Patent ID: 7709764

Claim:
A power supply apparatus for an electric discharge machine configured to perform melt-removal on a workpiece by supplying pulse-like power to a machining gap between an electrode and the workpiece, comprising: a second machining circuit that controls a voltage to be applied to the machining gap and to cause a discharge in the machining gap; a first machining circuit that supplies, when a discharge occurring in the machining gap in response to application of a voltage by said second machining circuit is detected in a first drive mode, a constant current to the machining gap, and also configured to operate to adapt a voltage source in said second machining circuit to output a constant voltage in a second drive mode; and connection means configured to close connection to a power supply to supply electric power through said second machining circuit in the first drive mode and also configured to open the connection to said power supply in the second drive mode so that said second machining circuit operates at a constant voltage supplied from said voltage source.