This paper focuses on the comprehensive comparisons of isolated and non-isolated DC-DC converters for maximum power point tracking (MPPT) purposes. First, MPPT capability is defined by a new mathematical approach which is based on the relationship between resistance seen by input of converter and duty ratio of pulse width modulation signal (PWM). With the help of this approach, topological constraints of some converters have been addressed with a few aspects. The contributions of this study can be explained by following three significant points. One of the researches of this study is to investigate the response time under uniform irradiance conditions for buck-boost converter topologies. In addition, a new criterion is proposed to choose appropriate topology in MPPT application based on the PV module technology which is another innovative part of the paper. Lastly, comprehensive comparisons are made in terms of implementation which consists of power circuit and control requirements, MPPT capability, measurement of PV module current, limit values of solar irradiance and load resistance with the help of published studies in literature. (C) 2016 Elsevier Ltd. All rights reserved.