HOW2POWER TODAY

ISSUE: October 2012

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IN THIS ISSUE:

» From the Editor's Desk

» Frequency-Foldback Technique Optimizes PFC Efficiency Over The Full Load Range

» Techniques For Implementing A Positive And Negative Output Voltage For Industrial And Medical Equipment

» Process, Packaging Combine To Advance High-Voltage Power MOSFETs

» Semiconductors In The Efficiency Era:
Is Silicon Carbide Technology Ready To Take Off?

» Special Report:
INTELEC Bridges The Telecom And Energy Worlds

» New Power Products

» Other Top Power News

Discussions about the potential of gallium nitride (GaN) and silicon carbide (SiC) technologies have been ongoing for some time now. But as more semiconductor manufacturers enter this field, and as more GaN and SiC power devices become available, these discussions become more practical and more relevant to a growing number of engineers. Because this field is rather dynamic, designers need to keep track of the current state of these two semiconductor technologies, particularly what’s happening in the marketplace, while also learning what developments are just over the horizon. Starting this month, Ashok Bindra will explore these issues and more in his column, “Semiconductors in the Efficiency Era,” where he will report and comment on the latest advances in power semiconductor technology and devices. Sponsored by Cree and EPC, this column will address not only GaN and SiC developments, but also the continuing evolution of silicon power discretes and modules. Meanwhile, in other parts of the newsletter, we’ll continue to bring you in-depth discussions of design techniques and advanced control methods, as in this month’s feature by Joel Turchi on a novel control method for improving the efficiency of PFC power stages. This issue also brings you effort-saving options for implementing positive and negative supply rails; a feature on high-voltage power MOSFETs; new power components and tools; and Kevin Parmenter’s report from INTELEC 2012. As a bonus, you will also get a chance to win a copy of Christophe Basso’s new book on designing power supply control loops.

HOW2POWER EXCLUSIVE DESIGN ARTICLES

Frequency-Foldback Technique Optimizes PFC Efficiency Over The Full Load Range

by Joel Turchi, ON Semiconductor, Toulouse, France.

“Green requirements” such as 80 PLUS aim to maximize power supply efficiency across a range of load conditions. So it has become critical that power supply designers address medium- and light-load efficiency in the PFC power stage. A popular approach to lowering losses under lighter load conditions is to reduce the switching frequency (frequency foldback.) While extremely efficient at very low power, this solution must be carefully implemented at intermediate power levels. This article clarifies how the switching frequency should be managed in a PFC boost converter to maximize efficiency across the load range. The converter’s MOSFET losses are analyzed under critical-conduction and discontinuous-conduction modes of operation. Then the operating principles for a relatively new method of frequency reduction, known as current-controlled frequency foldback (CCFF), are explained. This article also discusses the operation of controllers using CCFF and presents experimental results. Read the full story…

Instead of computing the switching losses of a PFC boost converter directly, this article describes an easier approach—predicting the trend in DCM losses as a function of CrM losses, with respect to switching frequency reduction

A variation on the flyback converter, the Fly-buck generates split-rail voltages with isolation, yet needs no optocoupler since it uses primary-side feedback.

Techniques For Implementing A Positive And Negative Output Voltage For Industrial And Medical Equipment

by Rich Nowakowski, Texas Instruments, Dallas, Texas

Many analog circuits in industrial and medical applications require both positive and negative supply voltages. A discrete switching regulator is often used to derive both positive and negative output voltages, but implementing an inverting buck-boost topology with a coupled inductor can be burdensome. However, recent advancements in dc-dc modules allow straightforward implementation of a split-rail power solution. This article surveys several discrete and module-based negative output and split-rail positive and negative output solutions for powering split-rail amplifiers, analog sensors, data converters, and audio amplifiers. Key factors such as complexity, component count, relative cost, and performance are explored. Read the full story…

Process, Packaging Combine To Advance High-Voltage Power MOSFETs

by Vipin Bothra, STMicroelectronics, Schaumburg, Ill.

There’s a significant amount of design activity today in power management involving voltages between 400 V and 1700 V, with the bulk of interest around 600 V at 2 kW. Applications include switched-mode power supplies, motor control, industrial machines, hybrid electric vehicles, and many others. Market pressures to make these end products smaller and more efficient place tremendous demands on the power components, especially the power MOSFETS. In response MOSFET vendors are improving the performance of their devices through advances in their process technology and packaging. This article discusses two examples of recent advances by STMicroelectronics—the MDmeshV process and the HV PowerFLAT 8×8 package. Data is presented to illustrate the improvements in device performance made possible by these innovations. Read the full story…

Package thickness is increasingly important with today's tight pc-board layouts and spacing

SEMICONDUCTORS IN THE EFFICIENCY ERA        
Sponsored by Cree and Efficient Power Conversion
A monthly column discussing the latest advances in power semiconductor technology and devices

Is Silicon Carbide Technology Ready To Take Off?

by Ashok Bindra, Technology Writer, Technika

Despite gains made in silicon carbide (SiC) technology, it continues to represent a very small percentage of the overall power semiconductor market. By some accounts, it could be less than 1%. But, going forward, the situation looks a lot brighter. With both SiC MOSFETs and diodes now available, and wafer makers continuing to deliver high-quality substrate materials while increasing the diameter, SiC is poised for rapid growth in the next five to ten years as usage proliferates in applications ranging from PFCs and UPSs to solar inverters to EVs/HEVs, motor drives, and others. Read the full story…

As SiC product portfolios expand and costs drops, these devices will expand into solar power inverters, motor drives, and many other applications in the next five to 10 years.

Special Report       

INTELEC Bridges The Telecom And Energy Worlds

by Kevin Parmenter, Contributor, How2Power Today

Exploring this year’s International Telecommunications Energy Conference, Kevin Parmenter discovered just how much the telecom power industry has changed over time. An industry that was once focused on ac-dc rectifiers and batteries for central offices now encompasses a range of energy- and power-related technologies to support a diverse telecom infrastructure, which often lacks access to a stable power grid. As Kevin explains in this special report, INTELEC 2012’s exhibition, conference program, and audience reflected this reality. For more details…

The INTELEC 2012 exhibit included suppliers of a
wide range of telecom power-related products.

  — POWER PRODUCTS IN 3 IMAGES OR LESS

OTHER TOP POWER NEWS