How to calculate and choose a power supply for an LED strip

LED strips allow you to organize the backlight and lighting. When using models with a 220V power supply, you need a small adapter with a diode bridge inside to connect. But to connect low-voltage LED strips to 12V or 24V, you will need a power supply. And for multi-colour models, there is also a controller. We will talk about how to choose and calculate the power supply for the LED strip in terms of current and power in this article.

Kinds led lights to strip 10 meter 

All of the following is true both for the common led lights strip 10 meter and for models with a supply voltage of 5V or 24 volts.

Before proceeding to the calculation of the power supply for the LED strip, you need to decide where it will be installed, it depends on which option to pay attention to.

According to the cooling method, there are two types of power supplies:

With active cooling;With passive cooling.

Active cooling consists of heatsinks and a fan (a cooler similar to those installed in computers). The advantage of this system is that the heatsinks on the power cells are smaller, which means the power supply will be smaller and lighter than a passively cooled power supply of the same capacity.

However, the good weight and size indicators of power supplies with active cooling are offset by a significant drawback - the cooler starts to work louder and louder over time, due to mechanical wear. Therefore, it is not recommended to use them in residential areas, since the hum during operation can cause discomfort to the user.

Power supplies with active cooling usually have a large power - from 100 watts or more, and therefore are excellent for connecting lighting in large rooms, public places or for connecting a long LED installation, for example, for street lighting (facade, billboards, etc.) from one source.

Passive power supplies are produced in a wide range of capacities, but models with power up to 100-150 watts are most widely used. Their advantage is that they are silent in operation. Therefore, they can be installed without hesitation in the bedroom or other living space. The dimensions of such devices are usually larger than those of active power supplies.

On the market, you can find products that differ in the class of dust and moisture protection (class IPxx), for example, IP22, IP44, and IP67. I prefer to divide them into two types:

Sealed (IP65 and above) or so-called "street" power supplies for LED strips. Their case often resembles a laptop power supply (black plastic bar), and sealed high-power power supplies are made in a metal casing with end caps.Not sealed. These are those that are made in a plastic non-hermetic case or in a metal case with perforation through which air convection occurs when the elements are cooled.

When you have decided where you will install the block, what protection class is needed and in what power range these blocks are sold, you can proceed to the calculation of the LED strip power supply circuit.

How to calculate the power supply

To get started, check out the power table of typical LED products.

Here the type of blue led light strips and the power value for a different number of pieces per linear meter, as well as typical values ​​​​of the luminous flux are indicated.

From it, you can calculate the total power of the LED strip in your installation. Let's say you bought a segment 4 meters long with SMD 5050 LEDs 60 pcs/m. The power of 1 meter of tape is 14.4 watts. The power supply is calculated as follows:

Determine how much the load consumes in total: The power supply must be 30-40% more powerful than the load connected to it. The stock is chosen based on the conditions of its operation - if it is well ventilated, then 30% is enough, if it is in a small enclosed space, then 40% may not be enough, especially if, for example, heating is going on nearby. Let's say we have the first case (we take a margin of 30%), then you need to buy a power supply unit with a capacity of at least:

We round up to 75-80 W l. You can do more, but not less - we choose the nearest value available in the store, in this case, it will most likely be a 100 W power supply.

But sometimes it happens that the label of the power supply does not indicate the power, but the maximum output current, then to calculate the current, you need to divide the power by the voltage:

That is, the output current must be (round off) at least 6 amperes.

The calculation is quite simple. But there are some features in connecting a long LED strip, which is especially important when lighting the ceiling around the perimeter of the room. Consider several typical connection schemes and rules that need to be considered.

The main rule is not to connect more than 5 meters of tape in one line - this applies to a 12V tape, while a 24V tape can be connected up to 10 meters in series. LED strips are sold in bays of 5 meters for a reason. Their conductive paths are designed for the current consumption of these 5 meters. If the following pieces of tape are connected to the end of such a segment, then there will be voltage drops at the end of the line, and it will heat up and quickly fail - with regards to the 12V tape.

If you need to connect more than 5 meters, then there are two options:

Route the cable from the power supply to each next run. Lay a 220V cable and connect them to a new power supply.

Conclusion 

In the first case, you need to take into account that the wire cross section for the 12V line must be at least 0.75 mm², and preferably 1.5 mm², it is accurately calculated by the current. For your information, 5 meters of SMD5050 60 pcs/m LED strip consumes 72W or 6A current. Here are some typical LED strip connection schemes.