This article was originally created by Hubei DUVTek Co., Ltd. and was first launched in experts. Please indicate the source of reprint.

With the advantages of small size, fast start-up speed and low power consumption, deep UV LED has opened up a new application scene in the deep UV sterilization market, and formed a trend replacement for UV mercury lamp, just like white LED ten years ago. From air-conditioning and air purification of air sterilization, water sterilization of water tank, direct drinking water, humidifier to surface sterilization of intelligent toilet and toothbrush disinfection, deep UV uvc-led began to show great application value and potential. Since 2018, the price of the original deep UV uvc-led lamp beads at home and abroad has been reduced to $0.6/mw, and the market demand has been boosted by continuous price reduction support. Haier took the lead in introducing uvc-led sterilization technology into its maternal and infant air-conditioning and Casati's high-end air-conditioning. Vantage, the kitchen and bathroom brand, added medical grade deep UV uvc-led sterilization technology into dishwasher, and Huida intelligent toilet introduced ultraviolet nozzle sterilization

The emergence of huge market opportunities also put forward higher requirements for solution suppliers and lamp bead packaging plants: how to make good use of deep UV LED? I think the market is asking you these three questions: 1. Where is the market for deep ultraviolet applications? 2. What specification of deep UV LED? 3. How to use deep UV LED?

Where is the application market of deep UV?  

Recent market: humidifier, air purifier, drinking machine, ice maker, intelligent toilet, food preservation box

Medium term market: commercial air conditioner, vertical air conditioner, milk bottle sterilizer, intelligent garbage can, direct water dispenser

Long term market: car air conditioner, hanging air conditioner, refrigerator

The logic behind this classification is the comprehensive consideration of application cost, solution maturity, product R & D cycle and technical competitiveness, which will not be repeated here.

What specification of deep UV LED is used?  

Just as white light manufacturers choose the light efficiency, wavelength and color, the selection of deep UV uvc-led also depends on the application scenarios. In the process of scheme design, it is the key to identify the most concerned parameters of application scenarios. In the same way, the packaging factory should also consider these when choosing chip parameters.

2.1 optical power

According to the current situation of products on the market, the available power levels of uvc-led range from 2 MW, 10 MW to 100 MW. When choosing the light power to be used, the sterilization effect and sterilization time should be given priority. It is known that a 3 MW uvc-led with an output angle of 60 ° can kill 99.99% E.coli on the surface in 10 seconds at a distance of 2 cm.

Therefore, humidifier, ice maker, drinking water tank bacteriostatic, intelligent toilet and other similar static sterilization scenarios, the mainstream use is to use a 2 ~ 4 MW light power uvc-led; air purifier, air conditioning and other moving air sterilization scenarios usually use 2 ~ 3 10 MW uvc-led; direct drinking water machine and other dynamic water sterilization scene total light power should be at least 50 ~ 100 MW. The scheme cost can be roughly converted according to the total MW.

2.2 Peak wavelength

When choosing the peak wavelength of uvc-led, we need to know the following technical points:

1、The most suitable wavelength for sterilization is 265 nm, not 254 nm. As shown in Figure 1 (right), UVC ultraviolet rays with wavelengths between 240 and 290 nm have good bactericidal effect;

2、For uvc-led, the germicidal efficacy depends on both peak wavelength and light power. For example, the germicidal efficacy of 270 nm is 30% better than that of 280 nm, and 30% higher light power is also 30% better. (therefore, it can be converted, the sterilization effect of 2.6 MW 280 nm uvc-led is the same as that of 2 MW 270 nm uvc-led). However, considering that the average value of peak wavelength of different manufacturers is not different, the light power is actually the most important index to measure the sterilization efficiency.

