Page 64 - Energize June 2022

TECHNICAL

2700 to 3000 K - are known as “warm white”
lighting. As the CCT increases, the colour will
change from yellow to yellowish white to
natural white (4000K) and then to a white
with a cooler, almost blue hue (6500K),
which is known as cool white.
Tuneable HCL LED lights consist of a
combination of LEDs with different CCTs.
Changes in overall color temperature are
achieved by varying the relative brightness
of the different components.
The simplest of white tuning systems
would use a mix of warm and cool white
LEDs and cross-dim between the two.
Typically, there would be one channel of
2700 K LEDs with the other channel of LEDs
Figure 4: Range of colours from single white LEDS (LEDS magazine)
closer to 6500 K. These diodes are usually
tightly packed together with some sort
of diffuser laid over them to aid in colour
mixing as the light passes through. This is a
simple method of tuneable white lighting.

Linear tuning
Linear tuning is the most common method
used in tuneable LEDs. This type of tuning
is detrimental to the CCT, as its linearity
pushes the CCT away from the curve of the
black body, as shown in Figure 5, leading to
an inaccurate CCT which produces a light
Figure 5: White LEDs spectral energy density 3 with a pink hue error.
Linear tuning using warm white and cool
The tuneable white led white leaves a gap in the spectral power
White LEDs are produced with a fixed CCT or spectral power density and are available in the distribution mainly in the “green” area.
range 2000 to 6000 degrees K. Figure 4 illustrates the range of lighting that can be achieved with This problem has been overcome in some
white LEDs. products by the addition of a green LED
Tuneable white light is a technology defined as the ability to control a light source’s colour which is controlled in addition to the dual
temperature output. Other terms referring to tuneable white LEDs are custom temperature, dim channel controls. The product is claimed to
to warm, dynamic/hybrid white, or variable white lighting. match the black body curve closely – see
Most LEDs are found within the 2700 K to 6500 K range. Lower temperatures in that range - Figure 6.

Figure 6: The effect of linear tuning on chromaticity (Lutron)

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