Nec Lighting, Ltd.

Toshiya Iwakiri

Shigeki Taniguchi

A light emitting element circuit includes a 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 the both electrodes when the constant current circuit () stops a current supply to the light emitting element (). A light emitting element failure detector () that detects a short-circuit of the light emitting element () in a light emitting element circuit includes a current instantaneous interruption circuit (), a voltage detector (), and a determiner (). The current instantaneous interruption circuit () is arranged on the current supply path different from the electric discharge path and instantaneously interrupts an electric current that the constant current circuit () supplies to the light emitting element (). The voltage detector () obtains an output of a voltage Vf between the anode and cathode of the light emitting element () during a period of the instantaneous interruption as a measuring object. The determiner () determines the existence of a short-circuit from the output.

Light-emitting element failure detector and method for detecting light-emitting element failure

A light emitting element failure detector () includes a light emitting element (), a constant current circuit () which supplies an electric current to the light emitting element (), and an electric discharge path which discharges an electric charge such as the light emitting element (). A light emitting element failure detector () further includes an instantaneous current interruption circuit () which instantaneously interrupts an electric current to the light emitting element () by a current supply path different from the electric discharge path, a diode (), a DC power supply (), and a current detector (). The DC power supply () generates a direct-current reference voltage having a positive value lower than a voltage between the anode and cathode of the light emitting element () in a normal state. The DC power supply (), the diode (), and the current detector () which are connected in series constitute a parallel electric path of the light emitting element (). An anode of the DC power supply () and a cathode of the diode () are arranged on the anode side of the light emitting element (). The current detector () detects an electric current which flows in the parallel electric path when an electric current is instantaneously interrupted.

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Tokyo, Japan

Toshiya Iwakiri