This paper proposes spread-spectrum clock modulation algorithms for EMI reduction in digitally-controlled DC-DC converters. In switching regulators using PWM, switching noise and harmonic noise concentrated in a narrow spectrum around the switching frequency can cause severe EMI. Spread-spectrum clock modulation can be used to minimize EMI. In conventional switching regulators using analog control it is very difficult to realize complex spread-spectrum clocking, however this paper shows that it is relatively easy to implement spread-spectrum EMI-reduction using digital control. The proposed algorithm was verified using a power converter simulator (SCAT).

This letter presents an analysis of characteristics of multiphase buck converters with coupled inductors. We derive equivalent inductances that provide both low per-phase steady-state ripple current and fast transient response. The characteristics of coupled-inductor circuits--low per-phase ripple current and fast response--were examined and verified by circuit simulation and experiments.