Self-tuning resonant power transfer systems
Systems and designs for tuning a wireless power transfer system are provided, which may include any number of features. In one embodiment, a wireless power transfer system can be configured such that resonant frequencies of the system move towards an operating frequency of the system as a coupling coefficient between the transmit and receive resonators becomes smaller. In another embodiment, a receive controller can be configured to control a current delivered to a DC load by comparing an actual current at the DC load to a current requested by the DC load and adjusting an angle or a magnitude of a voltage at the DC load to match the requested current. In another embodiment, a rectifier circuit can act as a controlled voltage source and be configured to tune resonant frequencies between the transmit resonator and the receive resonator. Methods of use are also provided.
1. A wireless power transfer system, comprising:
a transmit resonator coupled to a voltage source and a first impedance matching network; and
a receive resonator coupled to a second impedance matching network, the receive resonator being inductively coupled to the transmit resonator;
the system being configured such that resonant frequencies of the system move towards an operating frequency of the system as a coupling coefficient between the transmit and receive resonators becomes smaller.
2. The wireless power transfer system of 1 , wherein resonator tuning between the receiver and transmit resonators is optimized to keep a voltage gain within a specified range as the coupling coefficient varies.
3. The wireless power transfer system of 1 , wherein resonator tuning between the receiver and transmit resonators is optimized to maximize efficiency over a given range.
4. The wireless power transfer system of 1 , wherein resonator tuning between the receiver and transmit resonators is optimized to achieve a minimum amount of power transferred for a given source voltage.
5. The wireless power transfer system of claim 1 , wherein the system is self-tuning and does not require an external control system to operate.
6. A method of controlling a wireless power transfer system, comprising the steps of:
transmitting wireless power from a transmit resonator to a receive resonator; and
allowing resonant frequencies of the system to move towards an operating frequency of the system as a coupling coefficient between the transmit and receive resonators becomes smaller.
7. A wireless power transfer system, comprising:
a transmit resonator coupled to a voltage source and a first magnetic impedance matching network;
a receive resonator coupled to a second magnetic impedance matching network, the receive resonator being inductively coupled to the transmit resonator;
a transmit controller coupled to the first magnetic impedance matching network, the transmit controller configured to control a current in the first magnetic impedance matching network to generate a magnetic field in the transmit resonator; and
a receive controller coupled to the second magnetic impedance matching network, the receive controller configured to control a current delivered to a DC load by comparing an actual current at the DC load to a current requested by the DC load and adjusting an angle or a magnitude of a voltage at the DC load to match the requested current.
8. The system of claim 7 , wherein the DC load comprises a battery of an implantable medical device attached to the receive resonator.
9. The system of claim 8 , wherein the current requested by the DC load is determined by a battery charge algorithm executed on the receive controller.
10. A method of controlling a wireless power transfer system, comprising the steps of:
transmitting wireless power from a transmit resonator to a receive resonator; and
controlling a current delivered to a DC load connected to the receive resonator by comparing an actual current at the DC load to a current requested by the DC load and adjusting an angle or a magnitude of a voltage at the DC load to match the requested current.
11. A wireless power transfer system, comprising:
a transmit resonator coupled to a voltage source; and
a receive resonator inductively coupled to the transmit resonator and connected to a load with a rectifier circuit comprising a plurality of FETs, wherein the rectifier circuit acts as a controlled voltage source and is configured to tune resonant frequencies between the transmit resonator and the receive resonator.