Decryption bactericidal UVC LED technology

As performance UVC LED (UV-C LED) on the rise, this new technology is gaining momentum from the life sciences and environmental monitoring instrumentation applications. As with all new technologies, designers must understand the basic differences between existing programs and not take for granted that could "change that is ready to use." This allows designers to fully utilize all the benefits of UVC LED's. After carefully weighing using UVCLED design can reduce product size, lower power consumption and lower cost of ownership for end users.

UVC LED applications in instrumentation

Since UVCLED to meet the market for smaller, lower cost and instant trend measurement requirements, which the interest and spectroscopic applications is continuing to heat up. Deuterium or xenon flash compared to, LED output narrow spectrum light source, the light output element can be used for all measurements. Users can select specific peak wavelength of interest depending on the application requirements. For specific applications, we have developed a standardized method for measuring the wavelength of 254nm mercury lamp. For example, according to EPA standards when detecting water and air quality, it requires a close 254nm peak wavelength LED light source. Table 1 finishing in life science research, pharmaceutical production and environmental monitoring applications, a number of important organic compounds capable of spectral identification.

 

 

In instrumentation applications, select the source of another major criterion is the light output of the peak wavelength. Since only a single peak LED, the light output are concentrated on a specific wavelength, and which other ultraviolet (UV) light is not the same. Application of the absorption spectrum generally require low-level light output --1mW or less. However, in the case of the flow cell (flowcell) isolated from the light source, since the light signal before it reaches the flow cell of serious decay, so they need higher light output power. This may require the LED light output far more than 1mW.

In fluorescence spectral domain signal intensity is proportional to the light intensity. LED excitation power required depends on the detection of low tracer concentration, so in these cases a single LED may be greater than the desired light output of 2mW. UV light irradiance Figure 1 compares the instruments commonly used. Although the LED input power is much smaller, but UVA irradiance desired wavelength band is higher than other light sources, making it more efficient in a specific measurement source.

 

 

After selecting a wavelength of light output, another important parameter is the angle of view, it affects the entire optical system of the instrument. Broadly speaking, it has two options: a narrow view angle or wide viewing angles. Narrow view angle lens to achieve through ball, wide viewing angle is used plane window. Narrow viewing angle can be obtained high intensity light in a small area, and its packaging is typically used to focus light directly projected in the instrument application.

Flat-screen window with a wider radiation pattern when coupled with the distal end of the optical fiber when used simultaneously, with better tolerances. This applies particularly to the flow cell and the light source must be insulated from electronic circuitry applications (e.g., chemical process, or to monitor temperature of the solvent used is highly volatile chromatography). In practical applications: narrow corner lens allows the instrument to minimize the number of components; and wide angle plane window makes the design more flexible.

Optimized drive current, allowing design engineers to balance life and light output requirements of the application. Lower than the manufacturer's specification rating of the rated current drive LED, the light output will be reduced, but will also extend the life of the light source. Require high output power LED applications, some end users to select the current table above specifications drive the LED. In this way, increasing the drive current, the light output can be increased, but also risks sacrificing performance.

Overheating is a common problem, it may also have a negative impact on the LED light output and life cycle. Because LED transient switching characteristics, can quickly turn on and off periodically way LED. In general with higher optical output fluorescent applications, often using duty cycle (dutycycle This is the) operation, in order to more safely increase the LED current.

Duty cycle is defined as the percentage of time LED open in a cycle; wherein the cycle is complete a LED on - off cycles total time used. For example, LED 50% duty cycle operation, the opening and closing time exactly half and half.

 

Here we see the impact of different duty cycles standardized light output, while, LED turn-on time duration in 500μs. Standardized power is relative to the maximum rated current 100mA (installation of a suitable heat sink) light output relative to the optical output power to drive large LED currents will affect the LED junction temperature, thereby affecting their life and light output.

 

 

Best of the duty cycle allows increased drive current on the junction temperature is minimized, thereby protecting the LED performance. Figure 3 shows the effect on the duty cycle to maintain LED junction temperature possible. 5% duty cycle operation LED, can be at the lowest junction temperature on the case, the light output (Fig. 2) triple.

 

Figure 3: The figure shows the effect of different operating junction temperature cycle, wherein the LED turn-on time is 500μs

Excessive heat the LED light output and life have a negative impact. In the long run, the heat will shorten the LED life. Using UVCLED design, thermal management is extremely important, as compared to the longer wavelengths of the LED, the greater part of the energy driving UVCLED is converted to heat. Proper thermal management enables the junction temperature below the requirements of a particular application, and to maintain the performance of the LED. In addition to active and passive cooling methods, may be selected for better heat dissipation PCB.

 

 

FR4 because of the relatively low cost, is one of the most commonly used PCB material, but its low thermal conductivity. For systems with high thermal load system, the higher thermal conductivity of the metal core PCB is a better choice. With increasing cooling demand, designers often used to increase the PCB area and increase the heat sink ways of better thermal management. If you need more cooling, designers can also use a more active cooling technology.

With UVC LED performance improvements, designers begin their design flexibility advantages for use in spectroscopic instruments and disinfection reactors and other applications. Use LED In these applications, the tighter, more efficient, often more cost-effective design. With the continuous development UVC LED technology, clever designers will find more ways to take advantage of UVC LED's to cope with the challenges of these markets.

 

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