Inductive power transfer converters and system
An IPT system for wireless power transfer is provided, in particular an IPT system capable of operating at high frequencies. In one aspect there is provided an IPT transmitter comprising a push-pull resonant converter having a resonant frequency and configured to operate at a switching frequency below the resonant frequency and dependent on a switching characteristic of a second converter configured to inductively couple to said transmitter.
1. An inductive power transfer (IPT) transmitter comprising:
a push-pull resonant first converter having a resonant frequency, and configured to operate at a switching frequency below the resonant frequency and dependent on a switching characteristic of a second converter configured to inductively couple to said transmitter,
wherein a switching of the first and second converter is arranged to operate using phase angle control whereby a phase angle of the switching is adjusted in response to the switching characteristic.
2. The transmitter according to claim 1 , wherein the switching characteristic comprises one or more of the following: relative phase difference between switching signals of the first and second converters; a switching signal of the second converter; an indication of switch positions of the second converter.
3. The transmitter according to claim 1 , wherein the switching of the first converter is arranged to operate in synchronism with the switching of the secondary converter, or at an offset to said switching.
4. The transmitter according to claim 1 , wherein the switching frequency is set at a frequency sufficiently below the resonant frequency corresponding to a predetermined range of second converter loading and coupling between the first and second converters.
5. The transmitter according to claim 1 , further comprising:
means for determining a switching characteristic corresponding to the switching of the second converter when inductively coupled to the transmitter; and
a switch controlled in order to switch the first converter at the switching frequency.
6. The transmitter according to claim 5 , wherein the means for determining a switching characteristic comprises one or more of the following: a sense winding to measure magnetic fields produced by the first or second converter; communication means for receiving a signal from the second converter which is indicative of the switching characteristic.
7. The transmitter according to claim 1 , wherein the switching of the first and second converter is arranged to turn on/off in order to regulate power transfer of the first converter.
8. The transmitter according to claim 1 , having primary tracks or inductive power transmitter coils which operate as inductors for the push-pull resonant converter.
9. The transmitter according to claim 1 , and arranged to operate at a switching frequency above 1 MHz.
10. An inductive power transfer (IPT) system comprising an inductive power transfer IPT transmitter according to claim 1 , and a second converter inductively coupled to said transmitter.
11. The system according to claim 10 , wherein the second converter comprises a push-pull resonant converter in which a switching is arranged to switch in a manner corresponding to a switching of the inductive power transfer converter.
12. The system according to claim 11 , wherein the switching of the second converter is arranged to operate at a switching frequency below a resonant frequency of the second converter.
13. The transmitter according to claim 1 , further comprising switching means operated so as to regulate an input or output voltage of the resonant converter.
14. A method of operating an inductive power transfer (IPT) system comprising a first push-pull resonant converter having a resonant frequency, the method comprising:
determining a switching characteristic of a second converter which is inductively coupled to the first converter;
switching the first converter at a switching frequency below the resonant frequency of the first converter and dependent on the switching characteristic; and
switching the first and second converter using phase angle control whereby a phase angle of the switching is adjusted in response to the switching characteristic.
15. An inductive power transfer (IPT) system pick up to receive electrical power from a first converter, the inductive power transfer (IPT) system pick up comprising:
a push-pull resonant converter having a resonant frequency;
the push-pull resonant converter having switching means operated at a switching frequency below the resonant frequency,
wherein a switching of the first converter and the inductive power transfer (IPT) system pick up is arranged to operate using phase angle control whereby a phase angle of the switching is adjusted in response to a switching characteristic of the inductive power transfer (IPT) system pick up.
16. An inductive power transfer (IPT) system comprising a primary converter inductively coupled to an inductive power transfer (IPT) system pick-up according to claim 15 .
17. The system according to claim 16 , wherein the switching frequency of the primary converter and inductive power transfer (IPT) system pick-up are substantially equal.
18. The system according to claim 15 , wherein the primary converter further comprises means for determining a switching characteristic of the inductive power transfer (IPT) system pick-up and wherein the switching frequency is arranged to be further dependent on said switching characteristic.
19. The transmitter according to claim 13 , wherein the switching means is configured to be turned on/off in order to regulate.