| 摘要 |
PURPOSE:To effectively prevent the damage of a semiconductor laser due to a surge current by setting the breakdown voltage of a zener diode or ZNR (zinc oxide varistor) to more than sum of the voltages at both end of the semiconductor laser and a series resistor. CONSTITUTION:This circuit is constructed to satisfy the relationship of Vx= VL+RImax, where Imax represents the maximum allowable current, VL represents the voltage between the terminals when the current flows, and Vx represents the rising voltage of a voltage nonlinear element. When a positive impulse voltage is applied from a power source side, the rise of a zener diode 7 is abrupt in the voltage region above the Vx. Accordingly, the current flows to the zener diode 7 side, the current above the maximum allowable current will not flow at the side of a semiconductor laser 5, and the laser 5 will be protected. Since the low voltage is lower than the Vx at the ordinary operation time, the current flows only through the laser. |
