LED lighting requires a flow of consistent and constant electrical current at all times, at an exact voltage. Doing this also allows the LEDs to stay a consistent temperature; if an LED runs too hot, it may begin to malfunction and experience poor performance. LED drivers help LEDs achieve optimal conditions.
We spoke with Thomas Kent, manager of reliability at Eaton, about how LED drivers work.
TK: LED drivers are similar to ballasts for fluorescent lamps or transformers for low-voltage bulbs: they provide LEDs with the electricity they need to function and perform at their best.
LEDs require drivers for two purposes:
LED light output is proportional to its current supply, and LEDs are rated to operate within a certain current range. Therefore, too much or too little current can cause light output to vary or degrade more quickly due to higher temperatures within the LED, or thermal runaway.
In what applications are LED drivers used?
TK: LEDs that typically require an external driver include cove lights, downlights and tape lights, as well as certain fixtures, panels and outdoor-rated lights. These bulbs are often used for commercial, outdoor or roadway lighting purposes.
LEDs designed for household use contain internal drivers rather than separate, external drivers. Household bulbs usually include an internal driver, because this makes replacing old incandescent or CFL bulbs easier.
What are the types of LED drivers?
TK: There are two main types of external LED drivers: constant-current and constant-voltage. Each type of driver is designed to operate LEDs with a different set of electrical requirements:
What are things to consider when selecting an LED driver?
TK: Once you’ve determined whether you need a constant-current or constant-voltage driver, there are a number of other factors to consider:
How does dimming play a role?
TK: Depending on their specifications, some LED drivers can also facilitate dimming and/or color sequencing for the LEDs they are connected to. Both constant-current and constant-voltage LEDs and drivers can be made with a dimming capability. Dimmable external drivers often require an external dimmer, or other dimming control devices specified on the product data sheet (namely TRIAC, Trailing Edge, or 1-10V dimmers) to function properly. Dimming works with building controls and occupancy sensors to create a more efficient and effective environment.
Evaluating and selecting an LED driver can be simple with the right know-how. An understanding of current vs. voltage and dimming considerations can help identify the important features essential to optimizing any lighting system performance.