Capacitive sensing patent

• US 10,162,461 B2
• Filed: 05/25/2017
• Issued: 12/25/2018
• Est. Priority Date: 05/25/2016
• Status: Active Grant

• Current Assignee: Akivo Vekhter, Josh Vekhter
• Original Assignee: Akivo Vekhter, Josh Vekhter
• Inventors: Vekhter, Josh, Vekhter, Akivo
• Primary Examiner(s): Patel, Premal R
• Application Number:
  US15/605,142
• Publication Number:
  US 20170344178A1
• Time in Patent Office: 579 Days
• 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 3/04184 Synchronisation with the driving of the display or the backlighting unit to avoid interferences generated internally
• CPC Class Codes: G06F 3/0445 using two or more layers of sensing electrodes, e.g. using two layers of electrodes separated by a dielectric layer
• CPC Class Codes: H03K 17/9622 using a plurality of detectors, e.g. keyboard
• CPC Class Codes: H03K 2217/960725 Charge-transfer

Abstract

An electronic device that includes a first switch, a second switch, a capacitive sensing circuit, and control circuitry. The first switch is electrically coupled between a first terminal of a load and a first terminal for a power source. The second switch is electrically coupled between a second terminal of the load and a second terminal for a power source. The control circuitry is configured to perform operations including connecting the load to the first and second power source terminals by controlling the first and second switches to close during a first portion of a switching cycle, disconnecting the load from the first and second power source terminals by controlling the first and second switches to open during a second portion of the switching cycle, and detecting the capacitance of the load based on the output signal of the capacitive sensing circuit during the second portion of the switching cycle.

Claims

1. A capacitive sensing device comprising:

a first switch electrically coupled between a first terminal of a load and a first terminal of a power source;

a second switch electrically coupled between a second terminal of the load and a second terminal of a power source;

a capacitive sensing circuit electrically coupled to the first terminal of the load and configured to provide an output signal that indicates a capacitance of the load, the capacitive sensing circuit comprising;

an isolation circuit configured to protect the capacitive sensing circuit from a high voltage of the power source,

a sensor drive signal generator electrically coupled to the load through a first terminal of the isolation circuit,

an AC rectifying circuit coupled to the load through a second terminal of the isolation circuit,

an RC circuit coupled to the AC rectifying circuit, wherein the output signal that indicates a capacitance of the load is provided as an output from the RC circuit, and

a reset circuit coupled to the RC circuit; and

control circuitry configured to perform operations comprising;

connecting the load to the power source by controlling the first and second switches to close during a first portion of a switching cycle;

disconnecting the load from the power source by controlling the first and second switches to open during a second portion of the switching cycle, thereby, permitting the load to be at floating voltage;

resetting, during the second portion of the switching cycle, the capacitive sensing circuit by providing a reset signal to the reset circuit of the capacitive sensing circuit;

detecting, during the second portion of the switching cycle, the capacitance of the load based on the output signal of the capacitive sensing circuit.

2. The device of claim 1, wherein a load driving signal provided by the power source has a voltage that exceeds a voltage tolerance of the capacitive sensing circuit.

3. The device of claim 1, wherein the load is an electro luminescent (EL) device.

4. The device of claim 1, further comprising a voltage reduction circuit coupled between the power source and the control circuitry, and wherein the control circuitry is configured to sense a load driving signal supplied by the power source and synchronize the switching cycle with the load driving signal.

5. An electronic device comprising:

a first switch electrically coupled between a first terminal of a load and a first terminal for a power source;

a second switch electrically coupled between a second terminal of the load and a second terminal for a power source;

a capacitive sensing circuit electrically coupled to the first terminal of the load and configured to provide an output signal that indicates a capacitance of the load, the capacitive sensing circuit comprising an isolation circuit configured to protect the capacitive sensing circuit from a high voltage of the power source; and

control circuitry configured to perform operations comprising;

connecting the load to the first and second power source terminals by controlling the first and second switches to close during a first portion of a switching cycle;

disconnecting the load from the first and second power source terminals by controlling the first and second switches to open during a second portion of the switching cycle; and

detecting, during the second portion of the switching cycle, the capacitance of the load based on the output signal of the capacitive sensing circuit.

6. The device of claim 5, wherein the operations of the control circuitry further comprise altering an operation of the load based on the capacitance of the load.

7. The device of claim 5, wherein a value of the capacitance indicates a touch input to the load.

8. The device of claim 5, wherein the switching cycle is synchronized with a frequency of a load driving signal supplied by the power source.

9. The device of claim 5, wherein the switching cycle is between 50 Hz and 150 Hz.

10. The device of claim 5, wherein a load driving signal supplied by the power source is between 60 Hz and 3 kHz.

11. The device of claim 5, wherein the capacitive sensing circuit comprises:

a sensor drive signal generator; and

a peak detection circuit configured to convert a sensor drive signal supplied by the sensor drive signal generator into a direct current (DC) output signal that represents the capacitance of the load.

12. The device of claim 11, wherein the isolation circuit is configured to isolate the sensor drive signal generator and the peak detection circuit from a load driving signal supplied by the power source and to permit the sensor driving signal to pass to the load.

13. The device of claim 11, wherein the sensor drive signal has a frequency that is greater than a frequency of the load driving signal supplied by the power source, and

wherein the isolation circuit is a high pass filter.

14. The device of claim 11, wherein the sensor drive signal generator is an output of the control circuitry.

15. The device of claim 5, wherein the operations of the control circuitry further comprise resetting, during the second portion of the switching cycle, the capacitive sensing circuit.

16. The device of claim 5, wherein the capacitive sensing circuit comprises:

a sensor drive signal generator electrically coupled to the load through a first terminal of the isolation circuit;

an AC rectifying circuit coupled to the load through a second terminal of the isolation circuit;

an RC circuit coupled to the AC rectifying circuit; and

a reset circuit coupled to the RC circuit,

wherein the output signal that indicates a capacitance of the load is provided as an output from the RC circuit.

17. The device of claim 5, wherein a load driving signal provided by the power source has a voltage that exceeds a voltage tolerance of the capacitive sensing circuit.

18. The device of claim 5, wherein the load is an electro luminescent (EL) device.

19. The device of claim 5, wherein the load is an organic light-emitting diode (OLED) device.

20. A method of making a capacitive sensing device, the method comprising:

electrically coupling a first switch between a first terminal of a load and a first terminal for a power source;

electrically coupling a second switch between a second terminal of the load and a second terminal for a power source;

electrically coupling a capacitive sensing circuit to the first terminal of the load, the capacitive sensing circuit configured to provide an output signal that indicates a capacitance of the load, and the capacitive sensing circuit comprising an isolation circuit configured to protect the capacitive sensing circuit from a high voltage of the power source; and

electrically coupling control circuitry to the first switch, second switch, and capacitive sensing circuit configured,

wherein the control circuitry is configured to perform operations comprising;

connecting the load to the power source by controlling the first and second switches to close during a first portion of a switching cycle;

disconnecting the load from the power source by controlling the first and second switches to open during a second portion of the switching cycle, thereby, permitting the load to be at floating voltage;

resetting, during the second portion of the switching cycle, the capacitive sensing circuit; and

detecting, during the second portion of the switching cycle, the capacitance of the load based on the output signal of the capacitive sensing circuit.