| 摘要 |
PURPOSE:To prevent an overcurrent flowing into a laser by a method wherein an output control loop is provided with a voltage limiting circuit in a semiconductor laser device having the output control loop and a switching circuit is also provided in series with the laser to delay the switch at the time of turning on a power source. CONSTITUTION:When a series circuit consisting of a semiconductor laser LD, a transistor Tr1 and a resistor R1 is formed between a voltage source V and a ground, a switching circuit 4 is inserted between the voltage source V and the laser LD. An output control loop consisting of a photodetector 1, a comparator 2 in which a reference voltage (a) is applied, and an operational amplifier OP1 is provided and a voltage limiting circuit 3 is inserted between the comparator 2 and the amplifier OP1 when the output in the amplifier OP1 is connected to the base of a transistor Tr1. In this composition, the circuit 4 is delayed when a voltage source V is made in hot line condition and the driving current in the laser LD is limited by the circuit 3 to prevent the deterioration or breakdown of the laser LD. |
