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.
Setting 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.
- 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.
- 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.
|Search the online Automation Integrator Guide|
Case Study Database
Get more exposure for your case study by uploading it to the Control Engineering case study database, where end-users can identify relevant solutions and explore what the experts are doing to effectively implement a variety of technology and productivity related projects.
These case studies provide examples of how knowledgeable solution providers have used technology, processes and people to create effective and successful implementations in real-world situations. Case studies can be completed by filling out a simple online form where you can outline the project title, abstract, and full story in 1500 words or less; upload photos, videos and a logo.
Click here to visit the Case Study Database and upload your case study.