How to learn SMPS design  - Page 1
Forum section: electronics / beginners

author: NORange
author_rank: Contributor
timestamp: August 31, 2025, 07:34:26 pm
content: Hobbyist here trying to learn power electronics. I wonder what is the workflow when designing a SMPS (analog/microcontroller-based)? Can you recommend a portable oscilloscope suitable for beginner use (I'm a student renting, so I'm unsure if a bench one is a good idea). My previous post is just for getting comfortable with PCB layout from a given schematics. What are some other equipment that I might need to get?

author: Laval
author_rank: Regular Contributor
timestamp: August 31, 2025, 08:36:39 pm
content: Hello and welcome to the forum.It's not clear for me what your current background is or if you are a student in EE. As a hobbyist are you looking to be able to build SMPS from existing design (schematics) or are you interested to design the whole device from scratch ?Designing a SMPS from scratch can be quite tricky. You need to understand how PWN works even to be able to use a PWN IC correctly, you need to understand feedback too. You need to understand electromagnetics and how transformers and inductors are used in the different topologies (which is also something you need to learn about). Filtering is also an important subject as well as PFC.Don't get me wrong, I'm not trying to discourage you or to tell you you shouldn't do it. It quite an interesting field but it requires a lot of background which you will need to acquire.As for Oscilloscope, a small bench instrument could be a good idea. 100MHz to 200Mhz should be fine. 12 bits is nice especially for measuring low amplitude noise.Just to give you an idea:https://www.onsemi.com/pub/collateral/smpsrm-d.pdf

author: NORange
author_rank: Contributor
timestamp: August 31, 2025, 09:14:00 pm
content: I'd love to design custom SMPS devices. I transferred to EE in January and has since been considering doing power electronics/analog/RF related stuff for fun and for, hopefully, a career. Previously I took an analog circuit course and currently I'm learning antenna design which covers emag. This summerbreak I looked into designing a pfc + psfb SMPS, but was nonplussed. The design guides that come with SMPS ICs have confusing transfer functions and feedback networks that I had no idea how they're derived/designed. Hence the post.

author: petemate
author_rank: Regular Contributor
timestamp: August 31, 2025, 09:44:44 pm
content: Switchmode design isn't something you just pick up. Its several years worth of studying analog electronics, switchmode design, EMC and layout, feedback/control systems and magnetics. There is also a significant element of danger, since there may be mains power involved.Most engineers can put together something acceptable using off-the-shelf regulators/controllers, but understanding every aspect in details is much harder. I'd suggest you start with something simple, e.g. a 12V-to-5V buck converter based on a classic, generic controller chip(e.g. UCC3842 or something like that). It will teach you all the general aspects, and there are plenty of resources available online to guide you through the design steps. Then, move on to something with galvanic isolation, eg a flyback, and finally to something bridge-based.You can do much of this without hardware math, but if you desire to build mathematical models of your systems, you are in for a bit of studying. In that case, get a book, e.g. "Fundamentals of power electronics"(or perhaps something newer, this is getting pretty old but is still considered the bible on the subject).Stay away from PFCs for now. You need quite a bit of experience and special equipment when you are working with mains stuff.

author: Benta
author_rank: Super Contributor
timestamp: August 31, 2025, 09:55:11 pm
content: Here's a good (and free) start:https://www.onsemi.com/pub/collateral/smpsrm-d.pdf

