| 摘要 |
PURPOSE:To prevent an output voltage from becoming an overvoltage, by providing a voltage detecting circuit in parallel with a power supply circuit output and, at the same time, by transmitting the output of the detecting circuit to a photocoupler through the 2nd comparison amplifier circuit. CONSTITUTION:When an electric current is supplied to a load 4, a voltage proportional to an output current Iout is produced across both ends of an output current detecting element 3. The output current is controlled so as to maintain the current as a constant current by detecting the voltage and amplifying the difference after comparing the voltage with a reference voltage 6 at the 1st comparison amplifier 10, and then, transmitting the amplifier output to a main circuit 2 as a constant-current controlling signal through a photocoupler 9. Moreover, a voltage detecting circuit 11 detects an output voltage Vout and supplies the detecting signal to the 2nd comparison amplifier 12. The 2nd comparison amplifier 12 operates as an overvoltage suppressing circuit which controls the output voltage so that the output voltage does not exceed a fixed value determined by a reference voltage 15. Therefore, each output of the 1st and 2nd comparison amplifiers 10 and 12 is OR-connected and serially connected with the photocoupler 9. |
