| 摘要 |
PURPOSE:To reduce parts and increase safety by transferring both constant- voltage and constant-current signals to a primary side by one photo-coupler. CONSTITUTION:A constant-voltage detection is performed by a shunt regulator 9 connected in series with a photo-coupler 10 and is transferred to a primary side by said photo-coupler 10. In this case, an output end of operational amplifier 11 is connected with a junction of the photo-coupler 10 and the shunt regulator 9 via diode 14. Thus, a constant-current detection by a current sensing resistor 12 connected within a load circuit is performed, when the operational amplifier 11 is operated by an increase of load current to lower its output voltage to turn ON the diode 14 and the photo-coupler 10 is made to perform an operation corresponding to the constant-current value. As a result, both constant-voltage and constant-current detections can be transferred to a primary side by one photo-coupler 10.
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