Control of Voltage-Source Series-Resonant Inverters With Extended Topology Using Pulse-Density and Pulse-Frequency Modulations

This paper presents a control strategy for series resonant voltage-source inverters with extended topology using both pulse-density modulation (PDM) and pulse-frequency modulation (PFM). PDM regulates the output current for pulse density values from 0.5 to 1, while PFM applies for values below 0.5. The features of this strategy are: 1) when the half-bridge part of the extended inverter is utilized under PDM, the injection interval duration is a multiple of the half-cycle of the inverter output period, enabling the solution of the voltage imbalance problem; 2) using PFM completely avoids amplitude fluctuations in the output current, thereby inherently eliminating the voltage imbalance problem. Simulation results confirm the effectiveness of the proposed control strategy.