| US 7,554,316 B2 | ||
| Controlling inductive power transfer systems | ||
| Michael Craig Stevens, Mooloolaba (Australia); Alexander Charles Knill, Cambridge (United Kingdom); and John Robert Dunton, Suffolk (United Kingdom) | ||
| Assigned to Access Business Group International LLC, Ada, Mich. (US) | ||
| Appl. No. 11/569,029 PCT Filed May 11, 2005, PCT No. PCT/GB2005/001833 § 371(c)(1), (2), (4) Date Nov. 13, 2006, PCT Pub. No. WO2005/109598, PCT Pub. Date Nov. 17, 2005. |
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| Claims priority of application No. 0410503.7 (GB), filed on May 11, 2004. | ||
| Prior Publication US 2007/0216392 A1, Sep. 20, 2007 | ||
| Int. Cl. H01F 17/00 (2006.01) | ||
| U.S. Cl. 323—355 [307/104] | 37 Claims |
| 1. An inductive power transfer system comprising a primary unit, having a primary coil and electrical drive circuitry connected
to the primary coil for applying electrical drive signals thereto so as to generate an electromagnetic field, and the system
also comprising at least one secondary device, separable from the primary unit and having a secondary coil adapted to couple
with said field when the secondary device is in proximity to the primary unit so that power can be transferred inductively
from the primary unit to the secondary device without direct electrical conductive contacts therebetween, wherein the primary
unit further comprises:
a control unit operable to cause a circuit including said primary coil to operate, during a measurement period, in an undriven
resonating condition in which the application of said drive signals to said primary coil by said electrical drive circuitry
is suspended so that energy stored in said circuit decays over the course of said period; and
a decay measurement unit operable to take one or more measures of such energy decay during said period;
wherein said control unit is further operable, in dependence upon said one or more energy decay measures, to control the electrical
drive circuitry so as to restrict or stop inductive power transfer from the primary unit.
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