WIRELESS INDUCTIVE POWER TRANSFER

• US 20180366984A1
• Filed: 11/01/2016
• Published: 12/20/2018
• Est. Priority Date: 11/02/2015
• Status: Active Grant

• Current Assignee: Koninklijke Philips N.V.
• Original Assignee: Koninklijke Philips N.V.
• Inventors: JOYE, Neil Francis, LULOFS, Klaas Jacob, VELTMAN, Eddy Gerrit, VAN WAGENINGEN, Andries
• Granted Patent: US 10,536,035 B2
• Time in Patent Office: Days
• CPC Class Codes: H02J 50/12 of the resonant type
• CPC Class Codes: H02J 50/80 involving the exchange of data, concerning supply or distribution of electric power, between transmitting devices and receiving devices
• CPC Class Codes: H02J 7/00034 Charger exchanging data with an electronic device, i.e. telephone, whose internal battery is under charge

Abstract

A wireless power transmitter (101)) comprises a resonance circuit (201) comprises a transmitter inductor (103) for generating a power transfer signal for wirelessly transferring power to the power receiver (105). A driver (203) generates a drive signal for the resonance circuit (201) and a resonance modification circuit (505) aligns the resonance frequency of the resonance circuit (201) with the drive frequency of the drive signal by slowing a state change for resonance circuit (201) for a fractional time interval of cycles of the drive signal. A load estimator (509) generates a load estimate reflecting an equivalent load resistor for the transmitter inductor (103) reflecting the loading of the power transfer signal. A drive frequency adapter (511) then adapts the drive frequency in response to the load estimate. The invention may in particular improve load modulation communication quality.

Claims

1. A power transmitter for inductively transferring power to a power receiver, the power transmitter comprising:

a resonance circuit comprising a capacitive impedance and an inductive impedance, the inductive impedance comprising a transmitter inductor for generating a power transfer signal for wirelessly transferring power to the power receiver;

a driver generating a drive signal for the resonance circuit, the drive signal having a drive frequency;

a resonance modification circuit for aligning the resonance frequency of the resonance circuit with the drive frequency 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;

a load estimator for generating a load estimate reflecting an equivalent load resistor for the transmitter inductor reflecting a loading of the power transfer signal; and

a drive frequency adapter for adapting the drive frequency in response to the load estimate;

wherein the drive frequency adapter is arranged to adapt the drive frequency to be further away from a resonance frequency of a power receiving resonance circuit of the power receiver for a load estimate indicative of a first equivalent parallel load resistance than for a load estimate indicative of a second equivalent parallel load resistance, the first equivalent parallel load resistance being lower than the second equivalent parallel load resistance.

2. The power transmitter of claim 1 wherein a loading of the power transfer signal has a resistive component and a reactive component, and the load estimate is indicative of only the resistive component.

3. The power transmitter of claim 1 further comprising a receiver for detecting messages load modulated onto the power transfer signal by a varying reactive load.

4. The power transmitter of claim 1 wherein the drive frequency adapter is arranged to determine an operating range for the drive frequency in response to the load estimate and to restrict the drive frequency to the operating range.

5. The power transmitter of claim 4 wherein the drive frequency adapter is arranged to adapt the drive frequency within the operating range in response to an operating parameter other than the load estimate.

6. The power transmitter of claim 1 wherein the drive frequency adapter is arranged to operate a feed-forward adaptation of the drive frequency in response to load estimate, and to operate a control loop adaptation of the drive frequency in response to an operating parameter other than the load estimate.

7. The power transmitter of claim 1 wherein the drive frequency adapter is further arranged to adapt the drive frequency in response to a power loss of the resonance circuit.

8. The power transmitter of claim 1 further comprising a modulation depth estimator for determining a modulation depth estimate for a load modulation of the power transfer by the power receiver;

and wherein the drive frequency adapter is further arranged to adapt the drive frequency in response to a modulation depth estimate.

9. The power transmitter of claim 1 wherein the drive frequency adapter is arranged to adapt the drive frequency to be further away from a resonance frequency of the capacitive impedance and inductive impedance for a load estimate indicative of a first equivalent parallel load resistance than for a load estimate indicative of a second equivalent parallel load resistance, the first equivalent parallel load resistance being higher than the second equivalent parallel load resistance.

10. The power transmitter of claim 1 further comprising a receiver for receiving messages from the power receiver comprising load indications being indicative of a resistive loading of the power transfer signal by the power receiver, and wherein the load estimator is arranged to determine the load estimate in response to the messages.

11. The power transmitter of claim 1 wherein a resonance frequency corresponding to the capacitive impedance and the inductive impedance exceeds a maximum allowable resonance frequency for the power receiver.

12. The power transmitter of claim 1 wherein the drive frequency adapter is arranged to set the drive frequency such that a difference between the drive frequency and a resonance frequency corresponding to the capacitive impedance and inductive impedance is above a first value when the load estimate is indicative of an equivalent parallel load resistance above a first threshold and to set the drive frequency such that the difference is below a second value for the load estimate being indicative of an equivalent parallel load resistance below a second threshold, the first value being higher than the second value and the first threshold being higher than the second threshold.

13. The power transmitter of claim 1 wherein the drive frequency adapter is arranged to adapt the drive frequency in response to the load estimate during a power transfer phase

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

the method comprising;

generating a drive signal for the resonance circuit, the drive signal having a drive frequency;

aligning the resonance frequency of the resonance circuit with the drive frequency 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,

generating a load estimate reflecting an equivalent load resistor for the transmitter inductor reflecting a loading of the power transfer signal; and

adapting the drive frequency in response to the load estimate;

wherein adapting the drive frequency comprises adapting the drive frequency to be further away from a resonance frequency of a power receiving resonance circuit of the power receiver for a load estimate indicative of a first equivalent parallel load resistance than for a load estimate indicative of a second equivalent parallel load resistance, the first equivalent parallel load resistance being lower than the second equivalent parallel load resistance.

15. A wireless power transfer system comprising power transmitter and a power receiver, the power transmitter comprising:

a resonance circuit comprising a capacitive impedance and an inductive impedance, the inductive impedance comprising a transmitter inductor for generating a power transfer signal for wirelessly transferring power to the power receiver;

a driver generating a drive signal for the resonance circuit, the drive signal having a drive frequency;

a resonance modification circuit for aligning the resonance frequency of the resonance circuit with the drive frequency 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, a load estimator for generating a load estimate reflecting an equivalent load resistor for the transmitter inductor reflecting a loading of the power transfer signal; and

a drive frequency adapter for adapting the drive frequency in response to the load estimate;

wherein the drive frequency adapter is arranged to adapt the drive frequency to be further away from a resonance frequency of a power receiving resonance circuit of the power receiver for a load estimate indicative of a first equivalent parallel load resistance than for a load estimate indicative of a second equivalent parallel load resistance, the first equivalent parallel load resistance being lower than the second equivalent parallel load resistance.