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EDN Europe's Editor Graham Prophet posts a selection of comments and insights prompted by the many items of industry news and rumour that cross the editorial desk or are gathered on his frequent travels to interviews, press conferences and events around Europe - and further afield - and somehow never find their way to the magazine or the web site, recovering some of the information otherwise lost in the noise level...

Thursday, November 22, 2007

Power and control, or, the politics of system architecture

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The Digital Power Forum that Darnell Group ran last week, for the first time in Europe, provided some clarification. Firstly, on what digital power actually means, and on how designers view it. As so often happens, no sooner has the term entered common use than it already means several different things. There is digital power in the sense that the core control loop in the regulator device – controlling output voltage and/or current – is digital, using an ADC to sample the output, and a (software-programmed) microcontroller or DSP core to maintain the setpoint. Then, there is digital power on the larger scale wherein power levels are monitored, reported and perhaps commanded, via a hierarchy of digital networking that reaches from the individual control loop up to the system level. Or, both of the above.
Part of the thinking appears to be that as the power devices available to us are now so good, the further gains in efficiency we can expect to realise purely by relying on better and better power switches (MOSFETs, IGBTs, or whatever) are pretty limited. So, we had better look elsewhere. When converters are running at full power, efficiencies are now high there as well: hence the recent focus on cutting losses when power supplies are running at low- or standby-levels.
However, according to several presentations at the Forum, notably one from National Semiconductor, the next significant gains to be made in power efficiency are at the system level. When you have a complete chain of digital monitoring and control from top to bottom of your system architecture, you can command and configure its power supplies to always run at optimum efficiency and you might gain margins that could reach tens of percent.
My reaction to this is, who is going to do this system-level thinking? Are we going to persuade the system architects to pay attention to such mundane considerations at the same time they are working out data paths and processing resources? Or is the guy who actually designs the power supplies gong to get the authority to place control code in the upper layers of the system? In fact, is the power supply going to get designed at some stage earlier than the last minute, as it always has been?
I fear there is a mismatch with the structure of most design teams that will delay the time we reap the power-demand margins that this aspect of digital power promises. Or am I out of date on this one, is there a cadre of system-level-power-architects already in place out there? The other possible mismatch I can envisage is that we are looking at a context in which power supplies are conceived as a sophisticated and interactive system element, while their procurement remains with the purchasing department that regards them as a price-led commodity – but maybe that is too gloomy a view? What do you think?

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