LED DOWNLIGHTS

LED downlights are recessed systems those are designed and engineered for optimal operation of an LED module and also efficient regulation and precise distribution of its luminous flux. In conjunction with custom designed secondary optics, an array of discrete LEDs can be designed to provide uniform ambient illumination; a single-point LED can create a spot beam with the highest punch possible for accent lighting.

The integrated design allows the LEDs to make full use of the luminaire housing for heat sinking, thereby keeping the LED junction temperature under control and maximizing the performance potential of LEDs. In systems with co-located drivers, miniaturized LEDs or compact LED arrays make space for an electrical compartment that can accommodate full-featured driver and control circuitry while isolating thermal stresses from the LED module.

An integrated LED downlight generally consists of housing, an LED light module, a driver, and a trim.

Housing

The housing is the main component of a downlight, housing the electrical parts such as the lamp. It also allows the downlight to be attached to the ceiling, and serves as the platform to which the trim is mounted. 

In general, LED downlights are self-contained lighting systems that are designed for recessed installation through retention systems, such as torsion springs and friction blades.

These luminaires typically come with a fixture-as-heat-sink design. The aluminium housing works simultaneously as the heat sink and is exposed for maximum heat transfer. 

TRIM

Trim refers to the light exit assembly that provides optical regulation and aesthetical enhancement for a recessed downlight. The light exit assembly is designed to maximize delivered lumens, shape the radiation pattern of LEDs, conceal the LEDs from direct view, and seal the ceiling cut out for seamless architectural integration. Various types of trims are available, depending on the light distribution, visual cutoff, and/or optical aiming requirement.

Reflector trims produce a highly luminous aperture that is suited to high ambient lighting applications typically found in commercial facilities, office buildings, high ceiling spaces, and task areas.

Baffle trims trap extraneous light and soften aperture brightness using a series of light-absorbing, deeply grooved ridges. Baffles are installed in the lower inside portion of the light cone.

Downlights with baffle trims are typically used in intimate and living spaces such as cocktail lounges, night clubs, restaurants, living rooms, dining rooms, and bedrooms. 

Black baffle trims are used to dilute the brightness from recessed cans for a high level of visual comfort but at the expense of significantly compromised luminous efficiency. White baffle trims create a brighter aperture, but blend with white ceilings when they're off.

APERTURE

The aperture is the opening at the bottom of the recessed downlight through which light exits the trim cavity. The aperture size of round downlights can be as small as 1 inch and as large as 8 inches. 

Downlights with a round aperture create a rotationally symmetrical light distribution. Square or rectangular exit apertures are also available for producing beam patterns that are similar in shape to their exit aperture.

Commercial, open plan spaces usually need large-aperture downlights, whereas small residential rooms are typically suited to luminaires with medium or small apertures. 

LED MODULE

LED modules, also called LED arrays, are simple LED assemblies. They use one or more diodes arranged on a circuit board. The circuit boards that LEDs use involve printed circuit boards (PCB) made of materials designed to improve heat dissipation.

This module is to be integrated with other system components such as the driver and heat sink. 

The LED module may include a single LED package such as a chip-on-board (COB) LED, or a ceramic-based high power LED. This type of modules is generally used for directional lighting which requires a high flux density light source for focused, localized illumination.

Optics

LED downlights have varied requirements on light distribution and beam control. Optical design for downlights can encompass the entire spectrum from reflectors, lenses, refractors, and diffusers all the way to components for integrated optics.

Recessed luminaires that produce a wide flood beam usually employ reflectors to regulate luminous flux from the light source. It makes sense to use a reflector design when the size of the light source is large and cost is a consideration

Low profile downlights use polycarbonate (PC) or polymethyl methacrylate (PMMA) to distribute luminous flux from the LEDs uniformly to all directions thus do not create an image of the light source.

Ultra-thin profile downlights use edge-lit technology to deliver a fully luminous panel of soft, visually comfortable light. Light from the edge-mount LEDs is transported and evenly distributed across the surface of a light guide panel (LGP) through total internal reflection (TIR). The LGP refracts the beams down towards a diffuser, which spreads the light out for soft, homogeneous illumination.

Types of Downlights

For recessed downlights, controlling the light distribution is just as important as the light output and luminous efficacy. Depending on the beam spread, LED downlights fall into categories of spotlights and floodlights.

Floodlights that have a beam spread above 60° are referred to as having a very wide flood beam. These luminaires are generally used to provide general lighting or wall washing. Ultra-thin, flat panel LED downlights radiate across a beam spread of up to 120°. 

Recessed downlights that provide accent and task lighting use very narrow spot (5° or smaller), narrow spot (6°-9°), spot (10°-19°), narrow flood (20°-25°), flood (30°-40°), or wide flood (55°-60°) beams

COB (Chip on Board) LED 

COB LEDs are basically multiple LED chips (typically nine or more) bonded directly to a substrate such as silicon carbide by the manufacturer to form a single module. Multi LED chips are packed closely together as one lighting module. And when it light up, it appears like more of a lighting panel than multiple individual lights.

 

Since the individual LEDs used in a COB are chips and not traditionally packaged, the chips can be mounted such that they take up less space and the highest potential of the LED chips can be obtained. When the COB LED package is energized, it appears more like a lighting panel than multiple individual lights as would be the case when using several SMD LEDs mounted closely together.

 

COB LEDs are brighter, consume less power, and output a higher quality beam of light compared to older LED technologies. Because COB chips are built straight onto a circuit board, they are more efficient and less likely to fail. Further, COB LEDs will be able to offer you a greatly reduced level of energy wasted as unwanted heat. This results in a greater level of efficiency.

COB chips also only have 1 circuit and 2 contacts, regardless of the number of the diodes

When a COB LED package is energized, it appears more like a lighting panel than multiple individual lights as usually the case with other LED packages, like when using several SMD LEDs mounted closely together.​

Due to the small size of the LED chips (imagine a quarter), Chip-on-Board technology allows for a much higher packing density than surface mount technology (SMD).