This paper discusses about controlling the buck boost converter output voltage remains constant by comparing of loads resistor and battery. Buck boost converter output voltage tends to be unstable when given a disturbance with a variety of loads, for that it needs proper control to adjust the duty cycle. The controls that will be used are a combination of conventional control methods, i. e. Proportional Integral (PI) and intelligent control, i. e. Fuzzy logic. The results show that the combination of PI control and Fuzzy Logic can improve performance, i. e. small errors close to zero and the buck boost converter output voltage remains constant even though the load is varied, i. e. resistors and battery.