A new phase-controlled resonant inverter is obtained by paralleling the ac loads of two identical parallel resonant inverters. A phase shift between the drive signals of the two inverters controls the amplitude of the output voltage of the new inverter. A voltage-driven rectifier is used as an ac load of the inverter which results in a phase-controlled parallel resonant dc-dc converter. A frequency-domain analysis is performed for the steady-state operation of the inverter and two types of voltage-driven rectifiers and design equations are derived. The converter can be operated at a constant switching frequency which reduces EM1 problems. It is found that for switching frequencies higher than the resonant frequency by a factor of 1.07, the load of each switching leg is inductive which allows for the use of power MOSFETs as switches. The converter is capable of regulating the output voltage in the range of load resistance from full load to no load. An experimental prototype of the phase-controlled parallel resonant converter with a center-taped rectifier was built and extensively tested at an output power of 50 W and a switching frequency of 116 kHz.

A numerical analysis of a Class D zero-voltage switching (ZVS) inverter in the time domain is presented along with experimental results. A discrete-time state-space approach is used for simulation. The state-space description and simulation results provide a fast insight into the physical operation of the converter. The algorithm is fast, easy to implement, and suitable for systems with high spikes in the waveforms and variable inputs. The analysis shows that switching losses can be reduced by using a dead time in the transistor drive voltages and adding a single capacitor in parallel with one of the transistors. ZVS can be achieved above the resonant frequency and in a limited range of the load resistance. The numerical results are in good agreement with the experimental ones.

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