ISSUE: May 2019


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



» Optimizing Transfer Switch N+1 Redundant Power Architectures

» Another Look At The Refined Model Of Current-Mode Control

» What's New at HOW2POWER.COM

» Focus On Magnetics:
Power Magnetics Component Roundup

» Spotlight On Safety & Compliance:
An Introduction To Medical Regulations: Understanding The 60601 Standard

» New Power Products

» Industry Events:
- IWCE 2019 Takes The Pulse Of A Dynamic Wireless Market
- PCIM Asia Presents Latest Power Electronics Research And Innovation

» Other Top Power News

From the Editor's Desk

David G. Morrison
Editor, HOW2POWER TODAY       

Redundancy has long been a requirement in powering data centers and other mission critical applications. This requirement, however, is often overshadowed in discussions of power supply technology by the “eternal” pursuits of optimizing power supply size, efficiency and cost. But as Viktor Vogman illustrates in his latest article, the way in which redundancy is implemented can impact the overall size, efficiency, and cost of the power system. Designers have choices in terms of the power architecture—1+1, N+N, and N+1 are among the arrangements possible for the ac-dc power supply units, which may also include separate ac power feeds for redundancy, and in some cases, an active transfer switch. In his article Viktor shows that separating this switch’s isolation and power transfer functions creates opportunities to further optimize the power architecture to better meet those size, efficiency and cost goals. While Viktor’s article is thinking “outside the box” (i.e. the power supply), an article by Dennis Feucht dives back into that box with his return to the subject of current-mode control. Here Dennis provides a condensed review of the evolution of current-loop modeling and how it led him to develop his refined model. This issue also presents a Power Integrity Insights column in which Steve Sandler reviews the issue of negative input resistance in dc-dc converters, why it matters and how to measure it. Plus, we have the new Who’s Who In SiC & GaN Power Semiconductors list, the latest power component news (including magnetics), the Safety & Compliance column, and a report on the International Wireless Communications Expo that takes us into another mission critical realm.


Optimizing Transfer Switch N+1 Redundant Power Architectures

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

Automatic transfer switches (ATSs) have gained popularity in data center power distribution networks due to several advantages. They provide fail-safe ac power redundancy, achieve highly efficient power distribution in server racks, enable redundant power feeds for single ac power cord arrangements, and reduce UPS power conversion losses. In terms of ac redundancy, if the primary power feed becomes unavailable, the rack ATS will supply power from the secondary feed without interrupting server operation. At the same time transfer switch arrangements can advance traditional dc redundant architectures supporting seamless dc power flow to the server when one of the power modules fails. This article examines opportunities for adoption and optimizing of ATS techniques, specifically in N+1 dc redundant configurations where N>1. Read the article…

Techniques such as separation of the
safety isolation and power transfer
functions in the ATS and reduction of the
switched power level can lead to size and
cost reductions.

The historical development of
current-loop models started from the
inductor triangle-wave current
waveform and has resulted in various
waveform-based models.

Another Look At The Refined Model Of Current-Mode Control

by Dennis Feucht, Innovatia Laboratories, Cayo, Belize

The analysis of current-model control in power conversion has a long history, going back over four decades, encompassing different approaches that capture different aspects of converter behavior. These different forms of current-loop models have evolved over time as their developers have attempted to improve their accuracy or completeness. First-generation models by Middlebrook, Macsimović and Erickson were followed by Ridley’s sampled-loop model and then Middlebrook and Tan’s unified model. In a previous article series on peak-current control, the author described the development and evolution of these different current-loop models and how they led to his development of a new model called the refined model of current-loop control. For those not yet familiar with the refined model and those generally curious about modeling of current-mode control, this article offers a summary of the earlier seven-part series. Read the article…


Measuring The Negative Input Resistance Of DC-DC Converters

by Steve Sandler, Picotest, Phoenix, Ariz.

It seems that most power integrity engineers spend time focused on the output impedance of their board-level dc-dc converters. Many power integrity engineers argue that we don’t even need to include the dc-dc converter in our simulations, we can simply use a passive network to represent the output impedance. However, the power supply has many noise sources and sensitivities at both its input and the output and a passive network isn’t sufficient to model them. Such is the case with the negative input resistance of a dc-dc converter. In this article, the author explains why this negative resistance exists, why it matters and how to measure it more easily using a new device. Read Power Integrity Insights

Who's Who in Silicon Carbide And Gallium Nitride Power Semiconductors

An update to our previously published source lists of SiC and GaN suppliers, this new document offers more descriptive listings of manufacturers of SiC and GaN discrete power semiconductors, ICs and modules as well as companies providing related foundry services. Over 25 device and module suppliers—startups and established companies—are included here. View the list here or find it in How2Power’s SiC & GaN section

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

Power Magnetics Component Roundup

by David G. Morrison, Editor,

Automotive applications continue to drive the development of many standard inductors as manufacturers seek to meet demands for smaller surface-mount parts with higher performance in dc-dc converters and filter circuits. Many of these AEC-Q200-certified inductors also target dc-dc converters and switched-mode power supplies in industrial applications. And beyond these environmentally challenging designs, there are many high-performance VRMs and dc-dc converters for which suppliers are developing smaller, more advanced inductors. Meanwhile, gate-drive and flyback circuits are creating demand for many of the latest off-the-shelf transformers. Recently released parts are intended for a range of applications, including automotive and industrial, but also telecom and datacom, motor control, lighting and other SMPS uses. Read this article for a quick look at power inductors and transformers introduced over the past nine months. Read the full story…

