The step up DC-DC converter is known as boost converter. The main applications of the boost converters are in regulated DC power supply and the regenerative braking of DC motors. In this the average output voltage is always greater than the DC input voltage. The output voltage is controlled by controlling the switch duty cycle. When the switch is on, the diode is reverse biased, and hence isolates the output stage. During the switch on mode the inductor gets the energy from the supply and stores it. During switch off state, the diode becomes forward biased and the output stage receives the energy from the inductor as well as the input. Thus the net energy transferred to the output from input is always greater in a given switching cycle. The ratio of output voltage to input voltage is given by