A novel design of heatsink-less LED base fluorescent lamp retrofit

A new “heatsink-less” LED based T8 retrofit design is proposed in this study. The lamp consisted of light emitting elements directly attached on a flexible substrate. The substrate is mount on to the inner wall of a full cylindrical glass tube. The design is intended to simplify the lamp construction. However, since the metal-based heat sink is eliminated, the thermal design is a concern. Finite element analysis was performed to optimize the thermal design by varying metal line routing on the flexible substrate, and the glass tube structure. The optimal result shows that the junction temperatures of the LED inside the lamp is about 52°C driven under nominal current. The simulation result is comparable with the experimental measurement. In addition, Darveaux´s fatigue prediction model was implemented to calculate the thermal cycles for crack initiation and propagation, based on the inelastic strain energy density accumulated per cycle during thermal cycling. The details of the design and the optimization strategy is discussed.