A Comparative Study of PI and Fuzzy Controllers for Solar Powered DC-DC Boost Converter In this paper a fuzzy logic controller for Solar powered DC -DC boost converter is planned. Here for simplification, the PV system is taken as a constant DC Voltage source. The output response of the boost converter, is controlled by changing its duty cycle and the controller is planned to change the duty cycle. The simulation is formulated by MATLAB simulation program and PSIM software. Using fuzzy logic controller duty cycle of PWM signal is yielded. Taking into account the value of duty cycle simulation results demonstrate that the output voltage of the boost converter can be controlled. With the help of fuzzy logic tool box, fuzzy logic controller has been applied to the system. The assessing of output has been accomplished and equated by software simulation among PI controller and fuzzy logic controller. The simulation results shows that by using this technique output response of step-up Switching converter is regulated.