| 摘要 |
PROBLEM TO BE SOLVED: To provide a current driving element control circuit which can control a current in a plurality of current driving elements separately by a relatively simple circuit configuration and which consumes little power. SOLUTION: A plurality of laser diodes LD1-LDn are connected in series to a constant-current power supply (power supply) D0. Bypass circuits BP1-BPn are set up for the laser diodes LD1-LDn, respectively. For the bypass circuit BP1, for example, a negative feedback circuit is formed of a bypass current sensor BS1, a comparator A1, and a current control means B1. The same is applied to the other bypass circuit. If a driving current ID1 of the laser diode LD1 decreases due to characteristic variations, a bypass current IB1 is increased causing the driving current ID1 to go back to an initial value by negative feedback control. If a quantity of light emission of the laser diode LD1 decreases due to characteristic variations, an optical sensor OS1 detects the quantity of light emission of the laser diode LD1 and then controls the driving current ID1 to return the quantity of light emission to a normal value. COPYRIGHT: (C)2004,JPO&NCIPI |
