CAPACITANCE DETECTION CIRCUIT, CAPACITANCE DETECTION METHOD, TOUCH DETECTION APPARATUS, AND TERMINAL DEVICE

• US 20190079609A1
• Filed: 10/21/2018
• Published: 03/14/2019
• Est. Priority Date: 09/11/2017
• Status: Active Grant

• Current Assignee: Shenzhen Goodix Technology Co., Ltd.
• Original Assignee: Shenzhen Goodix Technology Co., Ltd.
• Inventors: JIANG, Hong
• Granted Patent: US 10,642,431 B2
• Time in Patent Office: Days
• CPC Class Codes: G01R 27/2605 Measuring capacitance capacitive sensors G01D5/24
• CPC Class Codes: G06F 3/04166 Details of scanning methods, e.g. sampling time, grouping of sub areas or time sharing with display driving Synchronisation with the driving of the display or the backlighting unit to avoid interferences generated internally G06F3/04184
• CPC Class Codes: G06F 3/0446 using a grid-like structure of electrodes in at least two directions, e.g. using row and column electrodes

Abstract

Provided are a capacitance detection circuit. The capacitance detection circuit (200) is used for detecting capacitances of N capacitors to be detected, the N is greater than or equal to 2, and the capacitance detection circuit (200) includes: at least N−1 first front end circuits (210) for converting capacitance signals of the capacitors to be detected into first voltage signals and performing differencing on the first voltage signals, at least one second front end circuit (220) for converting capacitance signals of capacitors to be detected into second voltage signals and performing summing on the second voltage signals, and a processing circuit (230); and the processing circuit (230) determines a capacitance value of each of the N capacitors to be detected according to a differential signal output by each of the first front end circuits (210) and a summation signal output by each of the second front end circuits (220).

Claims

1. A capacitance detection circuit for detecting capacitances of N capacitors to be detected, the N being greater than or equal to 2, wherein the capacitance detection circuit comprises:

at least N−

1 first front end circuits for converting capacitance signals of the capacitors to be detected into first voltage signals and performing differencing on the first voltage signals, at least one second front end circuit for converting capacitance signals of capacitors to be detected into second voltage signals and performing summing on the second voltage signals, and a processing circuit, wherein;

each of the at least N−

1 first front end circuits comprises a first input end and a second input end, and each of the at least one second front end circuit comprises a third input end and a fourth input end;

a first input end and a second input end of each of at least N−

2 first front end circuits are respectively connected to two different capacitors to be detected;

a first input end of a first front end circuit except the at least N−

2 first front end circuits is simultaneously connected to a capacitor to be detected and a third input end or a fourth input end of a second front end circuit, a second input end of the first front end circuit except the at least N−

2 first front end circuits is simultaneously connected to a capacitor to be detected and a first input end of a first front end circuit of the at least N−

2 first front end circuits, and the capacitors to be detected to which the two input ends of the first front end circuit except the at least N−

2 first front end circuits are connected are different capacitors to be detected;

a third input end and a fourth input end of each of the at least one second front end circuit are connected to two different capacitors to be detected, respectively;

each of the at least N−

1 first front end circuits outputs a differential signal of voltages corresponding to two connected capacitors to be detected;

each of the at least one second front end circuit outputs a summation signal of voltages corresponding to two connected capacitors to be detected; and

the processing circuit is connected to output ends of each of the first front end circuits and each of the second front end circuits, and is configured to determine, according to the differential signal output by each of the first front end circuits and the summation signal output by each of the second front end circuits, a capacitance value of each of the N capacitors to be detected.

2. The circuit according to claim 1, wherein the first front end circuit comprises a first control circuit and a first programmable gain amplifier PGA circuit, wherein

the first control circuit is connected to a DC voltage source, two capacitors to be detected to which the first front end circuit is connected, and the first PGA circuit;

the first control circuit is configured to control the DC voltage source to charge the two capacitors to be detected to which the first front end circuit is connected, and control discharge of the two capacitors to be detected to which the first front end circuit is connected; and

the first PGA circuit is configured to convert, when the two capacitors to be detected to which the first front end circuit is connected discharge, capacitance signals of the capacitors to be detected into first voltage signals, and perform differencing on the first voltage signals of the two connected capacitors to be detected, to obtain a differential signal of voltages corresponding to the two capacitors to be detected to which the first front end circuit is connected;

or the first front end circuit comprises a first conversion circuit and a second PGA circuit, wherein

the first conversion circuit is connected to a driving voltage source, two capacitors to be detected to which the first front end circuit is connected, and the second PGA circuit;

the first conversion circuit is configured to convert capacitance signals of the two capacitors to be detected to which the first front end circuit is connected into first voltage signals; and

the second PGA circuit is configured to acquire, from the first conversion circuit, the first voltage signals corresponding to the two capacitors to be detected to which the first front end circuit is connected, and perform differencing on the first voltage signals of the two connected capacitors to be detected, to obtain a differential signal of voltages corresponding to the two capacitors to be detected to which the first front end circuit is connected.

