Comparison of zero-voltage-switching converters at low temperatures

Abstract

In the last years 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 literature is focussing very much on the behaviour of separated turn-on or turn-off transitions of switching elements, and only few publications are considering 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 will be presented for single switching transitions and the overall converter efficiency during steady-state operation.It is shown that soft-switching at low temperatures is resulting no longer in a clear increase of power density and converter efficiency, but may even result in a reduction of converter efficiency.

Review of the State-of-the-Art in Power Electronics Suitable for 10-KW Military Power Systems

“…The switch characteristics of a hardswitching converter [57] and a zero-voltage soft-switching converter [56] at 77 K have been investigated. It was shown that hard-switching operation is improved and zero voltage switching maintained at 77 K. The advantages of soft-switching converters at RT, however, are not clear at liquid nitrogen temperature (LNT) [59].…”

“…Soft-switching circuits at LNT have not been thoroughly investigated, and different conclusions have been drawn. For example, Marx [59] comments that soft-switching at low temperature is resulting no longer in a clear increase of power density and converter efficiency, but may even result in a reduction of converter efficiency. However, Gardiner [46] concluded that soft switching must be employed to achieve acceptable switching power loss for a 3-phase inverter at LNT.…”

Investigation of Potential Benefits of MOSFETs Hard-Switching and Soft-Switching Converters at Cryogenic Temperature

“…The experiments and the analysis found that by doing simple modifications to the room temperature (RT) hard-switched converter, the device losses including switching and conduction are reduced and, converter efficiency, power density and EMI is thereby improved at low temperature. Although Marx [5] comments that zero-current, zero-voltage and multi-resonant soft-switching at low temperature no longer results in a clear increase of power density and converter efficiency, but may even result in a reduction of converter efficiency due to the fact that hard-switching is also improved at LNT, the findings in this paper demonstrate that the advantages of lossless snubber based soft switching are still achieved at low temperature, and the switching losses are considerably decreased with respect to those of RT soft switching circuit and LNT hard switching circuit.…”

Elektrische Antriebe 4

“…Bei bipolaren Bauelementen nehmen dagegen die Schaltverluste aufgrund der abnehmenden Lebensdauer mit abnehmender Temperatur ab, allerdings steigen die Durchlaßverluste[55,685,686,768]. Stellglied und Netz wurden realitätsnahe simuliert, als Lastströme wurden auf Magnetband aufgezeichnete Ströme eines Drehstromlichtbogenofens eingespeist.…”