Foreign object detection using wireless power receiver's response to modified transmitter behavior

Patent metadata

Field	Value
Publication number	US-11728690-B2
Application number	US-202016915940-A
Country	US
Kind code	B2
Filing date	Jun 29, 2020
Priority date	Jun 29, 2020
Publication date	Aug 15, 2023
Grant date	Aug 15, 2023

Abstract

A wireless power transmitter pulses the transmit power level unresponsively to the wireless power receiver's power requests in order to perform foreign object detection (FOD). The FOD is performed by the transmitter analyzing the receiver's responses to the pulsed power. Some embodiments avoid mistaking FOD for coil misalignment. Other features are also provided.

First claim

What is claimed is:

1. A system comprising a wireless power transmitter for performing a wireless power transfer (WPT) operation, the system comprising:
an input for receiving power;
a transmit coil;
a circuit configured to generate an AC power signal in the transmit coil from power received at the input in order to perform WPT from the transmitter to a wireless power receiver in the WPT operation, the circuit comprising a controller configured to operate the transmitter to:
(A) perform normal operation in which the transmitter generates the AC power signal to transmit power to the wireless power receiver, wherein in normal operation:
the transmitter receives feedback messages from the wireless power receiver; and
the transmitter adjusts the AC power signal in correspondence with the feedback messages;
(B) interrupt the normal operation to perform one or more foreign object detection (FOD) tests to detect FO interference, wherein each FOD test comprises a first operation, a second operation, and a third operation, and in each FOD test:
in the first operation, the transmitter changes the AC power signal not to correspond to the feedback messages; then
in the second operation, the transmitter receives one or more new feedback messages from the wireless power receiver; and
in the third operation, the transmitter determines whether or not the one or more new feedback messages match the AC power signal change in the first operation to indicate presence or absence of a foreign object.

2. The system of claim 1 , wherein:
the circuit comprises a memory for storing modification data which describe, for each FOD test:
(i) the AC power signal change for the first operation; and
(ii) a corresponding expected new feedback message for the second operation in the absence of a foreign object;
wherein, during the FOD test:
in the first operation, the transmitter changes the AC power signal in accordance with memory description (i); and
in the third operation, the transmitter determines whether or not the one or more new feedback messages received in the second operation match memory description (ii).

3. The system of claim 2 , wherein the first operation comprises the transmitter generating a pulse of the AC power signal, the modification data comprising a width of the pulse and an amplitude of the pulse.

4. The system of claim 2 , wherein:
the circuit is further configured to write memory descriptions (i) and (ii) to the memory during wireless transfer of power.

5. The system of claim 4 , wherein writing the memory descriptions (i) and (ii) to the memory comprises determining one or more AC power signal changes for (i), and for each determined AC power signal change for (i) performing, in the absence of a FO, operations of:
(a) operating the transmitter to perform the determined AC power signal change for (i) in the absence of a FO;
(b) receiving by the transmitter one or more feedback messages from the wireless power receiver in response to (a); and
(c) writing to the memory, the modification data describing the AC power signal change determined in (a) and the corresponding one or more feedback messages received in (b).

6. The system of claim 2 , wherein the circuit is configured to write the modification data to the memory when there is no wireless transfer of power.

7. The system of claim 2 , wherein the memory description (ii) describes a plurality of expected new feedback messages each of which is referenced in the memory to a coil alignment condition, wherein the circuit is configured to determine a coil alignment condition present in the WPT operation, and the third operation is performed using the expected new feedback message referenced to the coil alignment condition determined as present in the WPT operation.

8. The system of claim 1 , wherein the first operation comprises modifying a rms power wirelessly transmitted by the transmitter.

9. A system comprising a wireless power transmitter configured to generate an AC power signal to transmit power to a wireless power receiver, the transmitter being configured to receive, from the wireless power receiver, feedback messages regarding the AC power signal, the system comprising:
an input for receiving power;
a transmit coil;
a circuit for generating the AC power signal in the transmit coil from power received at the input, the circuit comprising:
a memory for storing modification data which describe one or more modifications of the transmitter's operation to be performed in one or more foreign object detection (FOD) tests, wherein in each FOD test the transmitter performs a modification to increase or decrease transmitted power in accordance with the modification data non-responsively to the feedback messages received by the transmitter from the wireless power receiver while wirelessly transmitting power to the wireless power receiver, wherein for each modification, the modification data further describe an expected subsequent behavior of the wireless power receiver in response to the modification performed by the transmitter in the absence of foreign object (FO) interference;
a controller configured to operate the transmitter to:
receive the feedback messages from the wireless power receiver;
generate the AC power signal outside of the FOD tests responsively to the feedback messages received by the transmitter from the wireless power receiver;
perform the one or more foreign object detection (FOD) tests to detect FO interference, each FOD test comprising:
operating the transmitter to perform at least one said modification non-responsively to the feedback messages from the wireless power receiver in accordance with the modification data stored in the memory, and determining if the wireless power receiver's subsequent behavior matches the expected subsequent behavior described by the modification data for the at least one said modification.

10. The system of claim 9 , wherein for each modification, the modification data comprises a pair of values <dPtx,dPrx>, wherein:
dPtx is a relative increase or decrease of transmitted power for the modification; and
dPrx is an expected subsequent relative change of power requested by the wireless power receiver in response to the transmitter changing the transmitted power by dPtx.

11. A method for performing a wireless power transfer (WPT) operation in which a wireless power transmitter transmits power to a wireless power receiver, the method comprising:
(A) generating, by the transmitter, an AC power signal transmitting power to the wireless power receiver, wherein:
the transmitter receives requests from the wireless power receiver regarding the AC power signal; and
the transmitter adjusts the AC power signal based on the requests;
(B) performing one or more foreign object detection (FOD) tests to detect FO interference, wherein each FOD test comprises a first operation, a second operation, and a third operation, and in each FOD test:
in the first operation the transmitter changes the AC power signal to differ from the requests; then
in the second operation, the transmitter receives one or more new requests from the wireless power receiver; and
in the third operation, the transmitter determines whether or not the one or more new requests match the AC power signal change in the first operation to indicate presence or absence of a foreign object.

12. The method of claim 11 , further comprising storing, in a memory of the transmitter, a description of the AC power signal change for the first operation, and storing in the memory a description of a corresponding expected new request for the second operation if no foreign object is present;
wherein the t

Assignees

• Renesas Electronics America Inc

Inventors

• Smith Nicholaus
• Mehas Gustavo
• Qi Tao

Classifications

• H02J2105/44

  Portable electronic devices · CPC title

• H02J50/60 Primary

  responsive to the presence of foreign objects, e.g. detection of living beings · CPC title

• H02J50/12 Primary

  of the resonant type · CPC title

• H02J50/80

  involving the exchange of data, concerning supply or distribution of electric power, between transmitting devices and receiving devices · CPC title

• H02J50/90

  involving detection or optimisation of position, e.g. alignment · CPC title