Wireless power receiver circuits that provide constant voltage or current to an electrical load, and methods

A method for receiving wireless power in a wireless power transfer system, the wireless power receiver circuit comprising:

• with a resonator circuit of a wireless power receiver circuit, operating in an active state or in an idle state, wherein in the active state, the resonator circuit resonates at a frequency of an ambient magnetic field generated by a wireless power transmitter of the wireless power transfer system and outputs a radio frequency (RF) output signal, the resonator circuit including an electrically-controllable switch that is controllable by a control signal to cause the resonator circuit to switch from a first state during which the resonator circuit is in the idle state to a second state during which the resonator circuit is operating in the active state, and vice versa;
• with an alternating current (AC)-to-direct current (DC) rectifier circuit, converting the RF output signal into a DC power signal and outputting the DC power signal;
• with a DC load circuit having a DC load and an energy storage device, charging the energy storage device when the resonator circuit is in the active state to cause a substantially constant DC current or voltage, depending on which is used by the DC load, to be delivered to the DC load;
• and
• with a first comparator circuit, receiving an output signal output from the DC load circuit, comparing the received output signal with a preselected reference voltage signal, and outputting a first sub-control signal;
• with a second comparator circuit, receiving an output signal output from the DC load circuit, comparing the received output signal with the preselected reference voltage signal, and outputting a second sub-control signal;
• and
• with a logical gate, generating the control signal based on a comparison of the first sub-control signal and the second sub-control signal, and feeding the control signal back to the resonator circuit to control the state of the electrically-controllable switch.