A power supply for an electroerosion machine having a switching element which controls the machining current in the gap. The value of the current is compared with a predetermined voltage and the signal generated based on this comparison is provided to a logic gate, advantageously an "AND" gate, whose output signal is applied to the control electrode of the switching element. The power supply supresses any arcing tendency during the gap short circuit conditions and increases the total current through the gap even when gap voltage is low in order to maintain a high machining rate. Electrode consumption is reduced by using a generally step-type current waveform signal. Machining current during the discharge period may be controlled to more closely approximate a square wave so that shifting to a faster machining rate can be easily accomplished by accepting some sacrifice in electrode consumption. Preferably, two or more switching and gating devices are used to permit gap current to flow intermittently during the entire discharge period.