PURPOSE: To contrive to reduce loss and to reduce noise by providing capacitors and diodes in parallel with a main switching element (MS) and by providing a circuit for releasing capacitor charge to a load or DC power supply side before the MS is turned ON.
CONSTITUTION: When a current is caused to flow through a load while MSSW1 is ON, energy is accumulated in a choke coil L0. When the MSSW1 is OFF, energy accumulated in the choke coil L0 is released. That is, the series circuit of a diode D2 and the primary coil N1 of a transformer T and an auxiliary switching element (SS) SW2 is connected in parallel with the MSSW1 and the series circuit of the secondary coil N2 of the transformer T and a diode D3 is parallel-connected with a DC power supply E. The SSSW2 is turned ON before the MSSW1 is turned ON so that the charge of a parasitic electrostatic capacitance Cs is discharged to the DC power supply E side to make zero- voltage switching possible. Also, when the MSSW1 is turned OFF, the current of the MSSW1 is commutated to the parasitic electrostatic capacitance Cs so that the reduction of loss is contrived.
KUMAGAI JO
KOIZUMI YASUYUKI
OZORA SHIZUO
NIPPON TELEGRAPH & TELEPHONE