The utilization of DC systems is increased. A photovoltaic (PV) is one of DC resource which is commonly used in small or large scale. The generated power is needed to convert other DC voltage, one of the step up and down DC converter is the buck-boost converter. The character of open loop buck-boost converter is able to convert DC rate, but the conversion results are not stable. In order to control the output voltage, this paper examines improvements to the buck-boost converter performance by using PID and fuzzy-PID controllers. PID controller is able to produce precision and stability. The fuzzy algorithm in PID shows good performance when it is implemented in non-linear system. The PID and fuzzy-PID controllers regulate the duty cycle of buck-boost converter so that the output voltage follows the reference voltage. These controllers also compensate the instability of the output system such as overshoot, oscillation, and error steady state. The results of the simulation of PID and fuzzy-PID controller implementation present that the recovery time of fuzzy-PID is faster than PID. The comparison also shows that the voltage deviation of fuzzy-PID is smaller than the PID. The performances of system with fuzzy-PID controller are better than system with PID.