No Easy RX for Managing Risk in Power Design

April 1, 2007
Engineers are frequently characterized as conservative, risk-averse individuals. However, a more realistic assessment may be that engineers are risk managers

Engineers are frequently characterized as conservative, risk-averse individuals. However, a more realistic assessment may be that engineers are risk managers who continually have to weigh the potential benefits of their engineering decisions against their potential liabilities.

For example, a new technology may promise better performance when adopted in a new product design. But then there's the risk that there will be unexpected complications in the design or manufacture of products using the technology. Or, if the technology comes from a new component supplier without a proven track record, there's the risk that the source may not be able to ensure delivery of its parts.

Focusing on medical power supplies in three articles, this issue of Power Electronics Technology addresses some of the risks inherent in designing and specifying medical power supplies. For instance, the cover story examines how the concept of risk management is being introduced into the medical equipment approvals process through changes in standards such as IEC 60601-1.

In “Evolving Standards Reshape Medical Power Supplies,” Peter Resca of Astrodyne writes that the “new standards will change the method of approving medical equipment from simple parameter testing to an involved collaboration of risk declaration and the methods applied to minimize those risks.” As the author explains, the goal in risk management is “to guide the development engineer through a process that ensures hazards are identified and mitigated.”

Meanwhile, in this month's Executive Viewpoint, Kevin Parmenter of Fairchild Semiconductor discusses another form of risk management — that encountered in specifying power supplies for medical equipment applications. As Parmenter illustrates with the tale of one customer's bad experience, not all medical power supplies are created equal. Simply having documentation that a supply meets certain medical device standards by no means guarantees the power supply's reliability. If the customer fails to perform due diligence in qualifying a power supply for use in an application, that customer risks not only the success of the product, but also quite possibly the life of a patient.

A third medical-related item, Spotlight on Medical Power Supplies, presents a roundup of new products that illustrate the performance levels being achieved in the latest crop of medical-grade supplies. As with their commercial-grade counterparts, medical supplies are achieving high levels of power density, efficiency and configurability, and even novel features such as ultracapacitor-based power back up.

Though this Spotlight doesn't specifically address design risk, even here the issue is implicit. For example, external power supplies included in this feature may offer compliance with Energy Star energy-efficiency guidelines or RoHS. Equipment designers evaluating a power supply must make the determination whether such compliance is demanded in their designs. And if not mandatory now, will such compliance be required in the future? If designers forego compliance today, will they pay double for it later when forced to repeat product development or qualification?

Then, too, there's the implied risk of selecting power supplies that promise leading-edge performance or heretofore-untried features. Ultimately, the customer will need to determine whether a power supply's promise of high performance is real or a matter of specsmanship. If it's the latter, then performance in the application may be compromised. And while the vendors whose power supplies appear in the Spotlight have established reputations, it's still incumbent on the medical equipment designer to verify the vendor's credentials and the reliability of its products.

Because of the critical role they play in supporting human health, medical power supplies present rather obvious examples of risk management. But risk, which pervades all engineering tasks, may be a growing factor in power-system design given the pressures designers face to achieve greater performance and functionality in so many power-supply applications.

In response to these pressures, there are now a wide array of new power-technology options available, including circuit topologies, digital control techniques, compound semiconductors and device packages. But, how do you gauge when a new technology is ready or when it's just too risky? Or is the greater risk that you may lose your competitive edge by not trying new technologies?

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