In July 2018 we started offering Citizen Electronics' new blue COB LEDs: chip-on-board arrays with a dominant wavelength of 455 nm, built on the same packages as Citizen's standard white CITILED COBs. For luminaire makers that meant a saturated blue source that drops into existing holders, heatsinks and optics without redesigning the fixture.
What Citizen launched
The first three blue parts we listed were the CLU038-1208C4-B455, CLU038-1210C4-B455 and CLU048-1212C4-B455. Citizen describes the colour as blue with a typical dominant wavelength of 455 nm (445 to 465 nm across the bin), produced directly by the dies rather than through a phosphor. Because the outer dimensions and light emitting surface match the white versions, the mechanical work done for a white COB luminaire carries straight over.
Key figures
The values below come from Citizen's current datasheets for the three original parts, measured at a case temperature of 25 °C. Blue LEDs are rated in radiant flux (watts of light) rather than lumens, because the eye's lumen weighting understates deep blue.
| Part | Size (mm) | Drive current | Typ. voltage | Radiant flux | Max input |
|---|---|---|---|---|---|
| CLU038-1208C4-B455 | 19.0 x 19.0 x 1.4 | 720 mA | 35.8 V | 11 to 17 W | 60.1 W |
| CLU038-1210C4-B455 | 19.0 x 19.0 x 1.4 | 900 mA | 35.8 V | 13 to 21 W | 75.1 W |
| CLU048-1212C4-B455 | 28.0 x 28.0 x 1.4 | 1080 mA | 35.8 V | 17 to 27 W | 90.1 W |
All three use an aluminium base, mount with M3 screws or a connector, and are UL recognised components. Thermal resistance from junction to case is 0.51 °C/W, 0.42 °C/W and 0.34 °C/W respectively, so the larger package is easier to keep cool at high drive currents.
Where blue COBs make sense
Citizen positions the blue range for swimming pools, landscape and security lighting. Those are applications where a single saturated colour is the point and a filtered white source would waste most of its output. Starting with a blue emitter gives a cleaner colour and better efficiency than putting a blue filter or gel in front of a white LED.
- Pool and fountain lighting, where the colour reads strongly under water.
- Landscape and facade accents that need a deep, even blue.
- Security and signal applications where a distinct colour matters.
The range today
Citizen still lists a CITILED Blue Color COB series, now larger than the 2018 line-up: alongside the three parts above it includes the CLU048-1812 and CLU048-1818, the 38 mm CLU058-1825 and CLU058-3618, and a CLU551 package. The datasheets for each part are on that page.
If you are building a coloured luminaire around a COB, we can help with the driver, heatsink and optics as part of our component and OEM services, or browse the lighting components we carry. For pricing and availability on Citizen parts, get in touch.