Soft-switching converter for tram auxiliary power supply

New prototype of an auxiliary soft-switching power supply for the tram of the city of Zagreb was developed and built based on specifications of the existing auxiliary hard-switching power supply. A new soft-switching topology for the input DC-DC converter is proposed. It was possible to compare two power supplies built to the same specifications with only one basic difference: switching technology. Switching frequency of both supplies is equal and to lower the audible noise is fixed at 20 kHz. Experimental results are shown. A high efficiency of 97 % is achieved for the input soft-switching DC-DC converter and overall efficiency of the new auxiliary power supply is 92, 5 %. Compared to the existing auxiliary power supply based on hard-switching technology, efficiency, weight and volume are substantially reduced.