Study and Design, Simulation of PWM based Buck converter for Low Power Application

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Now a day’s dc-dc switching converters are widely used for sophisticated application. By using these converters with given dc input voltage a stabilised output voltage can be obtained by using Buck (lower), Boost (higher) or Buck –Boost (generic) topology which improves the efficiency of dc-dc converter as compared to linear regulators. Most used technique to control switching power supply is pulse width modulation (PWM). In this way a particular dc-dc converter is designed by keeping the typical application in mind. A properly designed dc-dc converter provide low ripple, better noise rejection, reliable and efficient converter. For some typical application like powering LED needs constant current supply for constant illumination, hence feedback based closed loop converters becomes better choice. In the present thesis for low power application a PWM based closed loop dc-dc buck converter has been designed, analysed and simulated. A MOSEFET has been used as switching device and components has been designed for low ripple and low noise. With variation in load and variation in input power supply output supply voltage has been obtained as constant value by using PID controller. The performance of PID controller and switching frequency has been adjusted such that the output voltage maintain at 8 V. By rigorous simulation procedure it has been obtained that for load resistance in the range of 10Ω to 35Ω and with the value of P = 8, I = 20 and at a switching frequency of 100 KHz, the output voltage provides a constant value at 7.995 V approximately. The maximum ripple value obtained is 4%. MATLAB has been used as a tool for simulation. The performance of converter has been analysed by controlling PID controller. Keyword: Linear Regulator, Switching Regulator, Ripple/Noise, Converter, transistor switch, capacitor, diode, inductor, pulse-width modulating controller etc.