Popular Science: How to identify the quality of LED lamps

The data detected by the single LED white light on the aging board, and the data detected when the LED white light is assembled into a luminaire, is definitely a bit different. The size of this difference depends on the electrical parameters of the LED during operation and the design of the luminaire, as well as the environment in which the luminaire is used.

Method / Step:

1. What kind of LED lamp beads to choose?

This is very important, the quality of LED lamp beads can be said to be a very important factor. For some examples, the same is represented by a 14-mil white light-segment chip, which is made of a common epoxy resin and a white light glue and a packaged glue. The LED lamp bead is lighted in a 30 degree environment. After a thousand hours, the attenuation data is 70% light decay; if packaged with Class D low-resistance glue, the light decay is 45% in the same aging environment; if the C-type low-resistance glue is packaged, in the same aging environment , the light decay of 12 hours is 12%; if the B-type low-resistance glue is encapsulated, in the same aging environment, the light decay of thousands of hours is -3%; if the low-grade glue of type A, under the same aging environment, thousands of hours of light The decline is -6%.

Generally speaking, the thermal conductivity of ordinary epoxy resin is very small. Therefore, when the LED chip is lit, the LED chip emits heat, and the ordinary epoxy resin has limited thermal conductivity. Therefore, when you measure the temperature of the LED holder from the outside of the LED light source by 45 degrees, the chip center temperature in the LED white light may exceed 80 degrees. The temperature node of the LED is actually 80 degrees. Then, when the LED chip works in the temperature of the junction temperature, it is very tormented, which accelerates the aging of the LED light source.

2, LED light source working environment temperature

According to the data of the aging of a single LED light source, if only one LED light source is working, and the ambient temperature is 30 degrees, then the temperature of the bracket when the single LED light source is working will not exceed 45 degrees. . At this time, the life of this LED will be ideal. If there are 100 LED light sources working at the same time, the interval between them is only 11.4mm, then the bracket temperature of the LED light source around the stack may not exceed 45 degrees, but those LEDs in the middle of the stack It is possible for the light source to reach a high temperature of 65 degrees. At this time, the LED light source is a test.

Then, those LED light sources that are concentrated in the middle, in theory, the light decay will be faster, and the LED light source around the lamp stack will have a slower light decay. However, if the LED beads are separated by more than 25mm, then the heat that they disperse from each other will not accumulate. At this time, the temperature of each LED bead holder should be less than 50 degrees, which is more conducive to the normal operation of the LED.

If the LED working environment is in a cold place, the average temperature of the whole year may be only about 15 degrees, or less, then for LEDs, the life is longer. Or, when the LED is working, there is a small fan blowing next to it, which helps it to dissipate heat. This is also very helpful for the life of the LED. Anyway, everyone should know that LED is afraid of heat, the higher the temperature, the shorter the life of the LED, the lower the temperature, the longer the LED life. The ideal operating temperature of the LED is of course between minus 5 and zero. But this is basically impossible.

3. Design of working electrical parameters of LED lamp beads

According to the experimental results, the lower the driving current of the LED white light, the smaller the heat emitted, of course, the smaller the brightness. According to the survey, LED solar lighting circuit design, LED drive current is generally only 5-10mA; the number of lamps used in the lamp has a large number of products, such as more than 500, or more, the drive current is generally only 10-15mA However, the driving current of the general popular LED application lighting is only 15-18 mA, and few people design the current to 20 mA or more. The experimental results also show that under the driving current of 14 mA, and the cover is airtight, the air temperature inside reaches 71 degrees, the low-fat product, the light decay of zero hours is zero, and the light decay of 2000 hours is 3%. This shows that the low-light LED white light has reached its maximum level in such an environment, and the bigger one is a kind of damage to it.

Because the aging board for aging does not have a heat dissipation function, the heat generated by the LED operation is basically unable to be conducted to the outside. This is proved experimentally. The air temperature inside 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 few tens of degrees. This shows that the plastic cover designed has substantially no heat dissipation function. However, in general luminaire design, the function of heat conduction and heat dissipation is taken into consideration. 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 is irrelevant to increase the driving current of the LED white lamp, because the LED lamp bead works. The heat can be exported to the outside in an instant, and there is no damage to the LED, which is the best care for the LED. On the contrary, if the heat dissipation function of the luminaire is so sloppy, it is better to design the circuit to be smaller and let it put less heat.