High efficiency DC/DC converter circuit using charge storage diode snubber

The charge storage diode (CSD) has useful characteristics of the long carrier lifetime and fast shut down of a recovery current at reverse recovery. When using the CSD snubber circuit to the DC-DC converter, during the storage time, the snubber energy is returned to the input by resonance phenomenon of the magnetizing inductance of the transformer and the snubber capacitor. Therefore the efficiency is improved. Magnetizing current is recycled when the CSD snubber is applied to the forward converter. And the core loss decreases because the maximum magnetic flux density reduces if the amplitude ^B of magnetic-flux density of the transformer is designed to same value to the conventional circuit. Also, because the designer can use bigger capacitor to the CSD snubber than conventional snubber, the effect that is equal to active clamp circuit is achieved. Then the switching device that with lower withstands voltage can be used. In this paper, characteristic of the CSD is introduced, and operation is described using the example that applied the CSD snubber to the forward converter. Then, the effectively is shown by the experiment with the forward converter, the flyback converter and the buck-boost push-pull converter.. The efficiency is 2-3% improved compared with the conventional circuit and the surge voltage of the switching device is clamped. However, it is often accompanied with a little difficult to perform the control operation like the active clamp circuit because use the storage time of the CSD. Therefore, it is important to design the CSD snubber circuit. This paper provides its design method, too.