A Novel Design And Process For Improving The Efficiency And Reliability Of An Ac Direct Led Chip

We have developed a low-cost alternating current (AC) direct light-emitting diode (LED) chip in which bridge rectifiers are implemented within a multi-cell array. The chip was designed and fabricated to form a ladder type electrical circuit of integratied multi-cells for direct operataion with high voltage AC power source. Through a new isolation process technique, the luminous flux in the multi-chip LEDs increased by 5%, which is ascribed to the increase of active area in the chip. In this paper, we report on the effects of a cell array design on the luminous efficiency, and a new process to improve the device performance. The 2 W device exhibited a typical luminous efficiency of 85 lm/W at a color temperature of 3000 K and color rendeing index (CRI) 80. Furthermore, an advanced design to overcome the optical and electrical degradation by the high reverse voltage applied to a bridge rectifier are also discussed.