Modeling single-stage high-power-factor AC-DC converters for LED driving applications

In this paper a methodology to modeling high-power-factor (HPF) ac-dc converters in LED driving applications is presented. The proposed methodology is based on the averaging methodology applied to the converter under modeling. An averaged large-signal equivalent circuit is generated in this manner, which will be useful to perform extremely fast computer simulations. From the large-signal model both steady-state and small-signal analysis can be carried out to completely modeling the converter, achieving any desired steady-state characteristic and small-signal transfer functions. The proposed methodology is very intuitive and allows designers to achieve a natural understanding of the LED driver performance. The modeling procedure is illustrated with a HPF buck-boost converter operating in discontinuous conduction mode (DCM) designed to supply a 70W LED lamp. Simulation and experimental results demonstrate the validity of the proposed methodology.