Calculation of power supply power for LED strip 12V
LED lighting equipment consumes much less power than traditional incandescent or halogen lamps. But many LED devices, including strips, are powered by 12..36 volts. At reduced voltage, even moderate power causes the flow of sufficiently large currents. Therefore, the choice of power source for the LED canvas must be approached consciously.
Pulse or transformer
For many decades, network power supplies were built according to the scheme: step-down transformer - rectifier - filter. This principle has not become obsolete even now, in many cases this is the best option.. But with the development of electronics, switching power supplies began to be used more and more often. Despite the complexity of circuitry, they have undeniable advantages:
- ease;
- small dimensions;
- high efficiency, which in theory can be equal to 100%.
The disadvantages include the generation of high-frequency interference into the network (which can lead to malfunctions of sensitive devices powered by the same network) and into the load. To combat the first problem, PSUs are equipped with input filters (for inexpensive sources, they are performed according to a simple scheme or absent). The second problem for LEDs is not important. Therefore, the choice has been made - light and powerful switching power supplies are used to power LED devices.
Choosing a power supply for electrical characteristics
The calculation of the power supply for any LED strip must begin with voltage. It must correspond to the supply voltage of the tape. If the source voltage is higher, the lamp will quickly fail. If lower, it will glow in full.
The second important parameter is the maximum power. It is calculated using the following formula:
Pist \u003d Ore * L tapes * Kzap, where:
- Rist - the minimum power of the power supply;
- Rud - specific power consumption (power consumed by 1 meter of canvas);
- L tapes - the total length of the segments of the canvas;
- Kzap - safety factor, can be equal to from 1.2 to 1.4.
Some quantities need to be considered in more detail.
How to determine the power consumption of one meter of tape
The easiest way is to determine the power consumption of a web meter according to the technical specification. There this parameter is specified explicitly. If it is not there, but the type of tape is known, this characteristic can be found in various sources.
If this is not possible, then in many cases the specific consumption can be determined using a ruler. To do this, you need to measure LED dimensions and determine its form factor.According to this characteristic, you can find the power consumption of one LED, count their number per meter and multiply.
| Light-emitting diode | 3528 | 5050 | 5630 | 5730-1 | 5730-2 |
| Dimensions, mm | 3.5x2.8 | 5x5 | 5.6x3 | 4.8x3 | 4.8x3 |
| Power consumption, W | 0,06 | 0,2 | 0,5 | 0,5 | 1 |
| Consumed current, A | 0,02 | 0,06 | 0,15 | 0,15 | 0,3 |
The only problem is that some LEDs are available in different versions - with one crystal or with 2-3. In this case, the power will differ by 2-3 times. And the only way to find the desired parameter is to take the smallest piece of tape and power it from a source of obviously higher power. By measuring the current in amperes and multiplying it by the supply voltage (12 V or another), you can get the specific power of the segment (W). By counting the number of segments in a meter, you can reach the desired value.
If there is no ammeter, you can measure the resistance of the resistor installed on the segment before connecting to the power source (or count if the marking is available). After applying power, measure the voltage on it and find the current according to the known ratio: I=U/R, where I - the desired current in amperes, U - supply voltage in volts, R is the resistance of the resistor.
Why is the safety factor needed and what does it take into account
When choosing a PSU power without a safety factor, it will work at the limit of its capabilities. This mode has its drawbacks:
- "Chinese watt" may be less than a regular watt. Seriously, this means that the actual highest power of low-cost power supplies from Southeast Asia is often less than declared.
- Part of the electronic components at maximum current (and maximum heating) has a reduced service life.This is especially true for winding parts (transformers, chokes), which in inexpensive power supplies are made by hand in a handicraft way from thin wire with poor-quality insulation.
- If the power supply has poor-quality soldered contacts (this is quite a common case), then at maximum current they will heat up and the quality of the connection will deteriorate. This will cause even more heating, and so on in a circle until failure.
- With a slight increase in temperature in the room, the electronic unit goes to the limit mode and its service life is unpredictably reduced.
- The power consumed by the lighting system depends on the scheme (though not critically). The illuminator configuration may contain: dimmer(s), RGB controller, driver (or several), amplifier (maybe more than one), other devices.
All these devices consume currents for idling and for their own needs (power supply for the internal circuit, etc.), their efficiency is not equal to 100%. Compared to the currents consumed by LED lamps, they are small. But if the PSU is operating on the edge, this small addition can become critical.
Based on these considerations, according to the real situation, when 20, and when 40 percent should be added to the calculated power.
Other properties of the power supply
After calculating the electrical characteristics of the power supply for LED strips, you need to pay attention to other parameters.
Execution (degree of protection)
Power supplies are available in the following versions:
- sealed - it is recommended to install outdoors, as they are protected from precipitation;
- leaky - it is better to mount indoors, because they are cheaper.
In addition, hermetically sealed PSUs are less cooled, which means that they will be prone to overheating indoors.
Cooling type
In this category, voltage sources are divided into devices:
- with natural cooling;
- with forced cooling.
Forced ventilation of the internal space of the unit is carried out by installing a fan, which is switched on and off from the built-in temperature sensor. Such a construct has sufficiently powerful sources, and relatively low-current ones are performed without fans.
The use of a hood reduces the dimensions of the device by reducing the size of the radiators, but the fan is noisy. The closer to the end of life, the louder the noise. Therefore, such sources should not be installed in living rooms, as well as in rooms where people stay (office, etc.)
An example of calculating the power of a switching power supply
As an example, how to choose a suitable power supply for an LED strip, you can set the conditions:
- Apeyron 00-12 outdoor RGB tape acts as a lighting device;
- supply voltage - 12 V;
- power consumption - 14.4 W / m;
- the required length of the segments is 12 m.
You will also need an RGB controller, and to it (with such a length of the canvas), also an amplifier.
We calculate the required power using the above formula:
- L tapes=12 m;
- Rud=14.4 W/m.
The installation is outdoor, which means that the cooling will be good, but there are two additional consumers in the circuit. You can take the safety factor equal to 30% or 1.3.
Pist \u003d Ore * L tapes * Kzap \u003d 14.4 * 12 * 1.3 \u003d 224.64 W.
You only need to round up. 250 W sources are widely available.It is necessary to select such a device with IP68 in order to install it on the street.
Another variant. It is necessary to power the Apeyron SMD2835-60LED monochrome tape, rated for 12 volts. In total, 1.5 meters of tape are needed with an energy consumption of 9.6 W / m. Dimmer is not needed, other additional devices are not needed. The power supply can be installed to provide good airflow. Nearby other sources of elevated temperature should not be. The safety factor can be taken at the lower level, equal to 1.2. Power is calculated:
Pist \u003d Ore * L tapes * Kzap \u003d 9.6 * 1.5 * 1.2 \u003d 17.28.
A 12V 25W power supply will do. Devices with natural cooling are made for such power, hermetic design is not necessary.
Important! Sometimes PSU manufacturers indicate the highest operating current instead of power. It must be converted into power according to the formula Rist=Uwork*Imax, where Uwork is the power supply voltage, and Imax - the highest operating current.
At the end of the video is an example.
The issue of calculating the load capacity of the LED strip power supply must be approached responsibly. A mistake to the smaller side can cost the loss of an expensive node, and to a larger one - to unjustified financial costs.