How to calculate the LED Power Supply needed for your LED Strip

27 Jul 2016

One of the questions we often ask is, “How do I calculate the power supply I need for my LED strip?”

The answer is that it is not that difficult to do.

The first step is to check the data sheet of the LED strip you intend to use. It should show you the power consumption in Watts per Metre. Usually, it will be displayed in the format of 14W / m (14 Watts / Metre).

The second step is to calculate the length of the strip you will use in metres and multiply this number by the number of Watts used per meter.

Let’s say you are using 8.5m of LED strip, which consumes 14W / m.
14 x 8.5 = 119 Watts in total. So you need an LED power supply (sometimes called an LED driver) that can deliver at least 119 Watts.

However, it is recommended that you make allowances for unintentional overloads. To mitigate this, we recommend only using about 80% of the power supply's rated load. So, in this instance, you would most likely select a 150-watt power supply.

You can then browse through our range of LED drivers to select the most suitable model.

Remember to confirm the actual power output in the product data-sheet. The actual power output does vary from model to model within any one series of LED drivers. For example, an HLG-240H-24 has a power output of 240 Watts, whereas the HLG-240H-12 has a power output of 192 Watts.

If you are considering using a dimmable LED driver, then there are some further factors you need to consider.

Many dimmable LED drivers work by varying the amplitude of the current being delivered to the LEDs. If you are using more than one power supply to power multiple LED strips, the load on each driver must be matched as closely as possible to keep the dimming synchronised.

As an example, if one supply is loaded to 80% and a second supply is loaded to 50%, the first supply will start to dim once the dimming control is turned down below 80%, but the second supply won’t start to dim until the dimming drops below 50%. This difference is visible to the eye.

If your dimmable LED power supply has a PWM type output, such as the MEAN WELL PWM series or Power Source TRIAC Dimmable LED Drivers, it will dim evenly regardless of load. Power Supplies Australia stocks these LED drivers in 12V and 24V models.

The following PWM LED drivers are available to order through Power Supplies Australia:

We are on hand to help if required. Please do not hesitate to contact Power Supplies Australia if you have any further questions on selecting the correct LED power supply for your LED strip.