Patent ID: 8027132

Claim:
A failure detection device for a power circuit including a switching element having a main current flowing from a first main electrode to a second main electrode altered according to a control signal, said failure detection device comprising: a first rectifying element having a cathode connected to said first main electrode, a first resistance element having one end connected to an anode of said first rectifying element, and having the other end to which a voltage positive to said second main electrode is applied, and a failure determination unit determining whether a failure determination condition to detect failure in said switching element is satisfied or not, wherein said failure determination condition includes a condition that a monitor voltage between the anode of said first rectifying element and said second main electrode is lower than a first reference voltage that is determined in advance, said first reference voltage is set to a voltage lower than a sum of a voltage across the first and second main electrodes of said switching element at an ON state and a forward voltage of said first rectifying element, and higher than the forward voltage of said first rectifying element.