HOW2POWER TODAY

ISSUE: May 2021

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IN THIS ISSUE:

» Designing An Open-Source Power Inverter (Part 1): Goals And Specifications

» Raising The Plateau Level In Valley-Fill PFC Circuits Improves Efficiency

» Developing A 25-kW SiC-Based Fast DC Charger (Part 2): Solution Overview

» Focus On Magnetics:
Misconceptions In Power Magnetics

» Spotlight On Safety & Compliance:
Military- Vs. Commercial-Grade Resistors: Reliability, Performance And Cost Tradeoffs

» New Power Products

» Other Top Power News

Open-source is not a term usually associated with power supplies, a field in which the quest for better performance leads to development of proprietary designs using highly specialized, often customized components and packaging, by highly skilled engineering teams adept in various disciplines. However, there may be times when the open-source approach could benefit power supply users. In his design article in this issue, Dennis Feucht makes the case for an open-source power inverter, which he believes could overcome the lack of serviceability of the battery-powered inverters currently on the market. In part 1 of his new series, he outlines the structure and specifications for a scalable power inverter design that he will be presenting so that engineers and others with technical knowledge may build, modify or service the design. The series will also offer the opportunity to demonstrate Dennis’ magnetics design concepts, as regularly discussed in the Focus on Magnetics column. Additionally, this newsletter offers features on a new twist on the valley-fill PFC circuit that improves efficiency in high-power designs, a solution overview for the previously introduced fast EV charger, common misconceptions in magnetics design, and a comparison of military- and commercial-grade resistors. In the latest product news, you’ll find a heavy dose of gate drivers and power modules. All this and more in the May issue.

HOW2POWER EXCLUSIVE DESIGN ARTICLES

Designing An Open-Source Power Inverter (Part 1): Goals And Specifications

by Dennis Feucht, Innovatia Laboratories, Cayo, Belize

This is the first in a series of articles that will disclose the engineering of a kilowatt-level, scalable open-source battery inverter dubbed the “Volksinverter”—a product meant to be suitable for widespread use, and which can be built and/or serviced by technically savvy individuals. Its key characteristic is the open-source nature of this design. In this article series, the design of the Volksinverter will be described in enough detail that a technical owner will be able to maintain, repair, or even modify the design, including the magnetic components. Like Linux, the Volksinverter design will lend itself to discussion by user groups on the Internet who will be able to share ideas, observations, procedures, modifications, corrections and enhancements of it. Anyone will be free to manufacture and sell it, as-is or in modified form. Read the article…

A system-level diagram of the
Volksinverter shows its three main
subsystems.

In constant-power mode, lowering
the VF plateau level to increase the
conduction angle of the rectifier has
the side effect of increasing the
current stress on the dc-dc
converter’s active components.

Raising The Plateau Level In Valley-Fill PFC Circuits Improves Efficiency

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

The passive capacitive PFC circuit, which employs capacitor-diode networks in the valley-fill (VF) PFC configuration, can improve power factor and reduce harmonic distortion of the input line current with a reduction in volume versus active PFC circuits. However, the operating principle of the existing VF-PFC circuit causes excessive supply voltage variations resulting in higher current magnitudes and higher power dissipation in the power conversion stages that follow the PFC stage. These losses are influenced by the so-called plateau level in the VF-PFC waveforms. This article discusses the efficiency improvement made possible by a novel implementation of the VF-PFC in which a higher than usual plateau level is employed. Read the article…

Developing A 25-kW SiC-Based Fast DC Charger (Part 2): Solution Overview

by Oriol Filló, Karol Rendek, Stefan Kosterec, Daniel Pruna, Dionisis Voglitsis, Rachit Kumar and Ali Husain, ON Semiconductor, Phoenix, Ariz.

In the previous installment of this series, the authors introduced the main system requirements for a fast EV charger, outlined the key stages of the development process for such a charger and identified the team of application engineers which is developing the charger described here. Now, in part 2 they will take a closer look into the guts of the design and unveil more details of it. In particular, they’ll review the possible topologies, discuss their advantages and tradeoffs, and discuss the backbone of the system, which includes a half-bridge SiC MOSFET module. Read the article…

For this EV charger design, the team
selected a six-switch active rectifier
for the ac-dc stage and a dual active
bridge for the dc-dc converter stage
(shown here).

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

Misconceptions In Power Magnetics

by Dennis Feucht, Innovatia Laboratories, Cayo, Belize

Magnetic components appear to be so simple—just two parts, a core and some wire wrapped around it. How could that be very complicated? If you ask this question of yourself seriously enough, you begin your own descent into the abyss of magnetics design. As a “recovering magnetaholic,” I have learned that magnetics really is simple, but the path to simplicity has some misleading ideas and some that are not actually true, though they are widespread. More importantly, some basic concepts that should be widely known are not. This article is a chat about some of them. Read the full article…

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

Military- Vs. Commercial-Grade Resistors: Reliability, Performance And Cost Tradeoffs

by Kory Schroeder, Stackpole Electronics, Raleigh, N.C.

Military-spec resistors provide an essential function in high reliability and critical circuit applications. However, unless you are dealing with such applications regularly, understanding what military-spec (military-grade) resistors offer compared to commercial resistors can be challenging. There are many aspects of military-spec resistors that are unclear or unknown to many customers. For example, a key distinction among military-spec resistors is whether or not they offer established reliability. This article explains in broad terms how military specifications address reliability in the manufacturing, testing, inspection and processing of resistors, and how these aspects compare with those used to produce commercial- and automotive-grade resistors. Read the full article…

  — POWER PRODUCTS IN 3 IMAGES OR LESS

OTHER TOP POWER NEWS

On Wed., May 26, 2021, a free virtual IEEE LI lecture “Underexplored Three-Phase Power Failure Conditions" will be presented.

The JEDEC Wide Bandgap Power Semiconductor Committee has published a milestone document, “JEP184: Guideline for Evaluating Bias Temperature Instability of Silicon Carbide Metal-Oxide-Semiconductor (MOS) Devices for Power Electronic Conversion.”

APEC 2021 will be an online only event due to continuing Covid-19 concerns.

Professor Ćuk’s interactive, online Masterclass in Power Electronics will present intense lectures over six-weeks with two hours of lecture daily, starting June 21, 2021.