Research of DC/DC LLC soft switched converter for trolley application

DC/DC auxiliary converters for trolley application require low volume, low weight and high performance. Today various type of half or full bridge with hard switched devices are used. This is a limitation of increasing switching frequency and achieves better size of wounded parts. There is a need to implement soft switching for switched devices to lower switching losses. The LLC topology is a good candidate for it. But the principles of design, control strategy are different. This paper describes limitation for using the LLC resonant topology in a trolley supply application.