Design of IGBT over-current protection circuit

ZHANG Hai-liang， CHEN Guo-ding， XIA De-yin
（School of Information Engineering， Zhejiang University of Technology， Hangzhou 310023， China）

Abstract： In order to solve the over-current breakdown problem of insulated gate bipolar transistor（IGBT）in practical applications，short-circuit protection circuit and overload protection circuits were proposed according to the IGBT's collector current，after the analysis of IGBT's characteristics and over-current measures. When overload protection circuits detected over-current，it switched off IGBT immediately，IGBT's drive signal can be blocked continuously，for fixed time or for a single cycle based on different overload protection requirements；short-circuit protection circuit detected the over-current by measuring IGBT's on-state voltage drop，using dropping the grid voltage，soft switch-off and reducing IGBT's working frequency the circuit can decrease short-circuit current and switch off IGBT safely. Detailed elaboration of circuits' operating mechanism was given. The over-current testing of the all designed protection circuits  was done. The waveform graphs were obtained. The experimental results indicate that protection circuits can detect over-current in time and response accurately，IGBT is protected reliably under different over-current conditions.
Key words： instulated gate bipolar transistor（IGBT）；over-current protection；drop grid voltage；soft switch off