A high efficiency 150 W DC/DC converter

The authors have devised a series resonant circuit, for telecommunication power supplies, in which the charge stored in the parasitic capacitor of the switching device is discharged by the magnetizing current of the transformer in order to reduce loss. In this paper the authors study the details of this new soft switched multi-resonant zero-current-switching converter and report on the modal analysis and the experimental results. They have succeeded in obtaining a high efficiency of 96% in the conversion circuit in an experimental circuit with an input of 15O Voc and an output of 5O Voc at 3A. The features of this circuit are as follows: (i) this is a multi-resonant converter with three resonant operations; (ii) the voltage of the resonant capacitor is charged by the magnetizing inductor of the transformer and the constant voltage regulation is performed by charging the peak value of the resonant current greatly; the lower the switching frequency, the larger the power obtained; (iii) the switching frequency varies little in the whole range from zero to full load; (iv) the voltage in the primary winding of the transformer shall be a half or more of the input voltage; and (v) at turn-on both zero-voltage-switching (ZVS) and zero-current-switching (ZCS) are achieved, and at turn-off only ZVS is achieved