A low noise power supply based on buck converter for current regulation in an inductive load

High current regulations are widely required in tokamaks to generate a specific magnetic field for plasma confinement which is challenging for power electronics. For high current regulation, the stray inductance will cause high noise and surge voltage that may damage the power electronics. In addition, it is difficult to ensure both a fast response and a steady evolution. In this paper, a power supply based on a buck converter for high current regulation in an inductive load is described, in which insulated gate bipolar transistors are used as switches and two capacitor banks are used for energy storage. The first stage capacitor bank at a higher voltage ensures the fast current growth rate at the beginning of discharge and plays the role of wave filter later to reduce the noise. The second stage capacitor bank at a lower voltage provides the main energy required during discharge. A microcontroller is used to regulate the current by a feedback mechanism. This power supply can regulate the high current in an inductive load with low noise and fast response, which has been applied to the poloidal field coils and the ultrafast reciprocating probe system in the SUNIST (Sino-UNIted Spherical Tokamak) spherical tokamak.