This dc to dc buck converter works in two states, one when switch is closed and second one when switch is opened. When switch is in close state then diode becomes reverse biased then input source provides the energy to inductor as well as output load. Similarly, when switch is in open state then inductor becomes discharged through diode and transfers some of its stored energy to output load. Because the switch is open and close at high frequency therefore higher order of harmonic are generate which are filtered through low pass filter.

For on or off the switch at high frequency PWM (pulse width modulation) technique is used. The duty cycle of this PWM is calculated by the formula,Where D is duty cycle, Vo is output voltage and Vin is input voltage.We can see that the output voltage is directly proportional to duty cycle D means which duty ratio is increased then output voltage is also increased as well as when duty cycle is decreased then output voltage is also decreased.In this MATLAB Simulink model, an ideal switch is used for regulating the 20V dc voltages in to 10V dc. The ideal switch is on or off through pulse generator which gives the 20V amplitude switching pulse of 20KHz frequency at 50% duty ratio which is gained by the duty ratio formula. The output of this converter is not pure dc it contains the high frequency harmonic content which are removed through low pass filter. In this model 1mH inductor and 10μF capacitor has been used such as low pass filter.10-ohm resistor has been used such as an output load. When this model is simulated in MATLAB then we can see that it shows 9.562 output voltage and .8292 inductor current. Which are showed in below simulation results.