A self-controlled flyback DC/DC converter

In the present paper a self-controlled switch-mode DC/DC converter circuit is proposed for power supplies in low power applications where light weight, low cost and good efficiency are required. The use of a simple feed-forward flyback topology makes the circuit spontaneously switch at high operating frequency, so that it can transfer power to the loads via a DC/DC transformer. The turn-on condition is governed by transformer secondary voltage whenever the secondary side is not transferring power to the load. Turn-off is automatically triggered as soon as the no-saturation condition is reached in the switching device. DC output voltage is regulated by a very simple feedback circuit, which determines a continuous mode and frequency-controlled operation of the converter over the entire range of load and input voltage variations. The converter topology and the triggering control strategy proposed are suitable for bipolar power transistors as static switches, and allow them to operate with higher than usual switching frequency. Laboratory tests were carried out and switching and on-losses measured on line to assess the converter performance and efficiency