| 摘要 |
PROBLEM TO BE SOLVED: To improve the stability of the output voltage of an electric power supply circuit consisting of a three-terminal type switching regulator (SW-Reg). SOLUTION: The voltage Vi is inputted to the drain terminal DR of SW-Reg1 and the condenser C1 of the source terminal SO is charged, and the voltage of the control terminal CT is increased, and the FET becomes 'on', and pulses are outputted from the SO terminal, and the pulses are smoothed with the coil L1 and the condenser C2, and the direct current Vo is outputted. The voltage Vo is separated with the resistors R3 and R4, and the separated voltage is impressed to the base of the transistor Q, and the emitter of the transistor Q is cramped by the Zener voltage of the Zener diode D2. When the voltage Vo increases, the collector current in the transistor Q is generated, and the photo diode in the photo coupler PC becomes 'on', and the photo transistor becomes conductive, and the emitter current Id is flown to the CT terminal, and the width of the outputted pulses in SW-Reg is narrowed, and the output voltage Vo is lowered to the normal value. The voltage in the coil L2 electromagnetically connected to the coil L2 is rectified and smoothed, and supplied to the photo coupler as the power source.
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