Multiphase 48 volt conversion for low noise applications in an instrument grade power supply

This paper presents a switching power supply design that meets the accuracy, response time, noise level, and current requirements for today's ATE instruments. It focuses on minimizing high frequency parasitic ringing at the switching waveform edges that interferes with the linear regulator output. The noise reduction features include a transformer with flat planar construction of interleaved coils, a full-bridge with zero-volt switching for the primary control of the transformer, multi-phase circuits to enable maximum response time, and ferrite beads on all switches to control ringing.