SYSTEM AND METHOD FOR CONTROLLING RESONANT WIRELESS POWER SOURCE

• US 20140035384A1
• Filed: 08/01/2013
• Published: 02/06/2014
• Est. Priority Date: 08/03/2012
• Status: Active Grant

• Current Assignee: MediaTek Singapore Pte. Ltd. (MediaTek, Inc.)
• Original Assignee: MediaTek Singapore Pte. Ltd. (MediaTek, Inc.)
• Inventors: Satyamoorthy, Anand, Riehl, Patrick Stanley, Akram, Hasnain
• Granted Patent: US 9,722,462 B2
• Time in Patent Office: Days
• US Class Current: 307/104
• CPC Class Codes: H02J 50/12 of the resonant type
• CPC Class Codes: H02J 50/40 using two or more transmitting or receiving devices H02J50/50 takes precedence
• CPC Class Codes: H02J 50/80 involving the exchange of data, concerning supply or distribution of electric power, between transmitting devices and receiving devices

Abstract

A resonant wireless power system includes a source circuit having a source coil, an ac driver with a first resistance, representing the equivalent output impedance of the ac driver, and a matching network. A current probe measures the magnitude signal of the instantaneous source coil current. A voltage probe measures the instantaneous ac driver voltage. A phase detector compares the phase of the instantaneous source coil current and the instantaneous ac driver voltage, and produces a first output signal proportional to the phase difference. A first amplifier compares the magnitude signal and a target signal, and produces an error signal proportional to the difference. A first compensation filter produces the control voltage that determines the ac driver supply voltage. A second amplifier amplifies the first output signal. A second compensation filter produces the control voltage that determines the impedance of a variable element in the source circuit.

Claims

1. A resonant power source comprising:

a source circuit that includes a source coil, an ac driver with a first resistance, representing an equivalent output impedance of the ac driver, and a matching network;

a current probe that measures a magnitude signal of an instantaneous source coil current;

an amplifier that receives and compares the magnitude signal and a target signal, and produces an error signal proportional to the difference; and

a compensation filter that receives the error signal and produces a control voltage that determines an ac driver voltage of the ac driver.

2. The resonant power source of claim 1, wherein the ac driver voltage is linearly proportional to the magnitude signal.

3. The resonant power source of claim 1, wherein the current probe, the amplifier, the compensation filter and the source circuit form a feedback loop that forces the magnitude signal to be substantially equal to the target signal in steady-state.

4. The resonant power source of claim 1, wherein the source circuit increases the ac driver voltage when an impedance seen by the ac driver increases.

5. The resonant power source of claim 1, wherein the compensation filter provides range limiting or slew-rate limiting properties to control the behavior of the source circuit during transients.

6. The resonant power source of claim 1, wherein the current probe further measures a phase of the instantaneous source coil current, and the resonant power source further comprises:

a voltage probe that measures a phase of the ac driver voltage; and

a phase detector that receives and compares the phase of the instantaneous source coil current and the instantaneous ac driver voltage, and produces an output signal proportional to the phase difference;

wherein an impedance of a variable element in the source circuit is determined according to the output signal.

7. The resonant power source of claim 6, wherein the variable element is either a variable capacitance or a variable inductance.

8. The resonant wireless power system of claim 6, wherein the variable element becomes more capacitive when the phase difference is positive.

9. The resonant wireless power system of claim 6, wherein the phase difference between the ac driver voltage and instantaneous coil current is forced to zero.

10. The resonant wireless power system of claim 6, wherein the impedance seen by the ac driver is real.

11. The resonant power source of claim 1, wherein a variable component in the matching network is used to control the power delivered to the source coil.

12. A resonant power source comprising:

a source circuit that includes a source coil, an ac driver with a first resistance, representing an equivalent output impedance of the ac driver, and a matching network;

a current probe that measures a phase of an instantaneous source coil current;

a voltage probe that measures a phase of an ac driver voltage of the ac driver;

a phase detector that receives and compares the phase of the instantaneous source coil current and the instantaneous ac driver voltage, and produces a first output signal proportional to the phase difference;

an amplifier that receives and amplifies the first output signal, and produces an amplified signal; and

a compensation filter that receives the amplified signal and produces a control voltage that determines an impedance of a variable element in the source circuit.

13. The resonant power source of claim 12, wherein the variable element comprises either a variable capacitance or a variable inductance.

14. The resonant power source of claim 12, wherein the phase detector, amplifier, and compensation filter form a control loop configured so that the variable element becomes more capacitive when the phase difference is positive.

15. The resonant power source of claim 14, wherein the control loop thus forces the phase difference between the ac driver voltage and instantaneous coil current to zero.

16. The resonant power source of claim 12, wherein an impedance seen by the ac driver is real.

17. The resonant power source of claim 12, wherein a magnitude of the ac driver voltage is fixed.

18. The resonant power source of claim 12, wherein a variable component in the matching network is used to control the power delivered to the source coil.