LED drivers are returned because the current, the voltage window, or the dimming input was guessed from the wattage. Write the LED load the way the LED datasheet writes it, then the environment the driver sits in.
Match the driver to the string
A constant-current driver has an output current and a voltage window. Your series string must sit inside that window at the currents you will use, including cold and hot forward voltage. A constant-voltage driver has a fixed output, often 12 or 24 V, and the LED board must include its own current limit. Say which of the two you need. Do not write LED driver, 50 W and stop.
Input voltage is a range. A 220-240 V driver is the wrong part for a 120 V site. Power factor and inrush matter when many drivers share a breaker. Dimming, if you need it, is a control wire and a protocol, and it has a minimum dim level. Flicker requirements belong on the RFQ if a buyer specification cites them. Ask the maker for the measurement condition rather than inventing a percent.
- Constant current or constant voltage, with the number and the window.
- Input voltage range and whether it is phase to neutral or a low-voltage bus.
- Dimming method, or a clear statement that the fitting is non-dimming.
- Case temperature and IP rating of the driver, separate from the fitting.
- Inrush, if many units sit on one breaker.
| Load | Driver line | Mismatch |
|---|---|---|
| Series LEDs | mA and Vmin to Vmax | A 24 V constant-voltage part |
| 12/24 V strip | Constant voltage and watts | A current driver with no window match |
| Dimmed fitting | The protocol and the lowest level | A non-dim driver behind a dimmer |
Sample check
Read input and output markings before you power it. Confirm the output current or voltage on a meter with the real LED load or a load the maker accepts. Check the case temperature rise in a mock-up of the canopy if the fitting is sealed. Confirm dimming with the controller you will ship, not with a lab supply on the output. File the wiring diagram that shows polarity. Reverse polarity is a common field failure and a clear drawing prevents it.
What to lock on the order
Write the LED part number’s forward-voltage range next to the driver window so the match is visible on one page. Include the highest and lowest ambient the fitting will see, because both the LED voltage and the driver rating move with temperature. If the fitting is dimmed, name the controller you will actually connect and ask for a wiring diagram of that pair. State the inrush if you know how many drivers share a breaker, or ask the driver maker for the peak and the duration. On the order, separate the driver from the LED board so a substitution of one does not silently change the other. At incoming inspection, power one driver into the correct load and record output current or voltage. Then connect the dimmer if there is one. A driver that is electrically right and wired to the wrong control pair will be blamed on the LEDs later.
Questions buyers actually ask
Is the wattage the specification?
Wattage is the ceiling. The LED wants a current or a voltage. A 50 W driver that cannot reach your string voltage will not light the board.
Do I need dimming?
Only if you name the method: 0-10 V, DALI, PWM, or trailing edge. A driver without that input will ignore the dimmer you already bought.
Where does the heat go?
The driver case temperature is in the datasheet. A sealed canopy is not the 25 C on the first page.