A Simple Solution to LED Overtemperature Protection

What is not to love about LED lighting? A simple swipe of an app can turn the ambience of our homes from calming zen temples, to flashing multi-color 1970 discos. Such fun features are not just limited to our homes as some of the latest electric vehicles now bring this excitement on the road. Besides the frivolous, the explosion in LED usage has seen them becoming integral to such diverse implementations as hydroponic plant factories and smartphone backlights.

Compared to traditional lighting technologies such as incandescent and fluorescent lamps, LED lighting has a much longer life span, consumes far less energy and is robust against shock and vibration. LEDs produce very little heat and do not contain the toxic materials of its predecessor technologies.

You may be wondering if there are any downside to LEDs. One complaint that arises is that they tend to fail when they overheat. The fabled long life of LEDs is very much dependent on them remaining cool or at least not being subjected to heat shock.  

In these scenarios, there are numerous ways to protect LEDs such as using NTC thermistors as temperature sensors and then using an IC to try interpret and compensate for the inherent inaccuracies, NTC resistance vs. temperature dynamics and response time. Thermal fuses can also be used but unless that fuse is replaceable, then the board and LEDs will need to be replaced.

The arrival of Bourns® surface mount mini-breakers brings a degree of simplicity to the overtemperature protection of LEDs. The Model SA, SC and SD Series of surface mount mini-breakers can be used for LED overtemperature protection. These devices are sufficiently small to be mounted in thermal proximity to the LEDs. For example, the Model SD Series of mini-breakers are available with tripping values from 55 °C up to 150 °C and are guaranteed to trigger within ±5 °C. The simple schematic below illustrates how the power will be cut to the LEDs once the predetermined trip temperature of the LED is reached. Selecting a mini-breaker without the standard internal PTC means the mini-breaker will completely cut the current when tripped, and reset once the ambient temperature has cooled to the reset temperature.

This simple, yet highly effective solution allows designers to choose the precise trip temperature they require in their LED systems to ensure the LED system is adequately protected. We, as users can bask in their ambience for years and years to come.

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