Must Read – How MEAN WELL HLG LED Drivers Behave in a Short Circuit

How MEAN WELL HLG LED Drivers Behave in a Short Circuit
Installation Advice

Some of the MEAN WELL’s HLG series LED drivers have a particular characteristic, which can be problematic for installations with poor quality light fittings or LED strip.

The purpose of the LED driver’s short circuit protection is to protect the LED driver only. Therefore, it is important to understand how the LED driver behaves when a short circuit is present.

HLG-100H, HLG-120H, HLG-150H, HLG-185H, HLG-480H & HLG-600H series LED drivers will continue to operate at full current even if they are powering into a short circuit.  

Note - A short circuit generally has very little, or no, voltage across it. 

The other HLG models will enter hiccup mode in order to reduce the current as the voltage decreases. 

To explain this further let’s look at one possible scenario: 

MEAN WELL HLG-120H LED Driver with Poor quality LED Strip 

An HLG-120H-24 LED driver is powering a 24V LED strip. The LED strip is poor quality and one of the LEDs fails into short circuit. The HLG-120 will continue to supply full current to the failed LED even though the voltage has reduced. This can cause overheating. 

The following diagram shows the HLG-120H's behaviour in a short circuit situation. 100% current is powering into the short circuit even at zero volts, and even though the output is hiccupping. 

MEAN WELL HLG-120H-24 LED Driver Constant Current Limiting


Other HLG models will only provide full current down to half the voltage rating (in this case 12V), before starting to hiccup the current when the voltage decreases below 12V. This avoids excessive heat in the faulty LED.  

The following diagram shows how other HLG models hiccup the output current down to zero as the voltage drops below 50%. 

MEAN WELL HLG-80H-24 LED Driver Hiccup Mode


How to Avoid This Scenario 

There are two ways this scenario can be avoided.  

The first is to ensure that a good quality LED strip is used in your installation.  

The second is to use MEAN WELL driver that has hiccup mode short circuit protection instead of constant current limiting protection. The type of short circuit protection is indicated in the MEAN WELL data sheet: 

MEAN WELL LED Driver Short Circuit Protection Method as Shown in Data Sheet

If you cannot find an HLG LED driver with hiccup mode that has the required power output, then a MEAN WELL ELG series LED driver may be a better alternative.  

Please do not hesitate to contact ADM if you have any questions about using MEAN WELL LED drivers. A member of our expert team will gladly answer any questions that you may have.   


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20 August 2021