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Fully Digital Controlled Power Supply for PLS

Fully digital controlled 20-bit magnet power supplies have been developed and successfully tested for closed orbit correction of PLS(Pohang Light Source). The new digital power supply has used fiber optics for 25kHz 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 60Hz line frequency and switching frequency noise effectively. Overall performance of the power supplies have been demonstrated as +/- 2ppm short-term stability(<1 min), and +/- 10ppm long-term stability(<36 hours). All the existing 12-bit 70 power supplies for vertical correction magnets will be replaced with new digital power supplies during 2005 summer shutdown period. In this paper, we will describe the hardware structure and control method of the digital power supply and the experimental results will be shown.