How can LEDs be protected against overvoltage?

Sometimes lightning strikes or other phenomena can cause overvoltage in your LED lighting. LEDs can be protected against overvoltage by various measures. In this blog article, our lighting experts will introduce you to the possible options, explain what overvoltage is all about and give you helpful tips on how to avoid it.

The main advantages of LEDs are their energy efficiency and long service life. One disadvantage, however, is that the electronic components used are more sensitive to overvoltages than conventional light sources - outdoor LED lights in particular are often affected. An effective protection concept is crucial in order to guarantee the function of the lighting and prevent premature failures. Compact and time-saving connection technology also contributes to cost-effective installation.

LED lighting solutions are always optimized for energy efficiency. This is why electronic components are used that convert electrical energy into light with minimal losses. Due to their low immunity to interference, these components are particularly susceptible to interference pulses. As such unexpected interference often goes well beyond the tolerance limits of the components, they can be damaged or even destroyed under load.

The cause of interference pulses are the surge currents and overvoltages that occur in the power grid, which are caused by direct and indirect lightning strikes. Transient overvoltages (more on this in a moment) caused by switching operations in the supply network also contribute to this. Although lightning strikes are rare in some regions, they can cause considerable damage to LEDs due to their high energy content. Overvoltages are caused by direct lightning strikes to the luminaire or overhead line, or alternatively by indirect lightning effects, such as earth feedback or inductive coupling into the lighting system.

In the worst case scenario, a direct lightning strike, for example in an LED street light or in a building, can cause the entire LED lighting system to fail, as the luminaires are connected to each other via the power grid. Without suitable protective devices, the lightning current can quickly spread across the entire installation and cause major damage. Lightning strikes also generate voltage peaks of several thousand volts at the point of strike. If lightning strikes a building with external lightning protection or a nearby tree, for example, the earth potential is increased. This results in a considerable potential difference to the earthed parts, which can amount to several thousand volts. This exceeds the dielectric strength of the LED components and leads to insulation flashovers in the installation or in the built-in electronic components.

These six options are available to you to protect your LEDs from overvoltage and increase their service life:

Series resistor: A resistor in series with the LED lighting can help to limit the current flow and thus protect the LEDs from damage caused by overvoltage. The resistor is dimensioned so that the current through the LED lights remains within the safe range at the maximum expected voltage.

Zener diode: A Zener diode is connected in parallel with the LEDs. If a certain voltage (Zener voltage) is exceeded, it conducts the current around the LEDs, protecting them from overvoltage.

Transient voltage suppression (TVS diode): TVS diodes are specially designed to protect against transient overvoltages (voltage spikes). They are connected in parallel with the LED lighting and absorb the energy of voltage peaks.

Varistor (VDR - Voltage Dependent Resistor): A varistor has a non-linear resistance that decreases sharply as the voltage increases. This allows the varistor to dissipate current in the event of overvoltage and thus protect the LED lighting.

Protective circuit with MOSFET: A protective circuit with a MOSFET can be applied so that the LEDs are switched off if a certain voltage is exceeded. This type of protection is very effective, but also more complex to implement.

Voltage regulator: A voltage regulator is used to ensure that the voltage reaching the LEDs is always within the safe range, regardless of fluctuations in the input voltage.

There are many manufacturers of surge protection on the market. When selecting suitable products, you should bear the following points in mind:

• A high-quality surge protector should be tested in accordance with the IEC 61643-11 standard and meet the requirements of VDE 0100-534. This includes the integration of status indicators and disconnecting devices.
• As surge protective devices are often installed in places that are difficult to access, such as inside luminaires, visual signaling is not sufficient. A surge protection device that also disconnects the luminaire from the circuit in the event of a fault offers a simple means of indirect signaling.
• The size and installation method of the surge protection device must meet the requirements of the installation location.
• In application areas with high humidity or dust exposure, you should select a surge protective device with a higher protection rating (IP class).
• Surge protection devices must take into account the protection class (SK I or SK II) of the luminaires.
• In addition to protecting the 230 V supply, the protection of the control components, such as DALI, second control phase, 1-10 V or DMX, should also be considered. Surge protection devices that combine both AC and control protection are ideal for these luminaires and generally offer better coordinated protection than two separate devices.

There are various ways in which you can protect your LEDs against overvoltage. By combining several of these measures, an even higher level of protection can be achieved, especially in areas of application where frequent or high overvoltages are to be expected.

Sarah - last updated August 2024