Patent ID: 9709637
Date: 2017-07-18
CPC Classifications: G01R,H01L,H05B

Claim:
1. A light emitting element failure detector that detects a short-circuit of a light emitting element in a light emitting element circuit that includes the light emitting element, a current supply path to the light emitting element, a constant current circuit that supplies a current to the light emitting element via the current supply path, and an electric discharge path that discharges an electric charge accumulated at the light emitting element and at a region connected between both electrodes of the light emitting element when the constant current circuit stops a current supply to the light emitting element, the light emitting element failure detector comprising: a current instantaneous interruption circuit that is arranged on the current supply path different from the electric discharge path and that is configured to instantaneously interrupt an electric current that the constant current circuit supplies to the light emitting element, a voltage detector that obtains a voltage Vf between an anode and cathode of the light emitting element during a period of instantaneous interruption, and a determiner that determines that the light emitting element is short-circuited when the voltage Vf, obtained by the voltage detector during the period of instantaneous interruption, decreases to or lower than a threshold that is lower than a lower limit of a fluctuation of a voltage of a light emitting element at a normal state, wherein the period of instantaneous interruption is set to a time which is longer than a time for the voltage Vf to decrease to 0 V if the light emitting element is short-circuited.