AC COB Technology: How ZENITH Handles High Temperature Lighting

COB technology in high-temperature LED lighting

LEDEX uses driver-on-board / AC COB technology in ZENITH, our industrial high bay for ambient temperatures up to 90°C (194°F). For a facility with heat around the mounting position, that ambient rating is the starting point for fixture selection.

COB describes the light source inside the luminaire. To assess the complete fixture, you also need its thermal design, electrical configuration and installation conditions. A useful specification connects those details to the temperature at your ceiling or process line.

Multiple LED chips in one light source

A COB LED combines multiple LED chips on a common substrate beneath a phosphor layer. Designers can work with a concentrated light-emitting area when selecting a reflector or lens. Lumileds describes this construction in its guide to COB LEDs.

With a surface-mounted device (SMD) layout, designers distribute packaged LEDs across a board. Both approaches can serve industrial lighting. The package choice alone cannot establish which completed fixture will withstand more heat.

For a high bay, compare the resulting beam and light levels at the work surface. A compact source can help with optical control, but you still need the fixture's photometric data to assess coverage and glare.

Improvements in newer COB generations

COB is an established technology that manufacturers continue to develop. Current product families offer improvements in efficacy, source size and material choices. Cree LED, for example, lists newer metal-substrate COB families and upgrades that retain existing package dimensions in its COB portfolio.

Those developments give luminaire designers more choices. For a purchasing decision, ask for the finished fixture's rating and output under the conditions you will use.

ZENITH's driver-on-board / AC COB design

ZENITH combines the COB light source with onboard drive electronics for AC operation. For installers, this removes the separate remote-driver mounting point and the cable run between that driver and the light head.

For remote-driver systems with factory-attached wiring, you need to choose a suitable cool zone for the driver, measure the full installed cable route and give the factory the exact required cable length before production. This adds layout and ordering work, especially when the cooler area is far from the luminaire. ZENITH's onboard design avoids those remote-driver installation requirements.

Driver-on-board designs integrate the drive function into the board. Seoul Semiconductor describes this general approach in its AC-direct technology overview; that reference explains the architecture and does not identify ZENITH's component supplier.

The drive circuitry remains part of the fixture. Descriptions such as “driverless” refer to removing a separate driver unit, not to removing current regulation or thermal limits. ZENITH's 90°C rating applies to the completed luminaire under its specified conditions.

Overheating protection that reduces power to around 30 W

ZENITH also includes thermal protection that can reduce operating power to approximately 30 W during overheating. Reducing electrical power reduces heat generation and light output, helping protect the fixture from thermal stress.

Engineers call this behaviour thermal foldback. It comes from the fixture's control design; COB packaging alone does not give an LED fixture this function. The board must include the required sensing and control circuitry. Texas Instruments explains the general mechanism in its thermal-foldback reference design.

Plan normal illumination using the selected model's operating specifications. During thermal protection, the reduced light output may fall below the project's required light levels. Investigate the cause of overheating and keep the installation within ZENITH's specified 90°C maximum ambient conditions. That rating does not identify the protection's internal trigger temperature.

The thermal path still matters

Heat must travel from the LED junction through the array and its mounting interface to the heat sink, then into the surroundings. Hotter ambient air leaves less temperature headroom for that heat transfer. Bridgelux explains this thermal path and the relationship between ambient, case and junction temperatures in Application Note AN10.

Assembly matters too. The contact between the array and heat sink forms part of the thermal design; mounting and interface materials affect that connection. See Bridgelux's LED array assembly guidance.

In a plant, record conditions at the mounting position during production. Include nearby hot equipment, restrictions on airflow and the maintenance access needed to keep the fixture in its specified condition.

Three temperatures to keep separate

Temperature	What it tells you
Ambient, Ta	Air temperature around the equipment. Compare it with the complete luminaire's permitted ambient range.
Case, Tc	Temperature at a defined point on the LED module or driver. Use that component's limit and measurement point.
Junction, Tj	Temperature inside the LED semiconductor. Used in thermal design; it is not a room-temperature rating.

A fixture rated for 90°C ambient and an LED component with a 90°C case limit describe different conditions. The same distinction applies to the driver. Our companion post explains COB, remote drivers and the 80°C question.

ZENITH for ambient temperatures up to 90°C

ZENITH gives specifiers a high-temperature option for non-classified industrial areas. Its catalogue lists outputs from 16,000 to 72,000 lumens, with 100 W to 450 W configurations and U-bracket or hanging mounts.

Use the 90°C ambient rating to screen the application, then confirm the exact catalogue number, supply voltage and mounting conditions. Ask for the applicable output and lifetime information at your operating temperature rather than assuming catalogue values remain unchanged across the full range.

For other elevated-temperature applications, our high temperature lighting range also includes FORTRESS and TITAN at up to 65°C, and VECTOR at up to 70°C. Match the model's classification to the installation as well as its temperature rating.

Plan the fixture around the application

Send LEDEX the maximum ambient temperature at fixture height, mounting height, operating hours and supply voltage. Add a drawing and your target lux or foot-candles so we can review the light distribution along with the thermal requirements.

Request a high-temperature lighting review or view ZENITH configurations and documents.