SQUARE WAVE TIG WELDING POWER SUPPLY UNIT

摘要

PURPOSE:To enable stable arc to be generated continuously by applying base bias to the parallel connected transistors so as to unify their turn-OFF time. CONSTITUTION:At the turning ON, the constant current to the base IB1 of a power transistor 70' is flowed by way of resistances 73', 80 and diode 82. At the turning- OFF, the charges having been accumulated in the base region of the power transistor 70' are discharged by way of a diode 83, variable resistance 81 and driving transistor 72'. In this case, the accumulation time may be changed by regulating the variable resistance 81 according to the turn-OFF characteristics of the power transistor thereby changing the turn-OFF current IBR (discharge current).In this way, the accumulation time is individually adjusted by constant base current is flowed at the turning-ON of the transistors and changing the turn-OFF base current at the turning-OFF.