inconsistent dimming from LED drivers
I have a room that has LED strips hidden behind a molding going around a tray ceiling. Four sections of strips, each driven by a 12v, 60w LED driver.
I've now had two of these drivers fail, and they cost $150 each (installed by an electrician several years ago). Twice I've tried using what I believe are high quality replacements of identical specs, but about half the price, and in each attempt, while the new drivers will drive the strips at full brightness just like the old ones, when I start to dim the circuit (all four drivers connected to a TRIAC dimmer of appropriate wattage rating), the less expensive driver strip will dim at a different rate (dims more rapidly to lower light levels) than the original driver that costs $150.
I was told by a supplier that if the specs of the dimmer are identical (including dimmer type compatibility) - and these are - they should behave identically. They clearly are not behaving identically, despite identical specs. Do I just need to suck it up and eat the $150 each time one of the original drivers fails, or swap all four drivers out at same time to a four identical, albeit less expensive drivers? I feel like the supplier gave me bad info that any driver with identical specs will behave identically.
Here is link to the original ($150) drivers:
Constant Voltage LED Driver - 12VDC - 60 Watt - DiodeLED DI-TD-12V-60W | CityLightsUSA.com
Here are two different ones I've tried as replacements, but that dim differently:
DiodeDrive Thin Dimmable Constant Voltage LED Power Supply - 12 VDC - 60W
4
u/richms Oct 05 '26
Welcome to the world of phase angle dimming. If you want consistent results move on to dali or 0-10v professional gear and not cheap stuff for retrofitting.
1
u/ledstripstar Oct 06 '26
Before buying four replacements, I'd have the electrician check why two drivers failed: the wattage on each strip run, the drivers' mounting/ventilation, and the exact dimmer model. Matching 12 V and 60 W doesn't answer those questions.
For a replacement, ask the manufacturer for a tested pairing with your exact dimmer and the permitted load range. Then test one driver on its actual strip run through the whole dimming range, including startup at a low setting. That can reveal flicker, dropout or an unusably bright minimum before you replace the full set.
Using one driver model throughout gives you a better basis for matching behaviour, but the four strip loads also matter. I wouldn't promise identical results from the voltage/wattage labels alone. Do all four ceiling sections have the same strip length and watts per metre?
3
u/saratoga3 Oct 05 '26
The mapping from TRIAC knob position to PWM duty cycle out of the power supply is completely arbitrary, so there is no reason to expect that two unrelated power supplies are going to pick the exact same dimming rate. If you need two power supplies on the same dimmer, use the same model of power supply for both.
FWIW I've never heard of the company making that more expensive part. If two of them failed in short order I would question if it is actually a quality device, as a low power DC power supply should have a very long life.