Method and device for performing a presence check for wireless charging listener devices

Patent metadata

Field	Value
Publication number	US-12407195-B2
Application number	US-202217936926-A
Country	US
Kind code	B2
Filing date	Sep 30, 2022
Priority date	Sep 30, 2022
Publication date	Sep 2, 2025
Grant date	Sep 2, 2025

Abstract

A wireless charging (WLC) poller device and WLC listener device are provided. A method for performing a presence check of the WLC listener device includes providing a radio frequency (RF) presence check signal. An input signal from the antenna by the poller device is received concurrently with the transmission of the RF presence check signal. A rate of change of a magnitude of the input signal is measured during the transmission of the presence check signal. A difference between the input signal and an expected input signal is determined. A presence of the listener device is detected if an absolute value of the measured rate of change of the input signal is above a threshold rate of change, and the difference between the input signal and the expected input signal is within a predetermined distance. Prior to the presence check, a capacitor of the WLC listener device may be discharged.

First claim

What is claimed is:

1. A method for performing a presence check of a wireless charging (WLC) listener device by a WLC poller device, the method comprising:
transmitting a radio frequency (RF) presence check signal at an antenna of the WLC poller device;
sampling a input signal from the antenna by the WLC poller device concurrently with the transmission of the RF presence check signal;
measuring a rate of change of a magnitude of the input signal during the transmission of the presence check signal;
determining a difference between the input signal and an expected input signal; and detecting a presence of the WLC listener device if the measured rate of change of the input signal is above a threshold rate of change, and the difference between the input signal and the expected input signal is within a predetermined range.

2. The method of claim 1 , further comprising configuring an attenuator in a receiver circuit of the WLC poller device to provide uniform gain from the antenna.

3. The method of claim 1 , further comprising adapting attenuation of a receiver circuit in the WLC poller based on a gain of the input signal.

4. The method of claim 1 , further comprising discharging a capacitor in the WLC listener device before the RF presence check signal is transmitted.

5. The method of claim 1 ,
wherein determining a difference between the input signal and the expected input signal further comprises determining a difference between an average of input signals and an expected average of input signals.

6. The method of claim 1 , further comprising:
determining that the WLC listener device is present;
wirelessly charging the WLC listener device with the WLC poller device;
detecting completion of the wireless charging;
separating the WLC poller device and the WLC listener device to end the wireless charging;
detecting removal of an input signal from a capacitor of the WLC listener device; and
in response to detecting removal of the input signal, shorting first and second terminals of a capacitor through a switch, coupled to the first and second terminals and in parallel with the capacitor, to discharge the capacitor prior to transmission of another RF presence check signal.

7. The method of claim 1 ,
further comprising identifying a WLC listener device by detecting the change in the input signal on the antenna during transmission of the presence check signal.

8. The method of claim 1 ,
further comprising storing the input signal for use as the expected input signal in response to detection of the presence of the WLC listener device.

9. The method of claim 1 ,
wherein the RF presence check signal and the input signal include complex vectors.

10. A wireless charging (WLC) poller device comprising:
a transmitter circuit coupled to an antenna, the transmitter circuit configured to transmit a radio frequency (RF) presence check via the antenna;
a receiver circuit coupled to the antenna, the receiver circuit configured to sample an input signal at the antenna concurrently with the transmission of the presence check;
a control circuit coupled to the transmitter circuit and to the receiver circuit, the control circuit measures a rate of change of a magnitude of the input signal during the transmission of the presence check signal, determines a difference between the input signal and an expected input signal, wherein a presence of a WLC listener device is detected if the measured rate of change of the input signal is above a threshold rate of change, and the difference between the input signal and the expected input signal is within a predetermined range; and
a memory coupled to the control circuit.

11. The WLC poller device of claim 10 ,
wherein an attenuation of the receiver circuit is configured to provide uniform gain of input signals at the antenna.

12. The WLC poller device of claim 10 ,
wherein an attenuation of the receiver circuit is adapted based on a gain of the input signal.

13. The WLC poller device of claim 10 ,
wherein the RF presence check signal and the input signal are expressed as complex vectors.

14. The WLC poller device of claim 10 ,
wherein the WLC listener device is identified by detection of a change in a input signal on the antenna during the transmission of the presence check signal.

15. The WLC poller device of claim 10 ,
wherein the WLC poller device provides wireless charging according to a near field communication (NFC) protocol.

16. The WLC poller device of claim 10 :
wherein the expected input signal corresponds to an earlier seen input signal from a particular WLC listener device; and
wherein if the difference between the input signal and the expected input signal is within the predetermined range, then the WLC poller device knows that the WLC listener device is the particular WLC listener device.

17. A wireless charging (WLC) listener device comprising:
a receiver circuit coupled to an antenna, the receiver circuit configured to be coupled with a WLC poller device via the antenna;
a rectifier circuit having an input coupled to the receiver circuit, the rectifier circuit configured to convert a radio frequency (RF) signal from a WLC poller device to a direct current (DC) voltage at an output of the rectifier circuit,
wherein a capacitor having first and second terminals is coupled between the output of the rectifier circuit, and a reference terminal;
a switch coupled to the first and second terminals and in parallel with the capacitor and having a first terminal coupled to the output of the rectifier circuit, and a second terminal coupled to the reference terminal; and
a control circuit coupled to control operation of the WLC listener device,
wherein a battery coupled to the WLC listener device is charged in response to the WLC poller device receiving a favorable response to an RF presence check signal and the WLC listener device being within a charging range, and
wherein in response to the WLC listener device detecting withdraw of the WLC poller device from within the charging range, the control circuit configured to cause the switch to short the first and second terminals of the capacitor to discharge the capacitor before the WLC poller device transmits another RF presence check signal.

18. The WLC listener device of claim 17 ,
wherein the device is implemented on one or more integrated circuits.

19. The WLC listener device of claim 17 ,
wherein the device communicates with the WLC poller device using a near field communication (NFC) protocol.

20. The WLC listener device of claim 17 ,
wherein the RF presence check signal is expressed as a complex vector.

21. The WLC listener method of claim 17 ,
wherein a charging curve of the capacitor is used by the WLC poller device to identify the WLC listener device.

Assignees

• Nxp Bv

Inventors

• Wobak Markus
• Merlin Erich
• Neffe Ulrich

Classifications

• H02J7/80

  including monitoring or indicating arrangements · CPC title

• H02J7/40

  characterised by the exchange of charge or discharge related data · CPC title

• H01F38/14

  Inductive couplings {(for wireless supply or distribution of electric power using inductive coupling H02J50/10)} · CPC title

• H02J50/20

  using microwaves or radio frequency waves · CPC title

• H02J50/90

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