Electrical discharge power supply circuit

An electrical discharge machining power supply circuit comprising:

• a power supply circuit comprising only a single direct-current power source;
• a first circuit, connected in parallel with said power supply circuit, and comprising a first switching device and a first rectifying device connected in series with said first switching device, said first circuit having a first connection point between said first switching device and said first rectifying device;
• a second circuit, connected in parallel with said first circuit, and comprising a second switching device and a second rectifying device connected in series with said second switching device, said second circuit having a second connection point between said second switching device and said second rectifying device;
• an electrical discharge machining electrode and a workpiece which are in series between said first connection point and said second connection point, said first and second switching devices being controlled such that an electrical discharge is generated between said electrode and the workpiece;
• and
• first circuit means comprising a first circuit device, connected between said workpiece and said first connection point, for preventing an excessive voltage, generated in wiring inductance between said first and second connection points during switching of said first and second switching devices, from damaging at least said first switching device.