Ferroresonant DC‐DC converter with high‐frequency drive

Abstract

AbstractSince the switching loss in inverter circuits and the iron loss in ferroresonant circuits increase with frequency, the conversion efficiency decreases and the heat loss in the switching element and magnetic core increase at high frequencies. The requirement of radiating the heat has restricted the size reduction of power supplies. In view of the relation between the loss in the output transistor of an inverter and the switching frequency, it is found that the loss consists of the one independent of the switching frequency and the switching loss increasing in proportion to frequency. As the switching frequency increases, the latter becomes predominant. Hence, for a small and efficient converter at high switching frequencies, the switching loss has to be reduced. To this end, a relatively large capacitor is connected in parallel with the output transistor in this paper. As a result, sudden increase of the collector voltage at the shutdown of collector current is suppressed and the instantaneous collector loss is reduced. In the ferroresonant circuit for stabilization of output voltage, two saturable cores operating on a minor loop on the BH curve are used. Hence, the loss is small even at high frequencies and a superior constant voltage characteristic is realized by a feedback. The conversion efficiency is about 80% at the switching frequency of 500 kHz.