The main cause of white LED lamp bead failure or necrosis

The Main Causes of White LED Lamp Failure or Luminous Death

Release date: 2017-10-26 Source: Foreign station Share:

White LED lamp beads are highly sensitive to voltage. Under normal operation, they typically run at around 20 mA. However, due to various factors during use, the current can sometimes rise beyond safe limits. If no protection is in place, this increased current can cause the LED to fail or even "die" over time. The primary causes of LED bead failure include: 1. **Sudden Voltage Surge**: A sudden increase in supply voltage can overwhelm the LED, leading to immediate damage. 2. **Short Circuits**: Faulty components, damaged PCB traces, or other wiring issues can create partial short circuits that raise the voltage in certain areas of the circuit. 3. **Internal Short Circuit**: If an individual LED bead has a manufacturing defect, it may short internally, causing excess voltage to be transferred to other LEDs in the string. 4. **High Temperature**: Excessive heat inside the lamp can degrade the performance and lifespan of the LED beads. 5. **Moisture Infiltration**: Water entering the lamp can lead to electrical shorts and corrosion, which can damage the internal components. 6. **Static Discharge**: Poor anti-static measures during assembly can cause invisible but damaging static shocks to the LED beads, even if the voltage and current appear normal. So, how can we protect LED beads from these failures? 1. **Use a Fuse (Tube)** Fuses are commonly used for overcurrent protection, but they have limitations. They are one-time use devices, slow to react, and require manual replacement after tripping. For modern LED lighting systems—especially those used in urban infrastructure and large-scale projects—fuses are not ideal because they don’t offer fast, automatic recovery. The system needs a more reliable and compact solution that can quickly cut off power during faults and resume normal operation once the issue is resolved. 2. **Transient Voltage Suppressor (TVS) Diodes** TVS diodes are effective at clamping voltage surges and protecting sensitive electronics. They respond rapidly (in nanoseconds), can handle high-energy transients, and have low leakage currents. However, they are not ideal for protecting against overcurrent situations. Additionally, finding the right TVS device with precise voltage thresholds can be challenging, and their application in real-world LED systems often proves difficult. 3. **Self-Recovery Fuse (PTC)** A self-recovery fuse, also known as a PTC (Polymer Positive Temperature Coefficient) thermistor, is a smart alternative. It consists of a polymer matrix embedded with conductive particles. Under normal conditions, it remains in a low-resistance state. When an overcurrent or overheating condition occurs, the PTC heats up, causing the polymer to expand and break the conductive path, increasing resistance and limiting current flow. Once the fault is cleared, the PTC cools down and returns to its low-resistance state automatically. In practical applications, there are two common approaches: - **Branch Protection**: Each LED string can be protected individually by placing a PTC in front of each branch. This method offers high precision and reliability. - **Overall Protection**: A single PTC can be placed at the main power input to protect the entire lamp. This approach is simpler and more cost-effective, making it suitable for consumer products. By implementing proper protection mechanisms, the lifespan and reliability of white LED lamps can be significantly improved, ensuring better performance and fewer failures over time.

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