3. The circuit according to claim 2, wherein the first control circuit comprises a first switch group and a second switch group, the first switch group is connected to the DC voltage source and the two capacitors to be detected to which the first front end circuit is connected, and the second switch group is connected to the two capacitors to be detected to which the first front end circuit is connected and the first PGA circuit, wherein

when the first switch group is in a closed state and the second switch group is in an open state, the DC voltage source charges the two capacitors to be detected to which the first front end circuit is connected;

and

when the second switch group is in a closed state and the first switch group is in an open state, the two capacitors to be detected to which the first front end circuit is connected discharge to the first PGA circuit.

4. The circuit according to claim 2, wherein the first conversion circuit comprises a first voltage division resistor and a second voltage division resistor, wherein

the first voltage division resistor is connected to the driving voltage source, the second PGA circuit, and one of the two capacitors to be detected to which the first front end circuit is connected;

and

the second voltage division resistor is connected to the driving voltage source, the second PGA circuit, and the other of the two capacitors to be detected to which the first front end circuit is connected.

5. The circuit according to claim 1, wherein the second front end circuit comprises a second control circuit and a third PGA circuit, wherein

the second control circuit is connected to a DC voltage source, two capacitors to be detected to which the second front end circuit is connected, and the third PGA circuit;

the second control circuit is configured to control the DC voltage source to charge the two capacitors to be detected to which the second front end circuit is connected, and control discharge of the two capacitors to be detected to which the second front end circuit is connected; and

the third PGA circuit is configured to convert, when the two capacitors to be detected to which the second front end circuit is connected discharge, capacitance signals of the capacitors to be detected into second voltage signals, and perform summing on the second voltage signals of the two connected capacitors to be detected, to obtain a summation signal of voltages corresponding to the two capacitors to be detected to which the second front end circuit is connected;

or the second front end circuit comprises a second conversion circuit and a fourth PGA circuit, wherein

the second conversion circuit is connected to a driving voltage source, two capacitors to be detected to which the second front end circuit is connected, and the fourth PGA circuit;

the second conversion circuit is configured to convert capacitance signals of the two capacitors to be detected to which the second front end circuit is connected into second voltage signals; and

the fourth PGA circuit is configured to acquire, from the second conversion circuit, the second voltage signals corresponding to the two capacitors to be detected to which the second front end circuit is connected, and perform summing on the second voltage signals of the two connected capacitors to be detected, to obtain a summation signal of voltages corresponding to the two capacitors to be detected to which the second front end circuit is connected.

6. The circuit according to claim 5, wherein the second control circuit comprises a third switch group and a fourth switch group, the third switch group is connected to the DC voltage source and the two capacitors to be detected to which the second front end circuit is connected, and the fourth switch group is connected to the two capacitors to be detected to which the second front end circuit is connected and the third PGA circuit, wherein

when the third switch group is in a closed state and the fourth switch group is in an open state, the DC voltage source charges the two capacitors to be detected to which the second front end circuit is connected;

and

when the fourth switch group is in a closed state and the third switch group is in an open state, the two capacitors to be detected to which the second front end circuit is connected discharge to the third PGA circuit.

7. The circuit according to claim 5, wherein the second conversion circuit comprises a third voltage division resistor and a fourth voltage division resistor, wherein

the third voltage division resistor is connected to the driving voltage source, the fourth PGA circuit, and one of the two capacitors to be detected to which the second front end circuit is connected;

and

the fourth voltage division resistor is connected to the driving voltage source, the fourth PGA circuit, and the other of the two capacitors to be detected to which the second front end circuit is connected.

8. The circuit according to claim 1, wherein the first front end circuit comprises a first filter circuit and/or a first integration circuit, wherein

the first filter circuit is configured to filter an interference signal in a differential signal of voltages corresponding to two connected capacitors to be detected output by the first front end circuit;

and

the first integration circuit is configured to perform integration and amplification processing on the differential signal of the voltages corresponding to the two connected capacitors to be detected output by the first front end circuit.

