RESONANT WIRELESS POWER TRANSMITTER CIRCUIT AND CONTROL CIRCUIT AND CONTROL METHOD THEREOF

• US 20170085131A1
• Filed: 04/10/2016
• Published: 03/23/2017
• Est. Priority Date: 09/19/2015
• Status: Active Grant

• Current Assignee: Richtek Technology Corporation (MediaTek, Inc.)
• Original Assignee: Richtek Technology Corporation (MediaTek, Inc.)
• Inventors: Liu, Kuo-Chi, Wei, Wei-Hsin, Wang, Chih-Hsien
• Granted Patent: US 10,680,463 B2
• Time in Patent Office: Days
• CPC Class Codes: H02J 50/12 of the resonant type
• CPC Class Codes: H03H 7/38 Impedance-matching networks

Abstract

The present invention discloses a resonant wireless power transmitter circuit, which has an input impedance. The resonant wireless power transmitter circuit includes: a driver circuit coupled with a power supply, which includes at least a power switch; a switching resonant control circuit coupled with the driver circuit, such that the driver operates at a pre-determined or a variable resonant frequency; an adjustable impedance matching circuit coupled with the driver circuit, which includes at least a varactor; a transmitter circuit coupled with the impedance matching circuit and the driver circuit, which includes at least a transmitter coil; and an impedance control circuit coupled with the adjustable impedance matching circuit and the driver circuit, which provides an impedance control signal to control the reactance of the varactor, such that the input impedance of the resonant wireless power transmitter circuit is matched at the pre-determined or the variable resonant frequency.

Claims

1. A resonant wireless power transmitter circuit having an input impedance, comprising:

a driver circuit, which is coupled to a power supply, wherein the driver circuit includes at least a power switch;

a switching resonant control circuit, which is coupled to the driver circuit, and configured to control the driver circuit such that the driver circuit operates at a pre-determined resonant frequency;

an adjustable impedance matching circuit, which is coupled to the driver circuit, wherein the adjustable impedance matching circuit includes at least one varactor, and has an impedance;

a transmitter circuit, which is coupled to the adjustable impedance matching circuit and the driver circuit, wherein the transmitter circuit includes at least a transmitter coil, wherein the driver circuit is configured to drive the transmitter coil by switching the power switch thereof; and

an impedance control circuit, which is coupled to the driver circuit and the adjustable impedance matching circuit, and configured to operably generate an impedance control signal to control a reactance of the varactor so as to control the impedance of the adjustable impedance matching circuit such that the input impedance of the resonant wireless power transmitter circuit is matched at the pre-determined frequency.

2. The resonant wireless power transmitter circuit of claim 1, wherein the adjustable impedance matching circuit includes one of the following combinations (A) and (B):

(A) wherein the adjustable impedance matching circuit includes two or more varactors, and the two or more varactors are connected in parallel, in series, or in combination of parallel and series; and

(B) wherein the adjustable impedance matching circuit includes one or more varactors and one or more capacitors, and the one or more varactors and the one or more capacitors are connected in parallel, in series, or in combination of parallel and series.

3. The resonant wireless power transmitter circuit of claim 1, wherein the adjustable impedance matching circuit is configured to operably generate the impedance control signal according to a signal related to a phase difference between a voltage and a current of the transmitter coil.

4. The resonant wireless power transmitter circuit of claim 1, wherein the adjustable impedance matching circuit is configured to operably generate the impedance control signal according to a switching time signal of the power switch and a signal related to a current of the transmitter circuit or related to a current of the power switch.

5. The resonant wireless power transmitter circuit of claim 4, wherein the adjustable impedance matching circuit is configured to operably generate the impedance control signal according to a phase difference between the switching time signal of the power switch and the signal related to the current of the transmitter circuit or related to the current of the power switch.

6. The resonant wireless power transmitter circuit of claim 4, wherein the adjustable impedance matching circuit is configured to operably generate the impedance control signal according to a negative direction current of the power switch.

7. The resonant wireless power transmitter circuit of claim 4, wherein the adjustable impedance matching circuit comprises:

a negative direction current detection circuit, including;

a first comparator, which is configured to operably compare the current of the power switch and a first reference voltage to generate a negative direction current signal;

a delay circuit, which is configured to operably delay the switching time signal of the power switch to generate a delayed switching time signal;

a logic circuit, which is configured to operably mask the negative direction current signal by the delayed switching time signal to generate a negative direction current pulse; and

a filter, which is configured to operably filter the delayed switching time signal to generate a filter output signal, as a candidate of the impedance control signal.

