LEDs are low-voltage lamps, requiring a constant DC voltage or current to operate optimally. (Operating on low-voltage DC power enables LEDs to be easily adapted to different power supplies, permits longer standby power and increases safety.) An individual LED needs 2-4V of DC power and several hundred mA of current. When LEDs are connected in series in an array, higher voltage is required. The LED driver acts as this power supply. It converts incoming 120V (or other voltage) 60Hz AC power to the proper low-voltage DC power required by the LEDs.

During operation, the LEDs must be protected from line-voltage fluctuations because changes in voltage can produce a disproportional change in current, which in turn changes light output. (LED light output is proportional to current and is rated for a current range. If current exceeds the manufacturer recommendations, the LEDs can become brighter but their light output can degrade at a faster rate due to heat, shortening useful life. Useful life may be defined as the point where light output declines by 30 percent.) The LED driver regulates the current flowing through the LED during operation and protects it from voltage fluctuations.

Dimming does not result in a loss of efficiency. During dimming, the LEDs are still operated at the same voltage and current as during full light output. In addition, lamp life is not affected by dimming, as is sometimes the case with frequently dimmed fluorescent lighting. Rather, dimming LEDs may lengthen the useful life of LEDs, because dimming can reduce operating temperatures inside the light source.

Interoperability with other control devices. Most LED drivers are compatible with commercially available 0-10V control devices and systems such as occupancy sensors, photocells, wallbox dimmers, remote controls, architectural and theatrical controls, and building and lighting automation systems. LEDs can also work with devices governed by the DMX and digital addressable lighting interface (DALI) protocols and, in the future, may include wireless (RF) as a control option.