Design Article
Power supply solutions for flat-screen TVs
Tim Kaske, Jean-Paul Louvel, ON Semiconductor
4/24/2012 10:02 AM EDT
High-performance flat-screen televisions that deliver outstanding viewing experiences are also changing the way engineers design their power supplies
With the advent of flat-screen televisions offering ultra-thin profiles, the TV set has become more important as an item of home decoration. At the same time, generally larger screen sizes and new technologies such as high-definition, progressive scan, 200Hz refresh and more recently 3D are contributing towards better viewing experiences. Add to the mix the arrival of smart TV supporting content and services from the Internet, and the TV is becoming a focal point of many people’s home lives.
It should be no surprise, then, that TV performance is coming under intense scrutiny, not only by consumer groups but also by legislators; large screens, high-performance electronics and increasing usage have implications for the average household energy consumption that run contrary to demands for lower worldwide carbon emissions.
More out, less in
New Energy Star standards for televisions place greater emphasis on lowering power consumption when the TV is operating, in addition to existing restrictions on standby power. There is now a maximum permissible power limit calculated in relation to screen size, with an absolute maximum of 80W for any TV with screen size 50 inches or larger.
Innovations being employed to help meet current and future power consumption standards include LED backlighting, which improves efficiency compared to CCFL backlights while also allowing thinner dimensions. There is currently a dramatic market shift toward LED backlighting that will see 10 times as many LED TVs built, compared to units with traditional CCFL backlights, by 2015. Figure 1 illustrates TV production trends, including the shift from CCFL to LED backlighting.
Figure 1: Forecasts show a significant shift from CCFL to LED backlighting
In addition, more efficient and simplified power supply designs are emerging. These not only reduce energy losses but can also offer a more cost-effective solution than first-generation LED-TV PSUs. Figure 2 shows an estimate of TV power consumption in North America taking into account the increase energy usage due to larger screen sizes and additional functionality. As you can see, the new Energy Star standards will reverse this growing trend. If the same approach toward power semiconductors, converter topologies and backlighting were used, our total energy consumption in 2014 would be twice that in 2008. With the improvements our estimated energy usage in 2014 will be almost 20 percent lower. Assuming that a 500 MW coal plant equates to 3 TWh per year of energy usage this represents a significant impact on our economy and environment.
Figure 2: Effects of predicted screen size and TV shipments on energy consumption
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