HOW2POWER TODAY

ISSUE: January 2020

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IN THIS ISSUE:

» Injecting Noise In Power Supplies Improves Security For Communications Devices

» The Engineer’s Guide To EMI In DC-DC Converters (Part 11): Input Filter Impact On Dynamic Performance

» A Guide To Second Sourcing Rectifiers

» Focus On Magnetics:
Deflux Windings Benefit Forward Converters But Not Flybacks

» Spotlight On Safety & Compliance:
APEC 2020 Resources Help Engineers Address Power Supply Safety and Compliance Needs

» New Power Products

» Industry Events:
- CES 2020: Automotive And Health Fields Drive Much Tech Development
- 3D-PEIM Issues Call For Papers

» Other Top Power News

Most electronics industry events focus narrowly on one technical area or a particular application or market segment. Then there’s CES. Despite its consumer emphasis, it is a tech show with a very broad scope covering a long list of applications and technologies. With its thousands of exhibits from companies large and small, this very international trade show offers a unique opportunity to learn about not only specific innovations but also the larger technical trends, which have implications for the power electronics industry. In this issue, I share my initial observations on the recent CES 2020 in Las Vegas where I attempted to see as much of the exhibition as possible in the four days allotted. This issue of the newsletter also presents articles that continue discussions on dc-dc converter EMI and second sourcing rectifiers. One of the new topics addressed in this January newsletter is the operation of defluxing circuits, and why deflux windings work in forward but not flyback converters. However, we begin with a subject that is slightly exotic but in some ways very timely—the use of noise modulation of power supply switching waveforms to prevent eavesdropping on voice communications. This issue also looks ahead to APEC, and the safety and compliance resources it will offer, plus new product news and more.

HOW2POWER EXCLUSIVE DESIGN ARTICLES

Injecting Noise In Power Supplies Improves Security For Communications Devices

by Gregory Mirsky, Vitesco Technologies, A Spinoff Of Continental Automotive Systems, Deer Park, Ill.

In communication devices such as cell phones, voice-generated audio signals that pass through audio amplifiers modulate the dc supply voltage and thus they also modulate the switching waveforms that control and regulate switching power supplies. As any switching power supply has some electromagnetic emission at the switching frequency and its harmonics or unwanted derivatives (ringing), the modulating voice-generated information is emitted as well. There is a very simple way of safeguarding this audio information. This method hampers eavesdropping of any emitted signal, can be used with practically any existing switching power supply and is applicable to any device processing information, both digital and analog. The proposed method uses noise to modulate the power supply switching signal. Read the article…

A simple circuit for injecting noise
current into a power supply’s feedback
circuit, modulates the power supply’s
switching signal, masking any audio
modulation it may contain.

This two-port model is used to
analyze dc-dc converter dynamics
and derive equations that express
the system sensitivities to source-side
and load-side interactions.

The Engineer’s Guide To EMI In DC-DC Converters (Part 11): Input Filter Impact On Dynamic Performance

by Timothy Hegarty, Texas Instruments, Phoenix, Ariz.

Meeting electromagnetic interference (EMI) standards requires the insertion of an EMI filter between a switching-mode power converter and its source. As described in part 10 of this series, a dynamic coupling between a converter and its EMI filter effectively creates a feedback loop, where the source-side “minor-loop” gain is the ratio of the filter’s output impedance to the converter’s closed-loop input impedance. Given the negative input impedance behavior of a regulated, high-loop-gain dc-dc converter, part 10 showed that impedance shaping (via passive damping of the input filter to reduce its output impedance peaking) is normally required to ensure robust stability. However, there’s another concern as input-filter interactions may severely affect the transfer functions related to dynamic performance of the converter, particularly the loop gain and output impedance characteristics. The impact of those input-filter interactions on the converter’s dynamic performance are considered here. Read the article…

A Guide To Second Sourcing Rectifiers

by Jos van Loo, Taiwan Semiconductor Europe, Zorneding, Germany and Kevin Parmenter, Taiwan Semiconductor America, Chandler, Ariz.

