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Firmware—RGB colour mixing firmware for EZ-Color

Posted: 05 Feb 2010     Print Version  Bookmark and Share

Keywords:RGB colour mixing  HBLED controller  EZ-Color firmware 

Using EZ-Color to intelligently drive and control high-powered LEDs leads to useful applications and designs. The firmware in these applications is extensive and complex. This application note describes the firmware in an application that features dynamically programmable colour outputs, a high level of integration and minimal use of system flash. The firmware implementation of a RGB LED colour mixing application is also described. A considerable amount of external hardware and thermal design must accompany the firmware.

From a high level perspective, this firmware inputs values in CIE 1931 chromaticity coordinate form, and converts the coordinates into the appropriate dimming values for each of the three LED channels. A dimming value is the percentage of maximum luminous flux to which an LED must be dimmed. If an LED has its current quickly switched on and off in an intelligent fashion, the LED has its flux output controlled.

In other words, one chromaticity coordinate is input into the firmware. The firmware combines this coordinate with its pre-programmed knowledge of the LED characteristics in the system, along with LED junction temperature measurements. It then completes the necessary transfer function that correctly converts the chromaticity coordinate into a dimming value for each LED. This process enables their light outputs to mix together to create the colour of the chromaticity coordinate input into the system.

View the PDF document for more information.





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