| 摘要 |
<p>PURPOSE:To miniaturize a photocoupler, to reduce the cost and to surely absorb the energy stored in an induction load with a photo transistor(TR) so as to prevent the destruction of the photo TR due to an overvoltage. CONSTITUTION:When the state that a current flows to a light emitting diode 1 is transited to the state that the current is interrupted, a load current flowing to an inductive load 7 is not momentarily interrupted, and an overvoltage is generated between a collector C and the emitter E of a photo TR 2A. When the voltage reaches the Zener voltage of a Zener diode 3A or above, a current flows to the Zener diode 3A, a base current flows to the photo TR 2A and a collector current being the multiple of an hFE (DC current amplification factor of the photo TR 2A) with the base current is supplied between the collector C and the emitter E by the base current. Thus, most of the energy stored in the inductive load is consumed by the photo TR 2A and only a small current flows to the Zener diode 3A, then the Zener diode 3A of a small size and small capacity is employed.</p> |
