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A customer is bidding on a large project over 3000 SQF (300 SQM) of LED screens in Las Vegas, and since they have not budgeted or designed for air conditioning, What makes one company’s LED billboard heat-design superior to the next?
Las Vegas and Phoenix are literally situated in the desert and have an average of 140° F (60° C) in the hottest three months of the summer. One has to be extra cautious when designing for this application.
How do we ensure low service-calls and longevity?
…Drum Roll Please… The 7 Major Components Are:
1. PCBA (Circuit Board)
A well-thought-out PCBA Gerber design with a clean circuit pathway with enlarged copper trace (both in width and depth) will ensure heat dissipation is minimized.
2-layer boards may work for indoor video walls, but under the sun, a 4-layer PCB board is a must to ensure the proper disappation spacing between the heat generating traces and the other layers.
2. PSU (Power Supply)
As temperate raises, the load capacity of a power supply rapidly degrades until it auto-protects and shuts down to avoid permanent damage.
A good power supply design will enable utilization rate of 50% when the screen is at maximum full white or less than 25% during a typical play-back.
In addition in conjunction with the IC, one should use low voltage PSU (3V) vs. the typical 5V for additional power savings and temperature reduction.
Discrete LEDs or SMDs themselves should be of the highest MCD (millicandela) value and the chip–similar to the filament of a bulb–should be spec’d at the largest diameter.
This will ensure the lowest milliamp is loaded on the individual R, G, B at full utilization.
Lead-frame material must be Copper and not the inferior Steel which offers only 1/3 the heat conductance.
Nichia, CREE, Multicolor, and the highest bin Nationstar diode offers the flattest degradation curve per temperature and should be utilized.
As heat rises the degradation curve forms a gentle incline. It is observed that the CREE green actually rises in brightness after 1000 hours.
IC chipset should support an energy efficient PSU and low-voltage PCBA design converting electrical energy from 115/230AC down to a typical forward voltage (Vf) of 3V on the actual diode.
35% of the energy of the IC dissipates in the form of heat. High energy efficiency ICs reduces this to a minimum.
Large Fans with high RPM and CFM value should be used. In addition, the metallic body fans with ball-bearing and a 100,000-hour rated maglev motor will ensure the lowest mechanical failure.
The trending IP68 sealed module design are also ideal as they have no fans.
The caveat is that since all heat is now trapped inside the module, the heat-design must be even more stringent.
Most designs offer a type of heat-sink using heat-conductant gel to draw the heat out the back of the module. The effectiveness of the heat-sink and over-all heat management merits closer scrutiny.
Aluminum offers a better heat dissipation coefficient than steel and should be used for better heat exchange with the ambient.
Cabinet color should be white if it’s exposed in direct sunlight to reflect the energy and reduce any heat solar gain.
7. Silicone Potting
The silicone potting injected in the front of the LED module can make a large temperature difference–up to 3-5 degrees–depending on pitch.
Low tier supplier mixes their silicone with foreign substances to create the illusion of a heavier weight and to dilute the cost.
The foreign substances create a barrier to heat-transfusion that acts as a winter coat. A top-tier silicone will be pure, and with the highest heat-transfer coefficient.