8. The resonant wireless power transmitter circuit of claim 7, wherein the adjustable impedance matching circuit further comprises:

a second comparator, which is configured to operably compare the filter output signal and a second reference voltage to generate a selection signal; and

a multiplexer, which is configured to operably select the filter output signal or the second reference voltage to be the impedance control signal, or select the filter output signal or a third reference voltage to be the impedance control signal.

9. The resonant wireless power transmitter circuit of claim 1, wherein the transmitter coil and the varactor and/or one or more capacitors are connected in parallel, in series, or in combination of parallel and series.

10. The resonant wireless power transmitter circuit of claim 1, wherein the driver circuit is in one of the following forms:

a half bridge driver circuit or a full bridge driver circuit or a class E driver circuit.

11. The resonant wireless power transmitter circuit of claim 1, wherein the driver circuit is configured to be in the form of a differential class E driver circuit;

wherein the driver circuit includes a first transmitter coil, and a second transmitter coil connected in series, and wherein each of the first transmitter coil and the second transmitter coil is connected with the varactor, and/or one or more capacitors in parallel, in series, or in combination of parallel and series.

12. A method for controlling a resonant wireless power transmitter circuit which has an input impedance, wherein the resonant wireless power transmitter circuit comprises:

a driver circuit, which is coupled to a power supply, wherein the driver circuit includes at least a power switch;

a switching resonant control circuit, which is coupled to the driver circuit, and configured to control the driver circuit such that the driver circuit operates at a pre-determined resonant frequency; and

an adjustable impedance matching circuit, which is coupled to the driver circuit, wherein the adjustable impedance matching circuit includes at least one varactor, and has an impedance; and

a transmitter circuit, which is coupled to the adjustable impedance matching circuit and the driver circuit, wherein the transmitter circuit includes at least a transmitter coil, wherein the driver circuit is configured to operably drive the transmitter coil by switching the power switch thereof;

the control method comprising;

generating an impedance control signal; and

controlling a reactance of the varactor so as to control the impedance of the adjustable impedance matching circuit such that the input impedance of the resonant wireless power transmitter circuit is matched at the pre-determined frequency.

13. The method for controlling a resonant wireless power transmitter circuit of claim 12, wherein the adjustable impedance matching circuit includes one of the following combinations (A) and (B):

(A) wherein the adjustable impedance matching circuit includes two or more varactors, and the two or more varactors are connected in parallel, in series, or in combination of parallel and series; and

(B) wherein the adjustable impedance matching circuit includes one or more varactors and one or more capacitors, and the one or more varactors and the one or more capacitors are connected in parallel, in series, or in combination of parallel and series.

14. The method for controlling a resonant wireless power transmitter circuit of claim 12, wherein the step of generating the impedance control signal includes:

generating the impedance control signal according to a signal related to a phase difference between a voltage and a current of the transmitter coil.

15. The method for controlling a resonant wireless power transmitter circuit of claim 12, wherein the step of generating the impedance control signal includes:

generating the impedance control signal according to a switching time signal of the power switch and a signal related to a current of the transmitter circuit or related to a current of the power switch.

16. The method for controlling a resonant wireless power transmitter circuit of claim 15, wherein the step of generating the impedance control signal includes:

generating the impedance control signal according to a phase difference between the switching time signal of the power switch and the signal related to the current of the transmitter circuit or related to the current of the power switch.

17. The method for controlling a resonant wireless power transmitter circuit of claim 15, wherein the step of generating the impedance control signal includes:

generating the impedance control signal according to a negative direction current of the power switch.

18. The method for controlling a resonant wireless power transmitter circuit of claim 15, wherein the step of generating the impedance control signal includes:

comparing the current of the power switch and a first reference voltage to generate a negative direction current signal;

delaying the switching time signal of the power switch to generate a delayed switching time signal;

masking the negative direction current signal by the delayed switching time signal to generate a negative direction current pulse;

filtering the delayed switching time signal to generate a filter output signal; and

outputting the filter output signal as a candidate of the impedance control signal.

