The design of controller based on simplified models can lead to difference between expected and practical results or even instability of the converter. Therefore, obtaining an accurate model is of great importance. In this paper, firstly, the accurate model of non-inverting buck boost converter by considering all parasitic components is obtained. Then, two PI and Type 3 controllers are designed based on accurate model. Afterwards, the performance of these controllers is compared with controllers designed based on a simplified model. All tests are carried out on a prototype of a non-inverting buck boost connected a photovoltaic module. The obtained results show the controllers designed based on accurate model have superior performance in comparison with controllers designed based on simplified model. In addition, the bode diagram obtained based on analog method in PSIM software and the one obtained based on transfer function of accurate model confirm the accuracy of the derived model.