Contactless energy transmission for an isolated 100W gate driver supply of a medium voltage converter

In this paper, an innovative DC-DC converter is investigated which provides electrical power to the gate driver units of medium voltage level converters. For the discussed DC-DC converter, a galvanic isolation (isolation voltages of up to 35 kV) is required. This electrical isolation is achieved with a coreless transformer in order to obtain a cost-effective solution. Furthermore, the DC-DC converter contains a full-bridge converter being operated with low switching losses, a resonant compensation network to achieve a high overall efficiency and an output side rectifier. In this paper, the design of the coreless transformer, the appropriate compensation networks and the power electronics are discussed in detail. Moreover, measurement results obtained from a 100 W prototype, operated at a switching frequency of 410 kHz, are presented. With the proposed setup, a high overall efficiency of up to 80% and a transformer breakdown voltage of 55 kVrms is achieved. Thus, the proposed converter concept represents a very competitive solution with respect to the typically employed DC-DC converters with dry-type cast coil transformers.