Thermal barrier for wireless power transfer

#This application is the U.S. National Phase application under 35 U.S.C. § 371 of International Application No. PCT/EP2014/072702, filed on Oct. 23, 2014, which claims the benefit European Patent Application No. 13190789.1, filed on Oct. 30, 2013. These applications are hereby incorporated by reference herein.

#The invention relates to wireless power transfer and in particular, but not exclusively, to wireless power transfer for heating appliances.

#Many systems require a wiring and/or electrical contacts in order to supply electrical power to devices. Omitting these wires and contacts provides for an improved user experience. Traditionally, this has been achieved using batteries located in the devices but this approach has a number of disadvantages including extra weight, bulk and the need to frequently replace or recharge the batteries. Recently, the approach of using wireless inductive power transfer has received increasing interest.

#Embodiments of the invention will be described, by way of example only, with reference to the drawings, in which

#FIG. 1 is an illustration of a wireless power transfer system;

#FIG. 2 is an illustration of a wireless power transfer system;

#The following description focuses on embodiments of the invention applicable to a kitchen application, and in particular to a mixed cooking and preparation zone kitchen environment using wireless power transfer. However, it will be appreciated that the invention is not limited to this application but may be applied to many other applications and wireless power transfer systems.

#FIG. 3 illustrates an example of a power transfer system in accordance with some embodiments of the invention. The power transfer system comprises a power transmitter 101 which includes (or is coupled to) a transmitter coil/inductor 105. The system further comprises a power receiver 111 which includes (or is coupled to) a receiver coil/inductor 101. The receiver coil/inductor may in some embodiments be a conductive element such as specifically a heating element, i.e. it may be anything in which an electrical signal is induced when exposed to a varying magnetic field.

#The system provides a wireless inductive power transfer from the power transmitter 101 to the power receiver 111. Specifically, the power transmitter 101 generates a power signal which is propagated as a magnetic flux by the transmitter coil 105. The power signal may typically have a frequency between around 20 kHz to 200 kHz. The transmitter coil 105 and the receiver coil 301 are loosely coupled and thus the receiver coil 301 picks up (at least part of) the power signal from the power transmitter 101. Thus, the power is transferred from the power transmitter 101 to the power receiver 111 via a wireless inductive coupling from the transmitter coil 105 to the receiver coil 301. The term power signal may be used to refer to the magnetic or inductive signal between the transmitter coil 105 and the receiver coil 301 (the magnetic flux signal), but it will be appreciated that by equivalence it may also be considered and used as a reference to the electrical signal provided to the transmitter coil 105, or indeed to the electrical signal of the receiver coil 301.