JP2585691B

PURPOSE:To improve economical efficiency of the title device with its circuit simplified in its constitution, by initially charging a smoothing capacitor, thereafter actuating one arm of a bridge circuit performing chopping action and further charging the capacitor to be boosted. CONSTITUTION:An output of a chopping wave generator 201, serving as the carrier, is input to a comparator 202, and this comparator 202, which connects a conduction rate instruction generator 203 comparing its conduction rate instruction value K' with said chopping wave, outputs a pulse of desired conduction rate. This output pulse is applied to GTO thyristors 31, 32 of an upper arm in a bridge circuit 3 through gate circuits 204, 205. Further GTO thyristors 33, 34 of a bottom arm are fixed to be turned off in the time of starting. Then in the time of starting, an AC power source 1' initially charges a smoothing capacitor 4 previously to the peak value. And then the GTO thyristors 31, 32 of the upper arm are turned on and off further charging the capacitor 4 with energy accumulated in a reactor 2 in an AC side.