Power supply-control device for electrical discharge machining apparatus

A power-supply control device that controls a discharge pulse supplied to an electrical discharge machining apparatus that machines a workpiece by generating a pulse discharge in a machining gap between a machining electrode and the workpiece, the power-supply control device comprising:

• a high-frequency component detecting unit that detects a high-frequency component of discharge voltage at the machining gap;
• a voltage level detecting unit that detects a voltage level of the discharge voltage;
• a high-frequency component comparing unit that compares the detected high-frequency component with a reference high-frequency component to obtain a first comparison result;
• a voltage level comparing unit that compares the detected voltage level with a reference voltage level to obtain a second comparison result;
• and
• a pulse control unit that controls a first pulse off time, the first pulse off time being an interval between discharge pulses, based on the first comparison result, and cuts off the discharge pulse based on the second comparison result,
• wherein, the pulse control unit controls the first pulse off time to switch to a second pulse off time longer than the first pulse off time.