Why is the light from an LED getting dimmer and dimmer? Let’s take a look.

Release Date:

2022-06-25

　　 Light-emitting diode Optical attenuation refers to the weakening of an optical signal during transmission.

　　

Light-emitting diode

 

　　Light decay generally refers to the decline in luminous flux. When the photoconductor drum is charged, the accumulation of positive charges on its surface causes the surface potential to rise continuously until it reaches a “saturated” level—the so-called high potential. Over time, however, the surface potential gradually decreases; under normal operating conditions, the actual working potential is always lower than this saturated value. The entire process of this time-dependent potential reduction is known as “dark decay.” During exposure by the scanner, the potential in shadowed areas—i.e., those parts of the photoconductor surface that are not directly illuminated—continues to undergo dark decay; meanwhile, in the illuminated regions—those portions of the photoconductive layer directly exposed to light—the relative density of free electrons increases rapidly, leading to a sharp rise in conductivity and the generation of a photoconductive operating voltage. At the same time, the positive charges dissipate quickly, causing the surface potential of the photoconductor to drop precipitously. This phenomenon is referred to as “light decay.”

　　It is very common for LEDs to gradually become dimmer over time. Aside from simply being turned on or off, there are many other factors that can cause an LED light to dim; these essentially boil down to the following three points.

　　Controller damaged: Light-emitting diode LED chips are designed to operate on low-voltage DC (below 20 V), yet the common supply voltage is high-voltage AC (220 V). To convert this high-voltage AC into the low-voltage DC required by the LEDs, a device known as an LED constant-current power supply or LED driver is needed.

　　In theory, as long as the controller’s key parameters match those of the LED module, the power supply system can provide continuous power, and the lighting will operate normally. However, the controller’s internal circuitry is quite complex; common failures in components such as capacitors and electronic ballasts can alter the output voltage, resulting in dimmer illumination.

　　Controller failure is one of the common malfunctions in LED lighting; it can be resolved by replacing the controller.

　　Damage to light-emitting diodes: An LED lamp is composed of individual LED chips. If one chip or a portion of the chip fails to emit light, the entire illumination will dim. Typically, the chips are connected in series, and multiple strings are then connected in parallel; thus, a single faulty chip can easily cause an entire batch of chips to go dark. A damaged chip will exhibit a distinct black spot on its surface. To troubleshoot, simply connect a jumper wire across the terminals to short-circuit the faulty chip, or replace the chip with a new one to resolve the issue. Occasionally, a single LED chip may fail due to random, isolated causes; however, if failures occur frequently, the controller is likely the culprit. Another common symptom of controller malfunction is LED chip failure. Light depreciation in LEDs: Simply put, light depreciation refers to a rapid decline in the chromaticity of the light-emitting object. This phenomenon is particularly pronounced in fluorescent lamps and fluorescent tubes. While LEDs can also experience light depreciation, the rate is much slower, making the change difficult for the human eye to detect. Nevertheless, if proper maintenance is neglected—such as failing to clean fake LED assemblies or counterfeit LED boards—or if heat dissipation is inadequate, among other factors, it can lead to Light-emitting diode Light degradation occurs more rapidly.

More information

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