| 摘要 |
PURPOSE:To prevent the flowing of overcurrents through a laser diode by the abnormal operation of a circuit under the transient state on the making and breaking of a power supply by monitoring supply voltage, making bias currents to flow through the laser diode after a fixed time passes after the laser diode is brought to a stationary state and interrupting bias currents immediately after abnormality is generated at supply voltage. CONSTITUTION:A switch control signal 22 turns a switch 23 ON after a fixed time passes after supply voltage 20 are all brought to the stationary state. The switch 23 is turned OFF to interrupt bias currents 19 immediately after the abnormal state such as the lowering of supply voltage 20 is brought. Accordingly, supply voltage 20 is brought to the stationary state and a laser diode 11 is lit, and the laser diode is put out immediately after abnormality is to some extent generated at supply voltage 20, thus resulting in no possibility in which overcurrents due to the abnormal operation of a circuit are made to flow through the laser diode 11 under the transient state on the making and breaking of supply voltage 20. |
