What is the difference between backlite and sidelite LED panels?

What is the difference between backlite and sidelite LED panels?

A backlite LED panel consists of a series of LEDs mounted on a horizontal panel that shine vertically downward through a diffuser into the space to be illuminated. Backlite panels are sometimes referred to as direct-lit panels. 

A sidelite LED panel is made of a series of LEDs attached to the frame of the panel that shine horizontally into a light guide plate (LGP). The LGP directs light downward, through a diffuser into the space below. Sidelite panels are sometimes referred to as edge-lit panels. 

Are backlite or sidelite LED panels better?

Both structures have advantages and disadvantages. Sidelite LED panel lights were the first to be mass produced.

The sidelite design was chosen for a few reasons: 

- A light guide plate (LGP) is an effective and simple way to diffuse light and avoid the risk of light spotting. 

- The presence of the LGP means that the diffuser is not solely liable for diffusing the light evenly, so low-cost materials are often used, provided they do not yellow over time. 

- No lenses are required and the sidelite design works well with a variety of different LED beam angles. 

- Heat from the LED chips is dissipated through the frame, so the backboard can be lightweight, and not get hot, allowing the driver to be placed here if needed. 

Over time, the disadvantages of this approach became apparent. The best material for an LGP is acrylic (PMMA), but that can be quite expensive, so cheaper polystyrene (PS) was often used. Unless UV-stabilizing additives are added to it, PS LGP yellows over time so efficiency drops, the light output turns a dull yellow, and the center of the panel becomes dark while the periphery remains bright.

Technical advances have now allowed the introduction of the new generation of backlite LED panels. These are often more efficient and have a lower product cost than previous LED panels. 

- LEDs have become more efficient, so the thermal advantage of the sidelite design has become less important. Backlite designs are no longer so hot that the driver cannot be placed on the back. 

- Lenses have become cheaper to manufacture, and modern adhesives allow them to be securely attached to each LED to provide even light distribution without the risk of falling off - a flaw that occurred with some earlier and cheaper backlite panels. 

- Microprismatic diffusers have become more common, less costly and more effective, eliminating the need for the dual action of the LGP and diffuser combination. 

- The elimination of LGP in backlite panels means that there are no longer yellowing problems caused by PS LGP, and prices are now much more competitive as PMMA LGP is very expensive. 

The lighting market now accepts backlite LED panel light as well as sidelite LED panels and, because backlite panels do not require LGP or back reflector, they are often the most cost effective and efficient LED panels on the market.

At Cyanlite, we offer both backlite and sidelite LED panel lights. Backlite LED panels offer higher cost performance for standard sizes such as 600x600, 625x625, 300x1200 and 600x1200 models, while the Sidelite design is more flexible for customized dimensions and shapes for special projects.

What are the problems with cheap backlite LED panels?

Here are what to look out for.

1, Too few LEDs (normally 36 or less) means they have to be run at a high current to get the light output you need. Compared to designs that use more LEDs, this is often less efficient (LEDs operate most efficiently at low operating currents), generates more heat, shortens LED life, and accelerates lumen loss.

2, Plastic Housing. The better Backlite LED panel lights use an aluminum housing. This is more effective as a heat sink than a (cheaper) plastic housing. LEDs generate some heat that must be dissipated if their life is not to be shortened further.

3, The light distribution is not overlapping. In a good Backlite LED panel design, each LED is individually lensed, and the lenses are designed so that the light from each LED overlaps the light from its neighbors. This creates a uniform lighting effect. Poor lens design and a small number of LEDs will likely reduce the overlap between LEDs and increase the risk of bright and dark spots on the front of the fixture. 

4, Are the lenses firmly fixed in position? Only time will tell, but there is a risk of the lenses coming loose due to the heat generated by the LEDs combined with cheap adhesive poorly applied will cause the lenses to fall off. The result is going to be uneven light distribution and possibly glare.

5, Built-in driver. Manufacturers can save money by building the driver into the housing, but this has several drawbacks. It cannot be replaced if there is an issue, and heat dissipation for the driver is a problem.

6, Check the corners of the frame. On the cheaper panels, an unsightly joint will be evident.

UGR <19 with backlite and sidelite LED panels.

With the right front diffuser, both designs can produce excellent UGR performance. To compare different brands and models just look at the UGR tables that are part of the photometric data. Cyanlite backlite LED panel light achieves UGR<19 up to 4400 lumen output. Click here for more detailed information of Cyanlite Backlite LED Panel Light.