Phase-shift modulated full-bridge power inverters and methods of operation thereof

A phase-shift modulated full-bridge power inverter configured for use in a wireless power transfer system, the power inverter comprising:

• a leading bridge leg;
• a lagging bridge leg;
• a first output terminal connected from a leading bridge leg connection point in the leading bridge leg;
• a second output terminal connected from a lagging bridge leg connection point in the lagging bridge leg;
• and
• an augmented passive circuit comprising:
• a capacitor circuit branch, the capacitor circuit branch comprising a first capacitor and a second capacitor connected in series with one another at a capacitor branch connection point, the capacitor circuit branch being connected in parallel to the leading bridge leg and the lagging bridge leg;
• a diode circuit branch, the diode circuit branch comprising a first diode and a second diode connected in series with one another at a diode branch connection point, the diode circuit branch being connected in parallel to the leading bridge leg and the lagging bridge leg;
• and
• an inductor connected at a first inductor terminal to the capacitor branch connection point and the diode branch connection point and connected at a second inductor terminal to one of the first and second output terminals.

A method of operating a phase-shift modulated full-bridge power inverter in a wireless power transfer system, the power inverter comprising:

• a leading bridge leg comprising:
• a first power switch, the first power switch having a first power switch parasitic capacitance;
• and
• a second power switch, the second power switch having a second power switch parasitic capacitance;
• a lagging bridge leg comprising:
• a third power switch, the third power switch having a third power switch parasitic capacitance;
• a fourth power switch, the fourth power switch having a fourth power switch parasitic capacitance;
• and
• an augmented passive circuit comprising an inductor;
• the method comprising:
• operating the power inverter so that each of the power switches is switched on and off in a switching cycle;
• and
• switching a first one of the third and fourth power switches off when a second one of the third and fourth power switches is in a switched off state, for the inductor to combine with the third power switch parasitic capacitance and the fourth power switch capacitance to form a resonator and discharging energy stored in the parasitic capacitance of the second one of the third and fourth power switches before the second one of the third and fourth power switches is switched on.

A method of fitting an augmented passive circuit to a phase-shift modulated full-bridge power inverter configured for use in a wireless power transfer system, the power inverter comprising:

• a leading bridge leg;
• a lagging bridge leg;
• a first output terminal connected from a leading bridge leg connection point in the leading bridge leg;
• and
• a second output terminal connected from a lagging bridge leg connection point in the lagging bridge leg;
• the method comprising:
• connecting a capacitor circuit branch in parallel to the leading bridge leg and the lagging bridge leg, the capacitor circuit branch comprising a first capacitor and a second capacitor connected in series with one another at a capacitor branch connection point;
• connecting a diode circuit branch in parallel to the leading bridge leg and the lagging bridge leg, the diode circuit branch comprising a first diode and a second diode connected in series with one another at a diode branch connection point;
• and
• connecting an inductor at a first inductor terminal to the capacitor branch connection point and the diode branch connection point and connecting the inductor at a second inductor terminal to one of the first and second output terminals.

A kit of augmented passive circuit parts for fitting to a phase-shift modulated full-bridge power inverter configured for use in a wireless power transfer system, the kit of augmented passive circuit parts comprising:

• a first capacitor and a second capacitor to be connected in series with one another at a capacitor branch connection point in a capacitor circuit branch, the capacitor circuit branch to be connected in parallel to a leading bridge leg and a lagging bridge leg of the power inverter;
• a first diode and a second diode to be connected in series with one another at a diode branch connection point in a diode circuit branch, the diode circuit branch to be connected in parallel to the leading bridge leg and the lagging bridge leg;
• and
• an inductor to be connected at a first inductor terminal to the capacitor branch connection point and the diode branch connection point and to be connected at a second inductor terminal to one of power inverter first and second output terminals.