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IN THIS ISSUE:
» From the Editor's Desk
» Modeling The Effects of Leakage Inductance On Flyback Converters (Part 1): Converter Switching
» Leakage Inductance (Part 2): Overcoming Power Losses And EMI
» Free Tool Takes The Drudgery Out Of Designing EMI Filters
» Focus On Magnetics:
Power Magnetics Component Update
» New Power Products
» Other Top Power News
» Kudos2
From the Editor's Desk David G. Morrison
Editor, HOW2POWER TODAY
Many of the trends in power supply design such as the use of widebandgap semiconductors, higher switching frequencies, and higher power density can be expected to make designing for electromagnetic compliance (EMC) harder, not easier. To compensate, power supply designers will have to be proficient in addressing the causes of electromagnetic interference (EMI) and in designing effective filters. Design articles featured in this issue address both sides of the problem. Two of these articles shed light on a key factor in EMI—leakage inductance. Part 2 in Ernie Wittenbreder’s series on this topic describes the operation of various clamps and snubbers available to suppress leakgage inductance-induced ringing in power converters. Meanwhile, Christophe Basso sets out to analyze an effect of leakage inductance on flyback converters that is known, but not accounted for in existing flyback models. In this case, understanding the subtle effects of leakage inductance on the flyback waveforms may help designers to better optimize their choice of snubber components. And then on the subject of filtering, Franki Poon’s article explains how engineers can use a free simulation tool to more easily design and optimize input EMI filters. The EMI simulation tool also serves as a good learning aid, helping designers to see the impact of both component values and parasitics on filter response. This edition of How2Power Today also brings an update on recently introduced magnetic components, plus new power semiconductors, power modules and more.
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HOW2POWER EXCLUSIVE DESIGN ARTICLES 
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Modeling The Effects of Leakage Inductance On Flyback Converters (Part 1): Converter Switching
by Christophe Basso, ON Semiconductor, Toulouse, France
The frequency response of a flyback converter operating under voltage mode (VM) control and driven in continuous conduction mode (CCM) is that of a second-order system. If the vast majority of analyses predict a transfer function whose quality factor is solely affected by the various losses (ohmic paths, magnetic losses, recovery time-related losses and so on), very few tackle the damping effect brought by the leakage inductance. However, transient simulations predict the damping of output oscillations as the leakage inductance increases. Because formulas available in the literature do not reflect this effect, a new flyback converter model is necessary and will be described in this article. Part 1 of this series begins by explaining the leakage inductance-induced damping effect on flyback waveforms and then derives a new dc transfer function that accounts for this effect. Finally in this part, the leakage inductance effects are observed in measurements taken on a prototype circuit.
Read the article…
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Leakage inductance causes delays in both
the turn-on and turn-off of the current in
the output diode of the flyback converter,
while also altering its peak value. |
A non-dissipative LCD clamp
can be used in a single-ended
forward or flyback converter
to reduce clamp power losses
and offers other benefits. |
Leakage Inductance (Part 2): Overcoming Power Losses And EMI
by Ernie Wittenbreder, Technical Witts, Flagstaff, Ariz.
Leakage inductance is our foe when it creates problems such as power losses, EMI, or degraded regulation. In most isolated converters, leakage inductance contributes to both power losses and EMI, but there are ways in which power losses and EMI can be avoided by design. The first course of action is to design the transformer for low leakage inductance, but sometimes that approach is too costly or requires more space than is available, so other methods are needed. In this part 2, the various clamp and snubber options are discussed including RCD clamp, RC snubber, LCD clamp and active clamps. The pros and cons and varying requirements of the different approaches are discussed mainly within the context of the flyback topology, but also touching on the LCD clamp in the single-ended forward converter, and active clamps in the coupled-boost converter. Finally, this part looks at techniques for improving load regulation degraded by leakage inductance. Read the full story…
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Free Tool Takes The Drudgery Out Of Designing EMI Filters
by Franki N.K. Poon, PowerELab, Shatin, N.T., Hong Kong
A free online power supply design tool available at the PowerEsim website provides a very simply way to predict the EMI caused by the line ripple. This tool contains a complex model that considers all the parasitic elements of the input filter and an equivalent arbitrary current source. Engineers can change those parameters to predict the EMI that will be observed on the input of the power supply. If this level of simulation of EMI is not enough, engineers can go a step further and use PowerEsim’s converter build. This will allow engineers to immediately see the EMI result under any operating conditions. This article will explain how engineers can use PowerEsim’s EMI simulation tool to predict the EMI that will be generated by their power supply designs and to optimize their input EMI filters for maximum attenuation of this EMI.
