Digital Autotuning System for Inductor Current Sensing in Voltage Regulation Module Applications

Inductor current sensing is becoming widely used in current programmed controllers for microprocessor applications. This method exploits a low-pass filter in parallel with the inductor to provide lossless current sense. A major drawback of inductor current sensing is that accurate sense the dc and ac components of the current signal requires precise matching between the low-pass filter time constant and the inductor time constant (L/RL). However, matching accuracy depends on the tolerance of the components and on the operating conditions; therefore it can hardly be guaranteed. To overcome this problem, a novel digital autotuning system is proposed that automatically compensates any time constant mismatch. This autotuning system has been developed for voltage regulator module (VRM) current programmed controllers. It makes it possible to meet the adaptive voltage positioning requirements using conventional and low cost components, and to solve problems such as aging effects, temperature variations, and process tolerances as well. A prototype of the autotuning system based on a field-programmable gate array and a commercial dc/dc controller has been designed and tested. The experimental results fully confirmed the effectiveness of the proposed method, showing an improvement of the current sense precision from about 30% up to 4%. This innovative solution is suitable to fulfill the challenging accuracy specifications required by the future VRM applications.

[1]  Application Note AN-7 A Simple Current-Sense Technique Eliminating a Sense Resistor , 1998 .

[2]  Peng Xu.  Multiphase Voltage Regulator Modules with Magnetic Integration to Power Microprocessors , 2002 .

[3]  Fred C. Lee,et al.  Small-signal modeling of average current-mode control , 1993 .

[4]  Fred C. Lee,et al.  Design considerations for VRM transient response based on the output impedance , 2003 .

[5]  Seth R. Sanders,et al.  Quantization resolution and limit cycling in digitally controlled PWM converters , 2003 .

[6]  F.C. Lee,et al.  Adaptive voltage position design for voltage regulators , 2004, Nineteenth Annual IEEE Applied Power Electronics Conference and Exposition, 2004. APEC '04..

[7]  V. Vorperian.  Simplified analysis of PWM converters using model of PWM switch. II. Discontinuous conduction mode , 1990 .

[8]  F.C. Lee,et al.  A novel soft-switched, high-frequency, high-efficiency, high-current 12 V voltage regulator-the phase-shift buck converter , 2003, Eighteenth Annual IEEE Applied Power Electronics Conference and Exposition, 2003. APEC '03..

[9]  R. B. Ridley,et al.  A new, continuous-time model for current-mode control (power convertors) , 1991 .

[10]  D. Maksimovic,et al.  Modeling of Quantization Effects in Digitally Controlled DC–DC Converters , 2004, IEEE Transactions on Power Electronics.

[11]  Michael T. Zhang,et al.  Powering Intel Pentium 4 Generation Processors , 2001 .

[12]  G.A. Rincon-Mora,et al.  Current-sensing techniques for DC-DC converters , 2002, The 2002 45th Midwest Symposium on Circuits and Systems, 2002. MWSCAS-2002..

[13]  D. Maksimović,et al.  Modeling of Quantization Effects in Digitally Controlled DC–DC Converters , 2007 .

[14]  Enrico Dallago,et al.  Lossless current sensing in low-voltage high-current DC/DC modular supplies , 2000, IEEE Trans. Ind. Electron..

[15]  F.C. Lee,et al.  Critical bandwidth for the load transient response of voltage regulator modules , 2004, IEEE Transactions on Power Electronics.

[16]  M. T. Zhang,et al.  Powering Intel(R) Pentium(R) 4 generation processors , 2001, IEEE 10th Topical Meeting on Electrical Performance of Electronic Packaging (Cat. No. 01TH8565).

[17]  F.C. Lee,et al.  Optimal design of the active droop control method for the transient response , 2003, Eighteenth Annual IEEE Applied Power Electronics Conference and Exposition, 2003. APEC '03..