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

An Introduction To Medical Regulations: Understanding The 60601 Standard

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

This article aims to give an initial introduction to the rules and regulations that govern safety and compliance in medical equipment. This basic information does not go into details of medical power supplies. Rather, an attempt is made to enlighten those not familiar with the medical regulations and standards, including designers and specifiers of medical power supplies. In particular, we aim to shed light on the importance of medical equipment immunity from radiated and conducted electromagnetic emissions. Medical regulations are complex because they apply to the safety of both patients and medical practitioners. The 60601 standard, which is the focus here, applies to most locations throughout the world, and anywhere medical equipment is used: operating rooms, hospital rooms, intensive care units, nurseries, senior care facilities and even households. Read the full article…


ROHM Semiconductor’s
BM2SCQ12xT-LBZ series ac-dc
converter ICs.

AC-DC Converter ICs Add Built-In 1700-V SiC MOSFET For More Compact Designs

 Drawing: The ac-dc converter ICs adopt a dedicated package that incorporates a 1700-V SiC MOSFET along with the controller and SiC MOSFET gate-drive circuitry optimized for industrial auxiliary power supplies.

 Diagram: The internal SiC MOSFET and gate driver circuit improve efficiency by as much as 5% over conventional Si MOSFETs. Also, a quasi-resonant method is adopted for the control circuit that enables operation at higher efficiency and lower noise than conventional PWM designs.

See the full story…

Navitas’s NVE039 27-W ac adapter
reference design.

Adapter Reference Design Leverages GaN-Based, Active-Clamp Flyback To Achieve High Density

 Photo: Using a Navitas’ high-speed, half-bridge GaNFast power IC in the active clamp flyback (ACF) topology, the 27-W reference design measures only 39 mm x 37 mm x 16-mm (uncased) and achieves a power density of 19 W/in3 uncased and 11 W/in3, assuming a 2.5-mm case thickness.

See the full story…

Renesas Electronics’ ISL71043M PWM
controller and ISL71040M GaN FET

Rad-Tolerant PWM Controller And GaN FET Driver Come In Plastic Packages For SmallSats

 Diagram: These ICs are described as the space industry’s first plastic-packaged, radiation-tolerant PWM controller and GaN FET driver for dc-dc converters in small satellites (smallsats) and launch vehicles. The controller and low-side GaN FET driver are well suited for isolated flyback and half-bridge power stages, and motor control driver circuits.

See the full story…

Silanna Semiconductor’s SZ1105
active clamp flyback controller.

Fully Integrated Active Clamp Flyback Controller Extends Benefits To 60-W AC Adapters

 Diagram: The all-silicon design combines the simplicity of flyback controllers with the power density enabled by active clamp flyback controllers, yielding over 93% efficiency and 20-W/in3 power density for 60-W ac-dc power adapters.

See the full story…

Texas Instruments’ UCC21710-Q1,
UCC21732-Q1 and UCC21750
isolated gate drivers.

Isolated Gate Drivers Integrate Sensing For IGBTs And SiC MOSFETs

 Diagram: These single-channel isolated gate drivers for SiC/IGBT devices feature advanced protection and high-CMTI, while also improving total system efficiency in automotive and industrial applications.

See the full story…

More Power Products. . .

SJ MOSFETs Offer Fast Reverse Recovery And Design Flexibility For EV Charging Stations, Home Appliances

Automotive-Qualified GaN FET Improves Lidar System Resolution

650-V High-Frequency IGBTs Boost Performance With High-Speed Technology


IWCE 2019 Takes The Pulse Of A Dynamic Wireless Market

by Kevin Parmenter, Contributor,

Billed as the critical communications technology event of the year, the International Wireless Communications Expo (IWCE 2019), which was held March 4-8, 2019 at the Las Vegas Convention Center, focused on wireless communications for public safety and other mission critical applications. Kevin Parmenter attended this show, which is both expo and conference, to learn more about this fast growing and changing marketplace, and how trends in wireless communications may impact developments in the power supply world. In addition to providing a forum for showing the latest advances in wireless communications equipment, the IWCE 2019 exhibition provided a view of the diverse power product vendors who support this industry. Read the full story…

IWCE, an annual event for critical communications technology,
was held March 4-8, 2019 in Las Vegas.

PCIM Asia Presents Latest Power Electronics Research And Innovation

Known as one of the most important conferences for power electronics in Asia, the PCIM Asia Conference 2019 will once again enhance the academic and industrial development of power electronics by assembling the latest research results from around the globe. Professionals from industry and academia will cultivate innovations by giving in-depth analysis on various power electronic applications, technological breakthroughs and upcoming industry trends. Read the full story…


UT Austin to develop next-generation grid-forming PV inverters to enhance the resilience of the power grid.

GaN specialist Exagan opens power solutions center in Europe to bring electronics manufacturers GaN’s performance over a wide range of applications.

ABB wins 600 MW HVDC order to reinforce Japanese power supply through HVDC JV with Hitachi.

Aveox to launch high-efficiency ac power conversion modules with active PFC powered by GaN Systems.