Parallel operation of IGBT:
Parallel operation of IGBT is done for obtaining high current rating. Paralleling of IGBT reduces conduction losses and thermal stress. IGBT combines the qualities of BJT and MOSFET. So, IGBT have both negative and positive temperature coefficient. Means for collector current up to about 70% of rated value IGBT shows negative temperature coefficient and after that IGBT shows positive temperature coefficient. For example, if IGBT is rated for 10A then for up to 7A the IGBT will show negative temperature coefficient and after that up to 10A IGBT will show positive temperature coefficient.
For successful parallel operation of IGBT
1.Each IGBT should have its own gate resistor.
2.The arrangement of the layout of the chips should be such that the current flow path should be symmetrical.
3.The IGBT should be thermally coupled by mounting them on the same heatsink.
Problem faced during parallel operation of IGBT: