Dynamic tuning in wireless energy transfer systems

A wireless energy transfer system comprising:

• a split coil resonator comprising a first winding magnetically coupled with a second winding;
• and
• a variable capacitance device comprising:
• a first capacitor comprising a first-capacitor first terminal and a first-capacitor second terminal, the first-capacitor first terminal electrically connected to a ground, and the first-capacitor second terminal electrically connected to a first-winding terminal of the first winding of the split coil resonator;
• a first switch comprising a first-switch first terminal, a first-switch second terminal, and a first-switch control terminal, the first-switch first terminal electrically connected to the first-capacitor first terminal, and the first-switch second terminal electrically connected to the first-capacitor second terminal;
• a second capacitor comprising a second-capacitor first terminal and a second-capacitor second terminal, the second-capacitor first terminal electrically connected to the ground, and the second-capacitor second terminal electrically connected to a second-winding terminal of the second winding of the split coil resonator;
• a second switch comprising a second-switch first terminal, a second-switch second terminal, and a second-switch a control terminal, the second-switch first terminal electrically connected to the second-capacitor first terminal, and the second-switch second terminal electrically connected to the second-capacitor second terminal;
• and
• control circuitry coupled with the first-switch control terminal and with the second-switch control terminal,
• wherein the control circuitry is configured to adjust respective capacitances of the first and second capacitors by:
• in response to detecting a zero voltage condition across the first switch, causing a first control signal to be applied to the first-switch control terminal for a duration of time, wherein the first control signal causes the first switch to close;
• and
• in response to detecting a zero voltage condition across the second switch, causing a second control signal to be applied to the second-switch control terminal for the duration of time, wherein the second control signal causes the second switch to close.

A wireless power transfer system comprising an impedance matching circuit, the impedance matching circuit including a variable capacitance device comprising:

• a first capacitor comprising a first-capacitor first terminal and a first-capacitor second terminal, the first-capacitor first terminal electrically connected to a ground;
• a first switch comprising a first-switch first terminal, a first-switch second terminal, and a first-switch control terminal, the first-switch first terminal electrically connected to the first-capacitor first terminal, and the first-switch second terminal electrically connected to the first-capacitor second terminal;
• a second capacitor comprising a second-capacitor first terminal and a second-capacitor second terminal, the second-capacitor first terminal electrically connected to the ground;
• a second switch comprising a second-switch first terminal, a second-switch second terminal, and a second-switch a control terminal, the second-switch first terminal electrically connected to the second-capacitor first terminal, and the second-switch second terminal electrically connected to the second-capacitor second terminal;
• and
• control circuitry coupled with the first-switch control terminal and with the second-switch control terminal,
• wherein the control circuitry is configured to adjust respective capacitances of the first and second capacitors by:
• in response to detecting a zero voltage condition across the first switch, causing a first control signal to be applied to the first-switch control terminal for a duration of time, wherein the first control signal causes the first switch to close;
• and
• in response to detecting a zero voltage condition across the second switch, causing a second control signal to be applied to the second-switch control terminal for the duration of time, wherein the second control signal causes the second switch to close.