George Schuellein

A scalable multiphase buck converter with average current share bus

The paper presents a scalable multiphase synchronous buck converter which meets the tight requirements of the next generation microprocessors. Flexibility in the number of phases (1-16 phases) accommodates requirements of various applications. The converter can be easily expanded or paralleled with other voltage regulator modules (VRM) through an average current share bus. The distributed control IC architecture allows for local phase current signal processing, which minimizes induced noise and facilitates layout while reducing the gate driver to power stage impedance. The experimental results are given to show the advantages of the converter.

Multi-phase buck converter design with two-phase coupled inductors

Ever increasing demand for higher current, lower voltage and faster dynamic response imposes a challenge for multi-phase buck converter designs. Coupling the output inductors of multi-phase buck has the potential to reduce steady-state power losses while maintaining or even improving dynamic performance. Two-phase coupled inductors take advantage of magnetic coupling, have a physically symmetrical structure and with identical magnetic characteristics, and avoid the sub-harmonic output ripple current inherent in coupled inductor designs where the number of phases is larger than two. This paper presents the configuration and design methodology of implementing two-phase coupled inductor in multi-phase buck converters. Although the number of phases is preferred to be even, the design procedure has been extended to converters with any number of phases.

System Accuracy Analysis of the Multiphase Voltage Regulator Module

The paper analyzes the system accuracy of the multiphase voltage regulator module and identifies the influential factors contributing to load line errors. The load line equations for a three-phase buck converter are derived and applied to the worst-case and root-sum-square analyses of load line accuracy. The calculation results are compared with SPICE Monte Carlo simulation, a more realistic statistical method of system accuracy prediction, and verified by the experimental results of the three-phase synchronous buck converter

Design of a Redundant Paralleled Voltage Regulator Module System with Improved Efficiency and Dynamic Response

This paper discusses the design of true redundant, N+l parallel voltage regulator module (VRM) system with low droop resistance. Average current mode control and limited gain for voltage compensation is used to achieve droop current sharing between parallel modules without single point failure. Small signal model of the current sharing scheme is derived and experimentally validated. A novel local sense feedback is used to improve the dynamic performance of the parallel system. Experimental results from a prototype confirm the current sharing between two VRMs to be within 10 % and the dynamic response improvement by 33 % due to local sense feedback

System accuracy analysis of the multiphase voltage regulator module

This paper analyzes the system accuracy of the multiphase voltage regulator module (VRM), and identifies the influential factors contributing to the system errors. PSpice Monte Carlo analysis, a more realistic statistical method of system accuracy prediction, is used to simulate the load line of the multiphase voltage regulator module for the next generation microprocessors. The Monte Carlo simulation result is compared with a worst-case analysis, a root-sum-square method, and is verified by the experimental results of a three phase synchronous buck converter.