Power conversion design help

Tips and tricks: Setting up a power conversion circuit requires forethought to avoid headaches. Advice follows to ensure control loop stability.

04/02/2012


Tips and TricksSetting up a power conversion circuit requires forethought to avoid headaches. John Bottrill, senior applications engineer at Texas Instruments, offers advice to ensure control-loop stability.

Figure 1. Typical feedback circuit for the TI TL431, three-terminal adjustable shunt regulator. Courtesy: Texas Instruments

- The optocoupler loop gain requires that the designer know the optocoupler’s current transfer ratio (CTR).

- Plot the power converter’s open-loop gain as a function of frequency without the effect of the feedback circuit by multiplying all the converter’s various gain elements together.

- The converter operates at a specific-switching frequency. The designer knows that the total open-loop gain must cross zero dB at a point below one-sixth of that frequency. Most designers leave a margin for component tolerances. This usually can be accomplished by designing the loop to cross over at approximately one-tenth of that value.

John Bottrill, senior applications engineer at Texas Instruments. Courtesy: Texas Instruments- Ideal conditions in textbook examples can deliver the desired phase margin, but real-world conditions can differ. It may be necessary to filter the voltage source that provides the current to the optocoupler. This helps to remove a “sneak path” and to control the gain of the feedback loop with the components around the three-terminal adjustable shunt regulator.

See detailed online examples, four equations, and 18 figures to illustrate these tips in a Control Engineering tutorial: Gain consideration using a shunt regulator and optocoupler feedback, by John Bottrill, TI; edited by Mark T. Hoske, content manager, CFE Media, Control Engineering.

www.power.ti.com                   



The Engineers' Choice Awards highlight some of the best new control, instrumentation and automation products as chosen by Control Engineering subscribers. Vote now (if qualified)!
The System Integrator Giants program lists the top 100 system integrators among companies listed in CFE Media's Global System Integrator Database.
Each year, a panel of Control Engineering and Plant Engineering editors and industry expert judges select the System Integrator of the Year Award winners in three categories.
This eGuide illustrates solutions, applications and benefits of machine vision systems.
Learn how to increase device reliability in harsh environments and decrease unplanned system downtime.
This eGuide contains a series of articles and videos that considers theoretical and practical; immediate needs and a look into the future.
HMI effectiveness; Distributed I/O; Engineers' Choice Award finalists; System Integrator advice; Inside Machines
Women in engineering; Engineering Leaders Under 40; PID benefits and drawbacks; Ladder logic; Cloud computing
Robotic integration and cloud connections; SCADA and cybersecurity; Motor efficiency standards; Open- and closed-loop control; Augmented reality
Programmable logic controllers (PLCs) represent the logic (decision) part of the control loop of sense, decide, and actuate. As we know, PLCs aren’t the only option for making decisions in a control loop, but they are likely why you’re here.
This digital report explains how motion control advances and solutions can help with machine control, automated control on assembly lines, integration of robotics and automation, and machine safety.
This article collection contains several articles on how advancements in vision system designs, computing power, algorithms, optics, and communications are making machine vision more cost effective than ever before.

Find and connect with the most suitable service provider for your unique application. Start searching the Global System Integrator Database Now!

Control room technology innovation; Practical approaches to corrosion protection; Pipeline regulator revises quality programs
Cloud, mobility, and remote operations; SCADA and contextual mobility; Custom UPS empowering a secure pipeline
Infrastructure for natural gas expansion; Artificial lift methods; Disruptive technology and fugitive gas emissions
Automation Engineer; Wood Group
System Integrator; Cross Integrated Systems Group
Jose S. Vasquez, Jr.
Fire & Life Safety Engineer; Technip USA Inc.
This course focuses on climate analysis, appropriateness of cooling system selection, and combining cooling systems.
This course will help identify and reveal electrical hazards and identify the solutions to implementing and maintaining a safe work environment.
This course explains how maintaining power and communication systems through emergency power-generation systems is critical.
click me