| 摘要 |
PROBLEM TO BE SOLVED: To provide power supply circuit in which the waveform of input voltage is substantially equalized to that of power supply voltage by automatically varying the resistance division ratio of a voltage being applied to a multiplier for active filter depending on the magnitude of power supply voltage. SOLUTION: Resistances of resistors 14, 15 are set such that a voltage of 1Vop is applied to a multiplier 61 for power supply voltage of 140V and the division ratio of resistors 16, 17 is set such that a Zener diode 11 is conducted up to a power supply voltage of 140V. When the Zener diode 11 is conducted, transistors 18, 19 are turned on and the transistor 18 causes a transistor 13 to turn on while the transistor 19 causes the resistor 15 to be connected with a resistor 20. The transistor 19 is turned on continuously so long as the Zener diode is conducted. Resistance of the resistor 20 is set such that the resistor 20 is connected when the transistor 19 is turned on and the voltage being applied to the multiplier 61 drops thus applying a voltage of 1Vop for a maximum voltage of 240V. |
