Smart lighting management sensor for colour stability and lumen maintenance

Smart lighting management sensor for colour stability and lumen maintenance

New Products |
By Graham Prophet

AS7220 combines integrated tri-stimulus XYZ colour sensor and intelligent driver management for high accuracy closed-loop maintenance of LED outputs in industrial, commercial and high-end residential lighting products, and is applicable to new-generation higher-quality LED-based lamps and luminaires using closed-loop sensing to maintain more accurate correlated colour temperature (CCT) and lumen output while also lowering system bill of materials costs.


The device employs colour sensing by means of on-chip nano-scale interference filters to give wavelength selectivity to its sensors. This technique, ams says, offers long term, and temperature, stability compared to use of, for example, dye-based filters.


Following the launch in Jan 2017 of the AS7221 smart lighting manager that offered full white colour tuning and daylighting features, this latest member of the ams Cognitive Lighting Smart Lighting Manager family combines a precise calibrated-for-life colour sensor with an intelligent Cognitive Lighting Engine for standalone closed-loop maintenance of the output from strings of warmer and cooler white LEDs. The result is a luminaire which automatically adjusts for the colour shift and lumen depreciation of LEDs as a natural result of ageing, operating temperature changes and driver variation over lifetime.


In premium lighting systems marketed to commercial, industrial and high-end residential users, manufacturers must typically rely upon tightly-binned LED combinations to achieve the desired CCT. By employing sophisticated sensor-driven algorithms the ams AS7220 Smart Lighting

Manager enables the manufacturer to use a more loosely CCT- and flux-binned range of cool-white and warm-white LEDs to achieve a high and stable quality of light. This gives them a substantial competitive advantage by:

– broadening the competitive supply base from which LED production units may be sourced

– increasing production flexibility and easing the management of LED inventory

– easing the normal requirement for LED drivers and power supplies to provide precisely regulated outputs, loosening specifications and opening the supply base of those components


Integrated into LED lighting system designs, and after the desired CCT and/or full-output lumen values are programmed into it on the production line, it autonomously implements closed-loop colour and output control of the LEDs inside a luminaire or lamp. Control of the power supplied to LED strings is implemented via either digital switching of multichannel power supplies, or through a combination of PWM current steering combined with an analogue or digital output to standard single-channel 0-10V or PWM-input dimming ballasts or drivers.

ams adds, “While LEDs are well characterized for their first years of operation, longer term predictive models reveal variability in colour and brightness. In addition, LEDs are evolving so fast that the same parts are unlikely to remain the cost-effective choice for the same model of luminaire even as little as one year after going into production, introducing still more variation from light to light. By adding closed-loop sensing to their product’s architecture, luminaire manufacturers free themselves from these technology and supply constraints, lowering bill-of-materials costs and gaining both consistency and a wider basis for component selection, while delivering more precise lighting quality over lifetime”.


The AS7220 is pre-configured for optional operation with an external ams ambient light sensor to additionally provide for autonomous daylight harvesting using standard 0-10V dimming inputs. The Smart Lighting Manager also provides a direct interface to standard occupancy sensors to enable intelligent dimming control and energy-saving schemes.


Accurate and stable CCT control is enabled by the AS7220’s embedded tri-stimulus CIE XYZ colour sensor, which directly maps the sensor channel data to the CIE 1931 colour space. The sensor system’s LGA package, which measures 4.7 x 4.5 x 2.5 mm, includes a built-in aperture with a ±20.5° field of view.


Using logic capabilities integrated into the device, the chip is able to deliver factory-calibrated CCT values typically accurate to within .002 du’v’ (approximately 2-3 Macadam steps) across its -40 to +85C operating temperature range.


The AS7220 Smart Lighting Manager is priced at $2.81 in order quantities of 10,000 units.




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