Ixys Corporation

Joseph James Roosma

Kyoung Wook Seok

A combination switch includes an Insulated Gate Bipolar Transistor (IGBT), an anti-parallel diode, and a saturable inductor. The diode and inductor are coupled in series between a collector and an emitter of the IGBT. The inductor is fashioned so that it will come out of saturation when a forward bias current flow through the diode falls below a saturation current level. When the diode current falls (for example, due to another combination switch of a phase leg turning on), the diode current initially falls at a high rate until the inductor current drops to the saturation current level. Thereafter, the diode current falls at a lower rate. The lower rate allows the diode current to have a soft landing to zero current, thereby eliminating or reducing voltage and/or current spikes that would otherwise occur. Multiple methods of implementing and manufacturing the saturable inductor are disclosed.

IGBT assembly having saturable inductor for soft landing a diode recovery current

A flyback converter involves a bipolar transistor (BJT) and a parallel-connected diode as the rectifying element in the secondary side of the converter. The transformer of the converter has a primary winding, a first secondary winding, and a second secondary winding. A first end of the first secondary winding is coupled to the BJT base. A first end of the second secondary winding is coupled to the BJT collector and to the anode of the diode. The first and second secondary windings are wound such that when primary winding current stops, pulses of current flow out of the first ends of the first and second secondary windings. These currents are such that the BJT is maintained in saturation throughout at least most of the time current flows through the rectifying element, thereby achieving a low forward voltage across the rectifying element, reducing conduction loss, and increasing converter efficiency.

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Santa Clara, CA, United States of America

Joseph James Roosma