Contrary to Linear Regulators which step down the DC voltage by dissipating the heat, Buck Converters step down the DC voltage through switching regulators and also step up the output current. According to the law of power conservation, input power must be equal to output power.
Pin = Pout
Vin*Iin = Vout*Iout
So in the buck converter as the input voltage (Vin) is greater than output voltage (Vout), so the input current (Iin) is always less than the output current (Iout). The switching regulators provide more efficiency up to 90% if the SMPS is designed properly.
A Buck Converter can be designed in two ways –
Open loop buck converter – In open loop buck converter, there is no feedback from output to input contrary to the closed loop which has a feedback circuit. So, the output of an open loop buck converter is not regulated.
Closed loop buck converter – In closed loop buck converter, there is a feedback from the output to the input. So, the output of a closed loop buck converter is regulated.
There are certain design parameters involved in the designing of the buck converter. It is important to understand these design parameters. Any buck converter can operate in either of the two possible modes of operation. These modes of operation are as follow –
Continuous Conduction Mode (CCM)- In CCM, the current in the inductor is continuous in the entire cycle of the switching period. So a regulated voltage at the output is obtained but the output is regulated only if the current is drawn within the limits of CCM.
Discontinuous Conduction Mode (DCM)- In this mode, the current in the inductor is pulsating and it becomes zero for a part of switching time. So a regulated voltage is not received in DCM. But, the voltage can be regulated by connecting a feedback circuit from output to input.
In this tutorial, a non-isolated buck converter is designed which means the input and output share the same ground. The buck converter designed in this project will step down 12V DC to 5V DC with a tolerance limit of +/-0.5 V. The output voltage will be adjustable between 5V and 9V. Once the circuit is designed and assembled, the value of the output voltage and current will be observed using a multimeter. These values will indicate the efficiency of the buck converter designed in the project.
Project Source Code
Project Source Code
Filed Under: Electronic Projects