Resonant wireless power transmitter circuit and control circuit and control method thereof

• US 10,680,463 B2
• Filed: 04/10/2016
• Issued: 06/09/2020
• 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
• Primary Examiner(s): Barnie, Rexford N
• Assistant Examiner(s): Chowdhuri, Swarna N
• Application Number:
  US15/095,087
• Publication Number:
  US 20170085131A1
• Time in Patent Office: 1,521 Days
• Field of Search: 307104
• 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 which is controlled by a switching time signal to switch at a pre-determined resonant frequency;

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 the 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 power switch of the driver circuit is configured to switch with the resonant frequency to periodically conduct the power supply to drive the transmitter coil; and

an impedance control circuit, which is coupled to the driver circuit and the adjustable impedance matching circuit, and configured to operably generate an analog impedance control signal to control a reactance of the varactor in continuous analog form 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, wherein the reactance of the varactor is continuously adjustable in analog form;

wherein when the input impedance of the resonant wireless power transmitter circuit is matched at the pre-determined frequency, a current of the power switch supplies a half cycle of a resonant sinewave current, wherein the resonant sinewave current flows through the transmitter coil;

wherein the impedance control circuit is configured to operably generate the impedance control signal according to the switching time signal of the power switch and a signal related to the current of the power switch, wherein the switching time signal carries information of the switching time point of the power switch.

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 plural varactors, and the plural varactors are connected in parallel, in series, or in combination of parallel and series; and

(B) wherein the adjustable impedance matching circuit includes at least one varactor and at least one capacitor, and the at least one varactor and the at least one capacitor 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 impedance control 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 power switch.

4. The resonant wireless power transmitter circuit of claim 1, wherein the impedance control circuit is configured to operably generate the impedance control signal according to a signal related to a negative direction current of the power switch, wherein the negative direction current of the power switch flows in a direction which is opposite to a first direction in which the current of the power switch flows when the input impedance of the resonant wireless power transmitter circuit is matched at the pre-determined frequency, wherein the signal related to the negative direction current is determined according to the switching time signal of the power switch and the current of the power switch.

5. The resonant wireless power transmitter circuit of claim 1, wherein the impedance control circuit includes:

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 negative direction current pulse to generate a filter output signal, as a candidate of the impedance control signal, wherein the filter output signal is in a continuous analog form.

6. The resonant wireless power transmitter circuit of claim 5, wherein the impedance control 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.

7. The resonant wireless power transmitter circuit of claim 1, wherein:

(A) the transmitter coil and the varactor are connected in parallel, in series, or in combination of parallel and series;

or

(B) the transmitter coil and the varactor and at least one capacitor are connected in parallel, in series, or in combination of parallel and series.

8. 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.

9. 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;

(A) each of the first transmitter coil and the second transmitter coil is connected with the varactor in parallel, in series, or in combination of parallel and series;

or

(B) each of the first transmitter coil and the second transmitter coil is connected with the varactor and at least one capacitor in parallel, in series, or in combination of parallel and series.

19. The resonant wireless power transmitter circuit of claim 1, wherein the varactor is a varactor diode, wherein a control terminal of the varactor diode is coupled to the impedance control signal for adjusting the reactance of the varactor diode.

10. 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 which is controlled by a switching time signal to switch at a pre-determined resonant frequency;

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 the 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 power switch of the driver circuit is configured to switch with the resonant frequency to periodically conduct the power supply to drive the transmitter coil;

the control method comprising;

generating an analog impedance control signal; and

controlling a reactance of the varactor in continuous analog form according to the analog impedance control signal 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, wherein the reactance of the varactor is continuously adjustable in analog form;

wherein when the input impedance of the resonant wireless power transmitter circuit is matched at the pre-determined frequency, a current of the power switch supplies a half cycle of a resonant sinewave current, wherein the resonant sinewave current flows through the transmitter coil;

wherein the impedance control signal is generated according to the switching time signal of the power switch and a signal related to the current of the power switch, wherein the switching time signal carries information of the switching time point of the power switch.

11. The method for controlling a resonant wireless power transmitter circuit of claim 10, wherein the adjustable impedance matching circuit includes one of the following combinations (A) and (B):

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

(B) wherein the adjustable impedance matching circuit includes at least one varactor and at least one capacitor, and the at least one varactor and the at least one capacitor are connected in parallel, in series, or in combination of parallel and series.

12. The method for controlling a resonant wireless power transmitter circuit of claim 10, 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 power switch.

13. The method for controlling a resonant wireless power transmitter circuit of claim 10, wherein the step of generating the impedance control signal includes:

generating the impedance control signal according to a signal related to a negative direction current of the power switch, wherein the negative direction current of the power switch flows in a direction which is opposite to a first direction in which the current of the power switch flows when the input impedance of the resonant wireless power transmitter circuit is matched at the pre-determined frequency, wherein the signal related to the negative direction current is determined according to the switching time signal of the power switch and the current of the power switch.

14. The method for controlling a resonant wireless power transmitter circuit of claim 10, 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 negative direction current pulse to generate a filter output signal, wherein the filter output signal is in a continuous analog form; and

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

15. The method for controlling a resonant wireless power transmitter circuit of claim 14, 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.

16. The method for controlling a resonant wireless power transmitter circuit of claim 10, wherein:

(A) the transmitter coil and the varactor are connected in parallel, in series, or in combination of parallel and series;

or

(B) wherein the transmitter coil and the varactor and at least one capacitor are connected in parallel, in series, or in combination of parallel and series.

17. The method for controlling a resonant wireless power transmitter circuit of claim 10, 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.

18. The method for controlling a resonant wireless power transmitter circuit of claim 10, 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;

(A) each of the first transmitter coil and the second transmitter coil is connected with the varactor in parallel, in series, or in combination of parallel and series;

or

(B) wherein each of the first transmitter coil and the second transmitter coil is connected with the varactor and at least one capacitor in parallel, in series, or in combination of parallel and series.