افزايش بازدهي در منابع تغذيه سوئيچينگ ولتاژ پايين با استفاده از يكسو ساز سنكرون و تكنيك هاي باز يافت انرژي

چكيده انگليسي :

Improving the Efficiency of The Low Voltage Switching Power Supplies by Using Synchronous Rectifier and Energy Recovery Techniques Mohammad Hossein Vafaie mh vafaie@ec iut ac ir September 10 2011 Department of Electrical and Computer Engeneering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language FarsiSupervisor H Farzanehfard hosein@cc iut ac irAbstractRecent improvements in semiconductor technologies have made the design of efficient low voltage portableelectronic devices possible Buck converter is mostly used in low voltage power supplies because of itssimplicity and low cost However employing the traditional buck converter in a low voltage power supplywould result in low efficiency because of the freewheeling diode in the output path of the converter Synchronous rectifiers in which MOSFETs are applied to mimic the operation of diodes can resolve thisproblem Portability is another important parameter in designing portable devices Device portability requires aconverter with low weight and small size Integrating the converter is attractive approach which is used recentlyin portable devices to reduce the size and decrease the weight Portable devices are also supplied with batteriesand the internal resistance of the batteries increases by aging In other words the output voltage of the batteriesis variable during their life time Therefore employing a switching power supply for portable applications is avital requirement for creating constant output voltage However in switching power supplies applying a passivefilter is necessary to regulate the output voltage of the converter This passive filter usually consists of a largeinductor and a bulky capacitor Consequently the output filter of a switching power supply requires large areafor implementation This is a fundamental drawback of the switching power supplies in portable applications The size of the filter components decreases by increasing the switching frequency Therefore integratedswitching power supplies in which very high switching frequencies can be attained is used for portableapplications In integrated switching power supplies the switching frequency of the converter is increased up toseveral MHz By increasing the frequency the efficiency of the converter decreases significantly To resolvethis problem and improve the converter efficiency several techniques such as energy recovery energy recycling and energy reuse are employed In this thesis the stored energy in the converter output capacitor isused for supplying the converter drive circuits In addition a energy recycling technique is applied to improvethe converter efficiency This technique has achieved about 10 efficiency improvement Another applicationfor low voltage buck converter is in the microprocessor power supplies A fixed area on the motherboard isassigned to the processor power supply Therefore switching frequency of the converter must be increased toreduce the converter size Recent processors require low voltage and very high current power supply to operateproperly Creating these conditions is very challenging In addition these requirements would result in a verynarrow pulse width for driving the switch This narrow pulse create several drawbacks in converter operation Therefore this narrow duty cycle must be extended In previous works to extend the duty cycle transformersare applied to the converter In addition to improve the efficiency of the converter current source drivers areused In this thesis coupled inductors are used in the buck converter to extend the narrow converter duty cycle The energy stored in the leakage inductance of the coupled inductors is also recovered to supply the drivers ofthe switches Utilizing these techniques has resulted in 5 efficiency improvement Therefore the efficiency ofthe converter is increased up to 83 Keywords Low Voltage Switching Power Supply Low Voltage High Current Buck Converter Integrated switching power supplies Synchronous Rectifier Ener

وفائي، محمدحسين

افزايش بازدهي در منابع تغذيه سوئيچينگ ولتاژ پايين با استفاده از يكسو ساز سنكرون و تكنيك هاي باز يافت انرژي

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