Technical Insights > Benchtop

Stump the Pros With a Simple SMPS Question - What Are These Power Supplies Actually Called?

2020-09-04  |  7 min read 

"An SMPS by any other name would switch as sweet" - Shakespeare the power supply engineer, probably

What does the “S” in SMPS stand for?

Switch? Switched? Switching?

I thought I knew. Wow, was I wrong! Maybe. You'll have to read on and decide for yourself.

It all started as we were trying to name our new course exploring how to test switching power supplies (aka switch mode power supplies, aka switched-mode power supplies).

Side note: if you want to sign up for the course, it’s free and <1 hour!
Go check it out >>

I always thought SMPS stood for “switch mode power supplies.” As I did my due diligence, I found something really odd. A lot of companies call them “switched-mode power supplies” or simply “switching power supplies.”

Huh.

I had to know what the actual answer was. It was burning me up inside like a busted SMPS’s switching transistor.

I scoured the web to see what large, respected companies called these things. There was no clear answer.

People think SMPS stands for…

So, I had to bring my research to the streets. By "the streets" I mean “Twitter.” I put out a poll on my Twitter account (why not?) and got 102 responses. 67% of the respondents said it was “Switch mode power supplies.”

What does SMPS stand for? (Twitter poll)

Vindication!

I generally only post test gear and electronics content so the folks that follow me on Twitter are into that sort of thing (shameless plug: @DanielBogdanoff).

But, 26% answered “switched mode power supplies” and 7% said it could be either. It seems people feel strongly about one or the other - very few people said it could be both.

These results were far from satisfying and not as vindicating as I’d hoped they would be. When I find out I got the answer right on the first try it usually means I didn’t look hard enough. So, gosh darn it, I had to keep digging.

I broke out the big guns (metaphorically, but this is America so you have to be specific), and assembled a crack team of power experts here at Keysight.

Keysight Power Supply experts think SMPS stands for…

I went to my power mentors. They taught me everything I know about switching power supplies / switch mode power supplies / switched mode power supplies.
Google is now going to flag this post for keyword stuffing, I guarantee it.

Hilarity ensued.

Here are some of the comments from some folks that have literally spent years working with SMPS testing:

"Wikipedia says that SMPS stands for ‘Switched-mode Power Supply.’ Wikipedia is always correct. Right? I guess I now need to edit all of my application notes ☹."

"I guess it depends of whether you are referring to historical or contemporaneous power.” -uh, what?

“So I guess ‘switched’ is probably the most grammatically correct. I usually say ‘switch mode power supply.’ But some people say ‘switching power supply.’”

Clear. as. mud.

But it goes on:

“I thought it was “switch mode power supply,” however I am out voted by our own website [Keysight.com]:

Switched mode power supply: 3180 results
Switching power supply: 2630 results
Switch mode power supply: 2450 results
Switcher: 109 results, but I hear it in the hallway more than that.

And some feedback from a professional power engineer turned amateur historian:

“In the 1978 Power Supply Handbook, it only references ‘switching power supplies.’ – yeah and gas was $0.63 a gallon.

Here’s some extra help from @techca on twitter:

Gah.

This is going nowhere. Time to harness the power of big data. BIG DATA EVERYONE. My buzzword bingo card is starting to look a little better.

Google thinks SMPS stands for…

I pulled up good ‘ol Google Trends to see which search terms were the most popular:

SMPS Google Results

Clearly, “switching power supply” is the big winner, with “switch mode power supply” coming in 2nd place.

“Switched mode” and “switched-mode” came in last, with the non-hyphenated version taking a slight lead.
I love that the word “non-hyphenated” has a hyphen. Just gonna sneak that juicy tidbit in there for you.

The last bit of information is that Google considers “Switched-mode power supplies” to be a “Topic.” This means all these other terms fall under this topic. My best guess is that Google is using Wikipedia as the key indicator of term authority in the absence of another clear winner.

I hate to admit it (because I don’t like to be wrong), but there’s a strong case to be made for the term “switching power supplies.” @Sergej had it almost right maybe? If you speak German, check out his YouTube channel for some great electronics repair videos.

However, it doesn’t match up to the acronym SMPS soooooo I’m going to go ahead and say that I’ve been right all along. And - according to my Twitter poll - 67% of you are, too. Congratulations, us.

If you want to learn more about testing switching power supplies with an oscilloscope and escape the weird rabbit hole I’ve sucked you into, go check out the class “Switch Mode Power Supply Testing 101.” It’s free and can be done in less than an hour!

Switch Mode Power Supply Testing 101