WIRELESS INDUCTIVE POWER TRANSFER

• US 20170229911A1
• Filed: 09/14/2015
• Published: 08/10/2017
• Est. Priority Date: 09/16/2014
• Status: Active Grant

• Current Assignee: Koninklijke Philips N.V.
• Original Assignee: Koninklijke Philips N.V.
• Inventors: VELTMAN, Eddy Gerrit, ETTES, Wilhelmus Gerardus Maria, STARING, Antonius Adriaan Maria, LULOFS, Klaas Jacob
• Granted Patent: US 10,523,052 B2
• Time in Patent Office: Days
• CPC Class Codes: H02J 50/10 using inductive coupling
• CPC Class Codes: H02J 50/12 of the resonant type

Abstract

A wireless power transfer system includes a power receiver and a power transmitter providing power using an inductive power signal. The power transmitter comprises a resonance circuit (201) comprising a capacitive impedance (503) and an inductive impedance (501). A driver (203) generates a drive signal for the resonance circuit. A frequency modification circuit (505) controls the resonance frequency of the resonance circuit (201) by slowing a state change for at least one of the capacitive impedance (503) and the inductive impedance (501) for a fractional time interval of at least some cycles of the drive signal. The frequency modification circuit (505) is arranged to align at least one of a start time and an end time for the fractional time interval to transitions of a timing signal. In the power transmitter, the driver (203) generates the timing signal to have transitions synchronized to the drive signal. The slowing may be by impeding current flow between the capacitive and inductive impedance (503, 501).

Claims

1. A power transmitter for wirelessly providing power to a power receiver via an inductive power signal;

the power transmitter comprising;

a resonance circuit for generating the inductive power signal, the resonance circuit comprising a capacitive impedance and an inductive impedance;

a driver for generating a drive signal for the resonance circuit, the drive signal having an operating frequency and being arranged to generate the timing signal to have transitions synchronized to the drive signal; and

a frequency modification circuit for controlling a resonance frequency of the resonance circuit by slowing a state change for at least one of the capacitive impedance and the inductive impedance for a fractional time interval of each of at least a plurality of cycles of the drive signal, the frequency modification circuit being arranged to align at least one of a start time and an end time for the fractional time interval to at least some transitions of the timing signal.

2. The power transmitter of claim 1 wherein the driver is arranged to generate the timing signal to have transitions with a fixed time offset to a time instant of at least one of a zero crossing, a maximum and a minimum of cycles of the drive signal;

and the frequency modification circuit is arranged determine the at least one of the start time and the end time for the fractional time interval to have a fixed time offset to the at least some transitions of the timing signal.

3. The power transmitter of claim 1 wherein the driver comprises a switching bridge for generating the drive signal;

and wherein the driver is arranged to synchronize the transitions of the timing signal to transitions of a switch signal for a switch of the switching bridge.

4. The power transmitter of claim 2 wherein the frequency modification circuit comprises a switch and rectifier and the frequency modification circuit is arranged to align one of the start time and the end time to the transitions and to align the other of the start time and the end time to the rectifier switching between a non-conductive and a conductive state.

5. The power transmitter of claim 1 wherein the frequency modification circuit is arranged to slow the state change for the capacitive impedance by diverting current from the inductive impedance away from the capacitive impedance during the fractional time intervals.

6. The power transmitter of claim 5 wherein the frequency modification circuit comprises a current diversion path arranged to divert current from the inductive resonance away from the capacitive impedance, the current diversion path comprising a switch for connecting and disconnecting the current diversion path;

and the frequency modification circuit being arranged to align switching of the switch to the timing signal.

7. The power transmitter of claim 6 wherein the frequency modification circuit comprises a switch and rectifier coupled in a series configuration and the frequency modification circuit is arranged to align one of the start time and the end time to the transitions and to synchronize the other of the start time and the end time to the rectifier switching between a non-conductive and a conductive state.

8. The power transmitter of claim 5 wherein a first end of the current diversion path is coupled to a junction point between the inductive impedance and the capacitive impedance.

9. The power transmitter of claim 8 wherein a second end of the current diversion path is coupled to a voltage supply rail.

10. The power transmitter of claim 5 wherein the driver comprises a switching bridge generating the drive signal;

and the drive is arranged to synchronize the transitions of the timing signal to coincide with transitions of a switch signal for a switch of the switching bridge.

11. The power transmitter of claim 10 wherein the current diversion path comprises a switch and rectifier coupled in a series configuration, a first end of the current diversion path is coupled to a junction point between the inductive impedance and the capacitive impedance and a second end of the current diversion path is coupled to a ground supply rail for the switching bridge, and the power transmitter is arranged to align start times of the fractional time interval to a time of the rectifier switching from a non-conductive to a conductive state and to align end times of the fractional time interval to a switching of a switch of the switching bridge.

12. The power transmitter of claim 1 wherein the frequency modification circuit is arranged to slow the state change for the inductive impedance by impeding current flow from the capacitive impedance to the inductive impedance during the fractional time interval.

13. The power transmitter of claim 1 wherein the frequency modification circuit is arranged to slow the state change for the inductive impedance by blocking current flow from the capacitive impedance to the inductive impedance during the fractional time interval.

14. A method of operation for a power transmitter for wirelessly providing power to a power receiver using an inductive power signal, the power transmitter comprising a resonance circuit for generating the inductive power signal, the resonance circuit comprising a capacitive impedance and an inductive impedance;

the method comprising;

a driver generating a drive signal for the resonance circuit, the drive signal having an operating frequency, and generating the timing signal to have transitions synchronized to the drive signal;

a frequency modification circuit controlling a resonance frequency for the resonance circuit by slowing a state change for at least one of the capacitive impedance and the inductive impedance for a fractional time interval of each of at least a plurality cycles of the drive signal, the controlling of the resonance frequency including aligning at least one of a start time and an end time for the fractional time interval to at least some transitions of the timing signal.

15. A wireless power transfer system comprising a power receiver and a power transmitter arranged to wirelessly provide power to the power receiver using an inductive power signal;

the power transmitter comprising;

a resonance circuit for generating the inductive power signal, the resonance circuit comprising a capacitive impedance and an inductive impedance;

a driver for generating a drive signal for the resonance circuit, the drive signal having an operating frequency and being arranged to generate the timing signal to have transitions synchronized to the drive signal; and

a frequency modification circuit for controlling a resonance frequency of the resonance circuit by slowing a state change for at least one of the capacitive impedance and the inductive impedance for a fractional time interval of each of at least a plurality of cycles of the drive signal, the frequency modification circuit being arranged to align at least one of a start time and an end time for the fractional time interval to at least some transitions of the timing signal.