Easing the Transition to Digital Control and Reaping the Benefits

Feb 22, 2008 11:44 AM

Power-system designers are continually challenged to maximize the performance of their designs by applying new circuit design techniques and components. But the promise of the “new” can be offset by the perceived risk of trying the “unfamiliar.” Such may be the case with digital power control, which holds great potential for improving power-supply performance, but demands that experienced analog designers venture into the less-familiar realm of digital design.

Power-supply compensation is one issue that may engender apprehension among engineers contemplating a switch to digital control. In “An Analog-Friendly Approach Simplifies Digital Compensation,” Chris Young describes the challenge faced by some power-system designers as they move from Type III analog compensation to a digital proportional-integral-derivative (PID) filter for the voltage-loop compensation.

“Designers who typically move poles and zeros to achieve compensation may struggle with relating these nonintuitive digital PID parameters to what they observe on Bode plots,” writes Young. He addresses this issue by presenting “an intuitive set of PID filter coefficients that enable designers to compensate a voltage-mode, digital PWM controller quickly using Bode Plot measurements or a simulation tool.”

Being able to relate digital-control parameters to the familiar analog parameters overcomes one hurdle to digital design. Engineers also need to understand how digital control can meet fundamental design goals.

In “Digital Power Control Improves Multiphase Performance,” Dave Freeman describes how digital controllers can implement phase management to optimize the power-converter efficiency over a range of operating conditions. As Freeman explains, “Digital control not only enables phase shedding, but also related techniques such as phase ordering.”

Applying these techniques takes digital control beyond analog emulation, giving designers new options for dealing with component tolerances and thermal effects. As performance targets for multiphase power converters become more challenging such benefits of digital control will only become more compelling.