We have all heard that in order to sell a new power control or converter circuit, one needs a well-designed graphical user interface, commonly called a GUI. So, what has happened to the old Bode plots, loop stability calculations and the Venable instruments with their gain frequency displays of loop gain and phase shift versus frequency. Have the designers gone soft on us and lost their ability to design without the proper software?
While I nostalgically reminisce about the old times, I don’t miss the days when I practically wore out several slide rules, punched innumerable buttons on the red LED HP calculator, and modeled dc, ac and transient circuits using the slow GE Teletype circuit analysis programs.
Designing a power supply in those days required hard work. There were no ready-made ICs, and one had to design saw-tooth generators, one-shots, stable reference voltage circuits and differential amplifiers with discrete transistors, resistors, inductors and capacitors.
Computers changed all of this. Any designer worth his salt has been using the available circuit analysis and modeling programs like SPICE and a plethora of other acronyms for years.
The history of the GUI goes back to Doug Engelbart and his team at Stanford Research Institute, who used text-based hyperlinks manipulated by a mouse. The concept of hyperlinks was further refined and extended to graphics by researchers at Xerox PARC, who used a GUI as the primary interface for the Xerox Alto computer. The GUIs familiar to most people today are the Macintosh, X Window System or Windows interfaces.
While such GUIs have become ubiquitous for the general population, power-supply designers have — until recently — shied away from such programs when designing power supplies. It seemed that analog design and a digital GUI were like oil and water, and did not mix. But the shift to digital power conversion, and particularly digital control, was the catalyst that allowed the GUI’s acceptance by the power-supply engineering community.
Today, one just has to look at any of the power semiconductor companies’ websites to find a GUI program that allows you to design, debug and simulate a circuit. We’ve gone from laboriously manipulating a slide rule to easily sliding a mouse across a mouse pad.
In the figure, you’ll see one of the many GUI interfaces for point-of-load power converters (POLs). This screen shot shows the GUI’s capabilities for adjusting the circuit poles and zeros, while at the same time looking at the Bode plots of the converter and the surrounding circuitry. Additional screens in the same program (and which may be found in other vendors’ programs) provide you with the capabilities of adjusting the output currents, voltages, margining, alerts, and sequencing turn-on and turn-off of each POL in the system.
So, the question is, is the GUI a crutch or an aid?
I would argue that it is neither. It is another very useful tool in the power designer’s toolbox. It would be foolish to say that we should abandon the teaching and study of analog design. They are essential to understanding what’s displayed on the screen and how to manipulate parameters to get the optimum design. No matter what the display shows, you don’t have to believe it if it doesn’t make sense.
The ease of using a GUI not only speeds the design, but opens the door to many new designers, who can use a GUI to tailor standard devices to meet their particular needs. Xinwei Telecom, a large provider of SCDMA wireless services in China, used one vendor’s GUI to implement power conversion and power management in a complex base station control board.
Commenting on their experience, Xinwei’s chief scientist, Dr. Guanghan Xu, noted that using a GUI enabled Xinwei’s designers to configure a power system in less than 10 minutes, despite the board’s complex requirements, which included paralleled outputs, turn-on cascading, fault management and even on-the-fly reconfiguration. In this application, using a GUI to configure digitally controlled POLs saved weeks of design time versus what would have been required with analog power management.
With the pressure on designers to churn out designs faster, the debate over whether the GUI is a crutch or an aid definitely swings in the direction of being an aid. Not only does it allow designers to come up with quicker designs, it enables modeling, troubleshooting and testing for more optimized solutions.
I would be very interested in knowing what you think. Please feel free to e-mail me your comments at [email protected].