Read the article…
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PowerEsim’s EMI tool helps engineers
design a four-stage LC filter for
attenuating differential-mode EMI
produced by their power supplies. |
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FOCUS ON MAGNETICS
Sponsored by Payton Planar Magnetics
A monthly column presenting information on power magnetics design, products, or related technology |
Power Magnetics Component Update
This article reports on just over a dozen power magnetic components introduced over the past six months. Among the parts profiled here are transformers intended for switched-mode power supply applications, various isolation transformers, and several small, low-profile inductors for dc-dc converters in automotive and other applications. This article represents a follow-up to the Power Magnetics Component Update published in the June 2015 issue and other magnetics articles published in HOW2POWER TODAY.
Read the full story… |
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 — POWER PRODUCTS IN 3 IMAGES OR LESS
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STMicroelectronics’ MDmesh
K5 superjunction MOSFETs. |
Super-Junction Power MOSFETs Move Up To 1500 V
 Photo: Described as the first superjunction MOSFETs to offer a 1500-V rating, ST’s MDmesh K5 Power MOSFET family boasts the lowest RDS(ON) per area and the lowest gate charge (QG) on the market, according to the vendor.
Graph: Comparing turn-off energy of one of ST’s new 1500-V superjunction power MOSFETs with that of a comparably rated planar MOSFET.
More details… |
Vicor’s VIA DCMs. |
High-Density DC-DC Converters Come In Rugged Chassis-Mount Package
Photo: VIA DCMs take the DCM ChIP-style dc-dc converters and combine them with EMI filtering, transient protection, inrush current limiting, and a secondary-referenced control interface in a low-profile package that provides high efficiency, high power density, and simplified thermal management.
Diagram: The isolated VIA DCMs may be used with Vicor’s point-of-load regulators to create modular, power system solutions with high power density.
Photo: The VIA DCMs are initially being offered in two sizes. A 3.7- x 1.4-in. size provides up to 600 W with a 300-V nom input and a 3.4- x 1.4-in. size that delivers up to 320 W with 28-V nom. input.
More details… |
Enargy Power‘s BM60 series of BladeAdapter ac-dc supplies. |
Medical-Grade 60-W AC-DC Adapters Offer Ultra-Thin Profile
Diagram: The BM60 series medical adapters measure just 127 x 65 x 22 mm, making them 34% thinner and with 28% less volume than what’s typically available on the market, according to Enargy. They’re also compliant with new standards such as the 4th Edition of IEC60601-1-2:2014 and the U.S. DoE’s Level VI energy efficiency specification.
More details… |
Teledyne LeCroy’s
Harmonics Calculation option. |
Harmonics Calculation Software Expands Capabilities Of Motor Drive Analyzers
Screenshot: The MDA Harmonics Calculation software option extends the capability of the MDA800 series of motor drive analyzers (oscilloscope + power analyzer instruments) by adding the ability to measure and display harmonics values for current, voltage, and power on the ac line input or drive output. Results are displayed graphically with a spectral display and in a table format. The option also adds capability for per-cycle THD measurements and waveforms, and advanced harmonic filtering.
More details… |
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MORE POWER PRODUCTS:
• Liquid Cooled 20- to 25-kW Power Systems Target Heavy Industrial And Military Projects More details…
• Bus Converter Modules Are Non-Isolated And Bidirectional More details…
• Wireless Charging Antennas Deliver High Q, Low Heat, Extreme Thinness For Smartphones More details…
• PWM Controllers Feature 40-V Operation And PMBus Interface More details…
• Wireless Charging Solution Is Adopted By Tier I Computer Makers More details…
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OTHER TOP POWER NEWS
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Enargy Power, a supplier of high-performance ac-dc power supplies and dc-dc converters to China’s “Fortune 100” companies, announces its entry into the North American market with the addition of industry veteran Todd Hendrix as the director of sales and marketing.
IDT teams up with Digi-Key in a contest to create wirelessly powered devices.
An ISO17025 accredited test lab, Anecto explains the difference between linear and average temperature ramp rates when performing environmental testing on electronic products, how this relates to the choice of environmental chambers and why this matters for compliance with international standards.
Additionally, Anecto will host a two-day reliability seminar, Dec. 1 and 2 in Galway, Ireland with quality and reliability expert Martin Shaw.
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— RECOGNIZING 
