How to choose the right LED power supply?

The LED power supply (or LED driver) is an indispensable component to light up an LED fixture, which lots of users are not paying much attention to. LEDs can only be driven by low direct current (DC) instead of alternating current (AC) due to its intrinsic principle of luminescence and thus can not be connected directly to the mains electricity, like the fluorescent lamp does. So when you are using LED lights, a power supply should be applied to convert the AC household power to DC power. The relatively lower DC voltage (< 36V) has an extra benefit that humans can operate it safely. However, various factors need to be considered to choose a proper power supply, which we will go through in this post.

Constant voltage or constant current

To get started, you should find out that whether you need a constant voltage or a constant current power supply, both of which can be used to drive LEDs but must not be misused. A constant voltage driver is designed to maintain a stable voltage output during the operation which is independent from current variation, while the constant current driver is the opposite. As you may know that LEDs run with constant current, so for bare LEDs for instance, when you install a COB LED in your lighting system, constant current drivers should be applied. However, compared to the complicated and delicate constant current drivers, constant voltage drivers are more easy-going choices. Thus, most LED fixtures are designed with this consideration and can be driven by a constant voltage power supply which is made by selecting proper resistors as the voltage divider. In YUJILEDS store, all the LED strips and modules are driven by either 12V or 24V constant voltage. You could find related information in the specifications of each product.

Wattage and voltage/current

After you have determined the type of the power supply, the next step is to find out the power consumption and the rated voltage/current of your LED lights. Here, we will take one of our high CRI LED strips YJ-BC-RB-2835L as an example. There are two variants that can be selected on its product details page, one is CCT that varies from 2200K to 6500K, and the other one is the voltage that has  12V and 24V options. The two voltage versions have no noticeable difference in the luminous output, but need to be consistent with your power supply’s output voltage.

Regarding power consumption, it is labeled on this LED strip that it consumes 18W (Watts) per meter. LED strips can be cut into small pieces or connected to a longer one. So a user should calculate the total power consumption by multiplying the length of the strip by the unit Watts (18W/m here). We also recommend  remaining 25% capacity of the power supply to get a stable output.  Multiply the total watts by 1.25, and that is the final total power consumption a power supply should provide. For example, if you would like to run a 5-meter LED strip, the power supply should provide at least 18W/m * 5m = 90W, but it is better  to provide 18W/m * 5m * 1.25 = 112.5W or larger.

Notice: Avoiding surge current

Surge current (aka. inrush current, switch-on current) is the extremely large current drawn or delivered by an electric device at the moment it turned on. Most power supplies have this phenomenon due to the capacitors used in them. However, LEDs are very sensitive to small current change, and a much higher current will definitely cause inversible damage to them. Generally, we have two approaches to avoid this:

1. Use a professional LED power supply with overvoltage/overcurrent protection (or volt/amp limiter) in design.
2. Tune the current from a lower level gradually to the rated value, if the power supply does not provide the protection function.

Hopefully this post will help you find your right power supply among plenty of choices. For a good start, we recommend YujiElecs™ IP67 Waterproof Power Supply for LED Strips, 120W and Mean Well Power Supplies.

Freatured image credit: by Nicolas Thomas on Unsplash.