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

Applying the LED strip indoors is important for its functioning to be stable, durable and not have a negative impact on people's vision. The correct operation of such lighting devices is guaranteed by a power supply for the LED strip, which is selected in accordance with certain calculations. A correctly selected converter will protect the LEDs from power surges and premature loss of luminous flux quality.

The principle of operation of a switching power supply

The switching power supply is by far the most commonly used for LED strips. The principle of its operation consists in transforming the duration of the working part of the period for a pulsed current of a rectangular type, as well as in the duration of its supply to the device. These parameters are set in accordance with the zero level. This refers to the part of the period when the maximum allowable voltage can be observed. This characteristic is called latitude. Its transformations are carried out in the range of 0-100% and cause specific modifications in the indicator of the available voltage of the light source.

In such cases, the output current saves its own stability at the most optimal level. At the same time, the changes do not concern the spectral composition of the light flux, and the dissipation power is kept within the nominal values.

The power supply itself, when operating in a pulsed mode, bears minimal losses. Regulators of this class are the most optimal in order to implement a computer or digital method of controlling the degree of illumination.

The main disadvantage of such models is the increased level of flicker. But it is characteristic of extremely cheap power supplies. This effect is harmful to human eyes and can occur even at low brightness levels. Long-term tracking of such a light phenomenon can cause:

• the formation of unpleasant visual sensations;
• the development of a headache;
• increased fatigue;
• loss of care and visual acuity.

To avoid negative impact, it is better to give preference to branded power supplies. They are somewhat more expensive, but they are devoid of such an effect.

Main selection criteria

To choose a power supply for an LED strip, you need to pay attention to the following key characteristics of this device:

• the value of the output voltage - it must necessarily correspond to the indicator of the lighting device;
• device power indicator - calculated using a special formula;
• level of protection;
• availability of additional functions.

When choosing a power source, you also need to consider its cost. Models protected from moisture will cost more. Pricing is influenced by the conversion method of the device and its power indicators.

Conversion method

According to the conversion method, power supplies can be divided into 3 main types:

• linear;
• transformerless;
• impulse.

Linear power supplies were invented in the last century. They were actively used until the early 2000s, before switching devices appeared on the market.Now they are practically not used.

Transformerless models are of little use for powering LED lamps. They have a complex design - the voltage of 220V in them is reduced by means of an RC circuit with subsequent stabilization.

The most popular is the pulse-type converter. It is favorably distinguished by its increased efficiency, low weight and compact dimensions.

The main serious disadvantage is that the unit cannot be turned on without load. Otherwise, the power transistor may fail. On modern models, this problem was solved with the help of feedback. As a result, at idle, the output voltage does not go beyond the permissible indicator.

Cooling

Depending on the applied cooling system, power supplies are divided into 2 types:

• Active cooling - the device is equipped with an in-frame fan, which is responsible for the cooling efficiency. This design makes it possible to interact with sufficiently high powers. In this case, the fan can hum and it must be periodically cleaned, since dust gets inside the case with the air flow.
• Passive cooling - the device is not equipped with a fan (free cooling). Such power supplies are very compact, but at the same time they are suitable exclusively for use in everyday life, as they are designed for small loads.

Execution

By type of execution, power supplies are divided into the following designs:

• Small-sized plastic case. Such a device is outwardly similar to power supplies from laptops and has a collapsible plastic case. Models of this class function stably and will be the best option for use in dry rooms.
• Sealed aluminum housing. Structural features, tightness and durability of the material used make it possible to use such an LED unit in rooms with high humidity. It is resistant to moisture and stands out for a long service life.
• Metal casing with ventilation holes. Such devices are not protected from external influences, therefore they are mounted in special closed boxes. The open-type housing makes it possible to quickly reconfigure the unit.

When choosing a power supply, you need to pay attention not only to its design features, but also to functionality. Do not overpay, because the owner may simply not need some additional functions.

Output voltage

This characteristic sets the voltage rating to which the power source converts the original mains voltage of 220V. Usually it is 12V and 24V DC or AC type. The most common are 12V constant voltage LED strips. Accordingly, they need a DC12V marking power supply.

