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Title: High performance control of VRM circuits
Keywords: VRM, Multiphase converter, Current Mode Control, Critical Inductance, Current sensor, Current transformer
Issue Date: 4-Feb-2007
Citation: MARECAR HADJA (2007-02-04). High performance control of VRM circuits. ScholarBank@NUS Repository.
Abstract: Voltage Regulator Modules (VRM), which are used to power advanced microprocessors, have stringent efficiency and transient response requirements. The multiphase buck converter topology is popularly used for such application, because of its ability to handle large load current and to achieve fast dynamic transient response under large step-load condition.The first part of this thesis fully investigates this issue for three popular control schemes used currently: Voltage Mode Control (VMC), Average Current Mode Control (ACMC), and Peak Current Mode Control (PCMC). For each control scheme, a critical inductance value, for which the convertera??s transient and steady state performance are optimized, is emphasized. Analytical methods to estimate such value is also presented. Furthermore, for the three control schemes, the optimized systems are simulated and compared. It is demonstrated that the PCMC is the best candidate to ensure reasonable dynamic performance and equal current sharing in the multiphase converter. However, for such a control scheme to be implemented, an accurate, fast, small and efficient current sensor is needed.The second part of this thesis focuses on this topic. After a brief overview on existing current sensors used in DC-DC converters, a novel current sensing technique based on the use of current transformers and capable of high performance, is introduced. The requirements and the design of such a current sensor are presented. The accuracy of the novel sensing method is also analyzed. Finally, experimental results on a step down buck converter, controlled with peak current control using such a sensor, are provided to confirm its performance. The proposed technique can also be applied to several other types of power converters besides the multiphase buck converter.
Appears in Collections:Master's Theses (Open)

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