Wireless power transfer system

1 . A device comprising:

a power transfer coil, wherein the power transfer coil is arranged to generate a power transfer signal;

a power transfer driver,

wherein the power transfer driver is arranged to generate a power transfer drive signal for the power transfer coil,

wherein the power transfer drive signal uses a plurality of repeating time frames during a power transfer phase,

wherein each of the plurality of repeating time frames comprises at least a power transfer time interval and a communication time interval,

wherein the power transfer driver is arranged to generate the power transfer drive signal during the power transfer time interval and to not generate the power transfer drive signal during the communication time interval;

a communication coil, wherein the communication coil is arranged to generate a communication carrier signal;

a communication driver, wherein the communication driver is arranged to generate a communication drive signal for the communication coil so as to generate the communication carrier signal; and

a communication processor, wherein the communication processor is arranged to communicate with a power receiver using modulation of the communication carrier signal;

wherein the communication driver is arranged to generate the communication drive signal during the communication time interval and during the power transfer time interval except for a plurality of timing gaps,

wherein a total combined duration of the plurality of timing gaps is no more than 50% of a duration of the power transfer time interval,

wherein the plurality of timing gaps comprises a predetermined pattern.

2 . The device of claim 1 , wherein the communication driver is arranged to generate the communication drive signal such that a first timing gap of the plurality of timing gaps has a fixed time offset to a timing of the power transfer time interval.

3 . The device of claim 1 , wherein the power transfer time interval comprises the plurality of timing gaps.

4 . The device of claim 1 , wherein the predetermined pattern has a same duration and a same time difference between consecutive timing gaps in each of the plurality of repeating time frames.

5 . The device of claim 1 , wherein the predetermined pattern is selected from a plurality of predetermined patterns.

6 . The device of claim 1 ,

wherein the power transfer driver is supplied by a time varying power supply signal,

wherein the communication driver synchronizes a timing of the plurality of timing gaps to the varying power supply signal.

7 . The device of claim 1 , wherein the communication driver is arranged to synchronizes an end of a timing gap of the plurality of timing gaps to and end of the power transfer time interval.

8 . The device of claim 1 ,

wherein the communication processor is arranged to exchange a configuration message with the power receiver,

wherein the configuration message comprises an indication of a property of at least one timing gap of the plurality of timing gaps.

9 . The device of claim 1 , wherein the total combined duration of the plurality of timing gaps is no more than 5% of a duration of the power transfer time interval.

10 . A device comprising:

an power extraction circuit, wherein the power extraction circuit is arranged to extract power from a power transfer signal during at least one power transfer time interval,

wherein the power transfer signal comprise a plurality of repeating time frames of a power transfer phase,

wherein each of the plurality of repeating time frames comprises the power transfer time interval and a communication time interval,

wherein the power transfer signal is present during the power transfer time interval and not present during the communication time interval;

a communication coil,

wherein the communication coil is arranged to receive a communication carrier signal,

wherein the communication carrier signal is present during the communication time interval and during the power transfer time interval except for a plurality of timing gaps,

wherein a total combined duration of the timing gaps is no more than 50% of a duration of the power transfer time interval;

a communication circuit, wherein the communication circuit is arranged to communicate with the power transmitter using modulation of the communication carrier signal during the communication time interval; and

a synchronizer circuit,

wherein the synchronizer circuit is arranged to synchronize an operation of the power receiver to a timing of the plurality of timing gaps,

wherein the plurality of timing gaps comprises a predetermined pattern.

11 . The device of claim 10 , further comprising a power extractor circuit,

wherein the power extractor circuit is coupled to the communication coil,

wherein the power extractor circuit is arranged to extract a power signal from the communication coil,

wherein the power extractor circuit is arranged to provide power to the device.

12 . A method comprising:

generating a power transfer signal during a power transfer phase,

wherein the power transfer phase uses a plurality of repeating time frames,

wherein each of the plurality of repeating time frames comprises at least a power transfer time interval and a communication time interval,

wherein the power transfer signal is generated during the power transfer time interval but not during the communication time interval;

generating a communication carrier signal;

communicating with a power receiver using modulation of the communication carrier signal;

wherein the communication is present during the communication time interval and during the power transfer time interval except for a plurality of timing gaps,

wherein a total combined duration of the plurality of timing gaps is no more than 50% of a duration of the power transfer time interval,

wherein the plurality of timing gaps comprises a predetermined pattern.

