Electronic ballasts allow to the discharge lamps to improve the quality of radiation by operating at high frequency. In this work, the design of a high-frequency power supply is proposed (multicellular converter series 4-cell based electronic ballast) to supply a low-pressure mercury-argon Ultraviolet-C (UVC) lamp for sterilization with a sinusoidal current of 50 kHz frequency and an effective value of 0.65A to have a germicidal effect for water purification (a maximum of UV radiation at 253.7 nm). The objective is the elaboration of modern control laws for a discharge lamp powered by a series multicellular converter for water sterilization. The control that we have used is the higher order sliding modes "super twisting algorithm", and for the converter, we have adopted the direct control. The performance evaluation of the proposed regulators was carried out by conducting several closed loop robustness tests