Universal demodulation and modulation for data communication in wireless power transfer

• US 8,554,165 B2
• Filed: 09/11/2012
• Issued: 10/08/2013
• Est. Priority Date: 09/14/2009
• Status: Active Grant

• Current Assignee: ConvenientPower HK Limited
• Original Assignee: ConvenientPower HK Limited
• Inventors: Liu, Xun, Choi, Wai Pong
• Primary Examiner(s): Dao, Minh D
• Application Number:
  US13/610,578
• Publication Number:
  US 20130017798A1
• Time in Patent Office: 392 Days
• Field of Search: 455/293, 455/292, 455/309, 455/41.1, 455/41.2, 455/295, 455/312, 455/337, 340/572.4, 340/572.7
• US Class Current: 455/293
• CPC Class Codes: H02J 50/12 of the resonant type
• CPC Class Codes: H02J 50/402 the two or more transmitting or the two or more receiving devices being integrated in the same unit, e.g. power mats with several coils or antennas with several sub-antennas
• 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: H04B 5/26 using coils
• CPC Class Codes: H04B 5/72 for local intradevice communication
• CPC Class Codes: H04B 5/77 for interrogation
• CPC Class Codes: H04B 5/79 for data transfer in combination with power transfer

Abstract

The present invention provides a universal demodulation circuit, a load modulation circuit and associated method, and an associated power transfer system, all suitable for use in wireless power transfer. A power receiver with signal strength detection is also provided. Modulation of the impedance of the demodulation circuit is determinable by detecting the amplitudes of a first and a second electrical parameter, thereby demodulating data communicated by modulation of the impedance of the demodulation circuit. The modulation circuit has a communication modulator to modulate the impedance of the modulation circuit, to a predetermined minimum modulation depth, thereby to communicate data.

Claims

1. A modulation circuit for a wireless power transfer device, the modulation circuit having a communication modulator to modulate the impedance of the modulation circuit thereby to communicate data, the communication modulator selected to modulate the impedance to a predetermined minimum modulation depth, wherein the impedance has an active part and a reactive part, a vector sum of the active and reactive parts being equal to the impedance, and wherein the communication modulator modulates one or both of the active and reactive parts to modulate one or both of the amplitude and phase of the impedance.

2. A modulation circuit according to claim 1 including a second power transfer coil for inductive coupling with a first power transfer coil in a demodulation circuit, such that modulation of the impedance of the modulation circuit results in corresponding modulation of the impedance of the demodulation circuit, thereby allowing data to be communicated wirelessly from the modulation circuit to the demodulation circuit.

3. A modulation circuit according to claim 2 forming part of a wireless power receiver, wherein the second power transfer coil can receive power wirelessly from the first power transfer coil.

4. A modulation circuit according to claim 1 wherein the communication modulator includes a communication resistor connected in parallel with a load in the modulation circuit, the communication resistor adapted to be switched on and off to modulate the impedance of the modulation circuit.

5. A modulation circuit according to claim 4 including a first capacitor connected in series after a second capacitor, the communication resistor connected between the first and second capacitors and in parallel with the first capacitor.

6. A modulation circuit according to claim 5 including a second power transfer coil connected in series before the second capacitor.

7. A modulation circuit according to claim 4 including a capacitor connected in series before the communication resistor and the load.

8. A modulation circuit according to claim 7 including a second power transfer coil connected in series before the capacitor.

9. A modulation circuit according to claim 1 wherein the communication modulator includes a communication capacitor connected in parallel with a load in the modulation circuit, the communication capacitor adapted to be switched on and off to modulate the impedance of the modulation circuit.

10. A modulation circuit according to claim 9 including a second capacitor connected in series before the communication capacitor and the load.

11. A modulation circuit according to claim 10 including a second power transfer coil connected in series before the second capacitor.

12. A modulation circuit according to claim 1 wherein the active and reactive parts are in quadrature and the voltage across the modulation circuit can be assumed constant, such that the predetermined minimum modulation depth can be expressed as

13. A modulation circuit according to claim 1 wherein the active and reactive parts are in quadrature and the total current entering the modulation circuit can be assumed constant, such that the predetermined minimum modulation depth can be expressed as

14. A modulation circuit according to claim 1 wherein the modulation circuit is passive.

15. A method of modulating the impedance of a modulation circuit to communicate data, the method including:

determining the capacity of a communication modulator such that the communication modulator can modulate the impedance to a predetermined minimum modulation depth;

providing the modulation circuit with the communication modulator, such that the impedance of the modulation circuit can be modulated with the communication modulator, thereby to communicate data, wherein the impedance has an active part and a reactive part, a vector sum of the active and reactive parts being equal to the impedance, and wherein determining the capacity of the communication modulator includes determining the vector sum of the active and reactive parts such that the impedance can be modulated to a predetermined minimum modulation depth by modulating one or both of the amplitude and phase of the impedance with the communication modulator.

16. A method according to claim 15 including providing the modulation circuit with a second power transfer coil for inductive coupling with a first power transfer coil in a demodulation circuit, such that modulating the impedance of the modulation circuit results in corresponding modulation of the impedance of the demodulation circuit, thereby allowing data to be communicated wirelessly from the modulation circuit to the demodulation circuit.

17. A method according to claim 16 including connecting the modulation circuit into a wireless power receiver, wherein power can be wirelessly transferred from the first power transfer coil to the second power transfer coil.

18. A method according to claim 15 including providing the communication modulator with a communication resistor connected in parallel with a load in the modulation circuit, the communication resistor capable of being switched on and off to modulate the impedance of the modulation circuit.

19. A method according to claim 18 including providing the modulation circuit with a first capacitor connected in series after a second capacitor, the communication resistor connected between the first and second capacitors and in parallel with the first capacitor.

20. A method according to claim 19 including providing the modulation circuit with a second power transfer coil connected in series before the second capacitor.

21. A method according to claim 18 including providing the modulation circuit with a capacitor connected in series before the communication resistor and the load.

22. A method according to claim 21 including providing the modulation circuit with a second power transfer coil connected in series before the capacitor.

23. A method according to claim 15 including providing the communication modulator with a communication capacitor connected in parallel with a load in the modulation circuit, the communication capacitor capable of being switched on and off to modulate the impedance of the modulation circuit.

24. A method according to claim 23 including providing the modulation circuit with a second capacitor connected in series before the communication capacitor and the load.

25. A method according to claim 24 including providing the modulation circuit with a second power transfer coil connected in series before the second capacitor.

26. A method according to claim 15 wherein the active and reactive parts are in quadrature and the voltage across the modulation circuit can be assumed constant, and the method includes calculating the capacity of the communication modulator required to satisfy the predetermined minimum modulation depth by using the following expression:

27. A method according to claim 15 wherein the active and reactive parts are in quadrature and the total current entering the modulation circuit can be assumed constant, and the method includes calculating the capacity of the communication modulator required to satisfy the predetermined minimum modulation depth by using the following expression:

28. A method according to claim 15 wherein the modulation circuit is passive.