Temperature dependency in performance of solid state lighting drivers

Abstract

Solid state lighting (SSL) is a new lighting technology based on high brightness light emitting diodes (LED). This technology because of being much more energy efficient, having longer lifetime and design flexibility has attracted the attention of both manufacturers and consumers. This technology looks very promising because of its advantages with respect to conventional lighting systems. Especially for some applications like outdoor lighting and automotive applications, using SSL can be very beneficial. Nevertheless there is still requirement to study about the reliability and performance of these lighting systems in different environments [1]. Each SSL lighting system is constructed by two major parts; optical part and electrical driver. The effect of temperature on performance and reliability of SSL system electrical driver is the focus of this research. In the beginning we will discuss about the fundamental SSL electronic driver building blocks; control/information, switching and electromagnetic energy storage. It will be explained that the last two blocks, switching and electromagnetic energy storage, are the heart of power conversion and thus more sensitive to the temperature. In this paper we focus on electromagnetic energy storage part. Ceramic capacitors are the most commonly used devices as electromagnetic energy storage component in SSL drivers. Thermal studies generally focus on steady state temperature dependency of the devices and they ignore the transient part of the temperature variation. Although in applications like automotive SSL lighting and also outdoor lighting the transient part of the temperature change should be also taken into account. In this paper we show that the transient part of the temperature change can also play an important role in performance of the most common type of the electromagnetic storage part of an SSL driver.