Abstract: The main function of the rod position detector power supply in the nuclear power plant is to provide the sine wave current for the detector primary windings. The output accuracy and load variation response have effects on the rod position measurement accuracy. In order to improve the above performance of the detector power supply, this paper introduces the current hysteresis control for its characteristics of fast load tracking and response, and optimizes the traditional hysteresis control to make the switch frequency keep constant. However, not only does the control method have relationship with the switch frequency, but also the device parameters. This paper also analyzes the inductive effects of parameters on the switch frequency spectrum. Lastly, simulation is carried out to verify the theory analysis. The result of simulation verification shows that the improved control method overcomes the defect of the traditional hysteresis control, and improves the electrical performance of the detector power supply.