On the high-speed switching of the free-run DC-to-DC converter with a saturating core

The turn-off mechanism of the new free-run DC-to-DC converter with a saturating core is analyzed. This converter has a simple construction of the transistor core multivibrator, in which the current feedback is applied to the main switching transistor, and the voltage feedback is applied to the control transistor. The core flux changes along the minor hysteresis loop. The turn-off time is extremely shortened by the resonance between the base-emitter capacitance of the transistor and the saturated inductance of the current feedback transformer. As a result, the efficiency of 94% is obtained with the switching frequency of 400kHz.