Abstract: The switching frequency of switching power supplies using bipolar emitter-follower transistor amplifiers to drive field-effect output transistors is increased from a currently typical frequency of 100 KHz to at least 1.5 MHz. by reducing the heating in the bipolar transistors. The heating, which is caused by the inherent 0.7 volt drop in the base-emitter junction of the bipolar transistor, is eliminated by feeding back from a dual core output transformer, a compensating voltage equal to the junction drop, the feedback winding being wound over only one core, and the output signal windings being wound over both cores. The flux in the feedback winding core of the transformer is limited by means of a diode to keep the feedback voltage substantially the same as the forward voltage of the base-emitter junction of the bipolar transistor. The core of the transformer is temperature compensating to keep the feedback voltage correct over temperature extremes.

Abstract: A transformer coupled DC-to-DC converter provides a regulated output with only one active switch. The converter includes a switch, a diode and an inductor coupled to the primary of a transformer in a way which provides symmetry to the transformer as the duty cycle of the switch changes for regulation. The circuit may be current-fed by supplying an input voltage higher than the transformer ratio would indicate, or may be voltage-fed by providing an input voltage lower than the transformer ratio would indicate. The circuit is operated to charge an inductor through the switch and half the primary of a transformer and discharge the inductor through the other half of the primary so that equal energy is provided through the transformer during charging and discharging, thereby providing a symmetrical signal without the need for more than one switch.