| 摘要 |
PURPOSE:To eliminate the loss of electric power due to the addition of a constant current circuit, by connecting a constant voltage element circuit containing a constant current means to the output side of the series control elements. CONSTITUTION:A constant voltage diode Z1 is connected to the area between the input side of a transistor part of a photocoupler PC1 and the output side of a transistor TR1, and the collector-emitter voltage at the transistor part of the coupler PC1 is controlled to be set the Zener voltage at the highest. At the same time, a constant current circuit consisting of the TR2 and TR3 plus the resistances R4 and R5 is provided to prevent a current higher than the rated value from flowing to the diode Z1. Thus the voltage higher than the rated value is never applied to the transistor part of the coupler PC1. At the same time, no current flows to the diode Z1 by setting the Zener voltage VZ of the diode Z1 higher than the comparison reference voltage Vref of a comparison amplifier OP2. As a result, the loss of electric power due to the addition of a constant current circuit is never caused. |
