Perfecting Power Supplies

Control's Monthly Resource Guide. This Month We Look at Power Supplies

Every month, Control's editors take a specific product area, collect all the latest, significant tools we can find, and present them here to make your job easier. If you know of any tools and resources we didn't include, send them to, and we'll add them to the website.

"Efficiency—the Forgotten Feature" discusses the role efficiency—the difference between the input and the output power—should play in selecting a power supply. Any loss here is reflected in dissipated heat, which in turn affects the lifetime and reliability of the power supply unit, and can also lead to  increasing the size of enclosures or installing some form of cooling. The paper discusses the heat loss formula, considerations for choosing the properly sized enclosure, de-rating and energy savings.
PULS Power Supplies  

Choosing a power supply based on mean time between failure (MTBF) ratings alone is not a guarantee of the unit's reliability. This white paper examines the methods that can be used to correlate MTBF test data with calculated values. It discusses a variety of test methods, including MTBF, (demonstrated mean time between failure (DMTBF), and accelerated MTBF. The reliability equation is also explained. The direct link to the white paper is at

This white paper, "Magnetics Design for Switching Power Supplies" from Texas Instruments, covers basic design principles, including magnetic field principles, the energy plane, waveforms and more. It includes numerous diagrams, formulas, definitions and equations to assist users in the design of switching power supplies. The paper is free, and no registration is required. The direct link is at
Texas Instruments

This tutorial provides an overview of three-phase electricity basics and then discusses three of the most common power quality events: leading/lagging power, saq/swell/interruptions, and harmonics. The direct link is at
National Instruments

This free, no-registration-required tutorial, "Industrial Signal Conditioning," covers, among other subjects, the industrial measurement environment, loops and analog signals, signal integrity, and design examples such as servo control, aluminum smelting and grounded thermocouples. The direct link is at

Specifiers and users of Surge Protective Devices (SPDs) are adjusting to new terminology and requirements. UL revised its 1449 Safety Standard for Surge Protective Devices to increase safety. The National Electrical Code (NEC) incorporated specific language to require the use of these safer products. This tip sheet will explain some of the changes affecting specifiers and users. The direct link is at

This white paper discusses one of the problems of using switch-mode power supplies: the way they respond to overloads or short circuits. It shows causes of the problem and suggests a possible solution: a device installed between the power supply and its loads that provides adjustable over-current protection, selective coordination of load circuits and current limiting. The direct link is at The paper is free, but registration is required.
Siemens Industry

This website contains a wealth of materials on switched moded power supply (SMPS) basics. It covers circuits, schematics, PCBs, software, inverters, generators, topologies, software, transformers and more. It also contains an electrical engineering reference guide, formulas, information on PSUs, UPSs, thermal design, power for solar and other resources, including links to other SMPS design sites, freeware, tutorials and news.
Lazar's Power Electronics Guide 

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