LED bulbs are practical and popular because they are energy-efficient, long-lasting and low in heat generation. But to work properly, they need a different voltage than usually comes from the socket. That’s why people often talk about LED drivers, which are used for bridging. However, the term regularly causes confusion. This guide shows the differences between LED drivers as a constant current source and LED power supplies as a constant voltage source. It also explains what LED drivers can be used for.
Driver, transformer, power supply: is it all the same?
Basically, these three terms are often used as synonyms in connection with LEDs, but technically there are differences:
- An LED driver has the task of limiting the current that flows through an LED. LEDs themselves are not capable of doing this. An LED driver is a constant current source.
- The task of an LED power supply, on the other hand, is to convert the 230V alternating current that comes from sockets. This is because many LEDs need lower voltage on the one hand and direct current on the other for optimal operation. Consequently, an LED power supply is a constant voltage source.
- A transformer is similar to the LED power supply in the way it works. Unlike the power supply, a transformer does not output its power until a certain voltage is reached.
Constant current versus constant voltage
LEDs must be protected from both too high voltage and too high current. This is because of a despite good characteristic curve. LEDs generate heat due to their efficiency. The following applies: the warmer an LED gets, the higher the loss of efficiency. In the long term, this can lead to your LEDs burning out.
So for optimal operation, LEDs need either a constant voltage or a constant current source. Whether you need an LED driver or an LED power supply for your application depends on your LEDs. Follow this simple rule: In the product description of an LED you will find nominal ranges for voltage, current as well as power requirements. If your LEDs have a fixed value for voltage, you will need a power supply. If, on the other hand, you find a fixed value for the current, then you need a driver.
If you drive your LEDs with a driver, such as the SLF SLT3-350IS-1, they can no longer burn out due to the constant current flow. However, with a constant current source, you cannot easily change the number of LEDs connected to a driver. This could result in the driver no longer fitting. So constant voltage sources make LED systems more flexible, but there is a risk of overheating here. The problem can be prevented with the right LEDs with integrated current control circuits or series resistors.
New illuminant equals new dimming?
While other light sources can be dimmed in the blink of an eye by changing the voltage, the ratio of voltage to current is crucial for LEDs. For this reason, there are several ways to dim LEDs:
- With pulse duration modulation (PDM) or pulse width modulation (PWM), the period during which voltage is delivered is adjusted. The voltage itself, however, remains the same. In other words: With PWM, the LEDs are switched on and off again very quickly. The frequency for this is often over 100 Hz. Since the human eye can only identify flickering as such at 75 Hz at the earliest, the room appears darker to the human brain.
- Phase control and triac: Phase control dimmers or triacs are originally designed for 60W incandescent lamps, which shine dimly at a phase angle of 130°. However, LEDs are much more efficient and at the same time require less current to light up. As a result, LEDs are not very dim at a phase angle of 130°. Furthermore, at high dimming, the holding current may be too low to keep the triac in the conductive state. The result is flickering LEDs. However, some LED drivers are designed to bypass this problem internally.
- 1-10V: For this method, ballasts and control units are connected with a polarized two-wire control line. The control is done by DC voltage in 1-10V with increasing brightness depending on the voltage. In order to dim LED elements using the 1-10V method, they require their own power supplies. In addition, the control unit must be able to absorb the current supplied by the power supplies into the control line. Therefore, 1-10V dimming is more attractive in large lighting systems.
Wired or unwired – when do I choose what?
LED drivers are basically available both wired and unwired. Since the extra terminals that need to be installed are live – wired LED drivers should not be installed open. Unwired LED drivers, on the other hand, have their own connection terminals, where you only need to check the compatibility of the connection elements with the driver.
Smart Features: When even the lighting turns on a light
LEDs are not only more efficient than most light sources with them you can also implement smart features easier. Unlike conventional lights, they have an electronic ballast in the form of the LED driver. This is used to control individual light sources or entire groups separately. Most of the technologies for these features originate from building automation and are now used in large-scale lighting concepts. Since they are very scalable, they can also be transferred to small projects. Various solutions for controlling LED drivers for smart lighting are described below.
Digital Addressable Lighting Interface (DALI)
DALI is a standardized interface for controlling single or multiple luminaires. LED drivers with DALI interface, like the transformer MW LCM-40DA, can control several groups separately. Different groups and settings, such as dimming levels, can be assigned to each individual DALI string. Meanwhile, sensors and control panels can also be integrated in the more advanced DALI2 version.Casambi
Casambi, on the other hand, works completely wirelessly. Via BLE (Bluetooth Low Energy), all luminaires equipped with a Casambi module connect to each other and to the Casambi app. This allows, among other things, different light scenes, animations or dimming levels. Depending on the system, Casambi and DALI can be used together.
KNX
KNX is a bus system for building automation. With KNX, an actuator is installed between the luminaire and the mains voltage and connected to the KNX bus. In this way, it receives data for control, which comes from a computer or directly from a sensor. However, this means that two lines have to be laid: The supply line for the device and the bus line for the actuator. Unlike the other solutions, KNX can also control other systems, providing a professional solution for comprehensive building automation.
Print mounting and HighBay mounting
Depending on the requirements of the project, LEDs can be mounted in different ways: In smaller rooms, for example, you can use so-called SMD (surface mounted device) LEDs. These can be soldered onto printed circuit boards and thus do not require any cabling. However, make sure that all components are compatible with each other.The larger the room, the stronger the illumination must be. For this reason, high-power ceiling spotlights, so-called HighBay spotlights, are used especially in factory halls and department stores. These have to be wired individually, but are particularly durable. You can connect them to the usual 230V AC mains voltage. To prevent the LEDs from being overloaded, drivers such as the XBG-160-A are connected in front of them. These can actively limit the supplied current with an overload protection.
Conclusion
Similar to LEDs, LED drivers have various fields of application. With the wide product selection of drivers, power supplies and transformers, you too can illuminate your premises individually. Due to the high flexibility, you can not only dim your LED solution, you can also equip it with smart features in no time. In this sense, LED drivers are the keys to modern, efficient and cost-saving lighting.
Image: Adobe Stock
