By: Cunhui Wei/ Technical Service Center
weich@meanwell.com.cn

What is color temperature? Simply described,  color temperature is a measuring unit that expresses the color contained in light. Its concept is based on the various colors of light produced when an absolute black object is heated to different temperatures. For example, in the most frequent sunlight, the temperature is lower in the morning and evening hours, and the color temperature is warmer yellow; in the noon time, the temperature is higher, and the color temperature is cooler and whiter. The color temperature connection from 1000K to 10000K is shown in Figure 1. The lower the color temperature value, the redder the color; the higher the color temperature value, the bluer the color.

Figure 1 Color Temperature

Lamps with a single-color temperature cannot suit people's life and work requirements at the same time because people's light temperature needs vary with time. As illustrated in Figure 2 for hotel room lighting, cool white light or neutral white light is preferable for reading and communication during the day, while warm light can relieve physical and mental weariness, improving sleep quality at night. Undoubtedly, LED fixtures with tunable color temperature will become increasingly popular in residential, hotel, office, and other commercial lighting settings to provide customized lighting to fulfill the needs of different time periods.
 

Figure 2. Hotel Room Lighting
 

As illustrated in Figure 3 below, the LED lights with tunable color temperature and brightness use two sources of light output: cold （6500K）and warm （6500K）color temperature, each of which is relatively independent. As shown in Figure 4, the color temperature can be adjusted by modifying the ratio of the driving current of each light source. Under specified color temperature conditions, the brightness can be adjusted by setting the driving current of the two light sources in the same proportion.

Figure 3 Driving method of tunable color temperature LED fixture

Figure 4 Color temperature and Current value curve

With the advancement of the intelligent lighting industry, LED drivers with tunable color temperature and brightness and digital lighting control, ensure that the color temperature and brightness settings do not interfere with each other. This design has gradually substituted the "constant voltage source + DC/DC dual output module" as a new driving method dedicated to creating an intelligent, comfortable, and human-centric lighting environment.

MEAN WELL has recently launched a DALI-2-compliant LCM-40TW intelligent power supply with tunable color temperature and brightness. It can combine with MEAN WELL DLC-02, DALI-2 controller, and DALI-2 input devices (such as touch Panels, presence sensors, and so on) to provide the best solution for indoor intelligent lighting systems. The DALI-2 intelligent lighting configuration schematic is shown in Figure 5.

Figure 5 DALI-2 Intelligent Lighting

The LCM-40TW is a 40W dual-channel constant current mode tunable color temperature and brightness LED driver with a DIP switch that can be adjusted to DALI DT6 (LED lighting control device) or DT8 (color temperature control device) and delivers an output current ranging from 500mA to 1050 mA. LCM-40TW has a push-dimming function and allows users to alter the color temperature and brightness using a key switch (such as a wall switch), making it perfect for DALI building intelligent lighting. Click on the instructional video linked below to discover more about its product features.
 
MEAN WELL owns the complete DALI-2 intelligent product line. Shall you have any product or technical problems, you are sincerely welcome to contact our technical team. Also, please stay tuned on the online courses related to products and solutions of the MEAN WELL Expo.
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