Failure detection device of the chopper circuit

PROBLEM TO BE SOLVED: To accurately detect a fixing failure in a switching element with respect to a failure detector of a chopper circuit. SOLUTION: The failure detector includes a switching element SW, a rectification circuit that passes a current from the switching element SW side to the output side, a smoothing circuit that smoothes an output voltage, a drive control circuit that switching-drives the switching element SW so that the output voltage becomes equal to a preset voltage, a failure detection circuit that detects a fixing failure in the switching element SW based on the terminal voltage of the switching element SW, a differentiation circuit that calculates a time change component in the terminal voltage of the switching element SW, a non-stable section determination circuit that determines whether or not the calculated time change component deviates from a predetermined range close to zero, and a failure detection mask section setting circuit that sets a failure detection mask section in which detection of fixing failure in the switching element SW is interrupted, based on timing with which the switching element SW is switching-driven and the result of determination that the time change component deviates from the predetermined range. The failure detection circuit carries out detection of fixing failure in the switching element SW except the set failure detection mask section. COPYRIGHT: (C)2011,JPO&INPIT