LED保护器

为什么我需要使用LED保护器?

大功率LED提供长寿命,低功耗和低维护要求,这使得它们越来越流行的户外应用。

但LED是敏感的电子设备,可以通过系统切换,静电放电和附近的雷击引起的过电压和过电流瞬变损坏。

此外,与LED一起使用的开关模式电源不提供瞬态保护,电感镇流器替换在照明应用中。这使得静电放电保护必须。

LED String Vulnerability

LED通常设计用于将五到二十串联的串连接。通常,任何单个LED的故障都将取出整个字符串。

在街灯或机场跑道灯应用中,绳子的损失可能会暗淡或关闭光线,从而产生安全危险。在户外LED展示广告标志中,它可能会产生空白斑点并导致收入损失。

In any case, the failure of an LED string is often a costly maintenance issue in outdoor applications. Using LED protectors can help prevent this costly inconvenience.

Littelfuse Prode设备在哪里通常使用,他们做了什么?

Littelfuse PLED open-LED protection devices are often incorporated into the circuit designs of high-power LEDs in such applications as roadway lights and outdoor LED advertising display signs.

镀devices are connected in parallel with each LED in a series string. If one LED should fail open-circuit then the PLED connected to it will turn on and carry the current that would have gone through the failed LED. This keeps the rest of the string operating, so that only a single LED goes dark instead of the whole string.

In the off state, a PLED draws only a few microamps so it does not affect the circuit. When triggered it carries the full current of the string with a voltage drop of about 1.3 volts.

PLED设备有助于保护LED免受附近雷击和ESD事件引起的浪涌。此外,如果电源以反极性连接,则PLEDS包含反向电流二极管,该二极管将保护LED串。

镀devices are typically connected across each LED in a string, but units are available to connect across two or even three LEDs. This reduces the cost of protection but causes more than one LED to go dark if one fails.

Littelfuse Prope设备如何与其他电路保护技术进行比较?

  • A PLED provides open LED protection; an SCR does as well, but a zener does not, as string current will overload it and shorten its life.
  • A PLED provides reverse polarity protection, while an SCR and a zener do not.
  • PLED和齐纳均提供ESD /防雷,但SCR没有。
特征 可控硅 齐纳二极管
LED开路保护 是的 是的
反极性保护 是的
ESD / Lightning / EFT保护 是的 是的
响应时间 ~100ns ~5µs -
Major disadvantages

Large device size

Typically requires a resistive voltage divider network to set the trigger voltage

Variation of triggering voltage versus temperature is quite large

反向阻塞电压过高,因此不能提供反极性保护

当LED变为循环时,齐纳二极管必须进行所有电流。

齐纳二极管没有评级,因此它的生命将很短

为应用程序选择合适的PLED设备的步骤

以下是通常涉及为LED应用选择Littelfuse PLED设备的步骤:

  1. 定义Vf(正向电压),如果(正向电流),and the connection scheme of the LEDs.
  2. 定义LED串中的LED数,并了解电源的恒流源值和合规电压。
  3. 确定PLED设备适合VF,IF和PLED保护率,如下:
    1. PLED开关电流必须小于恒定电流源值
    2. 镀电电压必须小于电源合规电压。
    3. 每个PLED选择要保护字符串中的LED(1,2或3)。PLED6,触发6伏,保护一个LED;触发器在9伏特的PLED9可以与一对LED一起使用;并且PLED13可以使用三(注意,一个LED的失败分别导致两三个或三个外出)。
  4. 确定PLED设备的包装以适合照明环境。
  5. Define the ambient temperature of the PLED environment and provide adequate heat sinking if required.
  6. 通过使用受保护的LED旋转来对PLED进行测试。
  7. Review steps 2 and 3 to see if there is any issue.

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