Fingerprint recognition detection circuit and control method thereof, fingerprint recognition control chip

Patent metadata

Field	Value
Publication number	US-11568671-B2
Application number	US-202017261993-A
Country	US
Kind code	B2
Filing date	Apr 10, 2020
Priority date	Apr 10, 2020
Publication date	Jan 31, 2023
Grant date	Jan 31, 2023

Abstract

A fingerprint recognition detection circuit includes an operational amplifier, an integrating capacitor and a first switch connected in series, and a second switch. A non-inverting input terminal of the operational amplifier is coupled to a reference voltage terminal, and an inverting input terminal of the operational amplifier is coupled to a fingerprint sensing capacitor. The integrating capacitor and the first switch are coupled between the inverting input terminal of the operational amplifier and an output terminal of the operational amplifier. The second switch is coupled between the inverting input terminal of the operational amplifier and the output terminal of the operational amplifier.

First claim

What is claimed is:

1. A fingerprint recognition detection circuit, comprising:
an operational amplifier, a non-inverting input terminal of the operational amplifier being coupled to a reference voltage terminal, and an inverting input terminal of the operational amplifier being coupled to a fingerprint sensing capacitor; wherein a first terminal of the fingerprint sensing capacitor is coupled to a drive signal terminal, and a second terminal of the fingerprint sensing capacitor is coupled to the inverting input terminal of the operational amplifier;
an integrating capacitor and a first switch connected in series, the integrating capacitor and the first switch being coupled between the inverting input terminal of the operational amplifier and an output terminal of the operational amplifier;
a second switch, the second switch being coupled between the inverting input terminal of the operational amplifier and the output terminal of the operational amplifier, and the second switch being connected in parallel with the integrating capacitor and the first switch connected in series; and
a compensation capacitor, wherein a first terminal of the compensation capacitor is coupled to a compensation signal terminal, and a second terminal of the compensation capacitor is coupled to the inverting input terminal of the operational amplifier;
wherein the integrating capacitor is configured to discharge when the first switch is opened and the second switch is closed, and to store charges under an action of the fingerprint sensing capacitor when the second switch is opened and the first switch is closed;
the operational amplifier is configured to output a detection signal representing a capacitance value of the fingerprint sensing capacitor under an action of the integrating capacitor;
a compensation signal from the compensation signal terminal received by the first terminal of the compensation capacitor has an opposite phase to a drive signal from the drive signal terminal received by the first terminal of the fingerprint sensing capacitor; the compensation capacitor is configured to offset at least a part of an original capacitance value of the fingerprint sensing capacitor; and
the original capacitance value is a capacitance value of the fingerprint sensing capacitor when not affected by a fingerprint.

2. The fingerprint recognition detection circuit according to claim 1 , wherein the first switch includes a first transistor;
a control electrode of the first transistor is coupled to a first control signal terminal, a first electrode of the first transistor is coupled to the inverting input terminal of the operational amplifier, and a second electrode of the first transistor is coupled to the integrating capacitor.

3. The fingerprint recognition detection circuit according to claim 1 , wherein the first switch includes a first transistor;
a control electrode of the first transistor is coupled to a first control signal terminal, a first electrode of the first transistor is coupled to the integrating capacitor, and a second electrode of the first transistor is coupled to the output terminal of the operational amplifier.

4. The fingerprint recognition detection circuit according to claim 1 , wherein the second switch includes a second transistor;
a control electrode of the second transistor is coupled to a second control signal terminal, a first electrode of the second transistor is coupled to the inverting input terminal of the operational amplifier, and a second electrode of the second transistor is coupled to the output terminal of the operational amplifier.

5. The fingerprint recognition detection circuit according to claim 1 , wherein a capacitance value of the compensation capacitor is equal to the original capacitance value of the fingerprint sensing capacitor.

6. A fingerprint recognition control chip, comprising: at least one fingerprint recognition detection circuit according to claim 1 .

7. The fingerprint recognition control chip according to claim 6 , further comprising: a timing control circuit, wherein the timing control circuit has a plurality of drive signal terminals, and each drive signal terminal is coupled to at least one fingerprint sensing capacitor; and
the timing control circuit is configured to generate a drive signal, and transmit the drive signal to the at least one fingerprint sensing capacitor through the drive signal terminal.

8. The fingerprint recognition control chip according to claim 7 , wherein in a case where the fingerprint recognition detection circuit further comprises a compensation capacitor, the timing control circuit further has a compensation signal terminal; and
the timing control circuit is further configured to generate a compensation signal, and transmit the compensation signal to the compensation capacitor of the fingerprint recognition detection circuit through the compensation signal terminal.

9. The fingerprint recognition control chip according to claim 7 , wherein in a case where the fingerprint recognition circuit includes a first transistor and a second transistor, the timing control circuit further has a first control signal terminal and a second control signal terminal; and
the timing control circuit is further configured to generate a first control signal and a second control signal, and transmit the first control signal to the first transistor through the first control signal terminal and the second control signal to the second transistor through the second control signal terminal.

10. The fingerprint recognition control chip according to claim 6 , further comprising: a voltage generator, wherein the voltage generator has a reference voltage terminal; and
the voltage generator is configured to generate a reference voltage signal, and transmit the reference voltage signal to the non-inverting input terminal of the operational amplifier of the fingerprint recognition detection circuit through the reference voltage terminal.

11. The fingerprint recognition control chip according to claim 6 , further comprising: at least one filter, at least one comparator and at least one counter, wherein
one filter, one comparator, and one counter are sequentially connected in series, and the filter is coupled to the output terminal of the operational amplifier of the fingerprint recognition detection circuit;
the filter is configured to denoise a detection signal output by the fingerprint recognition detection circuit;
the comparator is configured to compare a voltage value of a signal output by the filter with a preset voltage value, and to output an enable signal if the voltage value of the signal output by the filter is larger than the preset voltage value; and
the counter is configured to stop counting and output a counting result under control of the inversion signal.

12. The fingerprint recognition control chip according to claim 11 , further comprising: a signal processing circuit, wherein the signal processing circuit is coupled to counters; and
the signal processing circuit is configured to process the counting result output by the counter, and to output a voltage signal representing fingerprint image data.

13. A fingerprint recognition apparatus, comprising: a sensing substrate and the fingerprint recognition control chip according to claim 6 , wherein
the sensing substrate has a plurality of sensing regions; each sensing region is provided therein with at least one fingerprint sensing capacitor, and each fingerprint sensing capacitor is coupled to the fingerprint recognition control chip; and
the fingerprint sensing capacitor is configured to sense a change in a capacitance value caused by a valley

Assignees

• Beijing Boe Sensor Technology Co Ltd
• Boe Technology Group Co Ltd

Inventors

• Liu Binbin
• Meng Chen
• Shi Wei
• Zhong Wenjie
• Hu Zhong
• Wang Yongbo
• Lu Zhenghua
• Hu Dahai
• Liu Guo
• Wang Guoan
• Liu Jiarong

Classifications

• G06V40/1306 Primary

  non-optical, e.g. ultrasonic or capacitive sensing · CPC title

• G06V40/1329

  Protecting the fingerprint sensor against damage caused by the finger · CPC title