Improved design methodology for LED lamps

The understanding of the interrelationships among the photometrical, electrical and thermal (photo-electro-thermal) parameters is extremely important to design lighting systems based on light-emitting diodes (LEDs). This paper proposes an improvement in the estimation of the luminous flux previously proposed in A General Photo-Electro-Thermal Theory (PET Theory), using information taken only from LED manufacturer´s datasheet. An analytic/graphic design methodology is also proposed. This methodology considers the heatsink thermal resistance, luminous efficacy and junction temperature when the forward current and number of LEDs are varied. Thus, the methodology provides, to LED systems designers, important guidelines for a direct and comparative design procedure to perform the lamp project. Experimental tests were performed in order to validate the proposed design methodology.