Capacitance detection circuit, semiconductor device, input device and electronic apparatus including the same, and method of detecting capacitance

Patent metadata

Field	Value
Publication number	US-11092633-B2
Application number	US-201916275834-A
Country	US
Kind code	B2
Filing date	Feb 14, 2019
Priority date	Feb 16, 2018
Publication date	Aug 17, 2021
Grant date	Aug 17, 2021

Abstract

A capacitance detection circuit for measuring an electrostatic capacitance, includes: a control signal generator configured to generate a control signal; a drive circuit having a push-pull type output stage and configured to apply a drive voltage to the electrostatic capacitance according to the control signal; a current detection circuit configured to generate a detection current which is a replica of a current flowing through the output stage of the drive circuit; and an integrating circuit configured to integrate the detection current to generate a detection voltage.

First claim

What is claimed is:

1. A capacitance detection circuit for measuring an electrostatic capacitance, comprising:
a control signal generator configured to generate a control signal;
a drive circuit including:
a push-pull type output stage, which is configured to apply a drive voltage to the electrostatic capacitance according to the control signal, and including a low-side transistor and a high-side transistor; and
a differential input stage whose output terminals are connected to a control terminal of the low-side transistor and a control terminal of the high-side transistor, respectively, to apply output voltages to the control terminal of the high-side transistor and the control terminal of the low-side transistor, respectively, so that a feedback signal corresponding to an output voltage of the drive circuit matches the control signal;

a current detection circuit configured to generate a detection current which is a replica of a current flowing through the output stage of the drive circuit, and including:
a first transistor having a control terminal connected in common with the control terminal of the high-side transistor; and
a second transistor having a control terminal connected in common with the control terminal of the low-side transistor; and

an integrating circuit configured to integrate the detection current to generate a detection voltage,
wherein the detection current depends on a difference between a current flowing through the first transistor and a current flowing through the second transistor.

2. The capacitance detection circuit of claim 1 , wherein the control signal is a pulse signal, and
wherein the drive circuit includes an amplifier configured to receive the pulse signal.

3. The capacitance detection circuit of claim 1 , wherein the electrostatic capacitance is obtained by calculating a difference between the detection voltage obtained during charging and the detection voltage obtained during discharging.

4. The capacitance detection circuit of claim 1 , wherein the integrating circuit integrates the detection current obtained during charging and the detection current obtained during discharging.

5. The capacitance detection circuit of claim 1 , further comprising: an offset capacitor having one end connected to an input of the integrating circuit, and the other end to which a correction signal corresponding to the control signal is applied.

6. The capacitance detection circuit of claim 1 , wherein the capacitance detection circuit is integrated on a single semiconductor integrated circuit.

7. The capacitance detection circuit of claim 1 , wherein the differential input stage includes:
a non-inverting input terminal to which the control signal, which is a pulse signal, generated by the control signal generator is input; and
an inverting input terminal to which the drive voltage is input.

8. A semiconductor device for measuring a plurality of electrostatic capacitances, comprising:
a plurality of sense terminals to which the plurality of electrostatic capacitances are connected; and
a plurality of capacitance detection circuits corresponding to the plurality of sense terminals,
wherein each of the plurality of capacitance detection circuits includes:
a control signal generator configured to generate a control signal;
a drive circuit including:
a push-pull type output stage, which is configured to apply a drive voltage to the electrostatic capacitances according to the control signal, and including a low-side transistor and a high-side transistor; and
a differential input stage whose output terminals are connected to a control terminal of the low-side transistor and a control terminal of the high-side transistor, respectively, to apply output voltages to the control terminal of the high-side transistor and the control terminal of the low-side transistor, respectively, so that a feedback signal corresponding to an output voltage of the drive circuit matches the control signal;

a current detection circuit configured to generate a detection current which is a replica of a current flowing through the output stage of the drive circuit, and including:
a first transistor having a control terminal connected in common with the control terminal of the high-side transistor; and
a second transistor having a control terminal connected in common with the control terminal of the low-side transistor; and

an integrating circuit configured to integrate the detection current to generate a detection voltage,
wherein the detection current depends on a difference between a current flowing through the first transistor and a current flowing through the second transistor.

9. The semiconductor device of claim 8 , further comprising: a current averaging circuit configured to generate an average current of a plurality of detection currents obtained by the plurality of capacitance detection circuits,
wherein the integrating circuit of each of the capacitance detection circuits integrates a difference between the corresponding detection current and the average current.

10. An input device comprising:
a touch panel including a plurality of sensor electrodes such that the electrostatic capacitances of a portion of the plurality of sensor electrodes in a vicinity of a coordinate touched by a user changes; and
the semiconductor device of claim 8 that is configured to measure the electrostatic capacitances of the plurality of sensor electrodes.

11. An electronic apparatus comprising: the input device of claim 10 .

12. The semiconductor device of claim 8 , wherein the differential input stage includes:
a non-inverting input terminal to which the control signal, which is a pulse signal, generated by the control signal generator is input; and
an inverting input terminal to which the drive voltage is input.

13. A method of detecting an electrostatic capacitance, comprising:
generating a control signal;
charging and discharging the electrostatic capacitance according to the control signal by using a drive circuit including:
a push-pull type output stage, which is configured to apply a drive voltage to the electrostatic capacitance according to the control signal, and including a low-side transistor and a high-side transistor; and
a differential input stage whose output terminals are connected to a control terminal of the low-side transistor and a control terminal of the high-side transistor, respectively, to apply output voltages to the control terminal of the high-side transistor and the control terminal of the low-side transistor, respectively, so that a feedback signal corresponding to an output voltage of the drive circuit matches the control signal;

generating a detection current which is a replica of a current of the output stage by using a current detection circuit including:
a first transistor having a control terminal connected in common with the control terminal of the high-side transistor; and
a second transistor having a control terminal connected in common with the control terminal of the low-side transistor; and

generating a detection voltage by integrating the detection current,
wherein the detection current depends on a difference between a current flowing through the first transistor and a current flowing through the second transistor.

14. The method of claim 13 , wherein the control signal is a pulse signal, and
wherein the drive circuit includes an amplifier configured to receive the pulse signal.

15. The method of claim 13 , further comprising: calculating a difference between the detection voltage obtained during charging and the detection voltage obtained

Assignees

• Rohm Co Ltd

Inventors

• Shimada Yuji

Classifications

• G06F3/04166 Primary

  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 title

• H03F2203/45528

  the FBC comprising one or more passive resistors and being coupled between the LC and the IC · CPC title

• G06F3/04182

  Filtering of noise external to the device and not generated by digitiser components · CPC title

• H03F3/70

  Charge amplifiers · CPC title

• G01R27/2605 Primary

  Measuring capacitance (capacitive sensors G01D5/24) · CPC title