A Driver Has to Match the Load in Three Ways
Choosing a driver is a matching exercise, not a shopping one. It has to match the load's output type, its total wattage with room to spare, and the dimming method the control system uses. Miss any one of the three and the result is a fixture that flickers, runs hot, or does not light at all.
Constant Current or Constant Voltage
This is the first and most consequential distinction, and the fixture's spec sheet states which it requires.
A constant-current driver holds a fixed current, expressed in milliamps, and lets the voltage float to whatever the LED array needs. That is what LED modules, engines, and most integrated fixtures are built around, because the light output of an LED tracks current rather than voltage. A constant-voltage driver does the opposite, holding a steady 12V or 24V while the current varies with how much load is connected. That suits LED tape, strip, and any application where sections are added and removed or wired in parallel.
The two are not interchangeable in either direction. Putting a constant-voltage supply on a fixture expecting constant current, or the reverse, damages the load. Read the fixture label before ordering the driver.
Sizing by Wattage, With Headroom
Total the wattage of everything the driver will power, then choose a driver rated comfortably above that figure rather than exactly at it. Running a driver at its absolute ceiling shortens its life through heat, and it leaves no room for a section added later. Roughly twenty percent of spare capacity is a sensible working target.
For tape and strip specifically, the calculation is watts per foot multiplied by the run length, and it is worth doing carefully because the per-foot figure varies widely between products. A high-output tape can draw several times what a basic one does over the same distance. Where a run is long enough that one driver cannot carry it, splitting it across two drivers fed from a common circuit is usually better practice than pushing one to its limit.
Dimming: Match the Driver to the Control That Is Being Installed
A driver only dims by the method it was built for, and this is where most field problems start. Drivers in this collection carry several different inputs. Some accept forward-phase or reverse-phase signals from a wall dimmer, which is the residential arrangement. Some accept a separate low-voltage control signal on dedicated conductors, which is the commercial arrangement and needs those extra conductors pulled. Some are non-dimmable and will not dim on any control, no matter what is wired to them.
Decide the control before ordering the driver, not after, because the control determines what has to be in the wall. Lumera's ELV and 0-10V dimmers collection covers the two control types that most commonly pair with these drivers.
What Class 2 Actually Means
Class 2 is a safety classification defined by limits on the driver's output power and voltage, not a description of its size or quality. A Class 2 output is low enough in energy that the wiring downstream of it is treated as a limited-energy circuit, which means it does not need conduit and the installation rules are far less onerous. Most LED tape systems and a great many fixtures specifically require a Class 2 driver for exactly that reason. It is also why splitting a large run across two Class 2 drivers is common practice: staying inside the Class 2 limit is often more valuable on site than the convenience of one larger supply.
Location, Access, and Heat
A driver has a service life and it will eventually need replacing, so where it goes deserves more thought than it usually gets. It has to remain accessible after the ceiling closes, which in practice means a junction box, a ceiling access panel, or a location above a removable tile rather than sealed behind finished drywall. Heat is the other consideration: drivers run warmer at higher loads, and one buried in insulation or crammed into a sealed cavity ages faster than the same unit with air around it.
Outdoor and damp locations need a driver rated for the exposure, with an appropriate ingress rating and a wet or damp location listing. An indoor dry-location driver put in a soffit or a landscape run fails, usually not immediately, which makes it a callback rather than an obvious install error. Lumera's junction and enclosure boxes collection includes low-profile driver enclosures built for that purpose, in both indoor and wet-location versions.
Voltage Drop on the Low-Voltage Side
One issue specific to constant-voltage systems catches people out. Once the driver has stepped power down to 12V or 24V, the DC run from the driver to the load is far more sensitive to distance than a line-voltage run is, because the same voltage loss represents a much larger percentage of a low supply. A tape run fed from one end will read visibly dimmer at the far end if the run is long or the conductor is thin. The fixes are the usual ones: heavier gauge conductor, a shorter run, feeding from the middle rather than one end, or moving the driver closer to the load. Twenty-four volt systems tolerate distance better than twelve volt ones for the same reason, which is worth knowing at the design stage.
Drivers Versus Transformers
The terms get used loosely and the products are different. A driver is an electronic supply that regulates output to an LED load, whether by current or by voltage. A magnetic transformer steps voltage down through a coil and is what traditional low-voltage landscape and older halogen systems were built on. LED loads generally want a driver, but some legacy systems and some landscape installations still run on magnetic units, and the dimming behaviour differs between the two. Lumera's transformers collection covers the magnetic side.
What the Driver Is Powering
Most constant-voltage drivers in this collection end up feeding flexible strip. The tape light collection covers those reels and their accessories.
For the higher-density and specialty strip formats used in cove and architectural detailing, the ribbon light collection covers that product line.
Installation
The line-voltage side of a driver connects to building wiring and should be terminated by a licensed electrician, who will confirm the input voltage matches the supply, that the enclosure and location suit the environment, and that the driver is accessible for future service. On the low-voltage side, observe polarity, keep terminations tight, and do not exceed the driver's rated output by adding load later without recalculating the total.
Common Questions About LED Drivers
What is the difference between constant-current and constant-voltage drivers?
A constant-current driver holds a fixed current in milliamps and lets voltage vary, which is what LED modules and most integrated fixtures need. A constant-voltage driver holds a steady 12V or 24V and lets current vary, which suits LED tape, strip, and parallel loads. The two are not interchangeable and using the wrong one damages the load.
How much bigger than my load should the driver be?
Add up the wattage of everything connected, then pick a driver rated above that total with roughly twenty percent spare. Running at the absolute ceiling shortens the driver's life through heat and leaves nothing for a section added later. For tape, multiply watts per foot by the run length, since that figure varies widely between products.
What does Class 2 mean on a driver?
Class 2 is a safety classification based on limits to the driver's output power and voltage. Staying within those limits means the downstream low-voltage wiring is treated as a limited-energy circuit and does not require conduit. Most LED tape systems and many fixtures specifically require a Class 2 driver.
Can I use any dimmer with a dimmable driver?
No. A driver dims only by the method it was designed for. Some accept phase-control signals from a residential wall dimmer, some need a separate low-voltage control signal on dedicated conductors, and non-dimmable models will not dim on anything. Decide the control before ordering the driver, since it determines what has to be wired.
Where should the driver be installed?
Somewhere accessible after the ceiling closes, such as a junction box, an access panel, or above a removable tile, because a driver is a serviceable part with a finite life. Keep it out of packed insulation and sealed cavities, since heat shortens its life, and use a wet or damp rated unit anywhere it will be exposed to moisture.
Why does my tape run get dimmer at the far end?
That is voltage drop on the low-voltage side. At 12V or 24V, the same loss over a run represents a much larger share of the supply than it would at line voltage. Use heavier gauge conductor, shorten the run, feed from the middle instead of one end, or move the driver closer to the load. Twenty-four volt systems tolerate distance better than twelve volt ones.