author: Smokey
author_rank: Super Contributor
timestamp: August 31, 2025, 10:38:01 pm
content: Quote from: petemate on August 31, 2025, 09:44:44 pmwhat he said... Even if you have all the right equipment, just probing switchers is a non-trivial problem that can lead you down many a dead end.But with that said, there is still lots of stuff to play with.Here are some good books (get them used off ebay or something, or find the PDFs):https://www.amazon.com/Power-Supply-Cookbook-Design-Engineers/dp/075067329Xhttps://www.amazon.com/Practical-Design-Power-Supplies-Lenk/dp/0780334582/ref=monarch_sidesheet_titleUnless you are doing something big and special, off the shelf solutions exist for most power supply jobs these days, and they perform significantly better than you could hack out of all discrete parts and home spun controllers.TI Webench is a great resource for fully defined schematics and they have parts for essentially any type of power supply topology:https://webench.ti.com/power-designer/switching-regulatorAnd this is my recommendation to anyone looking to get into power stuff and wants a practical project. Build an audio power amplifier (again, easy to find the PDF of this one).https://www.amazon.com/Designing-Audio-Power-Amplifiers-Cordell/dp/1138555444/While not a SMPS, a project like this will teach you all about a ton of basic important electronics principals that are much more widely useful and at a frequency that is more forgiving that 2MHz switching waveforms.There are a ton of threads about new EE's first lab equipment. Don't go cheaper than Siglent and you should be fine. Scope + Arb + 3 Output Power supply + multimeter at a minimum.Don't forget decent cables for all the bench stuff. Here are the ones I got a bunch of and I'm pretty happy with.https://www.amazon.com/Sumnacon-Inch-Multimeter-Test-Lead/dp/B07VDNHCFMhttps://www.amazon.com/Sumnacon-Stackable-Silicone-Multimeter-Electrical/dp/B07179VF5J

author: MariuszD
author_rank: Regular Contributor
timestamp: September 01, 2025, 10:06:33 am
content: Quote from: NORange on August 31, 2025, 09:14:00 pmThe first need is to acquire the knowledge how they work. Workflow is easy if you know what you want to do.Quote from: NORange on August 31, 2025, 09:14:00 pmTransfer functions are the most difficult thing. For that, you need to know the necessary mathematics.You write that the transition functions are confusing to you. Does that mean you know how to calculate transfer functions, but you don't know how they were derived, for a specific circuit, or you don't know how to calculate them?I learned the basic principles of how SMPS work as a teenager, but I only learned complex analysis in university. Only then could I understand the whole design process.Most non-isolated DC-DC converters have built-in compensation and do not require calculating these parameters, only selecting the parameters of the output LC circuit. You just need to stay within the manufacturer's planned limits.In isolated converters do you have to calculate the frequency compensation yourself.

author: Gerhard_dk4xp
author_rank: Frequent Contributor
timestamp: September 01, 2025, 12:56:53 pm
content: Get the book by Abraham I. Pressman: Switching Power Supply Design. McGraw-HillI wished I had bought it _before_ my first switcher design.Gerhard

author: PGPG
author_rank: Frequent Contributor
timestamp: September 01, 2025, 02:09:28 pm
content: Quote from: NORange on August 31, 2025, 07:34:26 pmOscilloscope and multimeter are really must-have tools. Other are in most cases optional.For 14 years I was playing with electronic having no oscilloscope (since I build my first radio receiver (being 10) till I build oscilloscope (being 24)).Others helpful:- power supply,- sin/triangle/square generator,- frequency counter.Quote from: NORange on August 31, 2025, 09:14:00 pmIf you need to be DCDC theoretician than you should learn it.If you just want to use DCDC ICs than in most cases their datasheets contains step by step design processes. If datasheet is not enough clear in it you can just select different IC.When in 2014 I was selecting IC for my use I have selected relatively new (designed in 2012) TI: LM5017.I really like that you can:- directly step down from 7.5V...100V down to 3V3,- have semi constant frequency from 0mA to full load (I even prefer semi constant over constant because of EMC),- need not be care of feedback network analysis,- reaction to load step change in one pulse (typical Current mode feedback DCDC need about 5..10 pulses to react).Reading IC datasheets (some are very extensive) is in my opinion good way to learn how they work.When those time I have read LM5017, LM5018, LM5019, LM25017, LM25018, LM25019, TPS54060, TPS54061, TPS54062 datasheets I have written to TI describing errors in their Application Information. Their application engineer agreed with all my complains and said that he sends all 9 datasheets to be revised. I was proud of myself until I saw these revised versions.They simply added a note telling:---------Information in the following applications sections is not part of the TI componentspecification, and TI does not warrant its accuracy or completeness. TI’s customers areresponsible for determining suitability of components for their purposes. Customers shouldvalidate and test their design implementation to confirm system functionality.---------and left everything as it was before.