Installation Guide

LED Lighting Surge Protection Modules

Design and Installation Guide

Modular Solution vs. a Solution Embedded into the

PowerSupplyUnit

Outdoor luminaires are easily affected by transient surges inductively coupled into power

lines from lightning strikes. IEEE C62.41.2

™

-2002 categorizes two different exposure levels

for outdoor locations (Category C Low and C High) with different suggested surge levels.

Similarly, some regions or countries may have different surge level requirements due to

different lightning strike density in the area. Although some LED luminaires feature surge

protection devices embedded in the power supply unit, Littelfuse recommends that the

surge protection circuit be provided as an independent module that’s separate from the

luminaire power supply; in this way, the same luminaire can be easily marketed globally by

attaching different surge protection modules to meet differing surge level requirements.

MOVs are widely used in surge protection circuits for their fast response times, high surge

energy handling, compact size, and cost-effectiveness. However, after MOVs absorb a

certain number of surge strikes, they will begin to degrade and can no longer provide the

same protection as new ones. Having a separate surge protection module allows for easy

replacement when the original module reaches its end of life.

Thermally Protected MOV for SPD Safety

MOV technology is not only inexpensive but also highly effective for suppressing transients

in power supplies and many other applications, such as the SPD modules that are often

placed upstream from an LED driver.

MOVs tend to degrade gradually after a large surge or multiple small surges. This degradation

leads to increasing MOV leakage current; in turn, this raises the MOV’s temperature, even

under normal conditions like 120Vac/240Vac operating voltage. A thermal disconnect

adjacent to the MOV (Figure 8) can be used to sense the increase in MOV temperature

while it continues to degrade to its end-of-life condition; at this point, the thermal disconnect

will open the circuit, removing the degraded MOV from the circuit and preventing it from

failing catastrophically.

Figure 8. A thermal disconnect can open the circuit, preventing a catastrophic failure of a

degraded MOV.

Modular Solution vs. a Solution Embedded and Thermally Protected MOV for SPD Safety