SMPS Control Loop Stability, Loop Compensation etc.. - Page 1
Forum section: electronics / general

author: David
author_rank: Frequent Contributor
timestamp: December 02, 2012, 01:03:40 pm
content: Hi all,Does anyone have any good reference material on SMPS loop stability? I am (like many) looking for practical approaches to measuring and improving stability. However a well written article on the fundamentals would be very useful.Cheers,Dave

author: Kremmen
author_rank: Super Contributor
timestamp: December 02, 2012, 02:46:36 pm
content: There is one reference that i always return to: The definitive book "Switch-mode Power Supplies - SPICE Simulations and Practical Designs" by Christophe P. Basso. ISBN 978-0-07-150858-2. While it is not a book about stability as such, it will give you a righteous going-over of all aspects of the common and some not-so-common switcher topologies. Read and understand this book and you will understand switchers. Of the 889 pages in the book, one entire chapter (ch 3; 100 pages) discusses issues of feedback and control loops. The emphasis is not on theoretical analysis but practical issues and techniques.What is really nice is that NI Multisim has the Basso SPICE models available, so you can simulate circuits exactly as done in the book, should you have Multisim available.http://www.amazon.com/Switch-Mode-Supplies-Simulations-Practical-Designs/dp/0071508589/ref=sr_1_1?s=books&ie=UTF8&qid=1354458839&sr=1-1You don't specify the level of sophistication for the articles so i hesitate to recommend any textbooks on control theory, unless maybe "The Control Handbook" by William S. Levine. It is actually a 3 part series: "Control System Fundamentals"; "Control System Applications"; "Control System Advanced Methods"http://www.amazon.com/Control-System-Fundamentals-William-Levine/dp/0849300533/ref=sr_1_13?ie=UTF8&qid=1354458737&sr=8-13Meanwhile, could the attached conference paper contain anything of interest?Edit: My bad, you did say 'fundamentals'...

author: Gall
author_rank: Frequent Contributor
timestamp: December 02, 2012, 04:20:12 pm
content: The easiest way to get into fundamentals is to consider the SMPS to be just a (PWM-mode) amplifier with a constant voltage at its input. First apply everything you know about amplifiers and then remember it is switch-mode so it has some ripple. Most likely you've read a lot about closed-loop stability already, so that's how this does apply here.

author: rbola35618
author_rank: Frequent Contributor
timestamp: December 06, 2012, 05:11:34 am
content: Hi EEVbloggers,I just posted these videos on the Product Review, Photos, and Discussion. These videos may help you.Part 1In this video I introduce a symplified average taught to me by my mentor Jack Alexander. I explain his method of compensating the loop which is mostly graphical in nature. You can use the simulator to calculate the poles and zero and set them to cancel each other.Part 2:In part 2, I used the Basso's Current Mode switching model to verify Jack Alexander's Average Model. The results agree witheach other thus verifying Jack Alexander's modelPart 3;In part 3, I show how to use the Jack Alexander's model to simulated a Voltage Mode Forward Convert. I explain what a Type 2 and Type 3 Error amps are and when to use them. I go step by step in compensating a second order output filter and show how to damp a second order output filter. Also show how to use SPICE to plot the frequency response of the power supply's Output filter as well as the frequency response of the Error Amp.Questions and comments are welcome. Hope you find the video useful.Robert