Review on retrofit G4 LED lamps: Technology, challenges, and future trends

G4 LED lamps have difficulties to reach high lumen output within the required small form factor. Current technology used in G4 LED lamps was at first reviewed by analysis of 7 current commercialized products. Theoretical limitation was calculated under different design strategy scenarios. Furthermore, a detailed analysis of driver systems were carried out under thermal infrared imager. It has been found that schottky diodes and capacitors are main challenges for drivers. Since current electrolytic capacitors are bulky and not reliable enough, novel capacitor technologies were further analyzed. Finally, a G4 LED prototype based on wafer level packaging were introduced. The prototype was fabricated in 2D and folded to 3D, in order to save space. All processes related are CMOS compatible. Planar rectifier consists of four schottky diodes which were fabricated separately are compatible for monolithic integration on such foldable substrate. With such technology, it is possible to integrate LED drivers, micro channels for heat dissipation, or other silicon based technologies by CMOS processing, together with the flexible hinges, in order to have a G4 LED package with high lumen output and small form factor.