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Brief introduction to the factors affecting the LED light attenuation

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Brief introduction to the factors affecting the LED light attenuation

As a new type of green energy saving and long life, it is highly respected by customers. but

The problem of LED light decay is another problem that LED lamps have to face. Uninterrupted light decay has seriously affected the use of LED lamps.

   From the current point of view, the decay of LED white light on the market may be one of the first problems to enter the civilian lighting. What causes the light decay of LEDs? In general, there are two main factors for the light attenuation of LEDs:

   First, the quality problems of the LED products themselves:

   1. The LED chip used is not in good health, and the brightness decay is relatively fast.

   2. There are defects in the production process, the LED chip heat can not be well derived from the PIN pin, resulting in the LED chip temperature is too high and the chip attenuation is increased.

   Second, the conditions of use:

   1. The LED is driven by constant current. Some LEDs are driven by voltage to cause the LED to decay.

   2. The drive current is greater than the rated drive condition.

In fact, there are many reasons for the decay of LED products. The most critical problem is thermal. Although many manufacturers do not pay special attention to the problem of heat dissipation in secondary products, the long-term use of these secondary LED products will pay more attention to heat dissipation than there are. LED products are higher. The thermal resistance of the LED chip itself, the influence of the silver glue, the heat dissipation effect of the substrate, and the colloid and gold wire are also related to the light attenuation.

   Three factors affecting the quality of LED lamps

   First of all, what kind of LED white light to choose.

   This is very important, the quality of the LED white light can be said to be a very important factor. To give some examples, the same LED white light encapsulated with ordinary epoxy resin primer and white light glue and encapsulating glue is represented by the 14mil white light segment chip of the wafer, and the single white light is lit in a 30 degree environment. After 1000 hours, the attenuation data is 70% light attenuation; if it is encapsulated with D-type low-decay glue, it will be 45% under the same aging environment; if it is encapsulated with C-type low-decay glue, under the same aging environment , 1000 hours light decay is 12%; if Class B low-failure glue is encapsulated, under the same aging environment, thousand hours light decay is -3%; if Class A low-failure glue, under the same aging environment, thousand hours light The decline was -6%.

  Second, the working temperature of LED lamp beads.

According to the aging data of a single LED white light, if only one LED white light works, and the ambient temperature is 30 degrees, then the temperature of the bracket when the single LED white light works will not More than 45 degrees. At this time, the life of this LED will be ideal.

If there are 100 LED white lights working at the same time, and the interval between them is only 11.4mm, then the temperature of the bracket of the LED white lights around the pile may not exceed 45 degrees, but the middle of the pile Those white LED lights may reach a high temperature of 65 degrees. At this time, the LED lamp beads are a test. Then, the LED white lights gathered in the middle will theoretically have a faster light decay, while the LED white lights around the pile will have a slower light decay.

  Anyway, everyone should know that LED is afraid of heat. The higher the temperature, the shorter the LED life, the lower the temperature, the longer the LED life. The ideal working temperature of LED is of course between minus 5 and zero degrees. But this is basically impossible.

   Therefore, after we understand the ideal working parameters of LED lamp beads, we try our best to enhance the functions of heat conduction and heat dissipation when designing the lamps. Anyway, the lower the temperature, the longer the LED life.

  Once again, the working electrical parameters of LED lamp beads are designed.

  According to the experimental results, the lower the driving current of the LED white light, the smaller the heat emitted, of course, the lower the brightness. According to the survey, the design of LED solar lighting circuit, the driving current of LED is generally only 5-10mA; products with a large number of lamp beads, such as reaching more than 500, or more, the driving current is generally only 10-15mA However, the driving current of general LED application lighting is only 15-18mA, and few people design the current above 20mA.

The experimental results also show that under the driving current of 14mA, and the cover is impervious to air, the temperature of the air inside reaches 71 degrees, low-decay products, zero light attenuation in 1000 hours, and 3% in 2000 hours This shows that the use of this low-fading LED white light has reached its maximum in such an environment, and the greatest damage is to it.

  Because the aging board for aging has no heat dissipation function, the heat generated by the LED during operation cannot be conducted to the outside. This is proved experimentally. The air temperature in the aging board has reached a high temperature of 101 degrees, and the surface temperature of the cover on the aging board is only 53 degrees, which is a difference of dozens of degrees. This shows that the designed plastic cover basically does not have the function of heat conduction and heat dissipation. However, in general lamp design, the function of heat conduction and heat dissipation is considered. Therefore, in summary, the design of the working electrical parameters of the LED lamp bead should be based on the actual situation. If the heat conduction and heat dissipation function of the lamp is very good, it does not matter if the driving current of the LED white lamp increases a little, because the LED lamp bead works The heat can be exported to the outside instantly, without damaging the LED, which is the best care for the LED. On the contrary, if the heat conduction and heat dissipation function of the luminaire is so-so, it is better to design the circuit to be smaller, so that it can release less heat.


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