| 摘要 |
PROBLEM TO BE SOLVED: To solve the problem that the life of a laser diode is shortened by the passage of an abnormal current through the laser diode at the time of rise or decay of a power-supply voltage. SOLUTION: The driving unit of the laser diode is provided with two systems of circuits (COMP1 and COMP2) for monitoring the voltage VCC. The monitor voltage V1 of the system for controlling switching of an inner bias voltage Vbias is set higher than the monitor voltage V2 of the system for controlling the output current. A reference voltage Vref1 is applied as a reference voltage Vref of a voltage-current converting circuit 14 instead of a reference voltage Vref2 until the inner bias voltage Vbias becomes stable when the power supply is turned on or before the inner bias voltage Vbias is cut and the circuit operations become instable when the power supply is turned off for controlling the output of the voltage-current converting circuit 14 in the direction of reducing the current to be fed to the laser diode LD and for preventing the passage of an abnormal current through the laser diode LD at the rise of the power- supply voltage VCC. COPYRIGHT: (C)2004,JPO
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