A device for converting electrical energy at a high operating frequency, supplied by an electrical network having a capacitor placed between a line and an earth of the device, the capacitance of the capacitor being such that the high-frequency noise is filtered and an inductor placed parallel to the capacitor and having a low resonant frequency corresponding substantially to the frequency of the electrical supply network. The device provide filtering in order to prevent the transmission of high frequency interference from the device to the electrical network while preventing, as far as possible, leakage currents through the filter. The device is useful in the electrical network for an X-ray apparatus.