Effect of Phosphor Encapsulant on the Thermal Resistance of a High-Power COB LED Module

With their many advantages, such as small size, energy efficiency, and long lifetime, light emitting diodes (LEDs) are conquering the lighting world. Blue LEDs, because of their high efficiency, are commonly used and a phosphor is used to convert blue light into white light. The remote phosphor concept has gained attention since it promises to deliver better efficacy than solutions in which the phosphor is applied directly on the LEDs. In this paper, the effect of phosphor packaging on the thermal performance of a high-power chip-on-board LED module is studied. Both simulations and measurements show that, despite the added thermal load caused by white light conversion losses in the phosphor, the average temperature of the phosphor-coated LEDs matches with that of noncoated LEDs. The phosphor encapsulant generates a parallel heat conduction path which reduces the thermal resistance from the LED chips to ambient and compensates the thermal power increase.