Power Electronics

GUIs: A Sticky Issue in Digital Power Design

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If you attended the recent Applied Power Electronics Conference (APEC) in Dallas, you couldn't help but notice that digital power continues to be a hot topic of discussion. It came up many times in the various technical sessions. And though there were few new digital power controllers or modules introduced at APEC, vendors with previously introduced digital power products used the occasion to demonstrate their operation.

I witnessed a few demonstrations of digitally controlled point-of-load converters (POLs). In these demos, the POLs were programmed using a graphical user interface (GUI). Like the products they were designed to work with, these GUIs varied from vendor to vendor. But despite their differences, the point of each demonstration was the same: Look how easy it is to program the POL! No power design expertise is required to produce a working design. Nor do users need to have digital programming skills.

Ease of use has always been the goal in developing power conversion ICs and modules. However, ease of use takes on added importance when the components employ digital control.

In general, new technologies need to be easy to use or they won't be readily adopted. But with digital power controllers, ease of use is one reason cited for their adoption. After all, it should be easier and quicker to change POL settings like output voltage with a software change instead of a hardware change like swapping resistors on a pc board. Also, the ability to configure a digital power controller using a GUI is considered a great way to make a controller-based design (or POL module) more accessible to system designers who are not power experts.

But when it comes to creating development tools for their digital power controllers, IC suppliers have the added challenge of satisfying expert power-supply designers, who have more complex needs and other ideas about ease of use. For example, the expert designer must be able to adjust the response of the control loop by setting poles and zeros. At the same time, the expert needs accurate models of the controllers that can be used to simulate power system performance.

One ease-of-use factor for expert designers is whether they can fully leverage their analog design experience when using digital control. Comments to this effect could be heard during the APEC rap session, “Is There Money In Digital Power?” During this session, power-supply designers listened as representatives of IC companies discussed digital power technology and its expected impact on the power-supply and IC businesses. Then, when it was their turn to speak, more than one member of the audience asked whether the migration from analog to digital power control would mean they now had to understand Z transforms to design power supplies.

Some members of the panel were quick to point out that their products did not require knowledge of Z transforms. Designers could continue to work in the S domain and the IC vendor's design tools would translate from S to Z domains. For example, in the GUIs provided, users could change settings for poles and zeros to modify feedback loop compensation, and then simulate transient response.

The Z transforms discussion underscores the apprehension in the power-supply design community about the transition from analog to digital control. Clearly, semiconductor vendors understand that hardware and software design tools will be critical in addressing the concerns of power-supply designers. More than one speaker in the APEC rap session noted the need for an easy-to-use GUI to foster adoption of digital power control.

So, are the currently available GUIs and other development tools sufficiently refined for expert and nonexpert designers alike? The IC vendors themselves express different opinions on this matter. Some say their own tools do provide the required functionality and usability, while others seem to regard their tools as more of a “work in progress.” How do you feel about the digital power development tools you've tried so far? Share your experiences with me at [email protected].

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