Rectifiers are usually not very high on the priority list of most designers. Once designed-in on a PCB and qualified, the sources of these components are rarely changed to other suppliers. However, if problems happen in the supply chain or a supplier end of lifes parts, then attempts will be made to second source them. This article describes some of the problems that can occur when you second source rectifiers. Although testing is necessary in many cases, by better understanding the manufacturing processes, datasheets and technology, the testing can be more focused and failures in mass production can be avoided. Test programs and statistics provided by the manufacturer should also be considered. We will start by discussing some general issues that arise when cross referencing standard rectifiers. Afterwards we will go into the details that apply when looking specifically at bridge rectifiers, fast recovery and fast efficient rectifiers, Schottky diodes, TVS diodes, small-signal products and zeners. Read the article…

Unlike derating curves, the typical V_f
curve cannot be manipulated by a
vendor and allows you to indirectly
determine die size.

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

Deflux Windings Benefit Forward Converters But Not Flybacks

by Dennis Feucht, Innovatia Laboratories, Cayo, Belize

A circuit technique that increases the efficiency of low to medium-power (<1 kW) converters with transductors (multiple-winding magnetic components) is to add a winding that conducts current during the on-time to off-time transition, returning the leakage-inductance energy to either input or output port. This article demonstrates how this technique for defluxing the primary winding works in the forward converter and also, why it is not feasible for flyback converters. This discussion thereby demonstrates the more detailed magnetics behavior of deflux circuits. For those familiar with active-clamp “reset” techniques, the method described here for recovering the transformer’s leakage energy is similar in function, but simpler in that it only requires the addition of a small winding and a diode. Read the full article…

SPOTLIGHT ON SAFETY & COMPLIANCE       
Sponsored by Power Integrations
A monthly column discussing standards and regulatory requirements affecting power electronics

APEC 2020 Resources Help Engineers Address Power Supply Safety and Compliance Needs

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

APEC season is coming up soon and this means the brightest minds and top suppliers in the power electronics industry will be gathered in one place. This year the IEEE Applied Power Electronics Conference (APEC 2020) will be in New Orleans, March 15-19 and as always, we will be there to participate. Over 300 exhibitors will be there this year showcasing their latest technologies and practical solutions to proximate problems in our industry. From a safety and compliance standpoint, this unique collection of suppliers and service providers presents a special opportunity to obtain the components, tools and advice we need as engineers to meet our regulatory requirements. Read the full article…

  — POWER PRODUCTS IN 3 IMAGES OR LESS

INDUSTRY EVENTS

CES 2020: Automotive And Health Fields Drive Much Tech Development

by David G. Morrison, Editor, How2Power.com

With more than 4000 companies exhibiting and over 170,000 attendees participating in the recently held CES 2020, the world’s largest technology show can be difficult to describe. Hosted by the Consumer Technology Association, and once referred to as the Consumer Electronics Show, this is a tech show that showcases all tech products for humans. With the word consumer attached to the show, we might think these products are just for personal use, at home or in our daily travels. But there are products at CES relating to nearly all imaginable aspects of daily life including products for the office, factory or other work settings. From a power electronics perspective, CES is a bellwether of the applications that will influence power semiconductor and power supply development now and in the future. As I toured the exhibit halls in the Tech West and Tech East venues at CES 2020 last week, I observed some of the dominant themes, technologies and power-related trends.

Read the full story…

3D-PEIM Issues Call For Papers

The Third International Symposium on 3D Power Electronics Integration and Manufacturing (3D-PEIM), which will be held June 22-24, 2020 in Osaka, Japan, has issued its call for papers. This symposium will bring together practitioners and researchers to share, discuss and roadmap the latest developments in circuits and systems enabled through advancements in 3D packaging, integration and manufacturing technologies.

See the call for papers…

OTHER TOP POWER NEWS

The U.S. Department of Energy’s Advanced Research Projects Agency-Energy (ARPA-E) has announced up to $55 million in funding for two programs to support the development of low-cost electric aviation engine technology and powertrain systems.

Infineon has announced a partnership with Rompower, a power conversion engineering firm with expertise in very high-efficiency, high-density systems design. The companies will collaborate to produce new reference designs for USB-PD (Power Delivery)-based compact fast chargers.

The PSMA and the IEEE PELS are jointly sponsoring the third annual Capacitors in Power Electronics Workshop on Saturday, March 14, just before APEC 2020. This year’s workshop is titled “How to Choose and Define Capacitor Usage for Emerging Applications.”