Patent ID: 6055161
Filing Date: 2000-04-25
Classification: H02M,Y02B

Abstract:
In a switching type power supply for use in an electric arc welder or plasma cutter, said power supply comprising an output transformer with a primary winding in a series circuit including a DC source having a selected input voltage and a switch with a conductive on state to pass a current pulse through said primary winding in a first electrical direction and a non-conductive off state disconnecting said DC voltage source from said winding and a large filter capacitor across said DC input voltage source, said switch being operated at a radio frequency with a known period of said off state, the improvement comprising: a snubber network for transferring energy due to the leakage inductance of said winding to said filter capacitor when said switch is shifted from said on state to said off state, said snubber network including a storage capacitor with a diode controlled resonant charging circuit wherein said winding is in a tank circuit with said storage capacitor to charge said storage capacitor in a charging cycle when said switch shifts from said on state to said off state and said winding has a first electrical polarity, and a diode controlled discharging circuit with said storage capacitor in series with said winding and said filter capacitor to discharge said storage capacitor into said filter capacitor when said winding reverses said polarity, the time of successive charging and discharging cycles being less than said known period.