Abstract: What is described here is a power supply unit for plasma systems such as plasma processing or coating devices, wherein electric arcs or disruptive breakdown may occur, which originate from an electrode in particular, comprising a d.c. voltage or direct-current source whose output terminals are connected via an inductive resistor and a power switch to the electrodes of the plasma system, and possibly a circuit for detecting electric arcs or disruptive breakdown, that operates the switch upon occurrence of an electric arc or disruptive breakdown, in such a way that electrical energy producing a plasma will no longer be applied to the electrodes. The invention is characterised by the provisions that the inductive resistor(s) is (are) each connected to a recovery diode and that the switch is a series switch.