Loss analysis for efficiency improvement of the integrated buck-flyback converter for LED driving applications

In this paper, a study of the losses in the integrated buck-flyback converter (IBFC) used as high-power-factor LED driver is presented. The final goal of this study is to investigate the possibilities of increasing the efficiency of this converter, which is usually in the range of 85-89%. The procedure of the improvement is done by obtaining the equations for the value of the current through each component in terms of the converter parameters. With these equations the converter can be redesigned in order to increase the efficiency. The value of the current is found in average value, or root mean square (RMS) value depending on the type of the parasitic element, whether it is modeled by a parasitic forward voltage source or by a parasitic resistance, respectively. The equations found are proved mathematically and verified by simulation. A chart for the losses in each part is illustrated using the proved formulas and the parasitic model of each element and verified from the designed IBFC prototype. The presented methodology can easily be applied to other integrated converters. Finally, the paper presents some ideas to increase the eificiency of the IBFC.