Patent ID: 6091049
Filing Date: 2000-07-18
Classification: B23K

Abstract:
A power supply apparatus for use with an arc utilizing device, comprising:an input-side rectifier for rectifying an AC voltage and developing a rectified voltage between two output terminals thereof;a pair of smoothing capacitors coupled in series between the two output terminals of said input-side rectifier;a pair of inverters, each of which is coupled across a respective one of the smoothing capacitors, each inverter being alternately rendered conductive and non-conductive in response to a control signal applied thereto, each inverter comprising a switching element for converting a DC voltage applied from the associated one of the smoothing capacitors into a high frequency voltage;a transformer receiving the high frequency voltage from each of the inverters;a converter for converting an output voltage from the transformer into a DC voltage for application to a load;an output detector for generating a signal representative of an output to be applied from the converter to the load;a first voltage detector coupled across the series combination of the smoothing capacitors for generating a signal representative of a first voltage to be applied to the inverters;a second voltage detector coupled across one of the smoothing capacitors, and, hence, one of the inverters, for generating a signal representative of a second voltage across the one smoothing capacitor; anda control unit receiving said output representative signal and said first- and second-voltage representative signals, and generating control signals for determining conduction periods of the switching elements of the inverters in accordance with the difference between the output representative signal and a predetermined signal, at least one of the control signals being modified in accordance with the difference between the first- and second-voltage representative signals, said control unit controlling one of the inverters in accordance with the modified control signal.