The invention provides a 12-pulse converter comprising an autotransformer having a primary winding connected in a delta configuration and two secondary windings connected in star configurations, the two secondary windings being connected to two rectifier bridges that are enabled to operate in parallel by two interphase chokes, the converter further comprising means for generating an additional magnetic leakage flux in at least one of the interphase chokes so as to incorporate a smoothing choke therein.