Optimizing the Power Architecture of Video Walls

July 22, 2016
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Video walls present an interesting challenge for power system designers: they need to develop power chains that are compact, light and highly efficient, as well as distributing this power over a relatively large distance. To power each panel in the display, engineers typically choose one of the four following architectures:

Distributed AC Power

This approach is by far the most common solution used today. AC is distributed to each panel and then converted to the DC voltages required by the LED drivers. Whilst it is conceptually simple, it suffers from several disadvantages. Bulky cabling with appropriate insulation is required, making routing more difficult and increasing weight. This approach also requires duplication of the AC front-ends, which are more expensive, heavier and dissipate more heat than the DC-DC converters used in the other architectures.

Distributed AC Power in LED Video Wall Application

Figure 1 – Distributed AC Power Solution

 

24 V DC Distributed Bus

By moving to DC power distribution, power designers can eliminate the heavy cables required for AC power. The power system in each panel is also simplified as no AC-DC conversion is required, and this approach also cuts the size and weight of each panel. Eliminating AC-DC conversion reduces the wasted heat on the panels, increasing LED lifetime and reducing the chance of hot-spots causing inconsistent illumination.

The power required by video walls, however, is considerable. Using a 24 V bus to distribute power requires large conductors and inevitably there are significant distribution losses due to the large currents flowing.

 24 V bus in LED Video Wall Application

Figure 2: 24 V Distributed Bus

 

48 V Distributed Bus

With the emergence of high-efficiency power components that can convert from 48 V direct to the voltages required by the LED drivers, power designers are able to move from 24 V to 48 V DC distribution. This retains all the benefits of using a 24 V DC bus and cuts the distribution losses by a factor of four. For many video wall systems this represents an ideal solution.

48 V bus in LED Video Wall Application

Figure 3: 48 V Distributed Bus

 

380 V Distributed Bus

In the largest video walls, which require very high power levels, the distribution losses at even 48 V can become significant. For these applications using a 380 V High Voltage DC (HVDC) bus is the ideal solution. This approach cuts losses in the cabling by 99.6% compared with a 24 V solution, whilst retaining the benefits of DC distribution. To maximize reliability some systems will deploy redundant HVDC busses, something that is possible because the high voltage reduces the current following, allowing much smaller conductor cross-sections.

380 V HVDC Bus in LED Video Wall Application

Figure 4: 380 V HVDC Bus

As with many applications that are required to distribute power in a large system, video wall manufacturers are moving away from AC for power distribution. Modern power components allow the conversion from 48 V in a single stage, which is ideal for many leading-edge video displays. The largest systems are moving to higher voltages, typically 380 V, using the latest power devices that enable efficient two-stage conversion in a compact, lightweight package.

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