Auxiliary Resonant Source Charge Extraction Circuitry for Enabling the Use of Super Junction MOSFETs in High Efficiency DC-DC converters

Abstract

In this paper a high efficiency DC-DC converter power stage employing silicon Super-Junction (SJ) MOSFETs is presented. These devices have low on-state resistances and fast switching capabilities. However, their intrinsic body diode has a very poor reverse recovery behavior and they have an output capacitance that has a highly non-linear inverse relationship with voltage. These characteristics lead to problematic charging currents when they are used in bidirectional voltage source converters.These problems are addressed through implementation of an auxiliary resonant source charge extraction circuit in conjunction with anti-series MOSFETs. The result is a 5-kW power converter with a power semiconductor stage full-load efficiency exceeding 99% and requiring no forced cooling.

Control of Incoming Drain Currents Drawn by Super-Junction MOSFETs in Voltage Source Bridge-Legs

“…The full-load efficiency was 98.7%, compared with 97.5% measured with a benchmark circuit using IGBTs. A feature of the technique is that compared to, for example, [6]- [9], little extra hardware is required. Also, the SJ MOSFETs do not have to support overvoltages during the resetting action of switching-aid inductors, as in [7].…”

“…Solutions include the use of auxiliary bridge-legs [6], switching-aid circuits [7], and intelligent commutation schemes such as those in [8] and [9]. SJ MOSFETs can be deployed in a VSC operating in the synchronous conduction mode.…”