Figure 1: spectrum comparison between low-pressure UV mercury lamp and typical uvc-led (left); germicidal efficacy of different wavelengths of ultraviolet (right)

2.3 life

Just like the arms race of major manufacturers in the early stage of white LED market, the life span of lamp beads of deep ultraviolet LED is also regarded as an important standard of product quality. With the lessons learned from white LEDs, I hope to tell readers that the right one is the best. Identifying the actual demand of application scenarios for life is conducive to reducing the cost of the scheme and bringing more market opportunities. Or take the mainstream uvc-led products in the market as an example. The highest life expectancy is 15000 hours, and the lowest is 2000 hours. But how long does the application need? If we analyze the product demand carefully, we will find that:

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Humidifier 0.8 hours / day * 30 days / month * 8 months / year * 3 years = 576 hours;

Direct drinking machine: 20 minutes / day * 30 days / month * 12 months / year * 5 years = 600 hours;

Water dispenser: 12 months / h * 30 years / day;

Air conditioning: 2 hours / day * 30 days / month * 6 months / year * 5 years = 1800 hours (evaporator and filter sterilization program);

Air purifier: 5 hours / day * 30 days / month * 12 months / year * 3 years = 5400 hours.

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Do you think 10000 hours of uvc-led is better than 5000 hours?

It is believed that uvc-led value can be maximized from the perspective of suppliers and customers by carefully calculating the life requirements of lamp beads in application scenarios and finding the most matching lamp beads and prices.

2.4Irritation angle

The material characteristics of deep UV LED lead to a higher ratio of lateral light output than vertical light output. Therefore, the light out angle of the lamp beads packaged with plane lens is usually between 120 ~ 140 degrees (most manufacturers have the light angle). If the spherical lens package is used, the light output angle can be adjusted between 60 ~ 140 degrees (at present, only DUVTek company provides multi angle lamp beads).

In fact, no matter how large the angle of view of uvc-led, you can design enough beads to completely cover the sterilization space you need. In particular, in the scene insensitive to the sterilization range, the small light angle can make the light more concentrated and thus shorten the sterilization time.

3 How to use deep UV LED?  

The problem at the solution level actually involves many details, especially the actual application scenarios. In the first section of the article, "where is it used?" For example, the deep UV uvc-led is used as follows:

3.1 Static surface sterilization

Intelligent toilet, food fresh-keeping box and intelligent garbage can: the uvc-led lamp beads are embedded in the side or top of the appropriate inner cavity, and the sterilization objects are directly sterilized by ultraviolet rays. The sterilization time is preliminarily converted according to the irradiation distance, area and sterilization efficiency requirements.

3.2 Near static water sterilization

Humidifier, drinking water tank, ice maker: it is characterized by small water flow or long-term bacteriostasis. Usually, a single uvc-led sterilization module is set at the top or the low end of the water tank, so that the ultraviolet rays can irradiate the whole water body to realize the sterilization and bacteriostasis of water.

3.3 Dynamic water sterilization

This kind of application water flow is usually 1 ~ 2 L / min, not more than 2 L / min, it is necessary to connect a special uvc-led sterilization module in the pipeline to complete the instant sterilization and disinfection of the flowing water inside the components.

3.4 Air sterilization

Air purifier, all kinds of air conditioning.

Haier's new maternal and infant air conditioner mentioned that the sterilization effect of 90% air sterilization rate in 2 hours. The problem is that babies living in a sterile environment will be less immune. This fact has been widely recognized and scientifically explained. It is not the mission of deep ultraviolet sterilization technology to completely kill bacteria in the air. Yes, any technology should not completely kill bacteria in the air. The entry point of deep ultraviolet air sterilization technology should be in the filter screen and evaporator which are easy to cause air pollution. In the long-term use, dust and water vapor gather in these places and become the breeding ground for all kinds of bacteria and peculiar smell, which directly leads to the deterioration of air quality in the living environment. Purification filter screen and evaporator should be the focus of deep UV LED technology.

3.5 About driving mode

A constant current circuit should be used to drive deep UV uvc-leds. as a result of:

1、The operating voltage of different batches of deep ultraviolet LED is usually different. In the application of batch production, the mode of constant voltage driving will lead to poor consistency of sterilization effect of products;

2、If the constant voltage drive is used, the LED temperature rise will lead to LED current increasing and the light power becoming uncontrollable. Constant current drive can avoid this problem.

4 reference material

[1] UVC lamp beads l280-swc1s15a600, 3.2 mW@20 MA

[2] The bacteria in the heat sink / evaporator of air conditioner exceed the standard and become a potential safety hazardhttps://www.duvtek.com/article/73/