Phase-Shift Controlled Push-Pull Class-E Inverter With Diode Balance for Load Impedance Variations

This article proposes a phase-shift controlled push-pull class-E inverter with diode balance for load impedance variations, along with its design method. The diode clamp absorbs the asymmetric inductive and capacitive impedance changes that occur as a side effect of the phase-shift control. As a result, the proposed inverter maintains the symmetrical waveforms between the single-ended inverters, achieving Zero-Voltage Switching under the phase-shift control. A general design framework for the phase-shift controlled push-pull class-E inverter is established with a circuit equation solver and a heuristic optimization algorithm. The design method eliminates the complex analysis for the asymmetric operation of the push-pull class-E inverter because the optimal circuit parameters are automatically explored by maximizing an objective function. This article gives the design example and performs an experiment with a prototype inverter operating at 13.56 MHz and 500 W output power. The prototype inverter achieved 87.8 % –89.0 % efficiency against resistive, inductive, and capacitive load impedance variations on the Voltage Standing Wave Ratio 2:1. The experimental results demonstrate the validity and effectiveness of the proposed inverter.