Light Panels for Outdoor Applications
Flat panel LED lighting typically is not suitable for outdoor use. There are several key technical reasons for this limitation.
Outdoor lighting and signs will typically see substantial increased ambient operating temperatures than indoor applications. These higher operating temperatures will result in higher LED operating temperatures that will significantly reduce the lifetime of the LED.
Wet or damp conditions will penetrate the LED lens material and reduce the lifetime of the LED.
Wet or damp operating conditions will damage sensitive circuitry which is driving the LEDs. This can result in a failure of the LEDs to “turn ON”.
LITEGRAFX developed technology has solved these problems.
Managing the Heat
The importance to properly manage the heat generated in an outdoor application is commonly overlooked or not understood. The Litegrafx solution involves both minimization of the heat generated in each LED and using highly efficient thermal extraction techniques to keep the LED operating at the lowest possible temperatures. This design approach minimizes the reduction in LED lifetime due to higher ambient temperatures.
The heat generated in each LED is determined by the electric current flowing through the LED. The approach of just reducing current in the LED is not a solution because this will also reduce the overall brightness in the light panel. However by reducing the pitch (the distance between adjacent LEDs) will allow operating each LED at a reduced current. This approach will significantly reduce the operating temperature of each LED and extend LED lifetime. Cutting corners by increasing LED pitch and compensating by over driving the LED will reduce LED lifetime and result in premature LED failure.
Reducing LED heat generation by lowering the current is only half of the solution to extending the lifetime of the LEDs in an outdoor application. There is still a significant amount of heat that is produced by each LED. Using advanced thermal extraction methods are critical to keep the LEDs running cool. A large surface area aluminum heatsink that is bonded to the LEDs is the first critical step to efficient heat extraction. Using a off the shelf U-channel extrusion, which is common, will not provide adequate surface area to dissipate the generated heat. Litegrafx uses a custom designed aluminum extrusion that has many times the surface area of a typical U-channel extrusion.
Between the point where the heat is generated in the LED and the aluminum heatsink multiple layers of thermally insulating materials exist. A critical design feature is to connect the hottest point of the LED directly to the heatsink with high thermal conductive material. All of Litegrafx’ designs incorporate a direct connection of the LED to the heatsink. This direct connection improves heat transfer in the system to insure the coolest operating LEDs.
Water and LEDs Don’t Mix
Electronic circuitry and components and water are normally incompatible. Left unprotected high humidity and water will absorb into the LEDs, printed circuit board and drive component of the light panel. This along with the higher operating temperatures of outdoor applications will result in reduced LED lifetime, circuit corrosion and early component failure. Protecting electronics from harsh outdoor applications is not a new problem. There are many encapsulating materials that are commonly used to protect sensitive electronic systems. However LED systems are unique. Each of the LEDs produces a significant amount of light that must pass through the encapsulating material. So the encapsulating material must be optically clear and it must have the same moisture resistant properties for commonly used encapsulants. This however is still not good enough. The material must remain optically clear even after thousands of hours of light exposure from the LEDs and after long exposure to high humidity and water. Litegrafx has developed a proprietary encapsulating material to withstand the harsh environments typical in outdoor applications. All light panel assemblies used for outdoor applications include our proprietary encapsulating material.
Advanced thermal management techniques and a high technology encapsulating process provide a long life, high reliability solution for outdoor illumination applications. Litegrafx has the right solution for outdoor use.
