AC-DC converter apparatus

Claim 1

A DC power supply apparatus comprising: rectifying means for rectifying an input AC voltage to develop a rectified voltage between two output terminals thereof; first and second smoothing capacitors connected in series between said output terminals of said rectifying means; first inverter means receiving a first voltage developed across said first smoothing capacitor, and second inverter means receiving a second voltage developed across said second smoothing capacitor, said first and second inverter means converting said first and second voltages into high-frequency voltages; voltage transforming means receiving said high-frequency voltages from said first and second inverter means and developing a voltage-transformed high-frequency voltage; converting means for converting the voltage-transformed high-frequency voltage into a DC voltage; voltage detecting means for detecting respective ones of said first and second voltages; comparing means for comparing the absolute value of the difference between said first and second voltages as detected by said detecting means with a reference voltage, and developing an output corresponding to the result of comparison, said reference voltage being the difference between the voltages developed across respective ones of said first and second smoothing capacitors when the voltage across one of said first and second smoothing capacitors is the rated voltage of said one smoothing capacitor; and disabling means responsive to the output of said comparing means developed when the absolute value of the difference between said first and second voltages is larger than said reference voltage, for disabling said first and second inverter means, said disabling means having a slow response to the output of said comparing means.