Precise control and regulation of LED colors for lighting design

Whether it be in businesses or in public buildings, in shops, restaurants, hotels, or private homes, thanks to their environmental and economic advantages, LEDs are gradually taking over as illuminants from traditional light sources. Unfortunately, however, the world of LED lighting is not entirely straightforward. Good and efficient LED lamps require an intelligent activation system. This activation system must solve a number of technical challenges, among them, the color and intensity of individual LEDs which depend on age, current and temperature.

Thanks to their better efficiency than other light sources, the heat developed by LEDs is relatively low. The operating temperature range for the application must therefore be more carefully considered. In mobile situations (such as in vehicles), LED systems must function reliably within a wide temperature range.

Since the power dissipated in an LED is, due to the low temperature difference to the surroundings, carried away primarily by conduction or by forced convection (fans), a considerable additional outlay may be incurred here. Temperature changes cause changes in the color and brightness of LED light. For example, temperature fluctuations from 25 to 70°C (77°F - 158°F) during operation lead to a color drift of up to Δu’v ‘= 0.03. This is equivalent to a factor of 6 above the perception threshold of the human eye for color differences. Also, high working temperatures cause LEDs to age faster. Additionally, the brightness of LEDs from the same batch can vary by up to 20 percent and the dominant wavelength of LEDs of the same type may be spread over ±8nm. Even after being classified (i.e. sorted into one of several ‘bins’ in a process known as ‘binning’) by wavelength group, the wavelength can still vary by ±3nm.