Power

In some situations, there is simply no need to calculate the power supply capacity. For example, if you need to connect 1 meter of tape on SMD class LEDs with a 12V supply, any unit with a constant voltage at the 12V output will do. If a more powerful load is expected, you will need to use the calculation formula.

You can select the power of the power source based on the maximum length of the LED strip and on the consumption rate of 1 meter of the product. To facilitate this task, manufacturers prescribe the requirements for the power source in the instructions for the LED strip.

Additional functions

In addition to the main characteristics, when choosing power supplies, attention should be paid to the presence of additional functions in them:

• can be trivial and solely provide food;
• more functional models have a built-in dimmer;
• some devices are equipped with an infrared sensor or a radio channel for control using the remote control.

The most expensive power supplies are equipped with a dimmer and remote control at once, which makes it possible not to clutter up the space of the room with separate blocks.

How to calculate the wattage of a power supply for an LED strip

To determine the required power of the power supply unit required in a particular situation, you can resort to using a simple calculation scheme.

As an example, we will consider the popular SMD5050 strip with a length of 3 meters, a power of 14.4V and a density of 60 LEDs. per meter of length.

First you need to calculate the energy consumption of the tape: 14.4V x 3m = 43V.

To take into account the power loss on the conductors, it is required to add 20% to the calculated power for the reserve: 43V x 1.2 = 52V.

The found figure says that the smallest power supply power for this tape should be 52V. Blocks with such indicators are not available, so the figure needs to be rounded up - a 60V device is suitable.

Connecting LED strip

Before installing it in its original place, the tape must be connected to the power supply. This process is simple and can be done independently. For example, a block with a metal casing with ventilation holes will be considered. Such devices are in greatest demand. Inside the case there is a rectifier with a terminal module, where the light source is actually connected.

Connection polarity

All power supplies are labeled with the main purpose and its key characteristics. All terminal screws are marked with a mark to ensure that the wires are connected correctly:

• L - phase, N - zero: this is the input of the power supply. Through these terminals, the unit is connected to the general network.
• G - for grounding connection. If there is no grounding in the apartment, this terminal is not used.
• + V and -V are 12V-converted output terminals.

Power supplies of this class are equipped with a work indicator - a green lamp. There is also a special swivel type mechanism, which is designated "V adj". It allows you to slightly adjust the voltage - within 12-13V.

Selection of wire cross-section

The choice of the wire cross-section is extremely important, because the possibility of power loss when the lighting device is heated depends on it. If, when connecting, the distance between the power source and the LED strip turned out to be large, it is necessary not only to eliminate the voltage drop on the connection cable, but also to level the power losses created by this cable.

The larger the cross-section of the cable, the less power loss is observed in this case.

To connect LED strips to the power supply, you need a cable with a cross section of at least 1.5 mm2. If the total cable length is more than 10 meters, it is better to use wires with a larger cross-section, for example, 2.5 mm2.

Choice of wiring diagram

Before connecting the LED strip to the power source, you need to bring the cables to the installation site. For such lighting devices, marking wires VVG-P 2x1.5 or VVG 2x2.5 are used. An outlet plug is installed on one end of the cable, and the other is stripped of the insulating layer to connect to the terminals of the power adapter.

The stripped wires are inserted into the sockets of the power supply, and then fixed with screws. The connection is made to the connectors marked L and N. A wire with a brown color is connected to the phase (connector L). The blue wire is connected to zero (connector N).

The main thing when connecting the LED strip is not to confuse the polarity, since these light sources operate on a constant current.

When connecting several LED strips to the power supply, certain rules must be followed.

Each tape should not be longer than 5 meters, it does not matter if it is solid or consists of several small sections.If the length is longer, the conductive tracks may burn out.

This arrangement assumes that all lighting strips are connected in parallel, not in series. It is also extremely important to observe correct polarity when connecting them.

Differences between the power supply and the driver

Power supplies are voltage sources that convert standard 220V to 12V or 24V. These devices are mainly used to power tapes on LEDs and those modules where a resistor acts as a limiter.

Drivers are current sources for LED devices. They are not labeled with the "output voltage" characteristic. Exclusively output current and maximum power. They are used for stand-alone LEDs and modules that do not have a current limiter.