why does your computer need a power supply anyway
you've already got tons of power coming right out of the wall
oh it blew the fuse
that's why but why didn't this work
and what does a power supply actually do to answer those questions we'll be
taking you through all the stages of your computer's power supply and how
they work sponsored by seasonic from the
wall you get alternating current or ac power which historically has been
cheaper to generate and efficiently transport over long distances which is
great but not for a computer computers work by
storing ones and zeros in logic gates and for logic gates to function a very
stable input voltage is required ac which goes from positive to negative
voltage many times a second could be
used but it's kind of like how you could also build a car with square wheels
you shouldn't so then our wall ac power needs to be
converted to direct current or dc which
has a constant voltage no problem
let's talk about linear power supplies
from the wall you're getting either 110 or 220 volt ac power since we're in
north america we'll be using 110 volt for our examples now that is still a way
higher voltage than what you want for your computer so the first major stage
is a transformer that takes us from 110
volt ac to 12 volt ac transformers are relatively simple
when ac current travels through a wire it creates a magnetic field this
magnetic field can be made much stronger by wrapping the wire into a tight coil
and then if you place another coil right beside it the changing magnetic field
will start moving the electrons in the second wire that voltage that you get on
the second wire is then determined by the number of turns in each coil so to
take our 110 volt down to 11 volt we
could have 100 turns on the primary side and just 10 on the secondary once we're
at a more manageable voltage we're ready to turn that ac into dc using
a rectifier rectifiers work on the basis that diodes
only allow electricity to flow in one direction so you chuck ac through it and
it spits out something a little bit like this
you just add a capacitor and bam dc now
the formal name for this circuit right here is single diode rectifier but more
commonly in electrical engineering circles you'll hear it referred to as
crap that's where something called a full
bridge rectifier comes in for a more detailed look at the full bridge
rectifier you can check out this classic from electroboom but we can get you
through the basics by using four diodes in this configuration on the positive
wave electricity flows through diode one and three to complete the circuit and
then on the negative wave it goes through diodes two and four that leads
to much less waste then from here you
just chuck a capacitor on the output and
boom you're good to go linear power supplies are actually still
used for many things including musical instruments thanks to their ability to
deliver very clean power but unfortunately you wouldn't want to
use one for your computer due to their 60 plus turd efficiency rating and then
there's also the fact that they only work for a single input frequency and
voltage so power supply manufacturers would have to make completely different
models of the same power supply capacity
for every different market so
wait a second why did i just explain linear power supplies then
because someone had to give them the background that they need for this next part about what we actually use
switching mode power supplies let's take a journey through your psus starting at
where the ac enters and leaving you know
where the dc goes to your motherboard before we can even worry about
converting from ac to dc we need to do a bit of filtering so these little blue
boys in here they are called y capacitors and the gray one right there
that's an x capacitor these guys prevent your computer from sending electrical
noise back into your house wiring which could cause problems with other devices
meanwhile we also have to filter the incoming power so your computer doesn't
get all screwy when your roommate fires up the blender to make some margaritas
my favorite part of this emi filtering stage is hidden in here it's called a
metal oxide vary resistor or mauve and it's cool because this changes its
resistance based on the input voltage so normally it's just chilling there acting
as an open circuit but when a voltage spike comes in its resistance drops and
that extra energy just gets chucked to the ground instead of you know blowing
up everything else in cheap power supplies the mob might be omitted and if
it is you should emit that power supply from your parts list once the signal is
clean we can turn our attention to power factor correction as ac flows through
inductors or capacitors the voltage and current will get out of phase with each
other resulting in wasted energy this bank of mosfets and bagel inductor make
sure that you get as much from your ac input as possible at which point is
chucked through a rectifier right there and out of that you get three to 400
volts of dc next these big chungus
capacitors smooth out the voltage of the dc current flowing from the main bridge
rectifier and side note i would strongly recommend not looking these
now let's talk about the most surprising part we've gone from ac which comes from
the wall to dc which your computer needs and now we're going to go back to ac
and stay with me here because the payoff is huge to do it we run dc through our
mosfets that are right there giving us ac power but in a square wave which is
fine except that every time that a mosfet gets turned on or off you lose
some efficiency to almost entirely reduce these switching losses a
technique called soft switching is used so in parallel to these mosfets is a
capacitor and an inductor that will begin to resonate as the mosfets are
switched the resonator creates a sine wave and by syncing up the mosfet switching
to when the sine wave is close to at zero you can almost entirely eliminate
the switching losses i'm not even going to pretend how to understand the math
behind how this works but if you think you've got the stuff here's a paper to
enjoy as part of your phd in electrical engineering long story short we now have
ac power again but it's perfectly power factor corrected and at a much higher
