| 摘要 |
PROBLEM TO BE SOLVED: To provide a compact and low-cost overvoltage protection circuit, protecting equipment from an instantaneous overvoltage.SOLUTION: A control unit 40, when turning off transistors Q3a, Q3b, Q4a, Q4b, Q5a, Q5b disposed on both upper and lower arms, controls to connect in a manner to associate balance circuits 33a, 33b with the transistors Q3a, Q3b and diodes D3a, D3b, and balance circuits 34a, 34b with the transistors Q4a, Q4b and diodes D4a, D4b, and balance circuits 35a, 35b with the transistors Q5a, Q5b and diodes D5a, D5b, respectively. Thus, a partial voltage value V1 given to both ends of the transistors Q3a, Q4a, Q5a and the diodes D3a, D4a, D5a of a switching element on the upper arm is equivalent to a partial voltage value V2 given to both ends of the transistors Q3b, Q4b, Q5b and the diodes D3b, D4b, D5b of a switching element on the lower arm, so that breakdown can be prevented. |
