This paper introduces a design of power supply source applied in high voltage electronic system.The energy is obtained directly from the power line by some tailor-made current transformer（CT）.By setting an inductance in series with the CT and the rectifier bridge

the voltage on the rectifier is reduced to the acceptable level and the output current from the CT is also limited to very small.Thus

the inductance helps steady the voltage and protects the follow circuit.It can resolve the problem of power supply in high voltage electronic instrument.