Power Electronics
APEC 2003 Charts New Course for Power Electronics

APEC 2003 Charts New Course for Power Electronics

Last week’s Applied Power Electronics Conference (APEC) and Exposition, in Miami Beach, Fla., kicked off with interesting plenary talks by experts that sparked new interest in power electronics. While Rap sessions provided fodder for thoughts on the use of programmable digital signal processors (DSPs) in power conversion and control, integration of semiconductor components in switching power supplies, and migration toward sixteenth brick and single-in-line package (SIP) solutions. Technical sessions spread across three and a half days unveiled newer topologies, architectures, and materials for a new generation of power supplies needed for myriad applications. And key vendors launched new products in the exhibition hall to raise the performance bar of eighth brick dc-dc converters to yet a higher level.

In preparing the attendees to challenges ahead posed by emerging multi-GHz microprocessors, International Rectifier’s CEO Alex Lidow presented a brief overview of innovations needed to overcome these hurdles. Lidow's paper focused on advances required in power semiconductors and packaging, controller architectures, and integrated solutions to cope with the stringent requirements of upcoming processors. “To supply 200 A worth of electricity at 0.6 V regulated to within 5-10 mV and slewing at 100 A/microsecond requires major changes in the architecture and componentry we use in power supplies that deliver energy,” stated Lidow. Toward that goal, the paper highlighted power silicon roadmap for control and sync FETs, evolution of power packages like DirectFET, and the creation of novel scalable architecture, the XPhase. The XPhase is a more flexible architecture crafted to overcome the drawbacks of existing multiphase solutions. In fact, IR's XPhase moves multiphase to the next level of design simplicity, scalability, and performance.

By combining advances in each of these individual technologies into one integrated solution, such as iPOWIR, the impact on next generation dc-dc performance can be truly revolutionary, asserted Lidow. Further improvements in iPOWIR integration promise to deliver higher power densities at frequencies as high as 2 MHz, while providing the benefits of innovations into functional building blocks (Fig.1).


Fig.1. Power loss versus frequency for discrete and integrated solutions.

Taking such advancements into account, the paper concluded that the system metric such as cost/amp, full-load efficiency, and current densities are expected to exceed today's benchmarks even under extreme future requirements of multi-MHz, 150 A and sub 1 V operation. Speaking of integrated packaging, researcher J.D van Wyk of Center for Power Electronics System (CPES) at Virginia Polytechnic Institute and State University hinted system level integration in a package as the emerging trend. In his talk in the plenary session, van Wyk described the development of a planar integration technology that involves building of dielectric/metallization thin-film interconnection directly on co-planar bare power chips embedded in a ceramic carrier (Fig.2).


Fig.2. Structural schematic of Embedded Power Module.

Implementing the new methodology, the researcher disclosed a 1 kW half-bridge switching module with built-in gate drivers. Electrical testing and simulation indicate that the developed module has demonstrated good electrical and thermal performance.

Other papers of interest in the plenary session came from Celestica Inc., National Semiconductor, and J-N-J Miller Design Services. Celestica's Mahmoud P. Sayani, now a consultant with SiMurg Technologies based in Markham, Ontario, Canada, explored trends in packaging and board mounted dc-dc converters, as well as identified key barriers to driving these trends. Based on previous developments and introductions, Sayani's paper speculated the introduction of a sixteenth brick delivering 35-50W by 2005-2007 (Fig.3).


Fig.3. Timeline of standard dc-dc package introductions.

However, he cautioned the need for such a package remains to be seen, as pin-out and dimensions of such a format has to be resolved by the industry. National’s vice president Ed Lam investigated the ever changing distributed power architectures, integrated PWM circuitry and the new distributed power topologies dictated by the rising power demands and increasing number of supply voltages in modern communications and computing systems. This paper discloses two new emerging cascaded converter topologies, the buck-follower and buck-fed, and a new high-voltage cascaded buck-fed PWM controller. In addition, the company has developed a new family of high voltage analog bipolar-CMOS-DMOS (ABCD) technologies with sufficient breakdown for 48V power systems. Together, National's solution is aimed at achieving multiple low-voltage and high output currents from a 48 V input with performance that is unprecedented. In essence, to overcome new challenges, Lam's paper emphasized the need to combine advances in high voltage technology with innovative ICs, improvement in planar magnetics, high performance MOSFETs, and smaller foot-print thermal packaging.

The interest in digital control and use of DSPs in power supply designs was evident from the large number of papers presented this year. To gauge interest in this area, a Rap session (No. 1) titled "Power Supply Digital Control- Real or Virtual" was organized by Arnold N. Alderman, president of Anagenesis. Panelists included Robert Corbet of Systel, Larry Woffard of Texas Instruments, Karl Rinne of Univeristy of Cork, Ireland, Mark Jacobs of Tyco Electronics, and Tom Duffy of Primarion. While TI's Woffard and researcher Rinne were optimistic about the role of DSPs in power supply designs, members from Systel and Tyco questioned the feasibility of using digital control in price sensitive power supply designs. In fact, majority of members in the audience were skeptical whether DSPs will be able to deliver high performance at low cost. However, Primarion's Duffy, a panelist demonstrated a digital multiphase controller that the company has readied for multiphase solution, competing head-on with analog solutions.

To show the designers that DSP based power solutions are here, TI was showcasing a digital power supply developer's kit in its booth. This kit, a complete hardware and software development environment, comprises a 750 W rectifier module with 48 V output, two DSP controller plug-in cards, Code Composer studio version 2.12, and JTAG emulator. A user's guide and an EZ start-up guide are also included with the kit. But, it comes at a cost. The price tag for this kit is $3,995.

Several papers spread across a number of technical sessions were a clear indication that digital control and DSPs are making progress on this front. Integrated magnetics and passives were also the focus in many sessions, as novel power conversion topologies and scalable multiphase converters received attention amongst power supply designers. While suppliers were exploring newer processes and structures for improving power semiconductor performance, solutions based on newer material like Silicon Carbide (SiC) were compared with the traditional approaches. Clever simulation techniques were explored, and thermal issues were examined.

APEC also provided the backdrop for Datel’s first nonisolated dc-dc product in an eighth brick form factor. Datel unveiled the non-isolated LEN series. “Considering that APEC Rap session on Bricks Versus SIPs lamented the lack of standardized non-isolated products, we couldn't get more timely with our announcement,” stated Robert E. Leonard Jr., marketing manager at Datel Inc. On the heels of this announcement came Artesyn Technologies’ latest generation isolated converter in the eighth brick format with 40A at 1.8V output. However, this output is at room temperature, and gets derated at higher temperture. Two dual-output quarter bricks with up to 20A per channel at 90% efficiency were also part of Artesyn's release at the show.

Meanwhile, Sweden’s Ericsson Power Modules continues to expand its eighth brick dc-dc PKB series, launched last fall, with higher output current at 1.5V and 1.2V outputs. By the month end, the maker intends to unveil an eighth brick member with 30A output current at 1.2V output voltage, in addition to a 28A unit at 1.5V. Another eighth brick player at the show was Ascom Energy Systems. Ascom launched Xena 50 dc-dc converter in an 1/8 foot-print with 1/4 brick pin-out. Xena 50 is designed to deliver 30A at 1.5V output voltage.

APEC 2003 has set the stage for new ideas and technologies to meet the challenges ahead, moving power electronics to a higher platform.

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