| 摘要 |
PROBLEM TO BE SOLVED: To provide an overcurrent protector exhibiting a good overcurrent detection sensitivity regardless of the temperature while suppressing power consumption. SOLUTION: Power is fed through a protector 70 to an emission element section 21 being driven through a driver 20. A voltage drop across an overcurrent detection resistor 704 in the protector 70 is amplified through an amplifier comprising transistors 707, 708. When an overcurrent flows through the emission element section 21 to cause voltage drop at a joint PA, the transistor 707 operates in unsaturated state to cause voltage drop at a joint PB. Since the voltage at the joint PB is divided and fed to the base of the transistor 707, a transistor 702 is controlled to reduce voltage drop across the resistor 704 thus reducing the current. Consequently, the light emission power of the emission element section 21 can be prevented from exceeding over a desired range. Furthermore, since the current is limited by means of a differential amplifier using the voltages at the joints PA, PB, a good overcurrent detection sensitivity can be attained regardless of the temperature while suppressing power consumption of the resistor 704. |
