Power supply unit for discharge apparatus which prevents excessive electrode wear

摘要

A power supply unit for a discharge machining apparatus which eliminates overshooting in current rise and improves the electrode consumption characteristics by preventing an operational amplifier as well as a current control element from being saturated, thereby eliminating overshooting during the rise time of the machining current, by clamping the output voltage of the operational amplifier during the stand-by time for electric discharge. The output is clamped by a plurality of resistors and diodes to a state where the output voltage is higher than a power-supply voltage (the output clamp level is set by a resistor). Namely, during the stand-by time when inverted amplification (feedback) via a resistor in an operational amplifier is being carried out, a constant state of feedback is maintained by the diodes.