Drain current injection circuitry for enabling the use of super-junction MOSFETs in a 5kW bidirectional DC-DC converter

The paper assesses the potential of employing super-junction MOSFETs in a high efficiency and low cost bidirectional DCDC converter for application in electric vehicle systems. Super-junction MOSFETs have a very low conduction loss, however, their poor intrinsic diode recovery behaviour and high output capacitances means that switching losses can be high in voltage source converters. A drain current injection technique is presented that can be used to mitigate the poor switching characteristics and thus realise excellent power conversion efficiencies. Experimental results are given for a circuit operating at 400V, 5kW and 25kHz and the means of achieving a power conversion efficiency >99% is outlined.