Voltage regulation in resonant power wireless receiver

Patent metadata

Field	Value
Publication number	US-9825553-B2
Application number	US-201414531520-A
Country	US
Kind code	B2
Filing date	Nov 3, 2014
Priority date	Apr 17, 2014
Publication date	Nov 21, 2017
Grant date	Nov 21, 2017

Abstract

A control system is provided for controlling a power receiving circuit which is configured for receiving power wirelessly and producing an output voltage. The power receiving circuit has a resonant LC circuit including an inductive element and a capacitive element coupled in parallel. The control system includes a switching circuit coupled in parallel to the resonant LC circuit, and a feedback loop circuit configured for regulating the output voltage by controlling duration during which the switching circuit is in a conductive state in each cycle of a voltage developed across the resonant LC circuit.

First claim

What is claimed is:

1. A control system for controlling a power receiving circuit configured for receiving power wirelessly, producing an output voltage and having a resonant LC circuit including an inductive element and a capacitive element coupled in parallel, the control system comprising:
a controllable shunt circuit coupled in parallel to the resonant LC circuit that, when activated, shunts substantially all current generated by the resonant LC circuit, and
a feedback loop circuit configured for regulating the output voltage by activating the controllable shunt circuit during only a portion of each cycle of a voltage developed across the resonant LC circuit so as to cause the output voltage to be at a pre-determined level, the feedback loop circuit comprising a pulse width modulation (PWM) control circuit that produces a PWM control signal responsive to a difference between the output voltage and a reference voltage, to control the controllable shunt circuit.

2. The system of claim 1 , wherein the feedback loop circuit further includes a zero crossing detect circuit configured for identifying a zero crossing of the voltage developed across the resonant LC circuit, to activate the PWM control circuit.

3. The system of claim 2 , wherein the zero crossing detect circuit is configured to operate in a single phase mode to identify a single zero crossing per sinusoid cycle of the voltage developed across the resonant LC circuit.

4. The system of claim 2 , wherein the zero crossing detect circuit is configured to operate in a dual phase mode to identify two zero crossings per sinusoid cycle of the voltage developed across the resonant LC circuit.

5. The system of claim 2 , wherein the PWM control circuit includes a ramp generator responsive to an error signal produced by the zero crossing detect circuit.

6. The system of claim 5 , wherein the PWM control circuit further includes a comparator for comparing the error signal with a ramp signal produced by the ramp generator.

7. The system of claim 6 , wherein the PWM control circuit is configured to control switching of the controllable shunt circuit based on an output signal of the comparator.

8. The system of claim 1 , wherein the feedback loop circuit is configured for controlling the controllable shunt circuit in response to a rectified signal produced by a rectifier circuit responsive to the voltage developed across the resonant LC circuit.

9. The system of claim 1 , wherein the controllable shunt circuit includes a first N-type field effect transistor (NFET) and a second NFET, drains of the first and second NFETs are connected together, a source of the first NFET is coupled to a first node of the resonant LC circuit, and a source of the second NFET is coupled to a second node of the resonant LC circuit.

10. The system of claim 9 further comprising a first bootstrapped driver configured for controlling the first NFET and including a first level shifter responsive to the PWM control signal for controlling a gate of the first NFET, and a first bootstrapped capacitor having a negative terminal coupled to the first node of the resonant LC circuit and a positive terminal coupled via a first diode to a DC voltage source.

11. The system of claim 10 further comprising a second bootstrapped driver configured for controlling the second NFET and including a second level shifter responsive to the PWM control signal for controlling a gate of the second NFET, and a second bootstrapped capacitor having a negative terminal coupled to the second node of the resonant LC circuit and a positive terminal coupled via a second diode to the DC voltage source.

12. The system of claim 1 , wherein the controllable shunt circuit is a switch controllable by a control signal.

13. The system of claim 12 , wherein the control signal is a PWM signal.

14. A method of voltage regulation for a power receiving system configured for receiving power wirelessly and producing an output voltage, the power receiving system having a resonant LC circuit including an inductive element and a capacitive element coupled in parallel, the method comprising the steps of:
coupling a controllable shunt across the resonant LC circuit that, when in an active state, shunts substantially all of the current generated by the resonant LC circuit, and
in response to the output voltage of the power receiving circuit, producing a pulse width modulation (PWM) control signal and controlling, based on the PWM control signal, the duration during which the controllable shunt is active during only a portion of each cycle of a voltage developed across the resonant LC circuit, so as to cause the output voltage to be at a pre-determined level, wherein the PWM control signal is responsive to a difference between the output voltage and a reference voltage.

15. The method of claim 13 further including a step of producing a control signal for controlling the controllable shunt based on an error voltage representing a difference between the output voltage and an error signal.

16. The method of claim 14 further including a step of identifying a zero crossing of the voltage developed across the resonant LC circuit.

17. The method of claim 15 , wherein the control signal is produced in response to the zero crossing.

18. A system for receiving power wirelessly to produce an output voltage, comprising:
a resonant LC circuit including an inductive element and a capacitive element coupled in parallel,
a rectifier for rectifying a voltage developed across the resonant LC circuit to produce the output voltage,
a controllable shunt circuit coupled in parallel to the resonant LC circuit that, when activated, shunts substantially all current generated by the resonant LC circuit, and
a control circuit configured for actuating the controllable shunt circuit to regulate the output voltage during only a portion of each cycle of a voltage developed across the resonant LC circuit, the control circuit producing a pulse width modulation control signal responsive to a difference between the output voltage and a reference voltage, to control the controllable shunt circuit.

Assignees

• Linear Tech Corp

Inventors

• Celani Jonathan Wayde

Classifications

• H02J50/12

  of the resonant type · CPC title

• H02M7/217 Primary

  using semiconductor devices only · CPC title

• H02J5/005

  Electricity · mapped topic

• Y02B70/1491

  Cross-Sectional Technologies · mapped topic

• H02J17/00

  Electricity · mapped topic