[기술]UV-C(극자외선) 살균 LED 라이트 및 LED 드라이버* INTRODUCTION
Ultraviolet C (UV-C) Sterilization LED Lighting is one of the Pandemic (Covid-19) blooming market that mainly aims to disinfect germs for surface contacts. Currently, Low-pressure Mercury UV-C Sterilization light is also used but it consumes more energy and requires wait time to start up the sterilization cycles. Thus, UV-C LED lighting has become popular that companies are investing resources to design UV-C LED light fixtures to be used in hotels, car trains or hospitals. Other companies are working to add UV-C LED light to existing products to disinfect frequently touched surfaces such as banking machines. This whitepaper discusses the UV-C LED and UV-C sterilization LED Light and suitable MEAN WELL LED drivers for UV-C LED Lighting.
* UV-C LED:
Unlike LED used for illumination, the UV-C LED emits violet or purple color spectrum at typically 275nm wavelength and the relative intensity peaks at 275nm wavelength as compare to the scattered wavelengths of illumination LED. Figure 1a shows the relative intensity of a UV-C LED with 100% relative intensity at 275nm vs the illumination LEDs of Figure 1b. To effectively sterilize germ, the UV-C LED is fabricated with 100% intensity concentrated at 275nm wavelength.
* UV-C sterilization LED Light:
UV-C sterilization LED light has two important parameters to disinfect a surface: Distances and Timing. Single UV-C LED that is about 2.5W can output 99.9% irradiance over a 5cm surface as illustrated in figure 3. Irradiance is amount of flux energy or brightness over a surface. In other words, it can sterilize 99.9% of germs over a 6cm surface. However, when the surface is a bit farther such 10cm, the sterilization rate drops to 25%. To increase the sterilization rate, longer time is required.
The curve of figure 2 shows the distance vs time that it takes about 5 mins for 45cm and about 18 mins for 100 cm to 99.9% sterilize the surface. Thus, time and distances are critical parameters of UV-C sterilization LED light. Also, it often designs with programmed on and off control to sterilize a surface by cycles such as 15 mins or 30 mins per sterilization.
Distance, time, and on/off control are directly related to select an appropriate LED driver to drive the UV-C LEDs. Table 1 shows LED driver output power needed for a UV-C sterilization LED light to sterilize 45~60 cm and 180~420 cm over the surface. For instance, a 20W LED driver can be used to power 18W UV-C LED array to sterilize 99.9% of germs over a 45~60 cm surface for about 5 mins. LED driver with dim-to-off function allows the light to be programed on/off for cycle sterilization. Similar to illumination LED, it can be driven by a constant current or a constant voltage LED driver that the former is directly drive the UV-C LED and the latter is indirectly drive with a built-in DC to DC step down LED driver.
In summary, UV-C sterilization LED light has a wavelength of about 275nm that the UV-C LED can be driven by either a constant current or constant voltage LED drivers. Also, it sterilizes a surface by cycles that utilizes the LED driver’s dim-to-off function. To shorten the sterilization time for a given distance, higher power LED driver is needed. Table 2 lists the MEAN WELL LED drivers models with dim-to-off function that are suitable for UV-C sterilization LED light for 45~60 cm and 180~420cm distance surfaces. Moreover, XLG-100/150/200/240 series higher power ratings are also available for 360-degree UV-C sterilization LED light.