Modelling and control of magnet power supply system with switch-mode ripple regulator

The dynamic modeling and control design of a newly proposed magnet power supply system are presented. This system is based on a conventional rectifier power supply with a series switch-mode ripple regulator (SMRR). It has been shown that this system offers excellent steady-state performance. A critical assessment of the dynamic performance of SMRR is presented here. Small signal dynamic models for the system are established. The function of the SMRR as a speed-up feedforward path during dynamic transients is analyzed. The regulator design criteria for the closed-loop system to achieve optimum performance are identified. The precise control of the magnet current can be achieved with several kHz regulation bandwidth and less than 10 ppm harmonic content. A systematic design procedure is outlined, and a design example is provided. Computer simulation and experimental results are presented to verify the theoretical analyses