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POWER MONITOR: Price and performance ensure digital-power domination

The recent introduction of a new series of 8-bit flash microcontrollers, within ST Microelectronics’ ST7Lite family, highlights the fact that digital-power ICs are beginning to reach price parity with analog alternatives. The ST7Lite is a natural fit for use as the processor in a digital-power-controlloop: ST says it designed the device specifically for simpler appliances, sensors and motor control.It has a 12-bit timer that its designershave structured for use in applicationssuch as lighting. The ST7LITE49M isavailable now, in SDIP (samples) andLQFP32 (volume) packages, priced at$0.78 (10,000). This confirms a trendtoward price parity for digital-powersolutions compared with today’s mainstreamanalogue controller ICs.

Darnell Group has determined that digital-power-controller ICs will reach pricing parity with existing analogue devices in 2008. It based this prediction on an analysis of the pricing of about 250 digital and analogue powersupply- controller ICs between January 2004 and June 2007: in a little over three years, average prices for digitalpower ICs have dropped from about $6 to under $3. Several digital-power ICs are already available for less than $1, as seen in the recent announcement by ST. Average prices for digital controller ICs will continue to drop and we predict they will fall below $2 in thefirst half of 2008.

While price parity is an important factor in the growing interest in digital power, superior performance will ensure digital power’s domination. Superior performance of digital control compared to analogue will be a key focus of the upcoming Digital Power Europe Conference (http://dpfeurope.darnell. com). For example, papers that Ericsson Power Modules and Texas Instruments will be presenting will be among those highlighting the performance benefitsthat digital-power techniques enable.

Ericsson’s paper will present a case study of energy management and digital control in a MicroTCA power system. This technical case study will demonstrate that users anticipate that digital power solutions will not only achieve the right tolerance and performance levels, but also improve design integration and meet power-density expectations. The authors will also show how one can find synergies, and improve performance even further, by allowing IPMI-based management components in the system to interact directly with power-conversion elements via a serial bus. System-level components can use such a serial bus to undertake “active” energy management to improve efficiency, and also to collect data ontemperature, voltage and current.

Authors from Texas Instruments will introduce a strategy embodied in a digital controller to optimise powerconverter efficiency. Power efficiency in a dc/dc buck converter with multiplephase operation maintains an optimised level using a different number of phases, based on real-time load conditions. This strategy can significantly increase efficiency at light load if a single phase is enabled instead of turning on all phases. Using that optimisation strategy, the plant is changed under single-phase operation compared to full-load operation when all phases are enabled. Therefore, the system must adjust the compensation loop so the converter can keep the same dynamic performance with varying phase configurations. In addition to changing the loop compensation, software needs to adjust phase shift among the phases in order to decrease outputvoltage ripple. A digital controller can adjust all these changes in real time in adigital controller.

EU “Hosts” Power OPERA

The OPERA 2 Consortium recently announced that the European Commission has endorsed OPERA 2 activities to develop a new-generation power-line-communications (PLC)-access standard. In a review meeting that took place in Lisbon (Portugal) to evaluate the work the 26-partner consortium has undertaken to date to promote the adoption of low-cost, high-performance broadband-access PLC, the European Commission stated that the work undertaken in Opera 2 is “excellent”. With the Universal Powerline Association (UPA), OPERA has jointly developed an Access Proposal that both parties have successfully submitted to the IEEE P1901 Group working on a Draft Standard for Broadband-over-Power-Line Networks. This group will develop an international, Medium Access Control and Physical- Layer Specification as the basis of an openly defined standard for high-speed communication devices via power lines. The joint proposal is part of the joint work referred to in the MOU (memorandum of understanding) that both parties recently signed. The IEEE group received three further Access Proposals. OPERA and UPA will continue to work together and with third parties to evolve the Access specification until a final standard emerges. Additionally, UPA and CEPCA, which counted on the active participation and support from OPERA, submitted a Coexistence Proposal to IEEE P1901. OPERA was at the recent IEEE P1901 meeting in Edinburgh, Scotland to present the UPA-OPERA Access specification and to contribute to the debate towards developing a single open standard for power-line-communications technology.

Jeff Shepard is president of Darnell Group. You can contact him atjshepard@darnell.com.