Solar energy plays an important role in renewable energy generation systems since it is clean, pollution-free sustainable energy as well as the increasing cost-of-electricity which causes high-growth demands amongst utility customers. This paper presents various circuit topologies of DC-DC converters in solar photovoltaic (PV) applications. There are three types of DC-DC converter presented in this paper that can be integrated with solar PV system which are buck, boost and buck-boost converter in various applications. This paper also presents the application on DC-DC converter in solar PV system for maximum power point tracking (MPPT) feature. The advantages and disadvantages of each topology will be discussed further in term of cost, components, efficiency and limitations.