Impact of Linear-Nonlinear Control in Multiphase VRM Design

The new generation of microprocessors has imposed more demanding design requirements for their power supplies, usually known as voltage regulator modules (VRM). The transient response of the converter is a critical design issue since tight output voltage regulation should be achieved at lower voltage values and higher current levels with faster transient slew rates. In order to meet the new specifications, multiphase interleaved synchronous buck converters are the most interesting solution from the VRM design viewpoint since this power topology allows increasing the current level minimizing the total equivalent inductance and the output capacitor. Regarding the converter control strategy, an existing control technique known as linear-nonlinear control improves the converter transient response with an easy saturation rule of the duty cycle since it is based on output voltage sensing. As a consequence, a reduction of the number of phases and the switching frequency of the multiphase VRM is obtained. This paper analyzes the impact of the reduction of the number of phases and switching frequency on the converter size in comparison with multiphase VRM with linear control strategy.