LED lighting main indicators
1. Luminous efficiency and luminous flux
2. Color temperature and Bronx curve
3. Color rendering and standards
4. Consistency issues
5. Temperature and lifespan
6. The efficiency of the power supply
7. The importance of lamp efficiency
8. Attach importance to the testing of LED lighting products
Compared with traditional light sources, LED lighting is based on the new way of semiconductor solid-state lighting (SSL). LED products have many different parameters, and the following parameter relationships need to be properly mastered.
1.Luminous efficiency and luminous flux
The luminous efficiency and luminous flux of traditional light sources do not change much, such as fluorescent lamps. If the power of the light source is determined, the luminous efficiency and lumen will not change much, and the LED light source will be different.
For example, the light flux of the lamp in the 5730 led lamp beads is 50 lumen, when the current is 150mA.
Vf=3.0-3.2V, the power of the LED is 0.45-0.48 watts, and the luminous efficiency is 111.11-104.17 lm/w.
Vf=3.3-3.5V, the power of the LED is 0.495-0.525 watts, and the luminous efficiency is 101.01-95.24 lm/w.
It can be seen that under the same driving current, the luminous efficiency of the lamp bead is greatly deviated due to the different junction voltage of the LED, and high lumen are not meant to be high-efficiency products. LED lighting products, high light efficiency is the main energy-saving indicator, the relationship between driving current and light efficiency is shown in the figure below. It can be seen from the figure that the luminous efficiency of LED light source products can be controlled.
2. Color temperature and Bronx curve
The color temperature of incandescent lamps and energy-saving lamps is easy to be consistent in batch products. Due to the characteristics of its manufacturing process, the color temperature deviation of each batch of products is very large, and the color temperature of the LED light source is expressed by the correlated color temperature (CCT). This means that there is a tolerance (Δuv) problem in the color space. This is a disadvantage of LED as a light source. The inconsistency of color temperature has always plagued LED lighting products manufacturers. The color temperature problem is also the same as the color temperature value test, but the light color is different, this called same temperature different color. And the other is the light color is the same but the tested color temperature values are different, this called same color different temperature. The lower the color temperature, these situation will more obvious, please see the the CIE1931 chromaticity diagram below for this problem.
For example, the light color of QM and QP of 3400K will be very different, and the difference between QO and PO light color will be lower than that. Therefore, when choosing the color temperature of LED, it needs to be carefully measured. Usually the color difference can be distinguished by human eyes. The scientific method is to determine the color temperature by spectral quantitative analysis. Here is a recommended method, which is to use a color temperature zone near the Bronx curve (the red line in the above figure) to avoid the same temperature different color. Chromatic aberration is a technical control problem of LED light source, high-quality lighting products, color control of different batches is relatively better, color temperature and color difference of inferior products will very great, and it is easy to be complained by customers.
To solve the color temperature problem, color matching can be adopted. The color matching needs to be carried out with professional technology. If the lamp has a diffusion cover, the color temperature control will be easier. When the color temperature of the product is strict, the COB package is also a good choice.
3. Color rendering and standards
Use the color rendering index (CRI) to measure the color rendering of LED has been controversial. At present, only can follow the standard specification. For high color temperature LED light source, the average color rendering index Ra75 does not mean that its color rendering effect is worse than Ra80. The scientific evaluation of chromaticity is a complicated technical problem. There is no excessive discussion here. For LED lighting product operators, products that pay too much attention to Ra>80 will be expensive, and the prices of the products sold on e-commerce platforms are very sensitive to customers. The operator can ask the manufacturer for a spectral analysis report of the LED light source, if the color coordinate of the test report (XY value @CIE1931) falls near the Bronx curve, the color rendering of this product can be expected. High color rendering is the best value to bring price war back to lighting quality. Operators need to learn to use this indicator to guide consumers back to life with quality lighting.
4. Consistency issue
The consistency of LED lighting products mainly includes the following aspects:
Under the constant current drive, the power is reduced as the lighting time increases, this phenomenon is normal. For a drive with a large constant current deviation, the power value will vary with the input voltage. Inconsistent power does not mean that there is a problem with quality.
