This disclosure provides systems, methods and apparatus for wireless power transfer and particularly wireless power transfer to remote system such as electric vehicles. In one aspect a circuit for wireless power transfer is provided. The circuit comprises an inductive element for receiving wireless power from a magnetic field associated with a wireless power transfer transmitter device. The circuit further comprises an output configured to be connected to a load. The circuit further comprises a voltage detector configured to detect the voltage across the load. The circuit further comprises at least one switching element between the inductive element and the output. The circuit further comprises a controller configured to maintain a current in the inductive element substantially constant as the voltage detected across the load varies.