Flood light factory|How to match the driver/power supply for the LED strip?|Sunshinelux

July 13, 2022

Constant voltage light strips

What is an LED driver/power supply

The LED driver is used to convert the city power supply (taking the mainland of China as an example, it is AC power with a power frequency of 50 Hz and a voltage of 220 V) into the voltage and current range required for the stable operation of the LED light source (usually DC voltage, current preferably constant).


So, how to choose the driver, the key lies in what your LED light source is.


When the LED is working, the current needs to be stable. Because according to the diode volt-ampere characteristics of the LED, you will find:


When the forward voltage is added above the dead-band voltage, slight voltage fluctuations will cause exponential fluctuations in the current flow through the light-emitting diode (LED). Therefore, it is necessary to pay attention to the fluctuation of the voltage and current of the LED during normal operation.


LED lamp bead volt-ampere characteristic diagram


Drive/Power Category

This is related to the classification of off-the-shelf drives, which are:


Constant voltage driver

Constant current driver

Constant current and constant voltage driver

We will not discuss the RC buck solution with poor quality and stability here.


Regarding the driver, there are many technical parameters, such as: input voltage, input current, output voltage, output current, power factor, conversion efficiency, harmonics, ripple, stroboscopic, ambient temperature, protection level, and so on. Faced with these professional terms, we don't need to panic. Generally, we only need to pay attention to: input voltage, input current, output voltage, and output current, and then we can match the driver and light source.


In terms of input, we only need to look at the input voltage. Our mainland China is the AC 220V input. If it is a foreign partner, it may be AC110V from Japan, the United States, or AC277V from the United States. Some countries, such as Malaysia, will be AC240V. Most countries in Europe, that is, AC220V voltage.


Regarding the output, it is necessary to clarify the output voltage and the output circuit before they can be properly matched.


Constant voltage driver

As the name implies, it is a driver whose output is a constant voltage, and it is common to output 5V, 12V, 24V, 48V, etc. Generally, it is DC direct current; suitable LED light sources are generally low-voltage light strips. There are also some light sources, such as outdoor pool lights, etc., which also require low-voltage 12V input. Mainly to avoid electric leakage to hurt people.


If you ask: if the voltage is constant, how is the current determined?


The current is determined by how long the light strips are. Almost all light strips have chip resistors on them. The function of the resistor is to limit the current to ensure that the current flowing through each lamp bead is relatively stable.


Because the principle of the light strip is that 3 or 6 lamp beads are connected in series first, and then in parallel. Therefore, the current will be the sum of the currents of all strings. The output current of the drive will be adaptively adjusted according to the length of the light strip.


Steps to match LED strips

Determine the voltage of the low-voltage lamp strip

Low-voltage light strips are very easy to judge, generally on the flexible version of the light strip, with a clear indication of DC12V or DC24V. As shown below:


12V LED Strip


24V LED strip


Therefore, you just need to find the right output voltage, and you are sure to be right, but it is only the first step. The second step will be to choose how much power is appropriate.


Choice of power.

It mainly depends on your light source load.


For example: your light strip is 12VDC, one meter is 12 watts, there are 4 meters of light strips in total, then the total wattage of the light strip is 12x4=48W. Then you need to choose a constant voltage driver above 48W. There are conventional wattages on the market, such as: 35W, 50W, 60W, 75W, 100W, 150W, 200W, 350W and so on. Then, there is no problem in choosing one larger than 60W.


Why can't I choose 50W?


Mainly because we need some margin for the constant voltage driver. Although the constant voltage driver of the big brand can output at full load, it is better to leave some margin than nothing. Not to mention those who falsely mark the maximum power. How much is generally reserved? The industry generally believes that about 20% is sufficient. Therefore, 20% more than 48W is about 58W, and there is no problem in choosing 60W.


So, can I choose a bigger one?


For example, there is a 150W 12VDC output constant voltage driver on hand, can it be used? Of course no problem. A car can carry 5 people, and now it only takes two people, it is the same reason. If it is a new purchase, then it is enough, and you don't need to spend unnecessary money.



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