History of Power semiconductor devices

    Power semiconductor devices are the heart and soul of the modern power electronic equipment. The modern power electronic equipment encompass power electronic converters that are widely used in applications like AC and DC power supplies, control of DC and AC motor drives, static VAR generation, heating and lighting controls, active harmonic filtering, robotics, electric vehicles, distributed generation, space and defense etc. Design of the power electronic equipment should have the knowledge of the characteristics of semiconductor devices employed in order to develop an efficient, reliable and cost effective system with optimum performance.  At present, the power electronic devices are silicon fabricated and are classified as, power diodes, thyristors or SCRs, BJTs, MOSFETs, Triac, Gate turn off thyristor(GTO), insulated gate bipolar transistor(IGBT), static induction transistor(SIT), MOS controlled thyristor(MCT), integrated gate commutated thyristor(IGCT).

    The diodes are available with the ratings of several thousands of volts and amperes. BJTs are available with the ratings of nearly 1000V and 600A. BJTs are usually employed in high power applications. These devices results in low conduction losses and the switching frequencies are limited upto 5KHz. MOSFET belongs to the FET family and are available with the voltage rating of 500V and current rating of 100A. MOSFETs are employed in low power applications where the switching frequencies ranges upto 20KHz and the conduction losses are high. IGBTs are available with the ratings of nearly 1000V and 500A. IGBTs are usually employed in medium power applications. These devices results in lower conduction losses than MOSFETs and the switching frequencies are in the range of 10 to 15KHz. GTOs are available with 2500V and nearly 2000A and the switching frequency is limited upto 1KHz. SCRs are usually used in very high power applications. These devices are available with voltage ratings of 4000V and current rating of 3000A. As per the literature IGCTs are available with voltage and current ratings of 4500V and 3000A.