9. The circuit according to claim 1, wherein the second front end circuit comprises a second filter circuit and/or a second integration circuit, wherein

the second filter circuit is configured to filter an interference signal in a summation signal of voltages corresponding to two connected capacitors to be detected output by the second front end circuit;

and

the second integration circuit is configured to perform integration and amplification processing on the summation signal of the voltages corresponding to the two connected capacitors to be detected output by the second front end circuit.

10. A capacitance detection method, applied to a capacitance detection circuit, the method comprising:

converting, by each of at least N−

1 first front end circuits, capacitance signals of two connected capacitors to be detected into first voltage signals, and performing differencing on the first voltage signals of the two connected capacitors to be detected, to obtain a differential signal of voltages corresponding to the two connected capacitors to be detected;

converting, by each of at least one second front end circuit, capacitance signals of two connected capacitors to be detected into second voltage signals, and performing summing on the second voltage signals of the two connected capacitors to be detected, to obtain a summation signal of voltages corresponding to the two connected capacitors to be detected; and

determining, by a processing circuit according to the differential signal obtained by each of the first front end circuits and the summation signal obtained by each of the second front end circuits, a capacitance value of each of N capacitors to be detected.

11. The method according to claim 10, wherein the first front end circuit comprises a first control circuit and a first programmable gain amplifier PGA circuit, and the first control circuit is connected to a DC voltage source, two capacitors to be detected to which the first front end circuit is connected, and the first PGA circuit;

the converting, by each of the at least N−

1 first front end circuits, the capacitance signals of the two connected capacitors to be detected into the first voltage signals, and performing the differencing on the first voltage signals of the two connected capacitors to be detected, to obtain the differential signal of the voltages corresponding to the two connected capacitors to be detected, comprises;

controlling, by the first control circuit, the DC voltage source to charge the two capacitors to be detected to which the first front end circuit is connected, and after charging the two capacitors to be detected to which the first front end circuit is connected, controlling discharge of the two capacitors to be detected to which the first front end circuit is connected; and

converting, by the first PGA circuit, when the two capacitors to be detected to which the first front end circuit is connected discharge, capacitance signals of the capacitors to be detected into first voltage signals, and performing differencing on the first voltage signals of the two connected capacitors to be detected, to obtain a differential signal of voltages corresponding to the two capacitors to be detected to which the first front end circuit is connected.

12. The method according to claim 11, wherein the first control circuit comprises a first switch group and a second switch group;

the controlling, by the first control circuit, the DC voltage source to charge the two capacitors to be detected to which the first front end circuit is connected, and after charging the two capacitors to be detected to which the first front end circuit is connected, controlling the discharge of the two capacitors to be detected to which the first front end circuit is connected, comprises;

when the first switch group is in a closed state and the second switch group is in an open state, the DC voltage source charges the two capacitors to be detected to which the first front end circuit is connected; and

when the second switch group is in a closed state and the first switch group is in an open state, the two capacitors to be detected to which the first front end circuit is connected discharge to the first PGA circuit.

13. The method according to claim 10, wherein the first front end circuit comprises a first conversion circuit and a second PGA circuit, and the first conversion circuit is connected to a driving voltage source, two capacitors to be detected to which the first front end circuit is connected, and the second PGA circuit;

the converting, by each of the at least N−

1 first front end circuits, the capacitance signals of the two connected capacitors to be detected into the first voltage signals, and performing the differencing on the first voltage signals of the two connected capacitors to be detected, to obtain the differential signal of the voltages corresponding to the two connected capacitors to be detected, comprises;

converting, by the first conversion circuit, capacitance signals of two capacitors to be detected to which the first front end circuit is connected into first voltage signals; and

acquiring, by the second PGA circuit from the first conversion circuit, the first voltage signals corresponding to the two capacitors to be detected to which the first front end circuit is connected, and performing differencing on the first voltage signals of the two connected capacitors to be detected, to obtain a differential signal of voltages corresponding to the two capacitors to be detected to which the first front end circuit is connected.

