Digital Power at APEC

March 06, 2007 by Jeff Shepard

It is no surprise that digital power electronics was a ‘hot’ topic at this year’s IEEE Applied Power Electronics Conference (APEC). APEC literally started and ended with digital power. The first session on day one was titled "Digital Control Applications." The last paper of the final session of this year’s APEC was also focused on digital and was authored by a team of authors from Astec/Artesyn and Texas Instruments.

The growing number of "commercial" papers on digital power was an interesting development this year. In addition to several papers from Intel (covered in yesterday’s issue), digital power papers were presented by Advanced Power Electronics Corp., Archangel Systems, Inc., and joint papers by Asahi Kasei Microsystems teamed with Fuji Electric Advanced Technology and Astec/Artesyn with Texas Instruments.

Low-voltage power conversion was the goal of "A Digital Predictive On-Line Energy Optimization Scheme for DC-DC Converters" presented by a team from Asahi Kasei Microsystems and Fuji Electric Advanced Technology from Japan. This paper presented an unusual energy conservation technique that resizes the output stage transistors in real time based on predicting the load current in a dc-dc converter. The experimental prototype included a digitally-controlled 3.6V to 1.8V dc-dc converter with an integrated, segmented power stage IC operating at 4-MHz. Initially targeted for use in portable audio systems, performance was measured using Rock, Classical and Jazz music, with corresponding energy savings of 21.2%, 27.7% and 38.3%, respectively.

Two authors from Advanced Power Electronics (a power semiconductor maker in Taiwan) discussed "Digital Controller Design for a Practicing Power Electronics Engineer." The paper focused on a direct-digital compensator design method where digital compensation tools are analyzed in the analog frequency domain. It concludes with experimental verification using a buck converter design.

"Control of a Single-Phase PFC Preregulator using an 8-bit Microcontroller" was the focus of a paper co-authored by Archangel Systems (a U.S. defense contractor) and Auburn University. By using the on-board peripherals of a PIC16C782 microcontroller, a one-chip solution was achieved. The proposed power factor correction (PFC) preregulator achieved a power factor above 0.99 for load power in excess of 100W. "Because of the simplicity of the circuit, the proposed PFC preregulator has low cost and high reliability," according to the authors.

As noted above, the last paper of the final session of this year’s APEC, "Data Communications Issues for Power System Management," was authored by a team of from Astec/Artesyn and Texas Instruments. Beginning with a brief discussion of the evolution of digital power management starting in the early 1980s, the authors then reviewed the requirements for data communications to implement effective digital power management. The paper concluded with recommendations for data communications in power system management for on-board power systems within a single chassis, for inter-chassis communication and for facility or campus-level communication.