Circular & Square LED Light Engine Technology

How ready-made circular and square LED light engines provide efficient, even light for downlights, bulkheads and panel luminaires, and how to choose and design them in.

Overview

What is an LED light engine?

An LED light engine is a ready-made LED board that forms the light source of a luminaire. Many mid-power LEDs are arranged across a round or square area on a metal-core PCB (MCPCB), wired in a series-parallel matrix and fitted with simple connectors. Paired with a constant-current driver, it gives luminaire makers an efficient, proven light source without designing an LED board from scratch.

Our circular light engines range from compact 50mm boards to 340mm Philips Fortimo LED CS modules, with 2835 and 5630 LEDs delivering up to 5,500lm and efficacy up to 201 lm/W. Our square light engines are Philips Fortimo LED Square modules producing 2,500lm or 5,000lm at up to 175 lm/W. Most are available in multiple colour temperatures with CRI above 80 as standard.

Ready-made light source for faster luminaire development
Circular boards from 50mm to 340mm diameter
Square Fortimo modules for panel and recessed luminaires
Efficacy up to 201 lm/W, output up to 5,500lm
Metal-core PCBs and poke-in connectors for easy assembly

Light engines at a glance

Shapes: Circular and square
Circular sizes: 50mm – 340mm
Square sizes: 380 x 380mm and 260 x 520mm
LEDs: 2835 and 5630 mid-power
Output: up to 5,500lm
Efficacy: up to 201 lm/W
Drive: Constant current
CRI: >80, >90 on request
Brands: Plus Opto and Philips Fortimo

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The technology

How a light engine works in a luminaire

The LEDs on a light engine are arranged in a series-parallel matrix: strings of LEDs in series set the forward voltage, and several strings in parallel share the drive current. Spreading many mid-power LEDs across the board gives a large, even light-emitting area with no single hot spot.

A constant-current driver supplies the rated current, which sets the light output. The driver's output voltage window must cover the light engine's forward voltage.

The board is mounted onto the luminaire housing or a heatsink with a thermal interface. The metal-core PCB carries heat away from the LEDs, and a diffuser or reflector shapes the light and hides the individual LEDs.

Simplified illustration: the driver powers the LED light engine, the heatsink removes heat through the metal-core PCB, and the diffuser spreads the light evenly.

Our range

Choosing a circular or square light engine

Match the shape and size of the light engine to the luminaire, then choose the output for the application.

Range	Sizes	Output	Efficacy	Best for
RM E series circular	50, 80, 120 and 160mm	2,040 – 5,210lm max	170 – 180 lm/W typ.	Downlights and general lighting
RM R series circular	90, 110 and 130mm	1,900 – 4,400lm	>150 lm/W	Downlights and high-output bulkheads
PAM / PA arrays	75 and 84mm	Up to 3,000lm	150 lm/W	Compact high-lumen general lighting
Fortimo LED CS	210 and 340mm	2,500 – 5,500lm	186 – 201 lm/W	Large round ceiling and bulkhead luminaires
Fortimo LED Square	380 x 380mm, 260 x 520mm	2,500 and 5,000lm	Up to 175 lm/W	Recessed and panel luminaires

Circular LED light engines

50mm to 340mm boards for downlights and bulkheads. View the range →

Square LED light engines

Philips Fortimo LED Square for panel and recessed luminaires. View the range →

Benefits

Advantages of LED light engines

Why luminaire makers build on ready-made light engines.

Faster development

A proven, ready-made light source removes the need to design and qualify a custom LED board.

High efficacy

Mid-power LEDs deliver up to 201 lm/W, cutting energy use and helping meet efficiency regulations.

Even light

Many LEDs spread across the board give a large, uniform emitting area that is easy to diffuse.

Good thermal path

Metal-core PCBs carry heat to the luminaire housing, keeping LEDs cool for stable output and long life.

Simple assembly

Poke-in connectors and standard fixing holes make production quick, with no soldering needed.

Easy retrofit

Standard round and square formats replace compact fluorescent and older LED boards in existing luminaires.

Design-in

Designing with light engines

Start with the luminaire: choose a shape and size that fits the housing and exit window.
Set the target lumens, allowing for diffuser and optical losses, and pick a light engine with headroom.
Choose the drive current: running below maximum current improves efficacy and lifetime.
Match the driver: its current must suit the light engine and its voltage window must cover the forward voltage.
Design the thermal path with a flat metal mounting surface and thermal interface material.
Choose CCT and CRI: CRI above 90 is available on request for retail, hospitality and healthcare.

Complete the luminaire

We supply the drivers and components to finish your design:

Ask an Engineer

201 lm/W

Peak efficacy

5,500lm

Max output

50–340mm

Circular sizes

3 SDCM

Fortimo colour consistency

Where light engines excel

Circular and square light engines power a wide range of indoor and outdoor luminaires.

Downlights

Recessed and surface downlights for commercial and residential spaces.

Bulkheads

Round and square bulkheads for stairwells, corridors and outdoor walls.

Panels & recessed

Square modules for recessed and surface panel luminaires.

Ceiling luminaires

Large round ceiling fittings for offices, schools and public spaces.

Retrofit

Upgrading compact fluorescent and older LED luminaires.

Luminaire OEMs

A ready-made light source for new luminaire designs.

FAQ

Light engine questions

It is a ready-made LED board, usually on a metal-core PCB, with many mid-power LEDs arranged to fill a round or square area. Fitted into a downlight, bulkhead or panel luminaire with a constant-current driver, it provides an even, efficient light source without the need to design an LED board from scratch.

LED light output and life depend on current, and a small change in voltage can cause a large change in LED current. A constant-current driver holds the current at the rated value, giving stable light output, consistent colour and long life. The driver's voltage window must cover the light engine's forward voltage.

A metal-core (aluminium) PCB conducts heat away from the LEDs far better than a standard circuit board. Mounted onto the luminaire housing or heatsink with a thermal interface, it keeps the LEDs cool, which maintains light output and extends lifetime.

Yes. Most of our circular light engines are available in multiple colour temperatures with CRI above 80 as standard and CRI above 90 on request. Fortimo LED Square modules are available in 3000K, 4000K and 6500K with 3 SDCM colour consistency.

Many of our light engines use solderless poke-in connectors, so the driver output wires simply push into the terminals. Always connect positive and negative correctly and switch off the supply before connecting.

Circular & Square LED Light Engine Technology