Multi-output ZCS-SR inverter fed high voltage DC-DC converter

The conventional pulse frequency modulated (PFM) zero current switching (ZCS) series resonant (SR) inverter fed dc high voltage power supplies have nearly zero switching loss. However, they have limitations like narrow variation of output voltage and poor control at light load. To alleviate these limitations, this paper proposes a multi-output ZCS-SR inverter fed high voltage dc-dc converter. The SR-inverter in the proposed system has four outputs that are connected to a single transformer linked load via four resonant capacitors each of which have distinct capacitance. Due to distinct values of resonant capacitors, the impedance of tank circuit and hence the power transformer rate is different for four outputs. Thus all the four inverter outputs are fed to load in parallel when maximum load power is desired and a single output that has highest tank circuit impedance is fed to load when lowest load power is required and vice versa. For the four inverter outputs there are sixteen possible combinations to feed them to load in parallel, thus the load power increase from its lowest value to highest in sixteen steps. Switching frequency is adjusted within in its narrow limits to adjust the voltage between two nearest steps. The proposed system has been simulated using PSPICE software. The obtained results show that proposed system has several advantages such as wide range of output voltage control, low output voltage ripple over the entire range and low current stress at light load.