| 摘要 |
PURPOSE:To protect light emitting diodes from damage when dynamically lighting on a plurality of light emitting diodes in a time division manner, by providing an access time interval monitor circuit to interrupt the lighting-on when the duration of a pulse current supplied to the diodes exceeds a prescribed value. CONSTITUTION:A decoder 2 and a driver 3 are provided for a plurality of light emitting diodes 1a-1n. The diodes are operated in a time division manner to perform dynamic lighting-on. A display unit is composed of the light emitting diodes. An access time interval monitor circuit 4 is provided to produce alarm information to stop the lighting-on when the duration of a pulse current supplied to the diodes exceeds a prescribed allowable length. The circuit 4 is made of a watchdog timer. A writing signal is applied to the timer. When a lighting-on control circuit does not perform prescribed action, the timer is operated to suppress an overcurrent by the driver 3. |
