High-power LEDs are increasingly being used in traffic lights, illuminated billboards, street lights, airport runways, railroad crossings, medical/surgical lighting, and driving signals. They have a long life (high-power white LEDs typically have a lifetime of 35,000 to 50,000 hours) and low power consumption. However, LEDs can also be damaged by lightning, electrostatic discharge (ESD) caused by overvoltage, overheating, or even reverse power connection.
Because the LEDs are usually connected in series in the string, if one of the LEDs in the string breaks open due to a fault, all of the LEDs in the string will go out. Littelfuse offers LED open circuit protectors. The protector can be connected in parallel with each LED in the string, which bypasses the LED with an open fault to keep the rest of the string working. The protector also acts when an overvoltage occurs in the circuit and an overcurrent occurs in the string, or when the electrode is reversed.
When an LED has an open circuit fault, the LED open circuit protector will begin to conduct, limiting its voltage drop to 1.3V and keeping the rest of the series in operation.
In order to do this, designers have tried many devices, such as Zener diodes, metal oxide varistors, and controllable 矽 rectifiers, but not as LED open circuit protectors, because LED open circuit protectors are designed for this application. Designed. As shown in Figure 1, when an LED has an open-circuit fault, the LED open-circuit protector senses that this voltage rises and begins to conduct, limiting its voltage drop to about 1.3V to keep the rest of the string working properly.
The LED open circuit protector has different characteristics and rated voltage options. Some protectors are designed to protect a single LED in a string; others allow designers to protect two, three, four or five LEDs with a single device to save cost. Littelfuse's new generation of LED open circuit protectors provide both ESD protection.
ESD and lightning protection
ESD can enter the LED string when assembled or installed in the field. Lightning can enter the LED string in two ways: nearby lightning strikes can cause transients in the power supply, can be coupled to the LED driver and enter the string; or nearby lightning strikes may be on the LED driver supply rail, or Electrical transients are caused on the line that receives the LED string.
A new generation of LED open-circuit protectors, such as the Littlefuse PLED 5 series, can handle ESD events with ±15kV air discharge, ±8kV contact discharge, and ±40A 5/50 ns EFT events (fast bursts).
Reverse polarity protection
When a string of LEDs with PLED5 is reversed, all protectors will begin to conduct, shunting the current on these protected LEDs to protect them from damage. After the reverse electrode is corrected, the protector will turn off and the LED will work normally.
Female headphones are specially designed for women, with pink, rose gold or rose red as the main color, which are very popular among female customers. Mainly divided into: headband female headphones, in-ear female earphones, diamond female headphones. With skin-friendly materials, it is comfortable to wear and beautiful in appearance.
Feminine Headphones,Waterproof Headphones,Disposable Headphone,Female Headphones
Shenzhen Linx Technology Co., Ltd. , https://www.linxheadphone.com