Patent attributes
A circuit including a source, a load, and an isolation circuit for controllably isolating the load from the source. The isolation circuit is disposed between the source and the load. The isolation circuit includes at least one insulated-gate bipolar transistor (IGBT) and at least one gate turn-off thyristor (GTO) in parallel with the insulated-gate bipolar transistor. When no fault condition exists, the GTO is configured to be ON to couple the load to the source. When a fault condition exists, the at least one IGBT is configured to turn ON. After the at least one IGBT turns ON, the at least one GTO is configured to turn OFF. After a predetermined amount of time, reflecting the post fabrication alteration to the GTO's minority carrier lifetime (e.g. electron irradiation), after the at least one GTO turns OFF, the at least one IGBT is configured to turn OFF. Alternatively, the circuit is used as an inverter switch, where at the command to turn ON is supplied, the at least one IGBT is turned ON, followed by the at least one SGTO. When commanded to turn OFF the at least one SGTO is turned OFF followed by the at least one IGBT. This alternative configuration allows the robust, controllable switching speeds of IGBTs and the superior conduction efficiency of SGTOs. The two configurations mentioned above utilize a wide range of SGTO performance, thus the ability to control the SGTOs turn-off speed by reducing its minority carrier lifetime after the device is processed is of large importance. The efficiency of all uses of the circuit can be optimized with the judicious selection of SGTO minority carrier lifetime and the ratio of active area between the SGTO and IGBT devices. In all cases there is a balance between the time the circuit can achieve hard turn-off without current commutation, the conduction efficiency of the circuit and the maximum amount of controllable current. In all cases both the conduction efficiency of the circuit is higher than an IGBT-only based circuit, and the switching performance is higher than a GTO-only based circuit.
