second reference voltage in a third stage. In some embodiments, a capacitive sensing method includes transmitting a first reference voltage to a first input of an amplifier circuit and coupling a second input of the amplifier circuit to an output of the amplifier circuit, wherein the second input is coupled to the output via a feedback capacitor and to ground via a capacitor under test, transmitting a second reference voltage to the first input in a second phase, adjusting an output voltage of the output and generating a control signal based on the output voltage and the second reference voltage in a third phase, and starting counting when the third phase is entered and stopping counting based on the control signal to generate a count value, wherein the count value is used to reflect a change in a capacitance of the capacitor under test. The features, implementation and effects of the present invention are described in detail below with reference to the preferred embodiments of the present invention in conjunction with the accompanying drawings. Drawings FIG. 1 is a schematic diagram of a capacitive sensing device according to some embodiments of the present disclosure; FIG. 2A is a schematic circuit diagram of the capacitive sensing device of FIG. 1, drawn according to some embodiments of the present disclosure; FIG. 2B is a schematic diagram of waveforms of the signals and voltages of FIG. 2A according to some embodiments of the present disclosure; FIG. 3A is a schematic circuit diagram of the capacitive sensing device of FIG. 1, drawn according to some embodiments of the present disclosure; FIG. 3B is a schematic diagram of waveforms of the signals and voltages of FIG. 2A according to some embodiments of the present disclosure, and Fig. 4 is a flow chart of a capacitive sensing method according to some embodiments of the present disclosure. Detailed Description All terms used herein have their ordinary meaning. The foregoing words are defined in commonly used dictionaries, and any examples of use of words in this document, including any discussion herein, are intended to be illustrative only and should not be interpreted as limiting the scope and meaning of the present disclosure. Similarly, the present disclosure is not limited to the various embodiments shown in this specification. As used herein, "coupled" or "connected" may mean that two or more elements are in direct physical or electrical contact with each other, or in indirect physical or electrical contact with each other, and may also mean that two or more elements are in operation or action with ea