AN ANALYSIS OF LED DRIVER PERFORMANCE USING TRIAC AND DC LINK DIMMING

摘要

The most common dimming control for medium power LED systems is triac dimming, which constitutes the major problem of input current waveform being significantly distorted due to chopping and the resulting system having high total harmonic distortion (THD) values along with low driver efficiencies. The Electromagnetic Compatibility standard EN 61000-3-2-2014 defines THD limits for lighting equipment above 25 W. However, the standard does not specify a limit for systems below 25 W, making triac dimmers appealing for dimming low power LED systems even though the resulting THD, efficiency and power factor values are unsatisfactory. This study aims at evaluating the dimming properties of a flyback LED driver below 25 W, therefore not limited by the EMC standard. For this aim, dimming is separately performed through triac dimming, primary side DC link control with and without power factor correction and the results are analysed.