In August 2017 we introduced Citizen Electronics' AC COB, an LED package that connects directly to mains voltage with no external driver. The COB sits in a holder that carries the components needed for mains operation, so a luminaire maker could design a fitting with no driver box to find space for.
How it worked
An integrated circuit in the package regulated the LED, which Citizen said gave more accurate control of luminous flux than a typical driverless design. One result was that every colour temperature and CRI version delivered the same output, in four steps:
- 750 lm
- 1000 lm
- 1500 lm
- 2000 lm
For a designer, that removes a common headache. With a conventional COB, the warmer and higher-CRI versions give fewer lumens at the same current, so a range offered in several colour temperatures needs different drive settings for each. Here the lumen package was fixed.
Sensors and dimming
The AC COB had a 5 V output, intended for accessories such as a motion sensor. That made it simple to add presence detection to a luminaire without a separate low-voltage supply.
The circuit was also compatible with ordinary phase-cut dimmers: both TRIAC (leading-edge) and transistor (trailing-edge) types. That suited retrofit and residential work, where the dimmer on the wall is usually phase-cut rather than DALI or 1-10 V.
Why it mattered for luminaire design
With no separate driver there are no driver losses to add on top of the LED, so the design kept reasonable efficacy even at low wattages. The small footprint and absence of a driver gave more freedom in the shape of the fitting, which mattered most in compact downlights, pendants and decorative pieces where a driver box is hard to hide.
There are trade-offs with any driverless approach. When specifying one for a project, check flicker performance, dimmer compatibility lists and how the luminaire will be serviced, since the electronics and the light source sit in the same assembly.
Where to go from here
Citizen no longer lists the AC COB in its current catalogue, so we can't point you to a live datasheet. The conventional route today is a standard COB, such as Citizen's CITILED COB Version 9 series, with a separate driver. If you are working on a compact luminaire and want to compare a driverless design with a conventional COB and a small driver, our OEM team can help, and our lighting components range covers the driver side. Contact us with your target output and dimming method.