ISSUE: December 2018


To ensure receipt of future issues, please add to your address book. Visit



» Options For Optimizing PFC Efficiency Over Wide Load And Line Ranges

» Optimizing Thermistor Placement For Accurate Power-Plane Current Sensing

» Need Uninterrupted Power? Let A Supercapacitor Come To The Rescue

» The Engineer’s Guide To EMI In DC-DC Converters (Part 7): Common-Mode Noise Of A Flyback

» Focus On Magnetics:
Power Magnetics Roundup: EMI Filters

» Spotlight On Safety & Compliance:
Proper Design Of The Power Supply’s Input EMI Filter Protects Against Power Line Transients

» New Power Products

» Industry Events:
INTELEC 2018 Highlights The Challenges Of Powering 5G ICT and Electronics In Harsh Environments Tackles Design For Reliability

» Other Top Power News

From the Editor's Desk

David G. Morrison
Editor, HOW2POWER TODAY       

As 2018 draws to a close, we can remember it not only for the events that occurred this year, but also some of its “anniversaries”. For example, 2018 marked the 40th anniversary of technical milestones such as the introduction of the first cellular mobile phone system by Illinois Bell and the first computer bulletin board system. Closer to the power electronics realm, 1978 also marked the publication of IEEE-555-2, a standard governing power factor in consumer electronics. This standard ushered in an era in which power factor correction (PFC) would become a requirement in more and more electronics applications. Four decades later, IEC 61000-3-2 and other standards dictate widespread use of active PFC stages in countless power supplies. Control schemes and controller ICs have evolved over the years to simplify the implementation of PFC and also to improve the efficiency of PFC stages. In this issue, a detailed article by Joel Turchi provides an overview of control methods and architectures for improving PFC stage efficiency over the ranges of line and load conditions. You’ll get another dose of compliance-related knowledge in the Safety & Compliance column, where Jim Spangler and Kevin Parmenter reveal the origins of requirements for power line transient protection and how power supply input stages address these requirements. In some cases, your input EMI filter may be enough! Discussion of EMI continues in part 7 of Tim Hegarty’s series on EMI in dc-dc converters and in the Focus on Magnetics’ news about EMI filter modules. All that and much more in this issue. Happy Holidays and all the best in 2019!


Options For Optimizing PFC Efficiency Over Wide Load And Line Ranges

by Joel Turchi, ON Semiconductor, Toulouse, France

This extensive article will first discuss the efficiency “nibblers”—the factors that degrade efficiency in power factor correction (PFC) stages. The impact on efficiency of these nibblers, relative to one another, is not the same at low, medium and full load and also varies with line voltage. Hence, it will be seen that the PFC stage cannot be operated the same way over all operating conditions when high-efficiency ratios are sought over wide line and load ranges. Instead, as discussed in the second section of this article, the controller algorithm needs to adapt the operating mode of the PFC stage to the line and load conditions. This is a multimode approach. In the third and final section, architectural aspects of PFC stages will be considered with a focus on the bridgeless and interleaved approaches. The merits of these solutions will be compared in a 300-W, wide input voltage application. Read the full story…

Clamping the switching frequency of a
PFC stage operating in critical conduction
mode (CrM) improves light load efficiency,
but introduces line-current distortion that
needs to be corrected by the PF controller.

When the temperature varies across the
power plane, placement of the temperature
sensor needs to be optimized for accurate
temperature sensing, which is then used
to compensate the current sensor’s
change in resistance with temperature.

Optimizing Thermistor Placement For Accurate Power-Plane Current Sensing

by Viktor Vogman, Power Conversion Consulting, Olympia, Wash.

