Tips for Distinguishing LED Light Quality

  • 2022-02-17

The data detected of a single LED white light on the aging board must have some difference from the one detected after a white-light-LED-lamp aging. The size of the differences depends on the LED work electrical parameters and the design of lamps and lanterns, as well as the environment of the lamps and lanterns application.

 

The quality of LED guide plate

This is important. the quality of LED guide plate plays a vital role. For example, take the same one of wafer-14-mil white light chip, after the LED guide plate made of common epoxy resin glue, white light glue and packaging glue LED working in 30 degrees environment for one thousand hours, attenuation data will be 70% of light failure; if it is encapsulated with low class D failure glue, in the same aging conditions, after thousands of hours of working the light failure is 45%; if use the C type low failure encapsulation glue, the light failure is 12%; if a class B low failure encapsulation glue, the light failure is 3%; type A low failure glue will have 6% light decline.

 

Generally speaking, the thermal conductivity coefficient of general epoxy resin is small, therefore, when the LED chip light work, it will emit heat. However, thermal conductivity ability of ordinary epoxy resin is limited, therefore, when you measure the temperature of the LED bracket has 45 degrees from the LED external light source, the temperature inside the center of white light LED chip may reach more than 80 degrees. The temperature limitation of LED light is 80 degrees, so it is very suffering for the LED working in such high temperature, which will speed up the aging of LED light source.

 

The temperature of working environment

According to the aging data of single LED light source, if only one light work, at the same time, it's environment temperature is 30 degrees, therefore, the stand temperature will be not more than 45 degrees. At that time, the service life of the LED will be ideal. If there are 100 LEDs light work at the same time and their interval is only 11.4mm, so the LED light source of the perimeter of the lamp stand temperature may also be no more than 45 degrees, but the lamp in the middle of the LED light source could reach the high temperature of 65 degrees. It is a test for the LED light source. Therefore, in the middle of the LED light source, their light failure will be theoretically a bit faster, while the light surrounding will be slower. But if the LED lamp is more than 25 mm apart, the heat they radiate to each other will be less accumulated, and the temperature of each LED stand should be less than 50 degrees, which is conducive to the normal work of the LEDs.

 

If the LED work environment is a cold place, where the average temperature all the year round may only be about 15 degrees, or smaller. For LED, its life will be longer. Or, when the LED is working, a small fan blowing can also help it to disperse the heat, which is helpful to the life of the LED. Anyway, you should know that LED is afraid of heat and the higher the temperature is, the shorter the LED life will be, while the lower the temperature, the longer the LED service life. The ideal working temperature of LED is between negative 5 to zero, which is almost impossible.

 

The design of LED working electrical parameters

According to experimental results, under the condition of lower drive current the white light LED has smaller heat emission quantity, and of course the brightness is smaller too. It is investigated that the LED drive current is generally 5-10ma; the LED products with large amount of LED guide plate, such as more than 500, or more, the drive current is normally 10 to 15ma; while popular application of LED lighting drive current is just 15 to 18 ma. There is seldom someone design the current to over 20ma. And the experimental results also show that in 14 ma driver power flow with no space and the inside air temperature is under 71 degrees, one thousand hours light failure is zero, while two thousands one is 3%, which means this kind of low failure LED white light has reached its maximum used in such an environment and a larger one will damage it.

 

Because there is no radiating function with aging board, therefore, the heat generated during the LED work cannot be transmitted outside. It is verified by experiment. The inside air temperature of aging board has reached 101, while the surface temperature is only 53 degrees. This means that the design of the plastic cover does not have heat dissipation and thermal conductivity function. But in the general design of lamps and lanterns, these functions should be taken into consideration. Thus, in summary, the design of LED electrical parameters should adapt to the actual situation, if the cooling function of thermal conductivity of lamps and lanterns is very good, it doesn't matter that the white light LED drive current increase a little, because the heat generated by the LED can quickly export to the outside, there is no damage to the LED, which is best for LED. On the contrary, if the cooling function of thermal conductivity of lamps and lanterns is not so good, the current should be designed to be a little bit small, so as to let it put less heat.

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