19. The method for controlling a resonant wireless power transmitter circuit of claim 18, wherein the step of generating the impedance control signal further includes:

comparing the filter output signal and a second reference voltage to generate a selection signal; and

selecting the filter output signal or the second reference voltage, or selecting the filter output signal or a third reference voltage, to be the impedance control signal according to the selection signal.

20. The method for controlling a resonant wireless power transmitter circuit of claim 12, wherein the transmitter coil and the varactor and/or one or more capacitors are connected in parallel, in series, or in combination of parallel and series.

21. The method for controlling a resonant wireless power transmitter circuit of claim 12, wherein the driver circuit is in one of the following forms:

a half bridge driver circuit or a full bridge driver circuit or a class E driver circuit.

22. The method for controlling a resonant wireless power transmitter circuit of claim 12, wherein the driver circuit is configured to be in the form of a differential class E driver circuit;

wherein the driver circuit includes a first transmitter coil and a second transmitter coil connected in series, and wherein each of the first transmitter coil and the second transmitter coil is connected with the varactor, and/or one or more capacitors in parallel, in series, or in combination of parallel and series.

23. An impedance control circuit, which is configured to operably control a resonant wireless power transmitter circuit which has an input impedance, wherein the resonant wireless power transmitter circuit comprises:

a driver circuit, which is coupled to a power supply, wherein the driver circuit includes at least a power switch;

a switching resonant control circuit, which is coupled to the driver circuit, and configured to control the driver circuit such that the driver circuit operates at a pre-determined resonant frequency; and

an adjustable impedance matching circuit, which is coupled to the driver circuit, wherein the adjustable impedance matching circuit includes at least one varactor, and has an impedance; and

a transmitter circuit, which is coupled to the adjustable impedance matching circuit and the driver circuit, wherein the transmitter circuit includes at least a transmitter coil, wherein the driver circuit is configured to drive the transmitter coil by switching the power switch thereof;

the impedance control circuit comprising;

a phase difference determining circuit, configured to operably determine a phase difference between a signal related to a current of the power switch (a current related signal) and a signal related to a switching time of the power switch (a switching time related signal); and

a control signal selection and output circuit which is coupled to the phase difference determining circuit, and configured to operably select and output an impedance control signal according to a determining result of the phase difference determining circuit, such that the input impedance of the resonant wireless power transmitter circuit is matched at the pre-determined frequency.

24. The impedance control circuit for controlling a resonant wireless power transmitter circuit of claim 23, wherein the adjustable impedance matching circuit includes one of the following combinations (A) and (B):

(A) wherein the adjustable impedance matching circuit includes two or more varactors, and the two or more varactors are connected in parallel, in series, or in combination of parallel and series; and

(B) wherein the adjustable impedance matching circuit includes one or more varactors and one or more capacitors, and the one or more varactors and the one or more capacitors are connected in parallel, in series, or in combination of parallel and series.

25. The impedance control circuit for controlling a resonant wireless power transmitter circuit of claim 23, wherein the phase difference between the current related signal and the switching time related signal relates to a signal which is related to a phase difference between a voltage and a current of the transmitter coil

26. The impedance control circuit for controlling a resonant wireless power transmitter circuit of claim 23, wherein the phase difference determining circuit determines the phase difference according to a negative direction current of the power switch.

27. The impedance control circuit for controlling a resonant wireless power transmitter circuit of claim 26, wherein the phase difference determining circuit includes:

a first comparator, which is configured to operably compare the current of the power switch and a first reference voltage to generate a negative direction current signal;

a delay circuit, which is configured to operably delay the switching time signal of the power switch to generate a delayed switching time signal;

a logic circuit, which is configured to operably mask the negative direction current signal by the delayed switching time signal to generate a negative direction current pulse which represents a; and

a filter, which is configured to operably filter the delayed switching time signal to generate a filter output signal to represent a determining result of the phase difference determining circuit.

28. The impedance control circuit for controlling a resonant wireless power transmitter circuit of claim 27, wherein the control signal selection and output circuit includes:

a second comparator, which is configured to operably compare the filter output signal and a second reference voltage to generate a selection signal; and

a multiplexer, which is configured to operably to select the filter output signal or the second reference voltage, or select the filter output signal or a third reference voltage, to be the impedance control signal.