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New Electronics Roundtable: Industry looks to support engineers as they address power supply design

Embedded power supply design needs more industry support

While power supply design is becoming increasingly important, knowledge is leaving the industry. How are suppliers responding?

It may not be apparent in your office, but electronic engineers are getting older and the ones that are retiring are taking with them specific skills. Whether you call them 'grey hairs' or 'silverbacks', these are the people who know how to design with analogue components and how to design power supplies.

Their departure leaves a gap and, when it comes to embedded power, the industry is having to step up to support designers who now have the responsibility for power supply design, but may not be completely comfortable with the technology.

Looking to explore the topic, New Electronics convened a roundtable with representatives from leading power component developers.

An indication of the issues involved came from a survey carried out amongst New Electronics' readers. We found that 70% of engineers spend less than 20% of their time on power supply design and that a third of you have less time available than previously for this particular area. And when asked about your knowledge, 71% could only say 'fair'.

Patrick Le Fèvre, marketing and communication director for Ericsson Power Modules, said: "We've had to offer more support over the last 10 years because there are fewer pure power designers, except in larger companies."
Alastair Boyd, UK managing director for Linear Technology, added: "It's becoming harder to support all the different companies, so we're developing web based tools: helping designers to help themselves."

Carey Windeatt, sales and marketing project manager for TDK-Lambda UK, said: "We see companies with in house experts, who are early adopters, but there are also those with little or no in house knowledge – and it's these we're trying to help."

Le Fèvre pointed out that, while more and more designers are struggling with power, time to market pressure is increasing. "This are now crucial," he claimed. And complexity is also increasing. "If you look at some high end communications routers, they feature more than 60 power rails, which all need to be synchronised."

Boyd added: "Shorter design cycles also reflect the need for companies to be quicker to market with their products: the quicker they are, the more money they make and penalty costs are becoming more common when companies don't deliver on time."

Le Fèvre sees the decline in power knowledge as part of an industry transition from analogue to digital electronics. "But digital will never replace analogue completely," he observed.

"Engineers are familiar with digital design, so they're a bit lost when it comes to power," he continued. "They can deal with 1s and 0s – they're the 'iWhatever' generation and often wonder what an analogue function is."

Even though he believes this transition is in its early stages, he says designers need to learn new skills quickly and implement them. "And we need to provide tools which are easy to use and to reuse."

The problem, he believes is that power supply design isn't core for them. "They don't deal with power every day, so we need to remove complexity and we need to provide support."

But he says it's a two way street, particularly when it comes to dealing with a new generation of engineers. "Suppliers have to understand how designers are thinking, because the newer generation of designers speaks a different language. Whatever we do has to be easy to understand, easy to use and must plug into the digital chain."

Le Fèvre believes one of the solutions is to provide graphical tools. But such an interface must be suitable. "They should be intuitive, open and able to take care of the whole board. The tool should also provide information from a range of suppliers." And Ericsson's view is that such a tool should take advantage of the PMBus; an open power management protocol that supports communication with converters and other devices in a power system. "The PMBus is familiar to the 'iWhatever' community," he claimed. "It simplifies communication." But will the PMBus approach migrate to the industrial sector? "I'm not convinced," said Boyd. Windeatt's view? "PMBus isn't a standard and it doesn't guarantee a device will work in a system."

Boyd sees pressure on power supply designers coming from greater use of fpgas. "Core voltages could be as low as 0.85V ±3%," he noted, "with currents in excess of 20A. The supply has to be close to the fpga, it needs dc accuracy and it's not just about parasitics within the power supply; there are also board and layout issues."

Le Fèvre added: "An fpga requires different supply voltages and these must sequenced in the right way. Voltages must be guaranteed so there is no damage to the fpga. Using a GUI, values such as voltage, margins, rise time and delay, can be set and validated. If there is a new sequence required, it's only a matter of entering the new values."

Boyd added: "FPGAs are driving demands because of their technology. With lower voltages and more current; design isn't trivial. This is forcing them to enter into dialogue with power supply companies, because they want to offer reference designs and recommended solutions when they bring out their next generation product."

Le Fèvre agreed. "The fpga community hasn't been used to this way of working. Now, they have to make sure there's something available."

But designers need to remember that reference designs aren't a solution; they are there to make an fpga work under most conditions. So the solution needs to be optimised.

Windeatt picked up the knowledge theme. "We're often addressing those designers who claim power is 'not my job'. They're faced with a range of confusing solutions and their lack of expertise is compounded by greater complexity and limited design time."

So Windeatt believes the route to take is 'solutions, not products'. "It's still a relatively new concept, but designers can see the advantage." Yet he sees obstacles. "Industry is conservative and risk averse," he claimed.

As far as TDK-Lambda is concerned, it needs to provide the key elements of a board level power solution. "These are trusted products which make solutions to complex problems easier to implement. The products are designed by experts, whose mission is to optimise the design without the need for additional components or tools."

Even so, it's far from 'plug and play'. "Because factors such as loop stability and parasitic inductance mean a product can become unstable, designers can't 'cut and paste' to save time. This isn't easy, because even small changes can have large effects."

And Boyd pointed out that poor power supply design can have implications. "We're looking to support quality and reliability; we don't want designers to compromise when health and safety is involved."

Dealing with this requires clarity from suppliers, said Windeatt. "We all need to provide clear information, so the device does what the datasheet says it will."

Nevertheless, suppliers are striving to remove complexity. "We want to create as much of a 'black box' as we can," Windeatt continued. But he noted other issues. "How big, what shape, where is it? We're trying to engage at the early stage, particularly with more complex designs, to get them to take an architectural point of view, rather than a solution based approach."

Boyd asked: "What is meant by standardisation? Is it commoditisation, where who can make it cheaper wins? If that's the case, it's not standardisation."

Le Fèvre sees problems with a black box approach. "There are attempts to standardise and pressure from OEMs for commoditisation. But it can be hard to understand who is trying to standardise what and the market is too large and fragmented – ranging from battery chargers to fpga sequencers."

Boyd sees issues with such variables as high operating voltages and transients. "But thermal management issues are also becoming important. Designers used to take heat out through the board; now, it's being taken out on top, so component height is critical. Meanwhile, switching frequencies are higher, so there is a need for low profile magnetics and that brings emc issues."

"Lack of expertise is a problem. It's a challenge to capture knowledge and to put it into products. Because Linear offers discrete components, we have power supply design tools where customers can put in a spec, select products, deal with compensation and so on.

"But the sheer variety of applications – from driving an led upwards – means we need to offer hundreds of power supply components."

Linear has taken its power supply expertise and packaged it in the form of the µModule. Boyd said: "We're taking our power supply expertise and putting it into a 15 x 15mm package. This is a complete power supply for digital engineers, with a controller, filtering, magnetics and fets. There are more than 40 of these thermally efficient devices; don't need air flow or heat sinks. good for low profile and one of fastest growing areas for Linear.

Despite its crucial role in every product, power is often left to the last moment. Sometimes, it's a question of priorities; the fpga may well have to be developed before the power supply can be designed. Concluding, Boyd said: "Engineers leave power supply design to the last minute because they assume there's a solution."

Author
Graham Pitcher

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