What is Buck Converter ? Block Diagram of Buck Converter

 

 

 

Buck Converter or Forward or Step Down Converter

when the transistor switch turn ON by the positive output pulse of the PWM, current follows through the indicator L and divides itself into two parts, are following through the output capacitor C and other through load RL. As the transistor start conducting the induced voltage in the inductor L buck the input voltage Vin.

When the output voltage exceeds the input voltage Vin, the transistor switch Q is turned OFF by the negative pulse of PWM. At this instate the stored energy in the inductor L reverse its polarity and send the current into the load via D is being used up.

The capacitor discharge and output voltage decreases, the diode D prevent this discharged of capacitor c through it.

          In this condition, the switch Q is turned ON and the process continuous. So, the output voltage is maintained very near to the input voltage Vin. Without Diode D the inductive kick (kicking voltage) would develop enough voltage to destroy the transistor.

In the output voltage is increasing because of any decrease in load, the error voltage will increase too. This enhance error voltage reduce the ON time of the Switching transistor Q, there by reducing output voltage to the desire voltage.