Why COB Fixtures Fail Without a True Constant Current Driver

Most driver failures on spotlight and downlight projects trace back to one mismatch: a constant voltage driver feeding a load that was designed for constant current. A bare COB chip or LED module has no internal current-limiting circuit of its own — it relies entirely on the driver to hold its operating current steady. Nucleo's DALI constant current range is built specifically for this job, holding output current fixed at the fixture's rated point regardless of how load voltage shifts with temperature or dimming, so chips run at their designed brightness for their full rated lifespan.

⚙ Built for the Fixture, Not Just the Wattage

Two drivers rated at the same wattage are not interchangeable if one is constant voltage and the other constant current. Before specifying, check whether your fixture's datasheet lists a voltage (12V/24V) or a current (mA) — that single number tells you which driver type the fixture needs.

Constant Current vs Constant Voltage

Constant Voltage Driver

Outputs a fixed voltage (12V or 24V DC). Matched to LED strips and profile systems that regulate their own current internally, segment by segment.

Constant Current Driver

Outputs a fixed current (mA) while voltage floats with the load. Matched to bare COB chips, LED modules, spotlights and downlights that need an exact current to set brightness and protect the chip.

DT6 or DT8 — Matching the Driver to the Control Need

Both protocol types share the same constant-current output stage; the difference is what the DALI bus can control.

①
DT6 — Single Channel
One DALI address, 0–100% brightness dimming only. For single-colour COB spotlights and downlights on any standard DALI-2 controller.
②
DT8 — Tunable White / RGBW
Drives warm and cool white channels independently for CCT shift (roughly 2700K–6500K) while dimming, or 4-channel RGBW. Needs a DT8-capable controller.

One Driver, Four Current Settings

Rather than stocking a separate driver SKU per fixture type, the output current on this range is selectable at installation to match whichever COB or module it's paired with:

350 mA
Low-power
small COBs
500 mA
Compact
spotlights
700 mA
Standard
downlights
1050 mA
High-output
COB spots

Always confirm the rated current on the LED module's datasheet before setting the driver — this is the single most common cause of premature chip failure on site.

Flicker-free at every dim level

Dimming runs on high-frequency PWM switching, well above the range where flicker becomes visible or physiologically noticeable — so brightness stays smooth from 100% down to near 0%. This matters most in offices, hospitals, classrooms and retail spaces where occupants spend extended time under the light.

Key Features

🔷
DALI DT6 & DT8
Full DALI-2 protocol support — single-channel dimming or tunable white / RGBW colour control from a standard DALI bus.
🎚
Adjustable Output Current
Selectable 350–1050mA output. One driver model covers a wide range of COB chips and LED modules.
✨
Flicker-Free PWM
High-frequency dimming with no visible or physiological flicker at any brightness level.
⚡
Up to 25W Output
Sized for the full residential and commercial COB spotlight and downlight range.
🛡
Built-in Protection
Short circuit, overload, over-voltage and over-temperature protection with automatic recovery.
🌡
Fanless, Convection Cooled
Silent operation rated for -20°C to +50°C ambient, with no moving parts to service.

Where This Driver Is Specified

Designed to drive Nucleo's COB spotlight and downlight range, and compatible with third-party LED modules within the selectable current range:

💡
COB Recessed Downlights
🔦
COB Spotlights
🛤
Track-Mounted Spots
🔄
Adjustable Cylinder Lights
🧩
Bare LED / COB Modules
🏢
Office & Commercial Fit-Outs
🏨
Hospitality & Retail
🏥
Healthcare & HCL Projects

⚙ Specifying for a Multi-Fixture Project?

Nucleo's team can help match driver current, protocol and DALI addressing across a full fixture schedule — from a single room to a BMS-integrated commercial building. Send your fixture list and floor plan for a specification review.

Technical Specifications

ParameterSpecification
Driver typeConstant Current (CC)
Max output powerUp to 25W
Output currentAdjustable — 350mA / 500mA / 700mA / 1050mA (selectable)
Input voltageAC 100–240V, 50/60Hz
DALI protocolDT6 (single-channel dimming) & DT8 (tunable white / RGBW)
Dimming range0% – 100%, smooth and flicker-free
Dimming methodHigh-frequency PWM
IP ratingIP20 (indoor, dry locations)
ProtectionsShort circuit, overload, over-voltage, over-temperature (auto-recovery)
Power factor> 0.90
Operating temperature-20°C to +50°C
CoolingConvection cooled (fanless)
ApplicationsCOB spotlights, recessed downlights, track lights, LED modules
SupplyPan India

Frequently Asked Questions

Why does a COB spotlight need a constant current driver instead of a constant voltage one?
COB chips and LED modules are current-driven — their brightness and lifespan depend on the exact current through them, not the voltage across them. A constant voltage driver lets current drift as load voltage shifts with temperature, which can over- or under-drive a bare chip. A constant current driver locks the output current so the chip always runs at its rated point. Spotlights, downlights and bare modules specify constant current; strips and profiles specify constant voltage.
How do I choose between DALI DT6 and DT8 for a spotlight project?
Use DT6 for single-colour fixtures that only need brightness dimming — one address, one channel, works with any standard DALI-2 controller. Use DT8 when you need colour temperature control: it drives warm and cool white channels independently for CCT shift (roughly 2700K–6500K) while dimming. DT8 requires a controller with DT8 colour-type support.
What output current should I set the driver to?
Match it to the rated current on the LED module or COB chip datasheet — typically 350mA, 500mA, 700mA or 1050mA. Overdriving a chip shortens its life and risks thermal failure; underdriving reduces brightness and colour consistency. Set the current via DIP switch or resistor before the fixture is powered on.
Will the lights flicker when dimmed low on this driver?
No. High-frequency PWM dimming operates well above the range where flicker becomes visible or physiologically noticeable, holding a smooth output from 100% down to near 0%. This matters in offices, hospitals, classrooms and retail spaces with extended occupant exposure.
Can one driver run more than one spotlight?
Yes, as long as the combined wattage of the connected fixtures stays within the driver's rated output (up to 25W) and they share the same required current setting. Fixtures needing different current settings should be split across separate drivers or DALI address groups.
Does Nucleo supply DALI drivers with project specification support across India?
Yes. Nucleo supplies DALI constant current drivers pan-India — Mumbai, Delhi, Bangalore, Hyderabad, Chennai, Pune, Ahmedabad, Kolkata, Jaipur and beyond — and can help with current selection, DT6/DT8 protocol choice and DALI addressing for projects of any scale.
What happens if the driver is overloaded or short-circuited?
Built-in short-circuit, overload, over-voltage and over-temperature protection shuts the output down automatically rather than letting it fail, and resumes normal operation once the fault clears — no manual reset or service call needed for a transient fault.