Designing an appropriate power supply is a crucial technological problem when manufacturing an electronic transformer. Several schemes are researched in this paper. Finally, a new structure for designing such a power supply using a special current transformer (CT) set, which has three iron cores. One is closed core. The other two are open cores. Different cores have their own work region. A model is presented. The results of the simulation and experiment demonstrate the feasibility of the scheme. Through rectifier filter, stabilization and DC-DC, the voltage induced from the bus bar is converted into three stable voltages supplying to the sensor head.