Monolithic bidirectional switches promise superior characteristics

The monolithic bidirectional switch, MBS, represents a new structure of a bipolar power device, which was invented five years ago. It is a bidirectional switch, which can block voltages of both polarities and turn on and off currents of either direction. Thus it is ideally suited for matrix converter applications. When inserted in a voltage source inverter the same MBS can play the role of the switch as well as the role of its antiparallel diode depending on actual operating condition. The MBS consists mainly out of intrinsic silicon and recombination centers are avoided at all. MOS gates control it. These gates are applied on both surfaces. This allows controlling the carrier concentration inside the base. Thus no compromise has to be determined for low forward voltage drop on one hand and low turn-off losses on the other. Instead a high carrier concentration is chosen in the on state and the device is discharged before proper turn-off. A tight control of the gate voltages even allows controlling the switching transients during turn-on and turn-off. This makes possible to adapt device characteristics to the actual demands of the circuit.