Sense circuit for piezoresistive sensor, circuit including array of piezoresistive sensors, and operation method thereof

• US 10,890,607 B2
• Filed: 11/30/2018
• Issued: 01/12/2021
• Est. Priority Date: 04/04/2018
• Status: Active Grant

• Current Assignee: BOE Technology Group Co., Ltd.
• Original Assignee: BOE Technology Group Co., Ltd.
• Inventors: Cheng, Chihjen, Ding, Xiaoliang, Wang, Pengpeng, Cao, Xueyou, Guo, Yuzhen
• Primary Examiner(s): Le, Thang X
• Application Number:
  US16/206,144
• Publication Number:
  US 20190310296A1
• Time in Patent Office: 774 Days
• CPC Class Codes: G01L 1/225 Measuring circuits therefor
• CPC Class Codes: G01R 19/0053 Noise discrimination; Analog sampling; Measuring transients measuring characteristics of individual pulses G01R29/02; digital sampling G01R19/2509; measuring noise figure G01R29/26
• CPC Class Codes: G01R 19/0084 measuring voltage only all subgroups of G01R19/00 take precedence
• CPC Class Codes: G01R 27/2605 Measuring capacitance capacitive sensors G01D5/24
• CPC Class Codes: G01R 29/22 Measuring piezoelectric properties
• CPC Class Codes: H03K 17/9622 using a plurality of detectors, e.g. keyboard
• CPC Class Codes: H03K 17/9643 using a plurality of detectors, e.g. keyboard

Abstract

A sense circuit for a piezoresistive sensor is provided that comprises: an energy storage circuit coupled to the piezoresistive sensor via a first node; a charge control circuit coupled to the first node and configured to charge the energy storage circuit to a predetermined potential; a discharge control circuit configured to allow the energy storage circuit to discharge through the piezoresistive sensor; and a readout circuit coupled to the first node and configured to output a sensed voltage based on a level of charges stored by the energy storage circuit.

Claims

1. A sense circuit for a piezoresistive sensor, comprising:

an energy storage circuit coupled to the piezoresistive sensor via a first node;

a charge control circuit coupled to the first node and configured to charge the energy storage circuit to a predetermined potential;

a discharge control circuit configured to allow the energy storage circuit to discharge through the piezoresistive sensor; and

a readout circuit coupled to the first node and configured to output a sensed voltage based on a level of charges stored by the energy storage circuit,

wherein the piezoresistive sensor has a first end configured to receive a first voltage,

the energy storage circuit has a first end configured to receive a second voltage, and a second end coupled to the first node,

the charge control circuit is configured to charge the energy storage circuit such that the first node is charged to the predetermined potential;

the discharge control circuit is coupled to the first node and a second end of the piezoresistive sensor, respectively, configured to control a discharge path for the energy storage circuit, which includes the piezoresistive sensor, to be turned on or off, so that the energy storage circuit can be discharged through the piezoresistive sensor in the case that the discharge path is turned on; and

the readout circuit is coupled to the first node and configured to output the sensed voltage according to the level of the charges stored by the energy storage circuit in response to a sense control signal,

wherein the readout circuit comprises;

a first switch transistor having a first end coupled to the first node, and a control end to receive the sense control signal;

a first capacitive device having a first end coupled to a second end of the first switch transistor; and

an operational amplifier having a first input coupled to the second end of the first switch transistor, a second input to receive a reference voltage, and an output coupled to a second end of the first capacitive device.

2. The sense circuit of claim 1, wherein the charge control circuit comprises:

a second switch transistor having a first end coupled to the first node, a control end to receive a charge control signal, and a second end to receive a third voltage.

3. The sense circuit of claim 1, wherein the charge control circuit comprises:

the first switch transistor;

a fourth switch transistor having a first end coupled to the second end of the first switch transistor, and a second end coupled to the output of the operational amplifier, and a control end to receive a charge control signal.

4. The sense circuit of claim 1, wherein the energy storage circuit comprises a second capacitive device.

5. The sense circuit of claim 1, wherein the discharge control circuit comprises a third switch device having a first end coupled to a second end of the piezoresistive sensor, a second end coupled to the first node, and a control end to receive a discharge control signal.

6. The sense circuit of claim 1, wherein the discharge control circuit comprises a third switch device configured to turn on or turn off, under control of a discharge control signal, a discharge path for the energy storage circuit, the discharge path including the piezoresistive sensor.

7. The sense circuit of claim 1, wherein the discharge control circuit is further configured to control the discharge path for the energy storage circuit, which includes the piezoresistive sensor, to be turned on such that the energy storage circuit is discharged through the piezoresistive sensor for a predetermined time period.

8. A circuit comprising:

a plurality of piezoresistive sensors arranged in an array;

a plurality of the sense circuits according to claim 1, wherein each of the sense circuits corresponds to one piezoresistive sensor of the plurality of piezoresistive sensors.

9. An operation method for a sense circuit for a piezoresistive sensor according to claim 1, comprising steps of:

S1) charging, by the charge control circuit, the first node to the predetermined potential in response to a charge control signal;

S2) discharging, by the discharge control circuit, the energy storage circuit through the piezoresistive sensor, in response to a discharge control signal;

S3) outputting, by the readout circuit, the sensed voltage based on a potential of the first node in response to a sense control signal,

wherein the piezoresistive sensor has a first end configured to receive a first voltage,

wherein the readout circuit comprises;

a first switch transistor having a first end coupled to the first node, and a control end to receive the sense control signal;

a first capacitive device having a first end coupled to a second end of the first switch transistor; and

an operational amplifier having a first input coupled to the second end of the first switch transistor, a second input to receive a reference voltage, and an output coupled to a second end of the first capacitive device;

wherein the charge control circuit comprises;

a second switch transistor having a first end coupled to the first node, a control end to receive the charge control signal, and a second end to receive a third voltage;

wherein the discharge control circuit comprises;

a third switch transistor having a first end coupled to a second end of the piezoresistive sensor, and a second end coupled to the first node, and a control end to receive the discharge control signal,

wherein the step S1 comprises;

setting the charge control signal at the control end of the second switch transistor to turn on the second switch transistor, and

setting control signals at the control ends of the first switch transistor and the third switch transistor to turn off the first switch transistor and the third switch transistor,

thereby charging, by the charge control circuit, the first node to the predetermined potential;

wherein the step S2 comprises;

setting the charge control signal at the control end of the second switch transistor to turn off the second switch transistor,

setting the control signal at the control end of the first switch transistor to turn off the first switch transistor, and

setting the control signal at the control end of the third switch transistor to turn on the third switch transistor,

thereby discharging, by the discharge control circuit, the energy storage circuit via the piezoresistive sensor;

wherein the step S3 comprises;

setting the charge control signal at the control end of the second switch transistor to turn off the second switch transistor,

setting the control signal at the control end of the first switch transistor to turn on the first switch transistor, and

setting the control signal at the control end of the third switch transistor to turn off the third switch transistor,

whereby outputting, by the readout circuit, the sensed voltage based on a potential at the first node.

10. The method of claim 9,

wherein the charge control circuit comprises:

the first switch transistor; and

a fourth switch transistor having a first end coupled to the second end of the first switch transistor, and a second end coupled to the output of the operational amplifier, and a control end to receive the charge control signal;

wherein the step S1 comprises;

setting a control signal for the first switch transistor to turn on the first switch transistor,

and

wherein the step S3 comprises;

sensing a potential of the first node and outputting the sensed voltage, by the readout circuit.

11. The method according to claim 9, wherein in step S2, the energy storage circuit is caused by the discharge control circuit to discharge via the piezoresistive sensor for a predetermined time period.