How to choose the right power supply for constant voltage LED strip light?

2021.12.07 05:23 PM By Mark Mai

LED strip lights becomes very popular in the recent years. You could use LED strip lights as cove lighting, or direct linear light.

It's most possible that this article would help solving how to choose the right power supply for your LED strip lights. Let's get start.

Before going on

You might need to classify what type is your LED strip lights. For the full definitive guide for LED strip lights, please check this page.

Constant Voltage LED strips: This is the most common type of strip lights. DC5V, 12V, 24V, etc.
Constant Current LED strips: This is not the common type but is also widely used in LED lights. You might need to know more for choosing the right driver for this type.
RGB or LED strips with ICs: Not only you need to consider choosing the right power supply, you might also need to worry about the controlling

Constant Voltage LED strip lights

Constant voltage LED strip lights means the input voltage of the LED strips are fix in voltage. For example, DC12V, or DC24V, etc.

Step 1

So first, you need to know what is the input voltage of your strip lights.

Easy, you can know from the surface of the LED strips in most cases.

If no, you might guess from how many LED chips per cut. 3 LEDs will be 12VDC input generally. 6 LEDs will be 24VDC.

Step 2

Identify the total power consumption of your LED strip lights.

It's related with the density and length of LED chips. The more LED chips and longer the LED strips, it's more likely to be more power consumption.

The power/meter can be found on the packing.

Tips:

Try not to use LED strip lights for over 5 meters. The reason will be the voltage drops for over 5 meters will have significant impact on the brightness.

Example

the labeling of the LED strips tells:

Input 12VDC, Power: 8Watts/m.

And you are going to use 3.5 meters.

The total power consumption for this LED strip lights will be:

8Watts/m * 3.5m = 28Watts.

Step 3

The last, we need to use a power supply to provide capacity bigger than the actual LED strip light's power.

Normally, capacity of 120% of the total led strips power will be enough.

So, back to the example.

28Watts * 120% = 33.6Watts.

Conclusion

Any power supplies in 12VDC output, and with capacity of over 33.5Watts will be okay.

You might found these powers are popular in the market: 35W, 50W, 60W, 75W, 100W, 150W, 200W, 250W, 300W, 350W, etc.

So, 35W of DC12V power supply will be the right choice. 50W or 60W will be alternative choice if you cannot find 35W.

Can I use 350W power supply for only 33.6W LED strips?

Of course you can, only it costs more and with much bigger size.

7 tips for choosing power supply for constant voltage led strips

If the label only shows: Power < 14.4W/m. How can I know the actual power per meter for the LED strips?

Well, that is a bit difficult. You might guess from the quantity of led chips per meter as follow:

60 chips/m, power is around 8 watts/m.
120 chips/m, power is around 14watts/m.
over 200chips/m, power is around 18-20Watts/m.

But this will vary for different formats of LED chips.

2. If you connect one end of the strips to the power supply, the longer strips you are using, the unit power per meters will be decrease.

For example, you are connecting 1 meter of DC12V led strip lights with 14Watts. What is the total power if you connect 5 meters of the same strip lights? 14Watts/M * 5 = 70Watts?

The actual power will 70Watts, should be around 60-65Watts. The reason is that the unit power consumption will decrease when you connect longer.

3. If you measure the total power consumption of the LED strip lights with power supply, you might found that the total power is actually bigger than the one you calculated from the LED strip light parameters

The reason will be the total power consumption consists two parts: the actual led strip light power consumption, and also the power consumption of the power supply.

Every single electrical device will have its own power consumption. The bigger it consumes, the lower efficiency it got. Good quality power supplies will have over 90% efficiency, meaning that only consumes maximum 10% of the total power consumption.

4. Not just focus on the output parameters of the power supplies, you must also pay attention to the inputs.

You need to know what is the electricity inputs of your region or country. There are many types of them all over the world, differ from AC110V, AC220V, AC240V, and AC277V.

So it's a MUST to make sure you also choose the right inputs for the power supply as well.

5. Connecting LED strips to power supply on only one end, please make sure the length of the LED strip light not exceed 5 meters. This is only advice for low voltage input led strip light, for example DC12V or DC24V.

If you really need longer than 5 meters length, try to connect both ends to the power supply. It might get better effects comparing to connecting only one end.

6. In most cases, people do not pay attention to the cables using for connecting LED strips and the power supply. But the fact is that it's very important for low voltage input led strip lights.

Let's do a simple maths.

Using 100Watts of power supply for 80Watts of DC12V led strip light in AC220V electricity:

The input current of the power supply is:

80W / AC220V = 0.3637A

The output current of the power supply is:

80W/ DC12V = 6.67A

Now you can see the difference.

So please make sure that you use the big enough cable for the output, and not for long.

7. For constant voltage power supply, as long as you use big enough capacity, it's okay to use much bigger capacity one for small power LED strip lights.

For example, using 400Watts power supply for only 10watts of led strip lights are

We will continue to introduce how to choose the right driver for the constant current led strips, and also controllers in the next blog posts.

How to choose the right power supply for constant voltage LED strip light?

Before going on