Improvement Effect of Input Current Waveform of a Soft Switching Boost Type Three-Phase Diode Rectifier

We propose a boost type three-phase diode rectifier with a current resonant switch to realize soft switching and reduce switching loss. From the simulation results of the proposed circuit, the circuit can decrease the THD of the input current compared with the hard switching circuit without the resonant switch. In the soft switching circuit, the DC short circuit occurs more easily and frequently because of the resonant operation. The DC short circuit starts after the switch turns off, and the diode bridge input current in the switch off period is decreased. Then the diode bridge input current in the switch on period increases relatively when the DC short circuit occurs. Therefore the soft switching circuit improves the input current waveform and it becomes sinusoidal. We analyzed and clarified the process and the reason for the input current waveform improvement in the soft switching circuit.