Avoiding LED Driver Inrush Current Problems.

23 March 2020
MEAN WELL NPF-120

A LED driver is a switch mode power supply that has specifically been designed to power LED lighting.

Like all switch mode power supplies, MEAN WELL LED drivers have an inrush current rating that is shown in the data sheet, typically around 40 to 70 amps and lasting 1 to 2 milliseconds.

This may sound insignificant, but most modern circuit breakers will notice the inrush current.

If you are using a single LED driver then it is highly unlikely that you will experience any problems. However, this may not be the case with larger installations.

Let’s take a single floor of a commercial building as an example. There could be numerous LED drivers in parallel. If they all switch on at the same time, the combined inrush current may cause the circuit breaker to trip. This won’t necessarily happen every time, only when the phase of the mains combines to boost the inrush.

So what can be done to prevent such a large combined inrush current?

Overcoming this problem is now easier, following the introduction of MEAN WELL's inrush current limiters.

Before this you would have had to have opted for one of the following solutuions:

MEAN WELL have several dimmable LED drivers that can be dimmed right down to zero. This type of LED driver can be left switched on, with the dimming control being used to steadily bring the LED lights up to the required brightness. Thus, avoiding any sudden inrush.

Below are some of the LED drivers with Australian approvals available through MEAN WELL Australia's partners, which can dim down to zero:

PWM Series (All models) LED Driver PWM-60
LCM Series (All models) LED Driver LCM-60
HLG-600H* LED Driver HLG-600H
ELG Series (Dimmable models) MEAN WELL ELG-240

*Other models within the HLG series dim down to 10% of rated output.

If there is not a model within the above range of products that is suitable, there are still a couple other options open to you.

The first one is to design the lighting system, so that you use groups of 8 LED drivers. On the last driver of each group you connect a relay coil of the right voltage across the driver output. Use the contacts of that relay to switch mains power on to the next group of 8 LED drivers. This way, the inrush surge happens one after the other and doesn't cause breakers to trip.

When using this method, we suggest using a few larger drivers rather than lots of small ones, and use the highest DC voltage that your light fittings will allow. Use the AC mains for longer runs and distribute the power as DC in the local area. This will minimise the copper losses on longer runs, and minimise the inrush problem.

If you are experiencing difficulties with inrush current contact MEAN WELL Australia.