Color temperature consistency
This inconsistency can be passed as long as the human eyes can pass. After all, the color temperature control is the problem LED lighting products always has, and the problem of low-priced products will be very serious.
Consistency of light efficiency
The consistency of light efficiency will lead to differences in luminous flux. High-quality products will be well controlled, but the consistency of light efficiency cannot be judged to be inferior products. High luminous efficiency does not mean high lumen, and the power of high-efficiency products is also low. Light efficiency is the main indicator to measure energy-saving effect. For LED light source and lamp users, light efficiency is the first indicator they concern.
Compared with traditional light sources, the consistency of LED products is not so good. After all, LED light sources are composed of multiple point sources, and the sluice fluid effect of the manufacturing process will always exist.
5. Temperature and lifespan
The traditional light source is not sensitive to temperature, and the LED light source is a product with a common fate with temperature. The ambient temperature and working temperature of the product directly determine the life of the product. The semiconductor device is temperature dependent. From this perspective, the life of the driving power source is also determined by the temperature, so the life of the LED lighting product depends on the temperature control. This temperature includes two aspects, one is the temperature of the working environment, the higher the ambient temperature, the lower the product life, and the other is the heat dissipation capability of the lighting product itself. The better the heat dissipation capacity, the longer the product life. However, when a product with high heat dissipation capacity is placed in a place with high ambient temperature, the life of the product is also low. The product operator needs to know the temperature of the working environment, then they can offer a reasonable warranty period. Otherwise, high-quality product after-sales service will reduce the credit on your e-commerce platform. The temperature and life of LED lighting source is an inherent problem of semiconductor solid-state light source.
6.Power supply efficiency problem
Many products are marked with light source efficacy, but often ignoring the efficiency of the driving power supply. Power efficiency is the ratio of the power supply’s output power to the input power. In simple terms, it is the power loss of the power supply itself, the internal loss of the power supply is low, the power efficiency is high.
The power supply produce less heat, the life will longer. Power supply efficiency should distinguish between isolated drive and non-isolated drive. The efficiency of non-isolated drive power is high, generally above 90%, the efficiency of isolated drive power is generally around 80%, but the isolated drive is more safe and the price is almost double as the non-isolated power supply. The efficiency of the driving power supply is a problem worthy of attention, and the efficiency of the driving power supply affects the life of the product.
7.The importance of lamp efficiency
Lamp efficiency is an important international indicator of lighting products. It is the main parameter for measuring the cost performance of lighting products. The lamp efficiency is the loss rate of the luminous flux of the light source. The more luminous flux the lamp loses, the lower the efficiency of the lamp. The different lamps efficiency is different, the lamp efficiency is between 50% and 90%. A light source with a luminous flux of 1000 lumen is placed in a lamp with a luminous efficiency of 50%, it will only 500 lumen of light output, the lamp efficiency will reduce the high luminous efficiency of the LED light source in the same level as the energy-saving lighting. The lamp efficiency is the final indicator to measure whether the lighting product is energy-saving. The lamp efficiency needs professional testing to get it. The operator needs to use the lamp efficiency as the main indicator to measure the cost performance. A customer get a 10W lighting product with 50% lamp efficiency, the lighting effect is only equivalent to purchase a 6W products with 90% lamp efficiency, the operators themselves will calculate how much the electricity costs they saved for consumers.
8.Attach importance to the test of LED lighting products
LED lighting products are a combination of multi-disciplinary technologies, with strong technical characteristics and knowledge content, can fast accurate and evaluation of product quality and cost performance, the need for scientific means and rely on professional photoelectric testing equipment to complete quality judgment. General optical testing instruments are very expensive and require professional testers. In order to improve the reliability of the evaluation of the products, the third party test report is usually used to check the performance of the products. At present, the Taobao has a professional LED product testing online store which are very helpful for the e-commerce operators. The product will appear in the original shape in front of the test instrument, and improve the marketing ability of the e-commerce. The essence is to improve the product quality credit of the operator in the customer’s mind. The real product performance is the premise of the credit, the technical test report of the products can explain many professional and technical issues in a straightforward manner.