A high input voltage and high step-down ratio double-ended Flyback Converter

A low power and high step-down ratio insulated DC-DC converter applied to energy conversion of medium to low voltage is proposed, analyzed and evaluated in this paper. Among its many applications, this work focuses in a compact, simple and low cost galvanic insulation auxiliary power supply. The proposed converter is a multilevel Flyback derived from the Double-Ended topology and it uses the NPC (neutral point clamped) technique to limit the voltage stress under its switches. The proposed modulation strategy equalizes the voltages on the input capacitors and allows the converter to reach a high step-down ratio with low inductance value. The Four-Level Flyback Converter operation stages are presented, as well its results for a 50 W auxiliary power supply with the following characteristics: 1200 VDC input voltage, 30 VDC outputs and switching frequency operating at 100 kHz.