Power Electronics

How Will New Design Tools Affect Analog and Digital Designers?

OF ALL THE DISCUSSIONS I had at the recent APEC, the one that stands out was an interview with Jim Templeton of Maxim, who described the company's new InTune™ system that we covered in our April issue. It's interesting how this developed from an IEEE paper.

The basis for the InTune patents was a paper in the IEEE Transactions on Power Electronics, Vol. 22, No. 6, November 2007, titled “Limit-Cycle Oscillations Based Auto-Tuning System for Digitally Controlled DC-DC Power Supplies,” by Zhenyu Zhao, Student Member, IEEE, and Aleksandar Prodic´, Member, IEEE.

This paper introduces a new method and system for parameter extraction and automated controller adjustment, suitable for low power digitally controlled dc-dc switch-mode power supplies (SMPS). The system allows closed-loop calibration throughout regular converter operation. During a short-lasting test phase, SMPS parameters, such as output capacitance and load, are estimated by examining the amplitude and frequency of intentionally introduced limit cycle oscillations in duty ratio control variable as well as from its steady state value. Accordingly, a digital compensator is automatically constructed to provide fast dynamic response and good output voltage regulation. In addition, the load estimation data are used for improving efficiency of a converter having segmented transistors. It is performed through a selection of driving sequence resulting in minimized sum of switching and conduction losses. The effectiveness of the system is demonstrated on an experimental 400 kHz, 9 V-to-3.3 V, 10 W, digitally controlled synchronous buck converter.

This is one example of how a technical paper can turn into a new opportunity. The patent applications were applied for in April 2008. Then, the patents were issued in September and November 2009. After that, Maxim purchased the patent rights and started developing the necessary circuits.

Now, we expect data sheet details in July 2011, which should provide additional guidance on how this works. If it works as advertised, it will automate power supply design. An obvious question is how this will impact present power supply designers.

As long as we're talking about automation, there is another interesting IC that was announced at APEC. It is the Analog Devices' ADP1047, a digital power factor correction (PFC) controller with accurate ac power metering. The IC provides accurate, RMS measurement of input voltage, current and power. This information can be reported to the secondary of the power supply via its PMBus interface. A unique aspect of this device is the ability to program the device via easy-to-use graphical user interface (GUI). Using a computer, the designer can set up the operating parameters without even realizing it was actually being programmed. An internal 8 kB EEPROM stores all the programmed values and allows standalone control without a microcontroller. Here, the designer can automate the PFC's operating parameters. Can this design technique be applied to other ICs?

I wonder if these two examples are an indicator that the industry is going to eliminate design features that are now performed manually, or by calculations that require a knowledge of analog principles. Does that mean that digital designers will soon be able to design the entire system?

I doubt if digital folks will soon take over all the tasks that were formerly in the analog domain. One area that will be foreign to the digital designers is the power output stage, which is now changing with the availability of GaN and SiC power MOSFETs. The key word here is “power,” that is, until it is completely digitized.

We welcome these new design tools and hope to see more to aid designers. Will these automation concepts make the analog designer's job easier, or will it allow digital designers to take over a portion of power electronics design? Perhaps it will help manufacturers get along with fewer analog designers, who are said to be in short supply.

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