The use of copper power planes or traces as current sensors does not require adding any components in the current path and thereby presents an attractive option for power monitoring. The impact of tolerances associated with their geometric (width and thickness) variations can be minimized with calibration. However, because copper trace and plane impedances are temperature dependent, such sensors also have thermal drifts that need to be considered. These drifts can be compensated through use of a small surface-mount (SM) thermistor to sense the power plane temperature. However, in cases where the power plane has noticeable temperature variation across it, the question of where to place the sensor becomes important. This article explores a simple procedure to determine the optimum sensor location on the PCB, providing minimal temperature sensing error. Read the full story…

Need Uninterrupted Power? Let A Supercapacitor Come To The Rescue

by Bonnie Baker, Maxim Integrated, Tucson, Ariz.

Disconnecting or removing the power source from always-on circuits creates a blackout event. When this occurs, it is possible to lose critical data. A supercapacitor or supercap can deflect a crash condition by providing a temporary backup current source. This sounds encouraging, but some of its characteristics can inhibit a smooth recovery. This article shows how to use a supercap as a real-world charge and discharge solution in a power backup application. In particular, the use of a boost function to overcome supercap voltage limitations and extract more of the supercap’s usable energy is explained. Finally, an integrated design solution based on the MAX38888 backup power regulator is presented. Read the full story…

Use of a boost converter enables
a supercap-based power backup
circuit to extract more
of the capacitor’s energy.

The common-mode noise of a
multiwinding flyback transformer
can be modelled with a two-capacitor,
lumped CM parasitic capacitance model.

The Engineer’s Guide To EMI In DC-DC Converters (Part 7): Common-Mode Noise Of A Flyback

by Timothy Hegarty, Texas Instruments, Phoenix, Ariz.

Parts 5 and 6 of this article series offered practical guidelines and examples to mitigate conducted and radiated electromagnetic interference (EMI) for nonisolated dc-dc regulator circuits. Of course, no treatment of EMI for dc-dc power supplies would be complete without considering galvanically isolated designs, as the power transformer in these circuits plays a significant role in terms of its contribution to overall EMI performance. In particular, it’s crucial to understand the impact of transformer interwinding capacitance on common-mode (CM) emissions. CM noise is mainly caused by displacement currents within the transformer interwinding parasitic capacitance and the parasitic capacitance between the power switch and chassis/earth ground. This article specifically analyzes CM noise for the dc-dc flyback converter, since it is so widely used as an isolated power supply. Read the full story…

Sponsored by Payton Planar Magnetics
A monthly column presenting information on power magnetics design, products, or related technology

Power Magnetics Roundup: EMI Filters

by David G. Morrison, Editor, HOW2POWER.COM

This column frequently focuses on the application of magnetic components in switched-mode power supply (SMPS) circuits where inductors, transformers and coupled inductors play a critical role in power processing. However, magnetics also serve another purpose in SMPSs within the EMI filters installed on power supply inputs. By attenuating the switching noise produced by the power supply, EMI filters enable compliance with conducted EMI standards. This article offers news about EMI filter modules introduced over the course of this year. Read the full story…

Sponsored by Power Integrations
A monthly column discussing standards and regulatory requirements affecting power electronics

Proper Design Of The Power Supply’s Input EMI Filter Protects Against Power Line Transients

By Kevin Parmenter, Chair, and James Spangler, Co-chair, PSMA Safety and Compliance Committee

In this article, author James Spangler examines the standards that address a power supply’s ability to withstand ac power line transients including those induced by lightning. He shares the results of his research on what standards apply and how they were developed. He then discusses the role that the EMI filter stage plays in providing protection against power line transients and how designers can determine whether changes or additions to this protection are required to meet the applications’ requirements. Read the full story…


Power Integrations’ BridgeSwitch
half-bridge motor driver IC family.

BLDC Motor Driver Eliminates Heatsinks, Slashes Certification Time For Appliance Designs

 Photo and Diagram: The BridgeSwitch family of integrated half-bridges dramatically simplifies the development and production of high-voltage inverter driven two- or three-phase PM or BLDC motor drives. It incorporates two high-voltage n-channel power FREDFETs with low- and high-side drivers in a single small-outline package. Offering inverter conversion efficiency of up to 98.5% in BLDC motor drive applications up to 300 W and a distributed thermal footprint, the IHB driver eliminates the need for a heatsink.

