Dynamic tuning in wireless energy transfer systems

Patent metadata

Field	Value
Publication number	US-10141788-B2
Application number	US-201615293443-A
Country	US
Kind code	B2
Filing date	Oct 14, 2016
Priority date	Oct 22, 2015
Publication date	Nov 27, 2018
Grant date	Nov 27, 2018

Abstract

Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for dynamically tuning circuit elements. One aspect includes a variable capacitance device. The device includes a first capacitor, a first switch, a second capacitor, a second switch, and control circuitry. The control circuitry is configured to adjust respective capacitances of the first and second capacitors by causing a first control signal to be applied to the first-switch control terminal for a duration of time in response to detecting a zero voltage condition across the first switch, and by causing a second control signal to be applied to the second-switch control terminal for the duration of time in response to detecting a zero voltage condition across the second switch.

First claim

What is claimed is:

1. A variable capacitance device comprising:
a first capacitor comprising a first-capacitor first terminal and a first-capacitor second terminal, the first-capacitor first terminal electrically connected to a ground;
a first switch comprising a first-switch first terminal, a first-switch second terminal, and a first-switch control terminal, the first-switch first terminal electrically connected to the first-capacitor first terminal, and the first-switch second terminal electrically connected to the first-capacitor second terminal;
a first comparator comprising a first-comparator first input terminal electrically connected to the first-capacitor second terminal;
a second capacitor comprising a second-capacitor first terminal and a second-capacitor second terminal, the second-capacitor first terminal electrically connected to the ground;
a second switch comprising a second-switch first terminal, a second-switch second terminal, and a second-switch a control terminal, the second-switch first terminal electrically connected to the second-capacitor first terminal, and the second-switch second terminal electrically connected to the second-capacitor second terminal;
a second comparator comprising a second-comparator first input terminal electrically connected to the second-capacitor second terminal; and
control circuitry coupled with the first-switch control terminal, with the second-switch control terminal, with a first-comparator output terminal of the first comparator, and with a second-comparator output terminal of the second comparator,
wherein the control circuitry is configured to adjust respective capacitances of the first and second capacitors by:
detecting a zero voltage condition across the first switch based on an output signal of the first comparator, and, in response, cause a first control signal to be applied to the first-switch control terminal for a duration of time, wherein the first control signal causes the first switch to close; and
detecting a zero voltage condition across the second switch based on an output signal of the second comparator, and, in response, cause a second control signal to be applied to the second-switch control terminal for the duration of time, wherein the second control signal causes the second switch to close.

2. The variable capacitance device of claim 1 , wherein a capacitance of the device depends on the duration of time for which the first and second control signals are applied to the respective first-switch control terminal and second-switch control terminal.

3. The variable capacitance device of claim 1 , wherein the first switch is a first transistor and the second switch is a second transistor.

4. The variable capacitance device of claim 1 , wherein the control circuitry is configured to receive an input signal and, in response to receiving the input signal, change the duration of time for which the first and second control signals are applied to the respective first-switch control terminal and second-switch control terminal.

5. The variable capacitance device of claim 1 , further comprising:
a third comparator comprising a third-comparator first input terminal electrically connected to a first reference voltage and a third-comparator second input terminal electrically connected to the first-switch control terminal; and
a fourth comparator comprising a fourth-comparator first input terminal electrically connected to a second reference voltage and a fourth-comparator second input terminal electrically connected to the second-switch control terminal;
wherein the control circuitry is coupled with a third-comparator output terminal of the third comparator and a fourth-comparator output terminal of the fourth comparator, and the control circuitry is configured to:
detect a first ON condition at the first-switch control terminal based on an output signal of the third comparator;
determine a first time difference, the first time difference being a difference in time from detecting the zero voltage condition across the first switch and detecting the first ON condition at the first-switch control terminal;
adjust a first timing of when the first control signal is applied to the first-switch control terminal so as to reduce the first time difference;
detect a second ON condition at the second-switch control terminal based on an output signal of the fourth comparator;
determine a second time difference, the second time difference being a difference in time from detecting the zero voltage condition across the second switch and detecting the second ON condition at the second-switch control terminal; and
adjust a second timing of when the second control signal is applied to the second-switch control terminal so as to reduce the second time difference.

6. The variable capacitance device of claim 5 , wherein the control circuitry comprises:
a pulse width modulation (PWM) generator comprising a first output terminal electrically connected to the first-switch control terminal and a second output terminal electrically connected to the second-switch control terminal,
wherein the first control signal is a first pulse width modulated signal and the second control signal is a second pulse width modulated signal, and
wherein the control circuitry is configured to control characteristics of the first and second pulse width modulated signals.

7. The variable capacitance device of claim 6 , wherein adjusting the timing of when the first and second control signals are applied to the respective first-switch control terminal and the second-switch control terminal comprises adjusting phases of the first and second pulse width modulated signals.

8. The variable capacitance device of claim 6 , wherein the control circuitry is configured to receive an input signal and, in response to receiving the input signal, change the duration of time for which the first and second control signals are applied to the respective control terminals of the first switch and the second switch by adjusting respective duty cycles of the first and second pulse width modulated signals.

9. The variable capacitance device of claim 1 , further comprising:
a third comparator comprising a third-comparator first input terminal electrically connected to a first reference voltage and a third-comparator second input terminal electrically connected to the first-switch control terminal; and
a fourth comparator comprising a fourth-comparator first input terminal electrically connected to a second reference voltage and a fourth-comparator second input terminal electrically connected to the second-switch control terminal; and
wherein the control circuitry comprises:
a controller;
a first counter coupled with the first-comparator output terminal, the third-comparator output terminal, and the controller, the first counter configured to:
start a first timer in response to receiving a zero voltage signal from the first comparator,
stop the first timer in response to receiving a first ON condition signal from the third comparator, and
send a signal indicating an elapsed time of the first timer to the controller; and

a second counter coupled with the second-comparator output terminal, the fourth-comparator output terminal, and the controller, the second counter configured to:
start a second timer in response to receiving a zero voltage signal from the second comparator,
stop the second timer in response to receiving a second ON condition signal from the fourth comparator, and
send a signal indicating an elapsed time of the second timer to the controller;

wherein the controller is configured to:
adjust, based on the first-time-difference signal, a first timing of when the first control signal is applied to t

Assignees

• Witricity Corp

Inventors

• Karnstedt Curt
• Buenrostro Christopher

Classifications

• H03H7/40

  Automatic matching of load impedance to source impedance · CPC title

• H02J50/90

  involving detection or optimisation of position, e.g. alignment · CPC title

• H02J50/60

  responsive to the presence of foreign objects, e.g. detection of living beings · CPC title

• H02J50/12 Primary

  of the resonant type · CPC title

• H02J7/025

  Electricity · mapped topic