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Why LED lights will become darker and flicker as they are used

August 02, 2021

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Before starting today's topic, let's not "do not do business properly", let's take a look at the production process of LED fluorescent lamps:


Now the production of LED lights must first go through rigorous computer programming, make the light board, and then enter the assembly line of the assembly workshop. We will not start the details.


Everyone has such a life experience


The LED lights just bought are always very bright.


But after a while, many lights will become darker and darker,


Why does LED lighting have such a process?


Today I will take you to find out!


To understand why your LED lights are getting dim


We must first understand a professional term


LED light decay


LED light decay


LED light attenuation means that after a period of time when the LED is lit, its light intensity will be lower than the initial light intensity and cannot be restored, that is, the reduced part is called the LED light attenuation.

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LED lights become darker as they are used because LED lights have light decay phenomenon.


The light decay of LED lamp products is the weakening of the light signal during transmission. At this stage, LED products made by major global LED manufacturers have different degrees of luminous decay. High-power LEDs also have luminous decay, which is directly related to temperature. It is determined by the chip, phosphor and packaging technology. At present, the light decay of white LEDs on the market is one of the most important issues in the march to civil lighting.


Light decay generally refers to its luminous flux. When the surface of the photosensitive drum is charged, as the charge accumulates on the surface of the photosensitive drum, the potential continues to rise, and finally reaches the "saturation" potential, which is the highest potential. The surface potential will drop over time. Generally, the potential during work is lower than this potential. This process of natural decrease in potential over time is called the "dark decay" process. When the photosensitive drum is scanned and exposed, the dark area (referring to the surface of the photoconductor that is not illuminated by light) is still in the dark decay process; the bright area (referring to the surface of the photoconductor in the light-illuminated portion) has a rapid increase in the carrier density in the photoconductor layer. The conductivity rises rapidly, forming a photoconductive voltage, the charge quickly disappears, and the surface potential of the photoconductor also drops rapidly. Call it "light decay".


It is a very common phenomenon that LED lights become darker as they are used. In addition to light decay, the reasons that can make LED lights dim are nothing more than the following two points.


Drive is damaged


LED lamp beads require low DC voltage (below 20V), but our usual mains is AC high voltage (AC 220V). To turn the mains electricity into the electricity needed by the lamp beads, a device called "LED constant current drive power supply" is needed.


In theory, as long as the driver's parameters match the lamp bead board, it can be continuously powered and used normally. The internal part of the driver is more complicated, any device (such as capacitor, rectifier, etc.) failure may cause the output voltage to change, and then cause the lamp to dim.


Driver damage is the most common type of failure in LED lamps, and usually can be resolved after replacing the driver.


LED burned out


The LED itself is a combination of lamp beads one by one, if one or part of them is not bright, it will inevitably make the whole lamp dim. Lamp beads are generally connected in series and then in parallel-so if one lamp bead burns out, a batch of lamp beads may not light up.


There are obvious black spots on the surface of the burnt lamp bead, find it, connect a wire to the back of it, and short-circuit it; or replace it with a new lamp bead, you can solve the problem.


The LED burns out occasionally, it may be a coincidence. If it burns frequently, the driver problem must be considered-another manifestation of driver failure is to burn the lamp beads.


Why does the LED light flash? What is the reason for the flickering of the LED light? . .


There is a capacitor in the driver of the LED lamp, which can be understood as a small capacity rechargeable battery: when the current passes through the capacitor, the capacitor will continue to charge-after fully charged, the capacitor will release all the stored electrical energy at one time .


The LED light flickers, which belongs to the latter case: the light is extinguished during the charging of the capacitor-because the internal current of the capacitor is small, the charging speed is very slow, so you can see that the light is extinguished with the naked eye. When the capacitor is fully charged, it releases electrical energy at one time and lights up the lamp. However, because of the small amount of stored electric energy, the light will quickly go out-repeatedly charging and discharging, and the naked eye can see the light flickering.


When the lamp is in normal use, no flicker can be seen, because the current through the capacitor is large and the charging speed is extremely fast.


So, what will cause a small current to flow inside the capacitor? The first is because the quality of the capacitor is not good-a high-quality capacitor has a lot of stored power, and the tiny current in the circuit is not enough to store energy in the capacitor. The average starter is only about 20 yuan, and the cost of high-quality capacitors is probably more than 20 yuan.


In addition, we can also start from the source of tiny currents.


Possibility 1: Switch to control the neutral line


The switch controls the neutral wire, which means that the live wire is directly connected to the light (capacitor). The live wire has a high potential. If there is a low potential in the line at this time, a potential difference will be formed-another name for the potential difference, called voltage. It's just that the potential difference at this time is much smaller than that of 220V. When voltage is applied across the capacitor, a weak current will be generated.


Therefore, the direct connection of the live wire to the electric light will inevitably cause the LED light to flicker. This is a construction problem, and there is no other way except to change the direction of the zero line of fire.


Possibility 2: The neutral line is live


If both ends of the lamp (capacitor) are connected to the zero line of zero potential, will everything be fine? Not at all! The neutral wire is easy to be charged-especially the neutral wire of an electric light. Mainly because the light switch is too unreliable.


The quality of the internal structure of the current light switch is very worrying. If the distance between the neutral wire terminal is too close, the insulation is not qualified, etc., it may cause the neutral wire of the electric lamp to be charged. If you don’t believe me, you can open the switch that you have connected to your home and test it with an electric pen. In theory, when the switch is off, only the Firewire terminal can light up the electric pen. But in actual use, the terminal connected to the zero line (lamp line) can also light up the electric pen in all likelihood.


It's just that most switches, even if the neutral line is charged, have a relatively low voltage, which is not enough to generate current in the line. But if the insulation is a little bit worse, the current generated is slightly larger, and the capacitor will be charged.


Another point: when the switch has an indicator light, the indicator light will light up when the light is turned off. At this time, a weak current needs to be generated-this part of the current will flow through the capacitor and be stored by the capacitor. These situations can be solved by replacing a better quality switch without indicator light.


Possibility 3: Induction electricity


If there are many wires around the capacitor, when other wires are working, induction electricity will be generated near the capacitor-one sentence explains the reason for the induction electricity: two conductors are placed in parallel to form a new capacitor.


Most people are at a loss when facing this situation. There are two solutions at this time:


1) Replace the electric lamp with a fluorescent lamp or an incandescent lamp.


2) Connect a 220V relay coil in series with the starter of the LED light. Use the coil to consume the induced electricity generated by the circuit.