Power Imbalance Compensation of Parallel Combining Twin Class-E Inverters by DC Current Detection Fed Back to Gate-Signal Phase Control

This paper proposes compensation scheme to address the power imbalance in twin class-E inverters that allow the combination of radio frequency (RF) output power in parallel. We start with a single class-E inverter with DC current consumption and RF output current formulate in terms of load impedance. We apply the derived formula to twin class-E inverters coupled in parallel and show that an RF output power imbalance can be detected by observing the DC current imbalance. A circuit simulation shows that it is possible to compensate for this power imbalance by adjusting the gate-phase delay. The simulation also shows that this adjustment can be performed automatically by feeding the DC current difference back to the gate-phase shifters. We then use this feedback scheme in a prototype experiment that achieves 490 W output power at 6.78 MHz. We demonstrate the reduction of the DC current imbalance from 10.3% is successfully suppressed down to 0.3% or lower.