As the beam-line users require more stringent beam stability for the advanced synchrotron experiments, fully digital controlled 20-bit magnet power supplies have been developed and successfully tested for closed orbit correction of Pohang Light Source (PLS). The new digital power supply has used fiber optics for 25 kHz switching of IGBT drivers, and implemented DSP, ADC, Interlock, DCCT cards in a compact 3U-sized 19" chassis.
Input-output low-pass filters suppress harmonics of 60 Hz line frequency and switching frequency noise effectively. Overall performance of the power supplies has demonstrated 2 ppm short-term stability (< 1 min) and 15 ppm long-term stability (< 12 hours). All the existing 12-bit 70 power supplies for vertical correction magnets replaced with new digital power supplies during 2005 summer shutdown period.
In this paper, describe the hardware structure and control method of the digital power supply test results were shown.