A Research On LED Drive Power Without Electrolytic Capacitors Based On Flyback Converter

LED is the acronym for light emitting diodes. Because of advantage of its energy efficient, safe, reliable, long life and low cost, LED is more and more widely applied to people’s daily lives in today’s energy crisis is increasing. Therefore, the performance of the LED driving power also becomes particularly important. This thesis is dedicated to the research on LED drive power without electrolytic capacitors based on flyback converter.Electrolytic capacitors typically used in conventional LED driver power supply. Because of large volume and short lifetime, Its lifetime become the main limitation of the LED lighting device’s lifetime. Therefore, this thesis proposes a method for removing the electrolytic capacitors in LED driver power supply. At the same time, it maintain high power factor. LED drive power’s main circuit is chosen the flyback converter and the discontinuous current mode for automatic power factor correction. The converters’peak-average ratio of the secondary current can’t too high for the stable and safe running for a long time of LED drive power. So, Using voltage feed-forward manner can reduce this ratio.The output current contains the AC current with twice the line frequency after removing the electrolytic capacitor. It can leads to flicker which should cause harm to the human eye. The method used in this thesis is to introduce a bi-directional converter to the filter capacitor on the output side. And then by calculating the parameters, select and design the appropriate components and circuit to eliminate this flicker.Finally, based on theoretical calculations to build a LED drive power equipment. And the experimental results show the method of introducing harmonic to control the converters’peak-average ratio is effective. At the same time, the introduction of bi-directional converter also can achieve the desired purpose.