| 摘要 |
PURPOSE: To improve the distortion of the input current of a power supply unit and reduce its size, by feeding an AC power to its load through controlling a first switching element. CONSTITUTION: When a switching element SW4 is turned on in the state of a capacitor C3 being charged, a current I1 flows through an inductance element L1 for a power to be stored in it. Simultaneously, a current I2 flows for the voltage V3 between both the ends of the capacitor C3 to be reduced and made substantially zero. Also, a voltage V2 between both the ends of a load Z is reduced to be made substantially zero too. At this time, the switching element SW4 is turned off to superimpose the voltage generated by the power stored in the inductance element L1 on an AC power supply voltage Vac . Thereby, a current I3 flows through the load Z to feed a power to it, and the capacitor C3 is charged to increase the voltage VC3 Further, a switching element SW5 is controlled by shortening its ON-term so as to reduce gradually the power fed to the load Z, and thereby, the power fed to the load Z can be made constant substantially. As a result, the number of the parts of a power supply unit can be reduced, and the distortion of its input current can be improved. |
