Parallel Energy Buffering LED Driver Achieves Electrolytic Capacitor-Less and Flicker-Free Operation

AC powered LED drivers experience imbalanced energy, between input and output, in a half line cycle. To achieve flicker-free operation, the imbalanced energy needs to be buffered, and often by energy-dense electrolytic capacitors. However, electrolytic capacitors are also well-known for short lifespan and the limiting factor of LED drivers' life. High voltage film capacitors and Buck converter had been used in the proposed LED driver to buffer imbalanced energy. When \mathbf{P}-{\mathbf{in}} > \mathbf{P}-{\mathbf{LED}}, the extra energy is transferred from AC input directly to the high voltage film capacitors. When P _in < PLED, the shortage energy is transferred from the high voltage film capacitors to the output by the Buck converter. The imbalanced energy goes through two times power conversion in the proposed LED driver, which is one time less than other comparable electrolytic capacitor-less designs. Therefore, an improved efficiency can be achieved. A 28W Flyback topology based experimental prototype had been built and tested to verify the proposed design.