Near-field wireless power transfer system with immunity to distance and/or load variations
View Patent ↗Wireless power transfer systems in accordance with embodiments of the invention are disclosed. In one embodiment, a wireless power transfer system includes a power transmitter driven by an oscillator, a power receiver including a resistive load, and a coupled resonator link configured to deliver power from a transmitter tank circuit to a receiver tank circuit, wherein the free-running oscillator automatically tunes to oscillate at a frequency that does not experience a phase shift due to the impedance of the transmit side of the coupled resonator link, wherein the power transmitter provides regulated voltage across a range of distances between the transmitter tank circuit and the receiver tank circuit, and wherein the power transmitter regulates voltage across a range of resistive loads of the power receiver.
1. A wireless power transfer system, comprising:
a power transmitter driven by an oscillator;
a power receiver comprising a resistive load; and
a coupled resonator link configured to deliver power from a transmitter tank circuit to a receiver tank circuit;
wherein the free-running oscillator automatically tunes to oscillate at a frequency that does not experience a phase shift due to the impedance of the transmit side of the coupled resonator link;
wherein the power transmitter provides regulated voltage across a range of distances between the transmitter tank circuit and the receiver tank circuit;
wherein the power transmitter regulates voltage across a range of resistive loads of the power receiver;
wherein quality factor for the transmitter tank circuit exceeds the quality factor for the receiver tank circuit;
wherein the oscillator driver is configured to minimize energy loss in the transmitter tank circuit; and
wherein the oscillator driver is configured with a tail current source that blocks a discharging path.
2. The wireless power transfer system of claim 1 , wherein the tail current source comprises a transistor having a drain voltage that is maintained above a threshold voltage during operation.
3. The wireless power transfer system of claim 2 , wherein the transistor at the tail current source remains in a saturation region of the transistor.
4. The wireless power transfer system of claim 1 , wherein the tail current source is controlled by a feedback loop that maintains the oscillation amplitude at a reference level over a range of resistive loads.
5. The wireless power transfer system of claim 1 , wherein the wireless power transfer regulates load voltage across a range of coil separations.
6. The wireless power transfer system of claim 5 , wherein the wireless power transfer system regulates the load voltage across a range of resistive loads.