Active rectifier for efficient wireless power transfer

1. A device for receiving a wireless power transfer, the device comprising:

an active rectifier;

rectifier input nodes;

a load circuit connected to the active rectifier, the load circuit comprising a voltage regulator; and

a controller operatively coupled to the active rectifier and the voltage regulator, the controller configured to control the active rectifier and the voltage regulator to modify an impedance at the rectifier input nodes by being configured to:

determine, based on one or both of circuit parameters or circuit measurements, a modification of the impedance at the rectifier input nodes, comprising a modification of one or more of a phase angle to induce a phase angle shift, an output voltage, or a duty cycle to result in one or both of a higher value of an efficiency of the wireless power transfer or a higher value of extracted power of the wireless power transfer; and

apply a control signal to the active rectifier,

wherein the control signal is based on the determined modification of the impedance at the rectifier input nodes, and

wherein the circuit parameters comprise a load resistance and a load reactance, and to determine the phase angle shift a load impedance is determined to raise the value of the efficiency of the wireless power transfer, wherein the value of the efficiency of the wireless power transfer is determined as a function of the load resistance and the load reactance.

2. The device of claim 1 , wherein the active rectifier comprises a plurality of switches, and the controller is further configured to control a timing of the switches relative to an alternating current received by the active rectifier, such that the timing of the switches modifies the impedance at the rectifier input nodes.

3. The device of claim 2 , wherein the controller is further configured to determine an impedance that would improve an efficiency of the wireless power transfer, and to control the timing of the switches to emulate the determined impedance, wherein the timing of the switches modifies the impedance at the rectifier input nodes by modifying at least one of:

a phase angle between the input current and the input voltage of the alternating current, or

a duty cycle of the switches.

4. The device of claim 2 , wherein the plurality of switches comprises four switches disposed between two conducting lines connected to a receiver coil and two conducting lines connected to the load circuit, such that the four switches are configured to rectify an alternating current received via the receiver coil, thereby generating a rectified current, and to transmit the rectified current to the load circuit.

5. The device of claim 4 , wherein the controller is further configured to modify the impedance at the rectifier input nodes by modifying a load voltage of the voltage regulator.

6. The device of claim 4 , wherein the voltage regulator comprises a DC/DC converter.

7. The device of claim 4 , wherein the voltage regulator comprises a low-dropout (LDO) regulator.

8. The device of claim 2 , wherein at least one of the switches comprises at least one of a metal-oxide semiconductor field effect transistor (MOSFET) or a metal-insulator semiconductor field effect transistor (MISFET).

9. The device of claim 1 , wherein the controller is further configured to control the active rectifier to modify a load voltage first harmonic generated by the active rectifier.

10. The device of claim 9 , wherein the controller is further configured such that being configured to control the active rectifier to modify the load voltage first harmonic comprises being configured to modify a voltage amplitude generated by the active rectifier.

11. The device of claim 9 , wherein the active rectifier comprises a plurality of switches, and wherein the controller is further configured such that being configured to control the active rectifier to modify the load voltage first harmonic comprises being configured to modify a duty cycle of the switches.

12. The device of claim 1 , wherein the controller is further configured to determine the phase angle shift repeatedly based on one or more new values among one or more values of the load resistance or one or more values of the load reactance.

13. The device of claim 1 , wherein the controller is further configured to receive one or more of the circuit parameters via one or more signal inputs, and to derive one or more of the circuit parameters based on the one or more signal inputs.

14. The device of claim 1 , further comprising a receiver coil configured for receiving the wireless power transfer, wherein the active rectifier receives the alternating current via the receiver coil.

15. The device of claim 1 , further comprising the active rectifier receiving the alternating current via a passive impedance matching network.

16. The device of claim 1 , wherein the controller is configured to control the active rectifier to modify a phase angle between the input current and the input voltage of the alternating current to result in in one or both of an improved efficiency of the wireless power transfer or a higher value of extracted power of the wireless power transfer.

17. A method for receiving a wireless power transfer, the method comprising:

determining, by one or more processors, based on one or both of circuit parameters or circuit measurements, a modification of an impedance at input nodes of an active rectifier that comprises a plurality of switches, comprising a modification of one or more of a phase angle to induce a phase angle shift, an output voltage, or a duty cycle, to result in one or both of a higher value of an efficiency of the wireless power transfer or a higher value of extracted power of the wireless power transfer; and

applying, by the one or more processors, a control signal to at least one of the active rectifier or a voltage regulator connected to an output of the active rectifier, wherein the control signal is based on the determined modification of the impedance,

wherein the applying comprises controlling a timing of the plurality of switches relative to an alternating current at the input nodes of the active rectifier, such that the timing of the switches modifies the phase angle between the input current and the input voltage of the alternating current,

wherein the circuit parameters comprise one or more values of resistance and one or more values of reactance, and

wherein determining the modification comprises determining the phase angle shift by determining a load impedance to raise the value of the efficiency of the wireless power transfer, wherein the load impedance is separate from the one or more values of reactance, and wherein the value of the efficiency of the wireless power transfer is determined as a function of the one or more values of resistance, the one or more values of reactance, and the load reactance.

18. An integrated circuit for controlling a wireless power transfer, the integrated circuit being configured to:

determine, based on one or both of circuit parameters or circuit measurements, a modification of an impedance at input nodes of an active rectifier that comprises a plurality of switches, comprising a modification of one or more of a phase angle to induce a phase angle shift, an output voltage, or a duty cycle, to result in one or both of a higher value of an efficiency of the wireless power transfer or a higher value of extracted power of the wireless power transfer; and

apply a control signal to at least one of the active rectifier or a voltage regulator connected to an output of the active rectifier, wherein the control signal is based on the determined modification of the impedance, to control a timing of the switches relative to an alternating current at the input nodes of the active rectifier, such that the timing of the switches modifies the phase angle between the input current and the input voltage of the alternating current,

wherein the circuit parameters comprise one or more values of resistance and one or more values of reactance, and

wherein to determine the modification comprises the integrated circuit being configured to determine the phase angle shift by determining a load impedance to raise the value of the efficiency of the wireless power transfer, wherein the load impedance is separate from the one or more values of reactance, and wherein the value of the efficiency of the wireless power transfer is determined as a function of the one or more values of resistance, the one or more values of reactance and the load reactance.