Patent ID: 8362639

Claim:
A light emitting diode drive device, comprising: a drive circuit section that applies a direct-current voltage to a light source including a plurality of light emitting diodes connected in series to allow the light source to light up; a voltage detection circuit section that detects a voltage across the light source; and a malfunction determination circuit section that determines that the light emitting diode is short-circuited when the voltage detection circuit section detects a voltage drop and a difference between the voltage before being dropped and the voltage after being dropped is equal to or more than a predetermined threshold value that is an amount corresponding to a voltage of at least one of the plurality of light emitting diodes, wherein the malfunction determination circuit section includes: a first holding section that holds a voltage detected by the voltage detection circuit section every predetermined sampling time; a second holding section that holds the voltage held by the first holding section before the first holding section holds a new voltage; a differential circuit section that outputs a potential difference between the voltage held by the first holding section and the voltage held by the second holding section; and a comparison circuit section that determines that the light emitting diode is short-circuited, when the output from the differential circuit section is equal to or more than the threshold value.