Wide band gap power semiconductor devices and their applications

Abstract

DC power supplies are being widely used in almost every modern day appliance. Basic DC power supply should only consist of AC/DC rectification unit with bulk capacitor. But irregular current drawn by rectifier pollutes the power system. Standards related to power quality puts a limit on harmonics that are being injected by a device into power system. To comply with standards Power factor correction (PFC) circuits are employed with rectification unit. Addition of an extra unit, puts a limit on overall efficiency of power supply. Advent of Wide Band Gap (WBG) power semiconductor devices have provided us with the opportunity to improve the efficiency of existing electronic circuits with relatively simple control schemes. According to recent research, it has been forecasted that GaN based devices are ideal choice for medium voltage and high speed applications. However, SiC based devices are estimated to take over high voltage applications.

Conventional PFC circuit based on bridged CCM average current controlled Boost converter was chosen for this study. Simulation was made to compare the performance of GaN, SiC and Si based switches. Results from simulation revealed that 38% reduction in switching losses can be achieved by using GaN HEMT instead of Si MOSFET. Practical evaluation was performed on Transphom Totem Pole PFC and All in One Power supply. Both of these devices are based on GaN HEMTs. Totem pole PFC is the major breakthrough achieved by GaN HEMT in the field of PFC circuit. Very low reverse recovery of switches made it possible to implement this circuit with very high efficiency for high power applications. 94% efficiency was observed during evaluation of DC power supply, which validates the claim of superior performance of WBG devices.