Zero-current zero-voltage transition inverters with magnetically coupled auxiliary circuits: analysis and experimental results

Hitherto, zero-current transition (ZCT) and zero-current zero-voltage transition (ZCZVT) inverters have provided desirable switching conditions for main semiconductors, chiefly for minority carrier ones, by means of a current impulse that unavoidably increases the reactive energy of the auxiliary circuit, penalising their efficiency and device ratings. This often offsets the benefits gained by the above-mentioned soft-switching techniques. This study presents a novel family of ZCZVT inverters that overcome this problem by using a non-resonant auxiliary circuit, which is magnetically coupled to the filter inductor, reducing the inverter component count, and associated circuitry. The principles of operation of the ZCZVT inverter with a magnetically coupled auxiliary circuit is presented and analysed. Experimental results from a 1 kW, 40 kHz, laboratory prototype are used to verify the theoretical analysis and also to compare different technologies applied to the auxiliary switches. The ZCZVT inverter with a magnetically coupled auxiliary circuit and MOSFET-based auxiliary switches presented the highest efficiency, achieving 96% at full load, meanwhile its insulated gate bipolar transistor (IGBT)-based counterpart reached 94.2%.