The best LED drivers and applications
The driver or transformer for LED lighting can vary in quality. There are still many questionable drivers on the market, resulting in a poor experience of the room or, in the worst case scenario, the LED light sources do not light up.
Since LED technology was created back in the mid-1900s, it has been low-voltage DC components. It is within the last 10 years that LEDs have been available that can be supplied directly with AC voltage, e.g. 230VAC, but the majority of LEDs are still powered by DC voltage. Installation can be done in series or parallel. The choice depends more on the requirements for the installation.
In this blog post, we'll take a closer look at what types there are and how the best drivers can be implemented in projects.
What types of drivers are used?
Most LEDs need to be supplied with a given voltage and fixed current. The higher the current, the more light is generated in the semiconductor, but too high a current also means lower energy efficiency and a shorter lifespan. It must therefore balance between the thermal properties of the heat sink, the LED and of course the expected ambient temperature. The first thing to consider is always whether it is a constant current driver or a constant voltage driver.
By far the most commonly used driver is the constant current driver. These drivers can supply the LEDs with typically 150mA - 1500mA and a varying voltage. Downlights, line luminaires, 60×60 panels are in most cases supplied from such a driver. The second type holds a constant voltage e.g. 12V or 24VDC, which can power LED strips or other lighting products. These types of lighting products are equipped with a resistor, without which the LEDs would burn out.
In the latter, the current varies depending on the load in the circuit being connected. It is always possible to tell the difference between the two types. The constant current driver has on the rating plate e.g. 5-36VDC - where the other type has a constant voltage e.g. 12V or 24VDC.
Select the best driver for the solution
With the supplied current, the voltage can vary across an LED. The voltage is approximately 2.6V - 3.2V. It can be seen on a constant current driver that the voltage range, as mentioned earlier, could be 5-36VDC. If there are 10 small buried spots in a driveway, the voltage could be 28V, so the 5-36VDC example would work if the current matches the LEDs, which could be 350mA. Other considerations are the physical size of the driver. There are waterproof drivers and drivers that should only be used for single LEDs. At the same time, there are drivers for e.g. street lighting that send out a high current, e.g. 1500mA. With a high current that is not dedicated to the LED, the LED will overheat. For the same reason, you should always consider what current the LEDs should be supplied with and the voltage should also match.
Dimming with drivers
In addition to the driver that matches the given type and quantity of LEDs, you need to look at dimming options. Leading edge and trailing edge are the two types that dim on the high-voltage side (230V). With these drivers, some challenges can arise if the dimmer has not been tested with the given driver.
With thousands of dimmers and drivers, you need to test before installation or get a test report from the driver manufacturer on which dimmers the driver is compatible with. However, DALI or 0-10V are some of the most stable dimming options for LED lighting. If the lamps are to be controlled individually and more complicated, DALI will be the preferred choice. Analog dimming is a control voltage between 0-10V. Here, all lights are controlled at once and can only be divided into zones if the installation is divided. To return to DALI, there are several versions available today. DALI version 8 is tied to multiple addresses. Multiple addresses that allow for variation of color temperature, light intensity and possibly multiple colors such as red, green and blue.
Strobe effect or flicker?
Before touching on this topic, it is important to look at how efficient a driver is. Power Factor (PF) is expressed as a percentage and gives an excellent indication of how efficient the driver is. For example, if it is 90%, it is a good driver and if it is below 80%, it may in some cases be a less good driver. Other parameters such as harmonic currents (THD) generated by a given number of LED drivers are a topic in themselves, but don't forget that this value should always be below THD 20%.
Når emnet er drivere, vil flimmer være en synd ikke at omtale. Det er formentlig den største udfordring LED markedet oplever i dag. For selvom det menneskelige øje måske ikke kan registrere den hurtige flimmer, så findes den stadig i mange flere lamper end, vi regner med. Der findes ældre standarder inden for den maksimale tilladte flimmer-værdi (Flicker <20 %). Fordi LED teknologien oplever store udfordringer, kommer der i 2019 nye standarder, som skal sikrer, at de helt dårlige drivere med høj flimmer-værdi ikke kommer ind på det Europæiske marked.
We're still waiting for the standards to be published, but until they are, we should all be wary of drivers with a high flicker value. The reason is simply a poor working environment, which can lead to headaches, neck pain and other tensions in the body. The flicker value can be measured today, and if the value is high, it will be clearly visible if a camera is held up to the light. There are drivers that are close to 0%.