Whiteboard of the Week: LED Display Panel for Traffic Management

November 18, 2014

One of the latest Whiteboard Power Chains of the Week is a power system for an LED display panel that was developed by Marco La Ciacera, our technical sales engineer for Southern Europe. Here’s what he told us about this design.



Click image to access the whiteboard

Can you explain a little more about the application?

The power chain was designed for a variable message sign (VMS), signs that can be placed in a wide range of places like highways, major road junctions, and urban arteries. Typically installed at the side or above the roadway, the VMS uses text and graphics in monochrome or color. VMSs use ultra-bright, low power LED technology to ensure maximum visibility in all weather conditions.


What were the key criteria for the design?

Power efficiency was very important, but the manufacturer also wanted to minimize the system cost. The power cabling was a major element of the total cost, so reducing this was an important goal.


Your power chain uses 48 V, whereas previous versions used 24 V. What are the benefits of the higher voltage?

The main advantage of the higher voltage is a reduction of the size of cable inside the panel. There can be more than 100 LED boards in a sign, which means that long cables may be required. By moving from 24 V to 48 V, a smaller cable is required, making routing easier as well as reducing cost.


How were the power components used in the design physically distributed?

At the main power inlet, single or three-phase AC is converted to 48 V DC. This is supplied to all cells of the VMS, where a BCM converts from 48 V to 12 V. Within each cell there are many boards that have an LED strip, which may require different voltages depending on the color of the LED used, so each board uses a Picor Cool-Power ZVS Buck regulator to covert from 12 V to outputs in the range of 3V to 5V. Depending on the current needed to drive the LEDs at the required luminosity, one, two or three regulators are used.


Were there any special environmental requirements?

The signs are obviously placed outdoors, so the environment is pretty challenging. It was great to be able to use Vicor components that offer an industrial operating temperature range.


You can view Marco’s power chain design, modify and analyze it by clicking here.


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