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Power Electronics Through the Looking Glass 2015

News
Lewis Carroll's "˜Alice' had a magic potion to grow smaller. While power electronics makers can't follow that formula, they still find that cutting size and boosting efficiency are winning strategies. Mark Andrews explains why.
Fiction writers have it easy. Need a solution? Imagination to the rescue. While imagination can enable innovation, designers and manufacturers still must deliver in the real world.  As recent trends in power electronics demonstrate, what worked before is still very much in demand.

 

Less Drain, More Gain

The recent APEC event in Charlotte, North Carolina (USA) saw many new product introductions. Some of the most notable shared a "˜more efficient solutions' common theme. But as no surprise, incumbent silicon technologies are not giving ground easily to gallium nitride insurgents.

Attacking the problem of always-on "˜vampire' current drains was Texas Instruments' new "˜zero standby' power controller chipset it claims to deliver the lowest standby power consumption in supplies up to 75W. Their new UCC28730 and 24650 tackle poor transient response performance while maintaining low standby power. Products utilizing fewer components and smaller capacitors are aligning with designers' intent to reduce power drains while a device is nominally considered "˜off.'

Also fighting the size / efficiency battle was a new inductor from Sumida Group in which a magnetic material forms the package around all inductor components. This change-about design paradigm allows for very low DC resistance and up to 96% efficiency, the company says. Sumida's new SPM1004/1005 series comes in a variety of output ranges in a smaller package that also runs 10 degrees cooler that competing solutions.

At Infineon Technologies AG, the company announced a new OptiMos 25V and 30V product family designed to further integrate the power stage with energy efficiency improvements of around 1 percent "“ One percent doesn't sound huge until one considers Infineon's previous solutions were 95 percent efficient in server voltage regulator applications. Every point counts.

NXP Semiconductors NV touted its new "˜GreenChip' power platform, TEA1916/1995, targeting PC, gaming, notebook adapters and large panel TVs. High efficiency was again the fame claim along with what the company described as easier design-in thanks to its novel cycle-by-cycle architecture.

 

The Wider View of Getting Small

Design advances made possible with silicon technologies are striving to keep and advance their role in power management. But they're not alone. Gallium nitride's (GaN) voice is getting louder.

While GaN advocates have long touted its small form factor benefits, faster switching, greater efficiency and higher power density, new products are emerging. The pace is slower compared to silicon, but this is typical for new technologies. If you're experienced enough to remember digital calculators that cost $1,200.00 it's easy to imagine GaN devices costing half or less than what they do today in the not-too-distant future. As more companies channel energies into GaN its potential will be more fully realized.

Google and the IEEE announced their "˜Little Box Challenge' last year to build a much smaller power inverter. The folks at Efficient Power Conversion (EPC) announced support with eGaN FETs for competitors.

Design teams interested in the $1M prize for a fits-in-your-pocket inverter are already stepping-up. One mechanical engineer in January offered a shift in design paradigm. Instead of using a string of smaller DC devices wired in series to fluctuate all-on/all-off to reach a peak voltage higher than a utility's AC voltage and then match it's sine wave pattern, the new entrant uses a series of transistors and microprocessors (among other COTS components,) to switch voltage rapidly, achieving a blended level and wave form to match the utility's.

This new inverter approach varies the number of devices connected at one time so the output from DC devices varies in sync with the grid. The proposal utilizes more transistors and relies on a microprocessor compared to existing solutions. But it offers the advantage of not having to fit batteries or solar panel banks in multiple sizes depending upon the application, thereby reducing the "˜shelf cost' of replacement parts while simplifying installation and avoiding wiring mix-ups that happen in the real world all the time.

A Different GaN Perspective     

While some gallium nitride advocates see its potential as a silicon replacement, a pioneer in that field, Alex Lidow, is focusing more on creating new markets as a long-range goal. Lidow co-invented a silicon mainstay: the metal oxide semiconductor field-effect transistor better know simply as MOSFET. He says even after that 1970s feat, he believed there was a "˜better way' to make a transistor and he has been working on alternatives through the ensuing years. While MOSFET underwrote his early successes, Lidow says he has found in GaN something that will ultimately be highly successful in ways silicon can't. He sees a time where each technology will play a role in systems that could make the most of silicon in memory, and mixtures of other technologies will flow into places where power density, faster switching and other benefits are needed most.

Lidow's Efficient Power Conversion (EPC) company expects to sell millions of GaN transistors this year besides the ones they're tossing into the Little Box Challenge. He believes GaN's ultimate future will evolve as short-term limitations are overcome and its capabilities are embraced by designers approaching it like a choice among many to solve vexing challenges.

