Anatomy of a Power Supply Unit (PSU)

[jtveg]

Thanks for sharing. ? ??

 

[QuantumPhysics]

Hehe a sucker born every minute. Much of the sales of power supplies is kids buying shiny objects, they want a red fan, purple light etc. And some just want higher numbers. Paint 10,000 watts on side they flock to them. Today you need even less than in the past for the average computer. We are getting MORE efficient. Some think the 1000 watts make their computers run way faster etc. Lots of wives tales with power supplies.

If I was running dual 2080Ti in SLI with my i9Extreme, yeah I’d have an EVGA 1000 or 1500

 

[Theinsanegamer]

Love the article. I recommend, if you ever need a power supply, either a seasonic or superflower based unit. They are well made and last FOREVER. My rosewill quark is going on 8 years now with no issues on its 4th build.

 

[tonyd]

What's the gloppy stuff?

Interesting question. You often see a type of electrical version of Silicone Sealant used to add some mechanical stability to large items like big Electrolytic capacitors, as they might pull the connection wire out of the soldered joint if the item was thrown around during shipping, and they joggled about.

 

[Ryan Barrett]

Love the article. I recommend, if you ever need a power supply, either a seasonic or superflower based unit. They are well made and last FOREVER. My rosewill quark is going on 8 years now with no issues on its 4th build.

I've been hearing about Seasonic forever but I generally don't see many specifically sold by them. Is there any kind of list you can point me to as to which brand/model PSUs are made by Seasonic? I currently have an EVGA 750W Green PSU which came in my Skytech Prebuilt (all made with name brand parts, Aorus 2080, team RAM, Asrock killer Mobo).

 

[Fimbulvetr]

Paid well over $100 for a Corsair PS. It lasted two days and quit. I put a cheap, no-name PS rated at the same watts in the same system, and it has run the system now for years, 24/7, with no issues at all. Sometimes you don't get what you pay for.

 

[Babbel13]

I recently built a Core i9900ks with EVGA 240mm AIO computer for one of my cousins. He chose a Corsair 850 and I ended up exchanging it for an EVGA model instead. Cables were too short.

The EVGA 850 had two power switches, longer cables and just felt like a higher quality product and it was only around $30 more.

I just wish PSU had an easily accessible, user replaceable fuse or circuit breaker as standard because the PSU is usually the first part to shut down if there's a short or a mistake made during the connection process.

In the end I felt so much better sticking with EVGA than the corsair.

He's happier as well.

There is really no use in having a fuse that is user replaceable in a switching supply. All the outputs are self protecting from short circuits and if the switching FETs short on the primary the fuse will blow but replacing it won't fix anything.

 

[Babbel13]

I am a retired power supply design engineer. The article did a nice job of explaining various components and how they work. The items on the front end are called EMI filters. Design flaws aside, power supplies using double sided boards are usually more reliable (the one shown is double sided). Also, note that only one output can be fed back to the primary pwm circuit for regulation. That use to be the 5V output but since the 12V output is usually the highest power for personal computers, that one is usually regulated by the PWM control. The post regulators (VRM) are usually called magnetic amplifiers (mag amps) and are very efficient.

Power supply design is very underrated and is not easy. It includes magentics, EMI filters, feedback loops, safety circuits. Supply topologies and a lot of component knowledge are also needed.

 

[Babbel13]

Efficiency also goes way down for linear regulators.

Switchers also tend to respond to transients far faster than linears.

I would disagree with that statement. Linear regulation has a shorter/ faster feedback loop (all on the secondary side of the transformer) than a switcher. Switching regulation feeds back from the secondary side to the primary side usually using opto couplers. The bandwidth roll off is kept fairly low to prevent oscillation. This longer loop using multiple components is slower. You might find an excellent switcher that is faster than a poor linear regulator but normally this is not the case.

Linear supplies use 60 Hz transformers which are big and heavy. Efficiency is usually around 50% but varies with line voltage. Switcher efficiency is pretty constant with line voltage since it just adjusts its duty cycle.

 

[grvalderrama]

Great reading! One question, I was told that inductors can store electrical energy even when the psu's unplugged and that's why opening a psu can be dangerous, is this true? And, whatever the answer is, for about how long do inductors store electrical energy? Thanks!

 

[neeyik]

Inductors store electrical energy in a magnetic field, but that's only present when there is a current flowing - no current, no field, no stored energy. Capacitors, on the other hand, do store energy, even if there's no current.

Small caps don't store that much, so they're fine, but PSUs are packed full of large capacitors - they don't store for hours on end, but they will store it long enough such that if you immediately unplug the PSU and then go poking around inside, there's a good chance you could empty the cap instantly across your fingers.

And that will hurt. A lot.

 

[grvalderrama]

Inductors store electrical energy in a magnetic field, but that's only present when there is a current flowing - no current, no field, no stored energy. Capacitors, on the other hand, do store energy, even if there's no current.

Small caps don't store that much, so they're fine, but PSUs are packed full of large capacitors - they don't store for hours on end, but they will store it long enough such that if you immediately unplug the PSU and then go poking around inside, there's a good chance you could empty the cap instantly across your fingers.

And that will hurt. A lot.

Thanks for your answer!

 

[BernieW]

I don't understand how two separate AC terminals go to the bridge rectifier directly from the mains line and neutral supply. Should there be some transformer or other device in the first stage of the PSU?

 

[cliffordcooley]

Should there be some transformer or other device in the first stage of the PSU?

When supplying lots of power, higher voltage levels are preferred.

Car stereo electronics for more than 30 years have inverted 12V to more than 30V. With higher power amps, the voltage levels are even higher.

With absolutely no knowledge as to whether the power supply transformers have been removed. I can understand why they would do so in high power units. Especially when you understand how difficult it is fighting ripple under large loads.