What are the critical factors in selecting an LED driver?
The first issue is whether the application requires constant voltage or constant current. If the supply is to drive the LEDs directly it will typically require constant current. Next, the output voltage and/or current must be specified as well as the overall output power rating. Then the input voltage range must be determined. Many lighting applications require operation from 277 Vac and so Inventronics offers products with a 90-305 Vac operating range. Also important is the operating temperature range and the ingress protection (IP) rating. For outdoor lighting applications lightning protection is often a critical factor. Finally, compliance to efficiency, safety and electromagnetic compatibility standards should be evaluated.
How are waterproof levels specified for LED drivers ?
Ingress Protection (IP) ratings specify the environmental protection the enclosure provides. The IP rating normally has two numbers with the first specifying protection from solid objects or materials and the second specifying protection from liquids (water). The first number is specified from 0-6 with 6 implying complete protection from dust. The second is specified from 0-8 with the following implications:
0 No protection.
1 Protected against vertically falling drops of water e.g. condensation.
2 Protected against direct sprays of water up to 15° from the vertical.
3 Protected against direct sprays of water up to 60° from the vertical.
4 Protected against water sprayed from all directions.
5 Protected against low pressure jets of water from all directions
6 Protected against high pressure jets of water from all directions
7 Protected against the temporary immersion
8 Protected against prolonged immersion
Most Inventronics drivers are rated IP67 which implies that the products are completely protected from dust and protected against temporary immersion in water.
Why are LED drivers often potted? Is it necessary ?
The purpose of potting is twofold. First, it enhances the ingress protection (IP) rating of the unit by providing a waterproof barrier protecting the components from the intrusion of water under most circumstances. This is critical for outdoor applications such as streetlights.
Second, since the potting compound normally has much better thermal conductivity than the air, the potting is used to conduct heat generated by the key power components to the surface of the enclosure. This helps to greatly reduce the thermal stress on these components and thus increases the lifetime and reliability of the drivers substantially. It is estimated that the potting can typically reduce the operating temperatures of some of the key power devices by 20-40C.
Why is it important to use long-life LED drivers? How are they different ?
There are two primary factors in the justification of most solid state lighting systems. The first is energy savings. However, there are other alternative lighting technologies that offer high efficiency for lower initial costs. The second justification, lower maintenance costs, is therefore critical. LEDs have the advantage of much longer life than most other lighting technologies. Reduced replacement and/or maintenance costs can be a very significant factor. However, if the power electronics in the system does not match the life/reliability of the LEDs then the justification of the system is in jeopardy.
The life of an LED driver is mainly determined by the lifetime of the electrolytic capacitors employed. Therefore, to achieve long life of the LED drivers, it is critical to select long-life, quality electrolytic capacitors. Also, since the life of electrolytic capacitors drops by half for every 10C increase in operating temperature, thermal management of these components is important. Two key factors for reducing the temperature of the capacitors are high efficiency design (dissipating less heat in the driver) and thermal design (effective conduction and/or convection of the heat into the ambient surroundings).