In order to improve the efficiency of current transformer power supply in the vicinity of starting current and to reduce the dead zone

we derived a relationship among the output power

filter capacitor voltage

and turns. Then

taking the minimum output power 0.5 W as the target

we simulated the influence of filter capacitor voltage and turns on output power in the vicinity of starting current. It is concluded that the maximum power is independent of turns when the voltage drop of rectifier is not considered. However

due to the voltage drop of real rectifier

the curve of maximum power and turns has saturation characteristic

and the turns are determined according to it. It is obtained that the stable operating point is the point of higher filter capacitor voltage by analyzing the stability of the operating point on the output power curve of current transformer. The phenomenon that the power supply may not be able to output normal power in the vicinity of starting current is analyzed

and the solution of controlling the starting of DC-DC circuit is given. A circuit is designed

and the correctness of the analysis is verified by experiments.