What Is an LED Driver?
An LED driver is a special power circuit that feeds an LED or LED array with constant current to provide stable brightness and long life.
Why Constant Current?
An LED's brightness is proportional to the current through it, and an LED is very sensitive to small voltage changes. If fed with constant voltage, current can run away with temperature and the LED can burn out; so the current is controlled.
Why a Driver Instead of a Resistor?
In simple projects a series resistor is enough, but it turns the excess energy into heat and the brightness wanders as the voltage changes. An LED driver, by contrast, holds the current constant with high efficiency.
| Method | Efficiency | Brightness stability |
|---|---|---|
| Series resistor | Low | Poor |
| LED driver | High | Good |
Dimming
Most drivers support PWM or analog dimming; brightness is adjusted by changing the current or the on-time.
Where Is It Used?
In LED bulbs, panel/strip lighting, display backlighting, automotive headlights and power-LED applications.
Series and Parallel LED Connection
Series-connected LEDs pass the same current, so their brightness is equal; the driver feeds this chain with a single current. Parallel branches may not share the current equally; so most power applications string the LEDs in series and, when needed, use multiple constant-current channels.
Common Mistakes
- Feeding with a voltage source: driving a power LED with constant voltage leads to thermal runaway.
- Wrong current: if the LED's rated current is exceeded, its life shortens.
- Dimming compatibility: not every driver is compatible with every dimmer.
Frequently Asked Questions
Is a buck/boost the same as an LED driver?+
Is a driver a must for a low-power LED?+
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