In a paper presented at the recent PCIM China conference, Ericsson Power Modules analyzed digital versus analog control techniques in board-mounted power converters, concluding that digital control enabled efficiency gains as well as higher current and power density. In “Digital Control Techniques Enabling Power Density Improvements and Power Management Capabilities,” performance of Ericsson’s PMH8918L 18-A analog-controlled point-of-load converter (POL) was compared with two digitally controlled designs.
One of the digitally controlled designs was a size-optimized, 20-A POL and the other was a 40-A POL module that was slightly smaller than the PMH8918L. The controller IC used in both digital designs was Zilker Labs’ ZL2005 stepdown dc-dc controller with power management.
The paper pays special attention to efficiency comparisons and concludes that “at the same current level, the efficiency of the digital designs is higher than that of the analog version. Efficiency improvements in excess of 1% are possible.”
The paper also states that “the digital designs exhibit drastically improved current and power densities when compared to the analog POL regulator.” The improvements in current and power densities range from 289% to 330%.
Overall, the electrical performance of the digitally controlled POLs was deemed as being “equal to or better than the analog version.” One caveat, however, was pointed out with respect to the 40-A digital POL. The paper noted that “with the increased integration of the 40-A digital design, the packaging limitation becomes heat removal rather than component area.”