The solar energy conversion system is very interesting alternative or addition the electric system generation, due to the president cost reduction of the overall system and cleaner power generation. The switching mode power supply requirement is quickly increasing up in the today’s world. In many technical applications it is required to convert a set voltage dc sources into a variable dc output voltage. This paper proposed to provide the design equations of DC-DC boost converter along with an example of boosting DC voltage from 25 to 100 for solar PV application. Because the output voltage from the solar panel is not constant and power from the panel is very low. Adding in or an extra voltage supply to a design is not always cost efficient. Results of simulation show that the switching converter will boost voltage from 25 volts to 100 volts with all data, tests and calculations.