Abstract: The invention relates to a power supply unit for bipolar power supply of a plasma technology or surface technology system having at least one controllable d.c. power supply (G1, G2), whose positive and negative outputs are connected to the input of at least one bridge circuit of electronic power switches (T1 to T4), said power switches being connected on the input side to at least one control signal conditioning device and on the output side to at least one current detection circuit for the open-/closed-loop control of the power switches, and being connected to the load of the system (A). By means of this invention, current pulses having freely variable amplitudes (Vo+, Vo−) can be generated for the positive and negative current pulses by providing for each bridge circuit (T1 to T4) at least two d.c. power supplies (G1, G2), and the positive output of the two d.c.