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How to Distinguish the Quality of LED Bulbs? Part.2
Entry level: identify without professional equipment
Check the packaging: As mentioned above, it is a way to distinguish the quality by looking at the details of the packaging. Take the products of Yuji lighting as an example, the hard corrugated paper box is used, and the design is simple and generous. The UV process is used to highlight the front lamp body and important parameters, and the silver pressing process is used for the decorative pattern to make the pattern look three-dimensional.
Check the appearance and process details of the product. The radiator has better quality without obvious injection marks, which indicates that the process level of the manufacturer is qualified.
Check the weight of the product, the product with better quality will be heavier. Although this is not a very scientific and reliable method, it is indeed a very simple and effective method.
Because generally speaking, the driving function of more components is more powerful and reliable. A larger radiator will bring more heat dissipation capacity, and of course, these will also bring more weight.
The weight of A60 10W of Yuji lighting reaches 91.7g, while the average quality product is only about 44.4g.
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If you have the opportunity to turn on the LED A60 Bulb, you can see the internal structure.
Check whether the bulb shell is fully fixed. The more difficult the bulb shell is to open, the better the quality of the LED A60 bulb. Good bulb shell fixation can provide more reliable torsion, so that the lamp will not fall off when it is screwed and disassembled on the lamp holder.
The LED A60 bulb with 3030 package LED component has better photoelectric parameters and reliability performance than which LED A60 bulb with 2835 package component.
The more components on the drive, the larger the size of each component, and the more reliable the lamp is.
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Check the contact area between the LED substrate and the lamp board. This determines whether the temperature transmission channel is smooth and fast. The larger the contact area, the more effective and rapid the temperature transfer, and the better the quality of the lamp.
It can be seen from the picture that the aluminum substrate of Yuji lighting products has a large contact surface with the lamp plate, while the aluminum substrate of general quality products has little contact with the lamp plate.
Yujilighting General quality products
Advanced version: it needs some simple equipment to distinguish
When you have some simple equipment, you can judge the quality of LED bulbs more intuitively and effectively. Such as power meter, mobile phone, etc.
1. Use a power meter to compare the power difference between the cold state of the same product just lit and the thermal stability time (about 1-2h lighting). The greater the power difference, the less guaranteed the product quality.
Taking Yuji 10W LED A60/A19 as an example, the difference between cold and hot power is in the range of 0.5 ~ 0.8W, which represents that the stability of the product is very good.
If the power difference is greater than 1W, or even up to 2W, the quality of this lamp is very poor. The reason is simple. The larger the power difference, the worse the heat dissipation, resulting in great changes in the driving and led working parameters.
2. Set the smart phone to the slow motion recording function, adjusting the frequency and clarity to the maximum (4K 240 frames), and make the camera as close as possible to the LED light. If the picture of the mobile phone is very stable and no flicker or dark lines are found rolling, then the LED bulb may be stroboscopic. On the contrary, it indicates that the light bulb has stroboscopic, and the quality is very ordinary. For the products of Yuji lighting, the luminous flux output is constant, the flicker frequency is 66666.7hz, which belongs to the high-frequency exemption frequency, the stroboscopic percentage is 5.3%, and the stroboscopic index is 0.013.
For general quality products, the luminous flux output is not constant, the flicker frequency is 120Hz (the flicker is not controlled, and the flicker frequency is grid frequency * 2), the flicker percentage is 6.8%, and the flicker index is 0.017
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Professional level: identification by professional equipment
Evaluation institutions or manufacturers often have professional equipment, such as driving performance analyzer, multi-channel temperature inspection instrument, integrating sphere photoelectric test system, etc.
3. Stability of driving output: Use the driving performance analyzer to input ± 150% rated voltage to the bulb and observe the change of driving parameters.
The more the parameter changes, the better the product quality. The greater the change of parameters, it means that the power or other parameters of LED bulbs will change with the fluctuation of power grid, which brings great potential quality problems.
The parameters of Yuji lighting products are stable under different voltage inputs. And the product parameters with poor quality will change with the change of voltage.
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4. Monitor the temperature of LED and driving important components: Use the test line of multi-channel temperature patrol instrument (usually 16 or 32 thermocouple test lines) to detect the temperature of LED and driving important components. The higher the temperature, the worse the quality of LED lamp. The lower the temperature, the better the quality of the LED lamp.
The temperature of the products of Yuji lighting is controlled within a reasonable range, and a certain margin is reserved. The temperature of low-quality products has been seriously out of control.
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Whether the temperature is effectively transferred: As the heat transfer requires time and temperature difference, the chain usually decreases from LED temperature to substrate temperature to radiator internal temperature to radiator surface temperature.
The judgment is based on the fact that the smaller the temperature difference of each node of the chain (within 10 ℃), the better the heat dissipation design, and the better the quality of the product. The larger the temperature difference is, it means that the heat of LED and drive is not fully transferred and radiated, and the worse the product quality.
This also answers the initial question. When you touch the LED bulb, the high and low temperature cannot be used as the basis for judging the quality of LED products. The high temperature of the housing does not mean that the quality of the LED bulb is poor, and the low temperature of the housing does not mean that the quality of the LED bulb is good. The key is to see whether the heat transfer is effective.
5. Change of cold and hot light parameters: Use the integrating sphere photoelectric test system to test the cold state and steady state light parameters respectively when the LED bulb is cold and lit for at least 1 hour.
The changes of luminous flux, color temperature, color rendering index and SDCM were compared. The smaller the change, the higher the stability of the LED. The greater the change, the worse the quality of the LED lamp.
The performance of Yuji lighting products in terms of heat and cold is that the luminous flux deviation is within 5%, the color rendering index is stable and increased, and the color tolerance is only increased to 2.1.
For the products with poor quality, the luminous flux decreased by 13.36%, and the color rendering index decreased from 96.5 to 94.8, which was inconsistent with the claimed 95 + color rendering index. The color tolerance has also increased to 4.2, indicating that the color has shifted.
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Generally speaking, low-quality products may be caused by the pressure of price competition and unreasonable pursuit of interests. To make high-quality products, we need to have sufficient technical reserves, profound product understanding and understanding of demand, perfect quality management process, and unremitting pursuit of high-quality products.
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