Patent ID: 7268314

Claim:
A power supply device for electric discharge machining comprising: a switching unit that supplies a discharge pulse current to an inter-electrode portion between an electrode and a workpiece serving as another electrode arranged to be opposed to the electrode at a predetermined interval; and a pulse width control unit that generates a control pulse signal of a predetermined pulse width in response to a detection signal for starting a discharge in the inter-electrode portion, wherein the switching unit comprises a first switching circuit comprising a first switching element suitable for a high-speed operation that performs a switching operation according to a first drive pulse signal generated in response to the control pulse signal; and a second switching circuit comprising a second switching element suitable for a low-speed operation that performs the switching operation with an overlapping period after operation start of the first switching circuit according to a second drive pulse signal generated in response to the control pulse signal, and wheren the first switching circuit and the second switching circuit receive the control pulse signal in parallel.