Practical Implementation Of A Highfrequency Current Sense Technique For VRM
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Practical Implementation Of A Highfrequency Current Sense Technique For VRM presented by : Sarath T S AE&I College Of Engineering, Trivandrum3 Practical Implementation Of A Highfrequency Current Sense.ppt (Size: 2.5 MB / Downloads: 50) Hi Friends, If you like this presentation, say hi to the author who has shared it with you at:+919895691446, sarathtsind@gmail.com Overview Introduction Traditional methods DCR method Theoretical basis analysis Effect of temperature Current sense methods comparison Problems and solutions Experimental results Example of VRM using DCR method Future works Conclusion Introduction VRM is voltage regulator module Tracking inductor current in high frequency dc/dc converters is difficult task when high output current and low output voltage are demanded by load. The main idea is to obtain an equivalent voltage using the dc resistance of the inductor and which used to produce the corresponding current Traditional methods Shunt resistor method Good accuracy Losses due to power dissipation in the sense resistor Current observer method No problem of losses, frequency Problems is choice of the converter and the observer models Equivalent serial resistance (ESR) Choice of components is limited May cause significant decreased accuracy MOS method Complicated due to non linearity Less accuracy due to the Rds temperature dependence Rds depends on the applied VGS and the VDS. DCR Method This sense method makes use of the inductor dc resistance (DCR) to obtain a proportional voltage of the inductor current Advantage of this technique Better accuracy Lossless Any resistor can be added. Can be used to supply laptop computers. Sense circuit using DCR Theoretical Basis Analysis Capacitor voltage Vc is proportional to the inductor current For a correct working of the sensor, we should match both time constants of (1) to have a linear relation between Vc(s) and IL(s) as in equation Effect Of Temperature Drawbacks of this sense technique loss of accuracy produced by temperature changes. temperature changes, DCR also varies, if temperature rises, DCR also increases Thus, higher gain for high frequencies Solving this temperature problem add a compensation circuit using a positive temperature coefficient thermistor Current Sense Methods Comparison Tracked the inductor current of a 4phased buck converter using following techniques DCR technique, the shunt resistor (Rs), and the Rds method Shunt resistor and the DCR technique methods gives good accuracy Rds method failed to give the real measurement of the current. Comparison Between Rds and DCR method Decrease in efficiency due to Significant losses introduced by the shunt resistor. Even if both time constant are correctly matched in DCR method addition of the secondorder currentsense system causes a reduction of the transient response Quantitative Comparison between different methods Problems And Solutions Associated To Sense Method The respective values of L and DCR must be known Rcs and Ccs are accordingly chosen Main difficulty is to recover the voltage image of the inductor current at the boundaries of Ccs. must be very careful with high frequency noises Overcome this noise problem Add a previous stage to the sense circuit in order to filter this high frequency noise. Selection of instrumentation amplifier (INA103) (AMP03) Experimental Results This dc–dc converter utilizes a currentmodecontrolled architecture for an easy compensation and a better line rejection. Experimented in different cases low current application medium current application high current application DCM operation INA103 AMP03 Future Enhancements Integration of passives to enhance power density since integration allows a drastic reduction of capacitors and inductors size Explore the integration of passive elements of this currentsense technique into a fullintegrated DCR current sensor and in its new operation in VRM applications Conclusion Analysed the practical use of the lossless DCR inductor currentsense technique for a highcurrent high frequency application. Also repeated the analysis for low current highfrequency dc/dc converters operating in CCM and DCM. Implemented and explained in detail each stage of the sense process in order to recover correctly an accurate equivalent voltage image of the inductor current. Experimental tests employing VRMs have been completed by demonstrating higher performances of the DCR current sense technique compared with Rshunt sense one. References [1] J. S. Glaser and A. F. Witulski, “Application of a constant outputpower converter in multiplemodule converter systems,” in Proc. 23rd Annu.IEEE PESC, Jul. 1992, vol. 2, pp. 909–916. [2] R. Giral, L. MartinezSalamero, and S. Singer, “Interleaved converters operation based on CMC,” IEEE Trans. Power Electron., vol. 14, no. 4,pp. 643–652, Jul. 1999. [3] H. Mao, Y. Liangbin, C. Wang, and I. Batarseh, “Analysis of inductor current sharing in non isolated and isolated multiphase dc–dc converters,” IEEE Trans. Ind. Electron., vol. 54, no. 6, pp. 3379–3388, Dec. 2007. Use Search at http://topicideas.net/search.php wisely To Get Information About Project Topic and Seminar ideas with report/source code along pdf and ppt presenaion



