An electrical supply device including: - a transformer with a secondary winding to feed a current to a load, - control circuitry (18, 22, 24; R12) for the device, - an auxiliary supply source for said control circuitry (18, 22, 24; R12), wherein said auxiliary supply source includes: - at least one output capacitor (Cp) across which a supply voltage is provided for said control circuitry (18, 22, 24; R12), - at least one charge accumulation capacitor (Cp3; Cp1, Cp2) to be traversed by the current fed to said load, - a comparator, and - a switch interposed between said at least one charge accumulation capacitor (Cp3; Cp1, Cp2) and said output capacitor (Cp), said switch coupled to said comparator, characterized in that the comparator is sensitive to the voltage on said at least one charge accumulation capacitor (Cp3; Cp1; Cp2) and is a comparator of the hysteresis type with a value DV connected in such a way to activate the switch above a voltage V ref and as to turn the switch off below a voltage V ref -DV, whereby when the voltage on said at least one charge accumulation capacitor (Cp3; Cp1, Cp2) reaches a reference level, said switch couples said at least one charge accumulation capacitor (Cp3; Cp1, Cp2) to said output capacitor (Cp) by transferring onto said output capacitor (Cp) the charge on said at least one charge accumulation capacitor (Cp3; Cp1, Cp2). - a transformer with a secondary winding to feed a current to a load, - control circuitry (18, 22, 24; R12) for the device, - an auxiliary supply source for said control circuitry (18, 22, 24; R12), wherein said auxiliary supply source includes: - at least one output capacitor (Cp) across which a supply voltage is provided for said control circuitry (18, 22, 24; R12), - at least one charge accumulation capacitor (Cp3; Cp1, Cp2) to be traversed by the current fed to said load, - a comparator, and - a switch interposed between said at least one charge accumulation capacitor (Cp3; Cp1, Cp2) and said output capacitor (Cp), said switch coupled to said comparator, characterized in that the comparator is sensitive to the voltage on said at least one charge accumulation capacitor (Cp3; Cp1; Cp2) and is a comparator of the hysteresis type with a value DV connected in such a way to activate the switch above a voltage V ref and as to turn the switch off below a voltage V ref -DV, whereby when the voltage on said at least one charge accumulation capacitor (Cp3; Cp1, Cp2) reaches a reference level, said switch couples said at least one charge accumulation capacitor (Cp3; Cp1, Cp2) to said output capacitor (Cp) by transferring onto said output capacitor (Cp) the charge on said at least one charge accumulation capacitor (Cp3; Cp1, Cp2). - at least one output capacitor (Cp) across which a supply voltage is provided for said control circuitry (18, 22, 24; R12), - at least one charge accumulation capacitor (Cp3; Cp1, Cp2) to be traversed by the current fed to said load, - a comparator, and - a switch interposed between said at least one charge accumulation capacitor (Cp3; Cp1, Cp2) and said output capacitor (Cp), said switch coupled to said comparator, characterized in that the comparator is sensitive to the voltage on said at least one charge accumulation capacitor (Cp3; Cp1; Cp2) and is a comparator of the hysteresis type with a value DV connected in such a way to activate the switch above a voltage V ref and as to turn the switch off below a voltage V ref -DV, whereby when the voltage on said at least one charge accumulation capacitor (Cp3; Cp1, Cp2) reaches a reference level, said switch couples said at least one charge accumulation capacitor (Cp3; Cp1, Cp2) to said output capacitor (Cp) by transferring onto said output capacitor (Cp) the charge on said at least one charge accumulation capacitor (Cp3; Cp1, Cp2).