14. The method according to claim 10, wherein the second front end circuit comprises a second control circuit and a third PGA circuit, and the second control circuit is connected to a DC voltage source, the third PGA circuit, two capacitors to be detected to which the second front end circuit is connected;

the converting, by each of the at least one second front end circuit, the capacitance signals of the two connected capacitors to be detected into the second voltage signals, and performing the summing on the second voltage signals of the two connected capacitors to be detected, to obtain the summation signal of the voltages corresponding to the two connected capacitors to be detected, comprises;

controlling, by the second control circuit, the DC voltage source to charge the two capacitors to be detected to which the second front end circuit is connected, and after charging the two capacitors to be detected to which the second front end circuit is connected, controlling discharge of the two capacitors to be detected to which the second front end circuit is connected; and

converting, by the third PGA circuit, when the two capacitors to be detected to which the second front end circuit is connected discharge, capacitance signals of the capacitors to be detected into second voltage signals, and performing summing on second voltage signals of the two connected capacitors to be detected, to obtain a summation signal of voltages corresponding to the two capacitors to be detected to which the second front end circuit is connected.

15. The method according to claim 14, wherein the second control circuit comprises a third switch group and a fourth switch group;

the controlling, by the second control circuit, the DC voltage source to charge the two capacitors to be detected to which the second front end circuit is connected, and after charging the two capacitors to be detected to which the second front end circuit is connected, controlling the discharge of the two capacitors to be detected to which the second front end circuit is connected, comprises;

when the third switch group is in a closed state and the fourth switch group is in an open state, the DC voltage source charges the two capacitors to be detected to which the second front end circuit is connected; and

when the fourth switch group is in a closed state and the third switch group is in an open state, the two capacitors to be detected to which the second front end circuit is connected discharge to the third PGA circuit.

16. The method according to claim 10, wherein the second front end circuit comprises a second conversion circuit and a fourth PGA circuit, and the second conversion circuit is connected to a driving voltage source, two capacitors to be detected to which the second front end circuit is connected, and the fourth PGA circuit;

the converting, by each of the at least one second front end circuit, the capacitance signals of the two connected capacitors to be detected into the second voltage signals, and performing the summing on the second voltage signals of the two connected capacitors to be detected, to obtain the summation signal of the voltages corresponding to the two connected capacitors to be detected, comprises;

converting, by the second conversion circuit, capacitance signals of the two capacitors to be detected to which the second front end circuit is connected into second voltage signals; and

acquiring, by the fourth PGA circuit from the second conversion circuit, the second voltage signals corresponding to the two capacitors to be detected to which the second front end circuit is connected, and performing summing on second voltage signals of the two connected capacitors to be detected, to obtain a summation signal of voltages corresponding to the two capacitors to be detected to which the second front end circuit is connected.

17. A touch detection apparatus comprising a capacitance detection circuit for detecting capacitances of N capacitors to be detected, the N being greater than or equal to 2, wherein:

the capacitance detection circuit comprises;

at least N−

1 first front end circuits for converting capacitance signals of the capacitors to be detected into first voltage signals and performing differencing on the first voltage signals, at least one second front end circuit for converting capacitance signals of capacitors to be detected into second voltage signals and performing summing on the second voltage signals, and a processing circuit,

each of the at least N−

1 first front end circuits comprises a first input end and a second input end, and each of the at least one second front end circuit comprises a third input end and a fourth input end;

a first input end and a second input end of each of at least N−

2 first front end circuits are respectively connected to two different capacitors to be detected;

a first input end of a first front end circuit except the at least N−

2 first front end circuits is simultaneously connected to a capacitor to be detected and a third input end or a fourth input end of a second front end circuit, a second input end of the first front end circuit except the at least N−

2 first front end circuits is simultaneously connected to a capacitor to be detected and a first input end of a first front end circuit of the at least N−

2 first front end circuits, and the capacitors to be detected to which the two input ends of the first front end circuit except the at least N−

2 first front end circuits are connected are different capacitors to be detected;

a third input end and a fourth input end of each of the at least one second front end circuit are connected to two different capacitors to be detected, respectively;

each of the at least N−

1 first front end circuits outputs a differential signal of voltages corresponding to two connected capacitors to be detected;

each of the at least one second front end circuit outputs a summation signal of voltages corresponding to two connected capacitors to be detected;

the processing circuit is connected to output ends of each of the first front end circuits and each of the second front end circuits, and is configured to determine, according to the differential signal output by each of the first front end circuits and the summation signal output by each of the second front end circuits, a capacitance value of each of the N capacitors to be detected; and

the touch detection apparatus determines a touch position of a user according to a capacitance value of each of N capacitors to be detected determined by the capacitance detection circuit.