Guide
This text is machine translated.
Light-emitting diodes (LEDs) are an energy-efficient and resource-saving alternative to other light sources. You need a voltage supply that is free of fluctuations, otherwise it will flicker, causing the light source to be perceived as unpleasant.
LEDs has become the shooting star of lighting technology in recent years. It is inexpensive to purchase and operate, lasts significantly longer than conventional light sources, generates virtually no heat, is small, light and mechanically quite insensitive. Their popularity is due to special, newly developed materials. These led to blue and finally to white lights. However, LEDs are quite idiosyncratic in terms of their energy supply. Here you can find out why so-called LED drivers are recommended for operation, how they work and what you should look out for when buying and connecting them.
Light-emitting diodes (LEDs) are an energy-efficient and resource-saving alternative to other light sources. You need a voltage supply that is free of fluctuations, otherwise it will flicker, causing the light source to be perceived as unpleasant.
The diode is heated by current flow and is thus more conductive. Since diodes cannot limit the current independantly, the increased conductivity would cause more current to flow and further heat the diode. To control this circuit, drivers are connected upstream that limit current flow or provide constant voltage.
Each LED module used for lighting therefore requires a circuit in the form of an electronic device that is connected upstream of this module. In the area of LED technology such a ballast is called a driver or power supply, whereby drivers provide for a constant current (CC), power supplies for a constant voltage (CV).
- Temperature behavior
in order to guarantee a uniform operation of the driver, the maximum temperature specifications of the manufacturers must be observed. Temperatures sometimes determine the lifetime of the LED drivers. Air circulation can positively influence the temperature behavior of a driver and thus increase the service life. - Withstand voltage and EMC
IEC 61547 specifies the requirements for light bulbs in residential, commercial and small businesses. The standard specifies which immunity requirements must be met. In addition, the test voltage of the drivers is specified.
EMC describes the electromagnetic compatibility for external interference signals and the immunity to line current and line voltage irregularities. The EN 55015 standard, which lists limit values and measuring methods, serves as the basis for compatibility between electronic devices. - The service life and failure rate
before a driver is installed must be clarified, which components are connected with each other and how high the voltages of the LED modules used are. In practice, the components are ideally matched to each other so that the system does not suffer any damage from inferior components. Depending on the quality of the drivers, an operating time of ≥ 50,000 hours can be guaranteed. On average, the failure rate for such a high-quality driver is about 0.2 percent per 1,000 hours. Lower-value drivers have an increased failure rate with a lower total runtime.
4. Protection classes and test marks
for LED drivers are subject to various standards. A distinction is made between safety tests (EN 61347), EMC tests (EN 50015, EN 61547, EN 61000-3-2), performance tests (ED 62384) and energy consumption tests (EN 62442-3). The IP numbers indicate the degree of protection of the driver. Drivers verified with IP20 are suitable for installation of standard interior lights. Devices with IP65 are mostly used for outdoor lighting.
5. Protection class I and II
for devices of protection class I, all electrically conductive parts of the housing must be connected to the protective conductor system.
Devices of protection class II have a reinforced or double insulation between the mains circuit and the metal housing. When using cables with a protective earth conductor, it must not be connected to the housing.
Installation of LED drivers
basically exists two types of mounting. On the one hand, there is a fixed mounting in the lights or in the housing of the light module, on the other hand, the drivers can be installed independantly in an intermediate ceiling. For independant electrical equipment, stricter EMC testing guidelines apply.
LED drivers are offered as a constant current source or as electronic transformers with a constant voltage. Drivers with constant voltage operation are, in fact, power supplies, since the mains voltage is first converted into the desired voltage.
If LED modules are to be operated on a constant current or voltage source, pay attention to the thermal load. Suitable LED drivers prevent excessive thermal load.
Dimmable drivers
A dimmable driver in combination with light control systems has several advantages:
- Dimming can save costs and energy due to the reduced energy output.
- Less CO2 load is produced.
- They can realize different bright light scenarios.
Dimmable drivers can be operated via different control units. Analogueue or digital control is possible, whereby the digital control has become more established on the market.
Conclusion
A number of factors must be considered in advance to select the appropriate LED driver. First and foremost, it is important to observe the required voltages and power ratings. The LED driver should never be selected too small. If different size units do not result in a consistent choice, choose a driver that has 1/3 more performance than is actually needed. Another decision criterion is the actual power consumption (in Ampère) of the LEDs. Also take into account the installation situation. If an LED driver is to be installed on a wooden element, a look at the thermal parameters and the manufacturer's guidelines and measured values is required. Typically, LED drivers are connected in series and are a constant power source. In the manufacturer's specifications, distinguish between decreasing and decreasing performance.
Are there also drivers or transformers that can be used to dim LED modules?
In contrast to conventional incandescent or halogen lamps, the brightness of an LED lamp cannot be reduced so easily. For conventional light sources, a lower voltage is simply sufficient. LEDs, on the other hand, flicker or switch off completely when the voltage falls below a certain level.
Today, pulse width modulation (PWM) is usually used to dim LEDs. Corresponding electronic modules switch the supply voltage on and off at a high frequency that is imperceptible to the eye - depending on the desired brightness. The circuits can be found both within dimmable LED lamps or integrated into dimmable LED drivers. In the latter case, attention must be paid to the designation "dimmable".
