LED Power supply

Why LEDs not work?

With the old bulbs, the respect of polarity was unnecessary. Because, as resistors, they work even if phase and neutral are reversed. All E27 and E14 lamp holders connect to the rear central contact and neutral on the threaded part at the international normative level. LEDs connected with the polarity reversed may work at first, but over time will be damaged.

Although they produce little heat compared to old lamps, they have tighter thermal limits and the need to dissipate heat. Therefore, they can poorly withstand environments without adequate ventilation. The evaluation of the installation environment must be done with awareness.

High-power LED lamps need an adequate heat sink. 

These poorly withstand vibrations should not be mounted on doors or gates that produce constant vibrations or other vibrating support.

As their electronic nature, minor problems may arise from electrical installations, often ancient. These can, however, be solved without too much difficulty. For example, the first time it is turned on, the LEDs may flash. Or a steady light after switching off. As you know, a lamp can’t turn on without electricity, so we should try to understand where there is the current passage.

Some checks to be made

Check that in the switch. The current circuit is broken on the phase. Reverse polarity (neutral instead of phase) is the most common error. Sometimes you have pairs of diverters (switches) to make the double ignition. In some cases, there may be supply anomalies of the LED lamp for polarity inversions.

Check that the switch or the diverter that manages the phase does not have a pilot lamp. It could lead to a minimum passage of energy.

Check that there are no transformers or ballasts because they will flash and damage the LED bulbs.

Check that the lamp holders are in good condition. 

Respect the polarization when required by the manufacturer.

Equip your electrical system with a high-sensitivity residual current device if you don’t have one. If your system is affected by overvoltages, protect it with a surge protector (SPD).

Conducted or induced electromagnetic interference can be transmitted to power lines and damage the LED (e.g., lightning).

The points listed above concern electrical disturbances, but there is also a chemical-physical one. LED lamps are treated with phosphor. It may happen that a light has been given an extra amount of phosphor so that it maintains a specific electrical charge after being turned off and produces a slight luminescence. However, this phenomenon disappears within a short time, and it would be a continuous light, not an intermittent one.

Things to avoid

Always avoid connecting electrical cords with only electrical tape because they don’t hold the wires together well, and weather and time can loosen the wires and short out the LED lamps. Use caps, mammoths, tin soldering where possible, or other connectors that hold the cables firmly and well in contact in special boxes with an appropriate degree of protection for the type of environment. Take care that no copper filaments are coming into contact with other cables.

Inserting LEDs in sealed ceiling lights that do not allow or limit heat dissipation will cause the LEDs to overheat. Remember that an optimal working temperature guarantees the life of the LEDs. The LEDs have a long life with an ambient temperature of 25 °C and an operating temperature of 45 °C. The LEDs have a long life. Still, the lack of air circulation can make the temperature of the chip rise to dangerous values (over 85 °C) and damage it irreversibly. So avoid using lamps with high protection degrees like IP65 in environments already protected. An IP20 dissipates much better.

Some people have custom-made mains connections made, with plugs to be inserted into the socket when needed. Should avoid this entirely because it quickly reverses polarities and ruins the luminaries, respecting polarization. Always use a fixed switch if it is not factory set to work with the plug!

Would you please avoid using current generators because they produce too strong surges and under voltages that burn out the LED chips? If you need to light when the power goes out or don’t have it available, use a battery and inverter power supply.

More complex situations

Lamp holders with transformers and ballasts make the LEDs flash quickly and shorten their life span. LEDs should use with LED drivers. In case of replacement with LED lamps, for these changes, always use specialized technicians.

On the market, there are two categories of LEDs: on/off and dimmable. The latter need specific dimmers with phase-cut designed for the type of LED bulb. There are hundreds of different dimmers on the market, tested and approved for each LED bulb. Each LED manufacturer provides a list of dimmers tested and approved for their products. Always use specialized technicians.

Dimmers in home automation networks. Such as my home, KNX, Dali, casaba, blue tooth, and ZigBee.Use only electronic specialists in home automation networks.

For LED strips, specific electronics, lighting technology, and mechanics skills are required to build the strip system and inst.

Final considerations

As we have seen, both in case of dim light and flashing may not be necessary to replace the LED bulb.

To contact experienced and qualified personnel who can provide technical assistance.

Wherever possible (e.g., new construction), dedicated to the LED lighting a line all its own since the electrical panel (separate from the rest of the system). Avoid connecting any equipment that at the start causes substantial input and related current distortions. Protect it with a differential magneto-thermal switch with very high sensitivity, calibrated on the absorption capacity of the lighting system.

Some problems examined are within reach of those with a minimum of technical knowledge and will be pretty easy to solve. For others who do not have such knowledge should always turn to a technician with the appropriate skills.

Some FAQ

Hi guys, I have a LED strip RGB. Suddenly, the white and blue lights do not work anymore. Only the first four lights come on, while the red and green work perfectly. Is there any way to solve this problem?

Do you mean that only 4 LEDs work for you and the others stay off? And that of those 4, only the red and green colors work? You must have skipped the blue line, and consequently, the white doesn’t work (since it needs all three colors). Maybe this problem has interrupted the rest of the strip.

I think the only thing to do is to replace the strip. Because if it’s not the transformer that’s not giving it enough current to run the whole strip (which I doubt because even if it gave a slight current, you’d have all the LEDs lit dimly or entirely off), the only problem is that the wiring inside the strip is torn and needs to replace.

The RGB chips are not repairable for one reason only … their conformation at the circuit level does not allow intervention on them. It is not physically possible for the size of the chips of the LED inside the LED itself.

In the image, I have highlighted the chip’s led’s morphology, the red, green, and blue, from which derives the nomenclature RGB is the three colors in English, which together form all other shades of color.




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5V power supply is widely used in LED display and some other conditions.

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