Release date: 2017-11-21 Source: Foreign station Sharing:

As a modern green lighting technology, high-power white LEDs offer benefits such as high light conversion efficiency, low energy consumption, long lifespan, and minimal maintenance. However, their longevity depends on a stable and safe operating environment. In LED lighting systems, two primary threats can significantly reduce the lifespan of the device: overcurrent shocks and overheating. Overcurrent occurs when the current applied exceeds the maximum rated value specified in the LED’s datasheet, often caused by overvoltage events. Overheating, on the other hand, can lead to gradual degradation or sudden failure of the LED. LED failures are typically attributed to issues with the power supply or drive circuit, as well as internal defects in the LED itself. The power supply is vulnerable to overcurrent surges (EOS) from the input voltage and open-circuit faults at the load. These surges can damage the driver chip and cause breakdowns in passive components like capacitors. A short-circuit at the load end may also result in overcurrent, potentially damaging the drive circuit. There are several common causes of LED device failure: 1. **Electrostatic Discharge (ESD)** ESD is one of the most frequent transient overvoltage hazards during the manufacturing, transportation, and use of highly integrated semiconductor devices. LEDs must meet IEC61000-4-2 standards, which require protection against 8kV contact discharge. An ESD event can damage the PN junction of the LED, causing partial or permanent failure. This type of damage might not be immediately visible but can reduce performance over time. 2. **Transient Overcurrent Events** These occur when the current through the LED exceeds its maximum rated value. Such events can be triggered by lightning strikes, switching power supplies, or fluctuations in the power grid. They often manifest as brief spikes in voltage or current. In automotive applications, for example, ISO7637-2 specifies the transient load dump surge that can affect LED performance. The damage caused by such events often affects the weld line, potentially leading to more extensive internal damage. In addition to electrical threats, thermal management plays a crucial role in LED longevity. Nearly 80% of the energy consumed by an LED is converted into heat, directly affecting the junction temperature. For every 10°C increase in junction temperature, luminous flux decreases by about 1%, and the LED's lifespan is halved. Therefore, proper thermal design and overheat protection are essential to ensure reliable operation. To protect LED systems, various components are used, such as PTCs (Polymer Positive Temperature Coefficient) for overcurrent and short-circuit protection, and surge protection devices like ROVs and POLYZEN series components. These solutions help safeguard both the power supply and the LED itself, improving system reliability and reducing repair rates. Even though many advanced LED drivers include built-in protection features, discrete component solutions are still necessary for comprehensive protection, especially in critical applications where reliability and long life are paramount.

Label: LED Power Protection Schemes and Common Causes of Damage

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