Abstract: A method, controller and lighting circuit are disclosed: the variation of chromaticity and luminosity of LEDs as a function of temperature over an operating temperature range is characterized; virtual LEDs, including a virtual white are defined, such that the chromaticity of each virtual LED can be achieved by combining component light from the LEDs for all temperatures within the operating range; the requested settings R, G, B of each of three primary colors, defining a requested chromaticity and a requested luminance, are used to determine a virtual white control setting corresponding to a maximum fraction of a total luminance at the requested chromaticity which can be provided by the virtual white LED; control settings for each of the other LEDs are thereby determined, and the setting for each of the LEDs is determined from the sum of that LED's component of the virtual LEDs.

Abstract: A method, controller and lighting circuit are disclosed: the variation of chromaticity and luminosity of LEDs as a function of temperature over an operating temperature range is characterised; virtual LEDs, including a virtual white are defined, such that the chromaticity of each virtual LED can be achieved by combining component light from the LEDs for all temperatures within the operating range; the requested settings R, G, B of each of three primary colours, defining a requested chromaticity and a requested luminance, are used to determine a virtual white control setting corresponding to a maximum fraction of a total luminance at the requested chromaticity which can be provided by the virtual white LED; control settings for each of the other LEDs are thereby determined, and the setting for each of the LEDs is determined from the sum of that LED's component of the virtual LEDs.