Fluorescent tube lighting is ubiquitous in commercial environments such as offices and factories. While this type of lighting is effective, the current trend is to replace tube lights as technology evolves into more advanced LED lighting. LED lighting is ideal because of its high efficiency and long life. Replacing ordinary fluorescent linear lamps with LED tubes to exploit the lumen power ratio provided by solid state lighting (SSL) technology presents design and optical challenges. To address this challenge, lighting manufacturers typically work with material suppliers and use advanced materials to achieve the desired lens aesthetics, assembly methods, and optical performance. This gives them a competitive advantage in terms of performance and cost.
In this article, we will discuss the use of polycarbonate in LEDs, describing their physical and optical properties and other features for LED lighting designers .
In order to produce materials for LED tubes, some criteria need to be considered. Plastics have become the material of choice, especially polycarbonate, because of its unique properties and versatility. Considerations include optical performance, mechanical properties, safety, and design flexibility. These are all introduced one by one in this article.
Optical performance
The LED can be a very bright, unidirectional source, and the material required by the manufacturer either allows the light to shine directly through the surface for maximum brightness or provides a uniform light distribution. LED manufacturers and designers know that it is difficult to find a material that hides the LED light source and allows the light to travel at optimum levels. This is not only important for aesthetics, but also ensures optimal energy efficiency.
The cover layer of the LED source adjusts the amount of light that is emitted or diffused. Customers often look for materials that provide high definition and purity to ensure optimum light transmission and maximum efficiency. However, manufacturers are also concerned about the consistency of light distribution. Polycarbonate can be tailored to specific needs and passed through a compounding process to meet the specific requirements of the application. For transparent polycarbonate resin, the light transmittance can reach more than 90%. In some cases, polycarbonate resins contain light-diffusing additives, which are typically polymeric materials having a particular geometry, particle size, and refractive index that help balance the desired light transmission and light diffusion. For these polycarbonate resins, excellent light uniformity can be achieved while hiding the LED light source, thereby eliminating "hot spots".
In order to achieve optimal light distribution, both to meet the needs of the supplier and to meet the end user's expectations, tests should be conducted prior to the start of production of the LED lens or housing to accurately quantify the light transmission and light diffusivity of these polycarbonate resins. When the D50 angle is determined (i.e., the amount of transmitted light is 50% of the amount of transmitted light at 0°), the effect of different light diffusing agents at different levels of concentration in the sample is measured using a variable angle photometer and a direct light source. The developer selects the appropriate diffusion technique based on the measured data.
Figure 1: Evaluation of the diffusivity of LED tube materials by measuring relative transmittance (percentage).
Adjusting performance is usually a careful balance because material additives for light diffusion can affect the efficiency of light transmission and illumination, and vice versa.
Mechanical behavior
LEDs are solid-state devices with no fragile parts or filaments and are therefore very rugged. In addition, LEDs have a very long lifetime compared to conventional light sources. Polycarbonate has excellent toughness, much better than acrylic and glass, and is ideal for use as a lens, cover or housing to ensure that LED lamps or luminaires are not damaged over their lifetime.
Although glass and acrylic resins meet some of the requirements for LED lighting, respectively, as shown in Figure 2, they are insufficient in terms of impact and heat resistance and design flexibility. In contrast, polycarbonate and polycarbonate blends are increasingly recognized as an ideal starting point for LED applications because they have the necessary basic properties and can be customized with other monomers, polymers or additives to meet specific Performance requirements.
figure 2. The main characteristics of polycarbonate in LED tube lighting compared to polypropylene and glass.
Silicon TVS / TSS:
Diode TVS (Transient Voltage Suppressor), also known as Transient suppression diodes, is widely used a new type of high efficient circuit protection device, it has a fast response time (the nanosecond) and high surge absorbing ability.When it ends of stand moments of high energy shock, TVS can bring the two ends at high rate from high impedance to a low impedance between impedance values, to absorb a large current moment, put it at both ends of the voltage restraint on a predetermined value, thus protecting the back of the circuit components are not affected by the impact of the transient high pressure spikes.
Silicon TVS Transient Voltage Suppresso,Silicon TSS Transient Voltage Suppresso
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