LED lighting protection solutions based on Littelfuse

As the cost of LEDs continues to fall and governments around the world pay more and more attention to energy conservation and environmental protection, the market prospects for LED lights are becoming increasingly broad. High-brightness LED lights have appeared in a variety of occasions, from outdoor billboards, TV LED backlights to traffic lights, airport runway navigation lights, and so on. The advantages of LED lights are also particularly prominent, such as long life, high energy efficiency, and rich colors. However, the first thing that LED lamp designers must consider is the reliability of the lamp. For many occasions, the importance of reliability is self-evident: for example, some outdoor lighting with high maintenance costs, and some applications that are prone to safety hazards, including traffic lights and navigation lights. LED is also a fragile semiconductor solid-state device. Its light-emitting principle is that the forward voltage bias of the PN junction of the diode generates a light source. Both the LED array and the power supply are at risk of being damaged by transient voltages, surge currents, and other electronic problems. Especially in outdoor lighting applications, electrostatic discharge (ESD) generated by nearby lightning strikes can easily cause LED failures.

Power supply protection scheme

In the switching power supply part, LF recommends the overcurrent and overvoltage protection scheme as follows:

TVS Tube

The AK6 and AK10 series are transient voltage suppressors (TVS) with extremely high rated currents, specially designed to protect AC and DC input circuits from transient voltage damage. They are rated at 6kA (8x20us) and 10kA (8x20us); 15KPA and 30KPA are TVS rated at 15,000 W and 30,000 W respectively, both of which are ideal for protecting LED lighting in harsh environments. The 1.5SMC series is a TVS rated at 1500W, which is ideal for protecting DC-DC converters from transient voltage damage. TMOV thermal protection varistors

TMOV integrates thermal components, helping TVSS modules meet UL1449 standards for cable-attached and permanent-attached applications using appropriate enclosures. TMOV offers faster thermal response and lower inductance than most discrete solutions, resulting in improved clamping performance for fast response to voltage transients.

Fuse

The AC line fuse uses the 464 series, which provides a minimized, fast-response surface-mount 250VAC fuse that complies with the IEC60127-4 standard. The 464 is specifically designed for power supply and lighting system design applications.

High-voltage DC fuses can be selected from the 477 or 505 series. Both series are designed for high-energy and power applications. The 477 series provides 400VDC/500VDC rated voltage, time-delay, and surge-resistant fuses in a 5x20mm package; the 505 series provides 500VAC/VDC rated voltage fuses with an upper limit current rating of up to 50kA in a 6.3 x 32mm package.

LED Array Partial Protection Solution - PLED Open Circuit Protector

The above solution can effectively deal with the surge threat generated by the power supply part and protect the LED from damage. However, we all know that LED lights are usually composed of a certain number of LED tubes connected in series or in parallel to form an array. The damage of a single LED will cause the entire LED array to stop working. Traditional fuses, MOVs, and TVS cannot guarantee such problems. Therefore, at the LED array end, LF has developed a PLED LED open circuit protector specifically for LED open circuits, as shown in the figure: