Power Electronics

Digital Conversion Invigorates the Power Supply World

As we celebrate our heritage, we know that three decades ago seeds were planted for our industry to shift from deep-rooted linear technology to switch-mode solutions. It was an uphill battle. But, with ongoing advances in PWM controller ICs, coupled with MOSFET enhancements and improvements in packaging technologies, switch-mode power supplies (SMPS) were able to overcome hurdles and dominate the market at all power levels. The improvements in size, performance and cost continues unabated as SMPS devices continue to strengthen their hold on all fronts. Linears, however, have not been completely removed from the scene. Fortunately, they have found niche applications that continue to depend on their unique attributes.

Now, 30 years later, we are witnessing yet another shift. Power designers are exploring the benefits of digital power conversion. While digital revolution has pervaded many other markets, analog-dominated power supplies have been rather slow to tap the benefits of true digital power conversion. Nevertheless, this digital transition started some 10 or so years ago when designers began to exploit the benefits of microprocessors for supervisory and management roles. While true conversion was analog, power management was accomplished using microprocessors. And with the advent of distributed power and intermediate bus architectures (DPAs and IBAs) with associated point-of-load (POL) converters, the role of digital power management has greatly expanded as the benefits have become obvious.

In the interim, true digital power controllers have continued to evolve since the late 1990s in the form of DSPs, ASICs and state machines. Today, they are at a crucial point in time where hardware, software and design tools have all come together to drive digital controllers onto the same power supply turf, where only a few years ago, at a panel session at APEC, they were chided as unnecessary and too expensive to compete with analog solutions. In fact, such debates still linger on.

From that standpoint, this year marks a milestone in the evolution of digital power conversion. Besides several cost-effective CMOS digital power controllers from a variety of sources that have entered the market, key power supply makers have also unveiled prototypes — both isolated and nonisolated — based on digital power conversion technology with production commencing next year. While a few have adopted the alliance-driven power management bus (PMBus), whose specs were released for the first time this year, others have taken the I2C route or implemented a proprietary communications bus. And the road map of these vendors raises the hope for digital technology in the analog-dominated power supply world. This list of power supply vendors and module makers is expected to grow as many more join the fray next year. On the semiconductor side, the list of suppliers of digital power controller ICs comprises both well-known names as well as innovative startups.

Interestingly, high-level design tools demonstrated at this year's Power Electronics Technology conference and exhibition in Baltimore dispels the fear of programming that haunts many seasoned power supply designers.

The high-level GUI offered by these tools eliminates the need for programming and simplifies power supply design, the two major impediments besides cost. The development time has been cut drastically and the efficiency seems to be comparable. Plus, it opens the communications line between the host CPU and the power supply, allowing software to configure the power supply on the fly without changing hardware. Furthermore, it also treats power supply as a system-level functionality.

With that change in the landscape, digital power is now expected to progress very rapidly. In fact, some optimistic marketing analysts predict a promising bright future for this upcoming technology. The rate at which true digital power conversion is progressing, analysts who follow this field closely predict that digital power converters will go head-to-head with analog-based solutions by the end of this decade. Eventually, digital power conversion will reign just as switching technologies have gained dominance in the marketplace over the years.

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