LED Driver Selection Guide
Constant current vs voltage, efficiency and lifetime.
1. Why it matters
The driver is the component that most often decides whether an LED product lives or dies — most field failures are driver failures, not LED failures. Selecting it correctly means matching electrical output to the LED load, choosing constant-current or constant-voltage for the topology, and specifying the protection, efficiency and lifetime the application demands. A cheap driver behind an excellent LED is a false economy.
2. Constant current vs constant voltage
The first fork is topology. Constant-current (CC) drivers hold a fixed current (e.g. 700 mA) and vary voltage — used for most single fixtures and modules in series. Constant-voltage (CV) drivers hold a fixed voltage (12/24V) and are used for LED strip and modules with their own on-board current control in parallel. Using the wrong one destroys the load or leaves it dim.
| Type | Holds constant | Typical load |
|---|---|---|
| Constant current (CC) | Current (mA), voltage floats | Fixtures, series modules, high power |
| Constant voltage (CV) | Voltage (12/24V), current varies | LED strip, parallel modules |
3. Size and specify correctly
A driver run at 100% of its rating gets hot and dies early; one run too lightly wastes efficiency. Aim to load it at 50-80% of rated wattage, and confirm the LED forward-voltage range falls inside the driver's output-voltage window at the design current. Then specify the parameters that separate a reliable driver from a bargain one.
- Efficiency ≥ 85-90% at full load (lower efficiency = more heat, less lm/W).
- Power factor (PF) ≥ 0.9 for commercial; some grids mandate it.
- THD ≤ 20% (≤ 10% for utility rebates in some regions).
- Protection: over-voltage, over-current, short-circuit, over-temperature.
- Rated life at Tc (e.g. 50,000 h at 75°C case) — the weak link, so demand it.
4. Environment, surge and dimming fit
The driver must survive its environment and its grid. For outdoor and industrial use specify surge protection to at least 4 kV (10 kV for exposed street/area lighting), an operating-temperature range that covers the enclosure interior, and an IP rating if it sits outside the sealed housing. If the fixture dims, the driver — not just the fixture — must support the protocol and the tested minimum dim level, because dimming behaviour lives in the driver.
5. Checklist
- Pick CC or CV to match the LED load topology
- Load the driver at 50-80% of its rated output
- Confirm LED Vf range fits the driver output window
- Specify efficiency, PF ≥ 0.9, THD, and full protection set
- Match surge protection and dimming support to the application