13 . A method comprising:

extracting power from the power transfer signal during at least one power transfer time interval,

wherein the power transfer signal comprise a plurality of repeating time frames of a power transfer phase,

wherein each of the plurality of repeating time frames comprises the power transfer time interval and a communication time interval,

wherein the power transfer signal is present during the power transfer time interval and not present during the communication time interval;

receiving a communication carrier signal,

wherein the communication carrier signal is present during the communication time interval and during the power transfer time interval except for a plurality of timing gaps,

wherein a total combined duration of the timing gaps is no more than 50% of a duration of the power transfer time interval;

communicating with the power transmitter using modulation of the communication carrier signal during the communication time interval; and

synchronizing an operation of the power receiver to a timing of the plurality of timing gaps,

wherein the plurality of timing gaps comprises a predetermined pattern.

14 . The device of claim 10 , wherein a first timing gap of the plurality of timing gaps has a fixed time offset to a timing of the power transfer time interval.

15 . The device of claim 10 , wherein the power transfer time interval comprises the plurality of timing gaps.

16 . The device of claim 10 , wherein the predetermined pattern has a same duration and a same time difference between consecutive timing gaps in each of the plurality of repeating time frames.

17 . The device of claim 10 , wherein the predetermined pattern is selected from a plurality of predetermined patterns.

18 . The device of claim 10 , wherein a timing of the plurality of timing gaps to the varying power supply signal.

19 . The device of claim 10 , wherein an end of a timing gap of the plurality of timing gaps is synchronized to and end of the power transfer time interval.

20 . The device of claim 10 ,

wherein the communication circuit is arranged to exchange a configuration message with a power transmitter,

wherein the configuration message comprises an indication of a property of at least one timing gap of the plurality of timing gaps.

21 . The device of claim 10 , wherein the total combined duration of the plurality of timing gaps is no more than 5% of a duration of the power transfer time interval.

22 . A non-transitory computer-readable medium storing a computer program, wherein the computer program when executed on a processor performs the method as claimed in claim 12 .

23 . The method of claim 12 , further comprising generating the communication drive signal such that a first timing gap of the plurality of timing gaps has a fixed time offset to a timing of the power transfer time interval.

24 . The method of claim 12 , wherein the power transfer time interval comprises the plurality of timing gaps.

25 . The method of claim 12 , wherein the predetermined pattern has a same duration and a same time difference between consecutive timing gaps in each of the plurality of repeating time frames.

26 . The method of claim 12 , wherein the predetermined pattern is selected from a plurality of predetermined patterns.

27 . The method of claim 12 , further comprising supplying a time varying power supply signal, wherein the communication driver synchronizes a timing of the plurality of timing gaps to the varying power supply signal.

28 . The method of claim 12 , further comprising synchronizing an end of a timing gap of the plurality of timing gaps to and end of the power transfer time interval.

29 . The method of claim 12 , further comprising exchanging a configuration message with the power receiver, wherein the configuration message comprises an indication of a property of at least one timing gap of the plurality of timing gaps.

30 . The method of claim 12 , wherein the total combined duration of the plurality of timing gaps is no more than 5% of a duration of the power transfer time interval.

31 . A non-transitory computer-readable medium storing a computer program, wherein the computer program when executed on a processor performs the method as claimed in claim 13 .

32 . The method of claim 13 , wherein a first timing gap of the plurality of timing gaps has a fixed time offset to a timing of the power transfer time interval.

33 . The method of claim 13 , wherein the power transfer time interval comprises the plurality of timing gaps.

34 . The method of claim 13 , wherein the predetermined pattern has a same duration and a same time difference between consecutive timing gaps in each of the plurality of repeating time frames.

35 . The method of claim 13 , wherein the predetermined pattern is selected from a plurality of predetermined patterns.

36 . The method of claim 13 , wherein a timing of the plurality of timing gaps to the varying power supply signal.

37 . The method of claim 13 , wherein an end of a timing gap of the plurality of timing gaps is synchronized to and end of the power transfer time interval.

38 . The he method of claim 13 , further comprising exchanging a configuration message with a power transmitter, wherein the configuration message comprises an indication of a property of at least one timing gap of the plurality of timing gaps.

39 . The method of claim 13 , wherein the total combined duration of the plurality of timing gaps is no more than 5% of a duration of the power transfer time interval.