A Smarter Grid

Power electronic devices are getting "˜smarter,' smaller and more efficient. While many of these innovations fit in your pocket, sit on a roof or in a driveway, they're all tiny compared to large-scale power generation and distribution"”the grid. Yet this commonality of contemporary society is poised to also change. Smart grid sensors and related technologies are going to rapidly expand, said lead researcher Fizza Arshad in a March IHS Inc. report. IHS is forecasting the market will increase nearly ten-fold between 2014 and 2021.

Today's smart grid market growth centers mostly in North America where there is a mix of large installations along with many smaller pilot projects. In 2014 the researchers saw a shift as more large-scale projects moved from talking-about-it stages to implementation. Growth will also become more widespread globally as systems prove their merit, they believe.

"Generally, installation of smart grid devices helps to reduce cost for utilities whether this is for applications like fault detection, renewable (energy) integration, power quality or asset management," Ms. Arshad said in an email interview. "These cost savings will show up on the consumer side as well, whether in the form of lower taxes or slower rate hikes, or feed-in tariffs for renewable energy."

While Ms. Arshad recognises some consumers worry that "˜smart grid' could be employed to charge more for peak power or other woes in an interconnected world, he and IHS expect benefits to outweigh risks. IHS sees the technology as also a potential boon to renewable energy markets when individual or community-based systems can feed power into the grid more seamlessly. Smart grid also provides better load balancing and could enable quicker outage repairs.

 

Taking "˜Smart Grid' Local             

As utilities grapple with how to handle the influx of renewable energy into their grids, owners of PV-based systems and other renewable energy sources are seeing more options for better performance and ways to feed power into utilities. 

PEW talked in March with Enphase Energy's Ilen Zaxueta Hall, Director of Product Management for Residential technology in the United States. Enphase announced a new system-level approach involving a number of new products built around the idea that PV-based systems need pathways to evolve and deliver optimal benefits for owners and their communities.

"Most solar power systems today are isolated. But clearly we're moving toward an integrated energy model in which passive or "˜dumb' systems aren't sustainable. Right now solar is a blip in a much bigger system. But that is changing quickly. We need to move from platforms that are static and inflexible to those that are networked, active, intelligent and adaptable," she said.

Ms. Hall described new Enphase products that offer a combination of benefits utilizing microprocessor based approaches to add intelligence and connectivity for communications with the local grid or better system management without grid connections. Thanks to quality component manufacturing and cloud-based analytical software, what used to be island-like systems can to an extent improve themselves as well as contribute to utility grids where such connections are allowed.

According to Enphase, the future of solar will depend as much on how well a system can manage itself based on owner preferences as it does on the ability to integrate with public utilities.

Other new Enphase products include the S-Series Microinverter and the Enphase AC battery that allows for simple modular upgrades. Weighing in at 18 Kg, each battery unit is designed for one-person handling and installation. The system will work with existing utility infrastructure and can adapt as more utilities add smart grid functionality. According to Ms. Hall the system's ability to evolve with changing needs and circumstances is its greatest asset and a reason why the company believes it will pay benefits beyond greater efficiency and dependability.

"Imagine how a family's needs change if they have a baby, or someone starts working from home that didn't do so before. Today's average PV system can't adapt or be scalable very easily because it wasn't built to adapt. Our approach changes that," she added.

 

Different, Yet Connected

Whether looking back or looking ahead there are common threads across power management and the electronic devices at its core. Technology we use in-home, for business and everywhere else is changing rapidly. While some manufacturers are focused on improving quality and versatility through silicon innovation, others are looking to new materials including gallium nitride. But whether it's the computer in your pocket, rooftop energy, a vehicle or even grid-level utilities they all share many of the same approaches to performance enhancement:

1) Technology is getting "˜smarter.' Programmable / adaptable microprocessors are enabling better performance. With IOT connectivity, devices that once functioned as islands are poised to interact, changing basic premises about how we communicate with our devices and they with us;

2) How energy is generated, stored and utilized is becoming more central to whether technology is judged useful. Reducing size and weight while enhancing functionality will continue to take center stage. Products that can do all of these at once will be clear winners;

3) GaN is playing a larger role in the marketplace. Choosing the "˜right' technology is not an either/or gambit. More solutions will emerge that place GaN in modules with silicon and other semiconductor technologies in ways that are not yet practical today. 

 


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