The invention relates to a generator of non-thermal plasma produced as jet, at atmospheric pressure, which is provided with an electric power supply system which outputs, in the absence of load, a high direct voltage, in the range of kilovolts, the said supply system being also characterized by high equivalent internal resistance, so that its operation is electrically similar to the operation of a current source or a voltage source with current limiting. The direct voltage provided by the supply system may vary in time, adapting to the state of electrical discharge which generates the plasma, triggering the electrical discharge, retriggering it in case of failure, and, after triggering the electrical discharge, maintaining the plasma jet in stable state. According to the invention, in one embodiment, the electric power supply system comprises: a direct voltage source (8), a commutation circuit (9), a voltage step-up transformer (10), a rectifying and filtering network (13), a current sensor (14) and a control circuit (15).