Comparison of zero-voltage-switching converters at low temperatures

The investigation of switching power devices´ behaviour at liquid nitrogen temperature has gained more and more significance with respect to developing superconducting applications. Most of the previous work in the literature focuses very much on the behaviour of separated turn-on or turn-off transitions of switching elements, and only a few publications consider the continuous switching operation in a power converter at low temperatures. In this paper different soft-switching converters and their hard-switched counterpart are compared regarding their performance at room temperature and at 77 K. Current and voltage waveforms at the switching elements is presented for single switching transitions and the overall converter efficiency during steady-state operation. It is shown that soft-switching at low temperatures no longer results in a clear increase of power density and converter efficiency, but may even result in a reduction of converter efficiency