More details…

Triad Magnetics’s CST25 series
current-sense transformers.

Current Sense Transformers Feature Built-In Sense Winding Capability

 Photo: Intended for monitoring currents in high-frequency applications such as switch-mode power supplies and LED lighting, these current sense transformers are offered with a built-in sense winding capability, eliminating the need for additional wiring and jumpers. These fully encapsulated transformers feature 4000-Vac isolation between primary and secondary windings.

See the full story…

Maxim Integrated’s MAX38888
reversible buck/boost regulator.

Buck/Boost Regulator Simplifies Power Backup Using Supercaps

 Diagram: The first member of the Continua family of backup power regulators, the MAX38888 charges and discharges a backup supercapacitor or capacitor bank to deliver power to critical systems when the main power is off. It operates with up to 95% efficiency during charge and discharge operations.

See the full story…

Renesas Electronics’ ISL784x4
100-V half-bridge drivers..

Half-Bridge Drivers Enhance Design Of 12-V to 48-V Automotive Hybrid Powertrains

 Diagram: Renesas has expanded its support for automotive powertrain design with a new family of automotive-grade 100-V, 4-A half-bridge n-channel MOSFET drivers. Designed for efficiency, the ISL784x4 family is the first to combine gate-sensed adaptive deadtime control with independent source/sink pins for slew-rate control, according to the vendor.

 Diagram: Application of the ISL78444 half-bridge driver in a 12-V to 48-V bidirectional dc-dc converter.

See the full story…


• Wide Input Range Eases Transient Protection For DC-DC Converters     More details…

• Isolated High-Side Power Switch Offers SPI And Many Other Features    More details…

• Programmable DC Power Supplies Deliver Up To 50 kW In 8U     More details…

• ORing FET Controller Protects Automotive Electrical Systems     More details…


INTELEC 2018 Highlights The Challenges Of Powering 5G ICT

by Donovan Davidson, INTELEC Conference Steering Committee Chair

The 40th anniversary INTELEC 2018 conference was held in the beautiful and historic city of Torino, Italy on October 7-11th. The theme of this conference was 40 years of Inspiration, Research and Exploration in Power and Energy for ICT (information and communications technology). The conference informed upon and debated the growing issues facing society in powering information and communications systems. The conference opened with a special presentation by Alan Mantooth, president of the conference’s sponsor IEEE PELS. Mantooth talked about the importance of power electronics in today’s society and the role that wide bandgap power devices will play in the future expansion of power electronics into more areas including increasingly higher voltage and higher power applications. Read the full story…

Electronics In Harsh Environments Tackles Design For Reliability

by Tanya Martin, SMTA Executive Director

SMTA Europe is proud to announce the 2019 Electronics in Harsh Environments Conference, April 2-4 2019 in Amsterdam, Netherlands. This global conference is a two and a half day technical event focused on building reliable electronics used in power electronics and harsh environments. Thermal, power and signal integrity requirements can present challenges in devices that operate within harsh environments. Component integration, paired with a growing complexity of the package architectures, larger form factors and higher interconnection densities increase the risk of in-field failures. Overpowering or overheating of a device can have serious consequences including internal package failure, downstream device errors and second-level interconnect solder joint failures. Read the full story…


Submit a digest for ECCE 2019 by January 15, 2019. Secure the opportunity to present your technical knowledge on the largest platform for the electrical and electromechanical energy conversion field. See the call for papers and submit your paper proposals on the ECCE 2019 submission portal.

For the fourth year running, the PSMA and IEEE PELS are co-sponsoring a daylong workshop on  "Power Magnetics @ High-Frequencies" on the Saturday before APEC 2019.

Professor Ćuk will teach a second Masterclass—“Power Electronics: 50 Years Covered In 4 Days!” on March 25-28, 2019 at the UC Irvine Campus. Register at

The Department of Energy has announced $98 million in funding for 40 transformative energy technology projects.

The PSMA Board of Directors is seeking one or more volunteers interested in providing leadership for the Energy Management Technical Committee.