voltage and frequency compared to what's coming out of your wall this allows the
main transformer right here to be both much smaller and a lot more power
efficient as it converts into 12 volts ac which is then fed into the rectifier
right there and you have 12 volts dc for your pc
for those of you paying very close attention that was it we finally came back around
to how your computer uses a linear power supply but not quite like we talked
about before just with extra steps hey there it is i knew we were gonna
make it back here then we take that 12 volt dc and we add some hefty capacitors
for filtering and to improve transient response
in layman's terms this 3300 microfarad
capacitor here is going to do a lot to prevent a voltage drop if your rtx 3090
decides it suddenly needs 500 or 600
watts for a few milliseconds not everything in your pc uses 12 volt
however so we also need these dc to dc
buck converters to get us 3.3 and 5
volts giving us everything we need to run a computer except
the ability to turn it on see this other mini transformer over
here this little fellow takes our high voltage dc from before and turns it into
5 volt standby which is always on even when the computer is turned off allowing
it to power things like motherboard RGB and always on usb charging ports
oh right and also it powers the power button so that you can fire up your
machine and get on with important tasks like visiting ltdstore.com where we have
great merchandise like these high quality t-shirts fantastic water bottles
and even but none of that really explained why good power supplies can
cost anywhere from one to five hundred dollars something you've probably heard
talked about in community forums and even power supply marketing is component
quality with japanese capacitors coming up a lot but do they even make a
difference these days probably not
but that doesn't mean they're a bad thing between 1999 and 2007 there was a
capacitor plague where capacitors made in taiwan experienced a higher than
expected failure rate due to issues with the raw materials used to manufacture
them while capacitors in japan experience no such problems
since then capacitors made in china and taiwan have greatly increased in quality and the
vast majority of japanese capacitors are just japanese branded capacitors they're
actually manufactured in china with that being said there is still some
value to japanese capacitors because typically they are designed and tested
to meet the quality requirements laid out by the japanese companies overseeing
their production to figure out if any individual company is good though tom's
hardware created a capacitor tier list that you can reference when trying to figure out if a specific component is
good or not the overall capacitance of your power supply can be a double-edged sword
though one thing people often get wrong is automatically assuming high
efficiency equals high quality but unfortunately this isn't always true an
easy way to boost the efficiency of your power supply is to reduce the capacitance you no longer have to worry
about charging up those big old caps so you waste less power but you could fire
up a game and end up rendering nothing but a black screen and do we have
hardware info computer
and that my friends is why you don't buy your power supply on aliexpress.com
evaluating how different power supply manufacturers have balanced efficiency
and transient response is beyond the scope of this video but we wanted you to know that filtering
by 80 plus rating and sorting by price isn't the way to go low capacitance can
also be a problem for small form factor power supplies there's simply less space
to add capacitors in general this won't be a problem but if you're building an
sff pc that is high powered maybe consider over speccing the power supply
a bit just to be on the safe side also to be on the safe side never mix
modular cables between two different power supplies even if they look
identical there's a chance they are different and if they are it's magic
smoke time it's always bothered me why they aren't standardized though and i
was finally able to ask turns out the answer is pretty simple everyone
developed modular power supplies around the same time and the connectors were
almost arbitrarily chosen by each company based on their current pcb
layout and the connectors easily available from their suppliers maybe
modular cables can get standardized if the specs change
and there is a good chance the spec for power supplies could change soon the atx
standard has only gotten relatively small revision since it was created by
Intel way back in 1995 and there are some problems with this like power
supplies in 2020 needing to output 3.3 and 5 volts despite these voltages
barely being used by modern hardware but this could be changing soon in june
2020 version 2.53 of the atx standard
was added where the power supply would only be delivering 12 volts and the
motherboard would be responsible for dc to dc conversion as i showed in this
video this should result in significant real-world efficiency improvements
especially at idle but the people we talked to wished Intel had gone even
further and switched to 24 or 48 volts like you might find in industrial
applications basically higher voltage means less
current at a given power and less current means less heat generated and a
higher efficiency which brings us to the final reason why buying a quality power
supply is a good idea good old mother earth as much as electronics makers try
and put a positive spin on their environmental progress apple
pretty much every component in your pc will offer up mediocre performance in a
few years or be downright broken high quality power supplies though can last
you through multiple upgrades see sonic the sponsor of this video has up to
freaking 12 year warranties on some of their units so at least that's one part
that won't end up in a landfill anytime soon so huge thanks to sonic for
sponsoring this video providing us with technical support for this piece and
thanks again to johnny guru for his insight as well thanks for watching this
video and if you were looking for another turbon i can't do it
and if you're looking for another turbo nerd video maybe check out how
motherboards work turbo turbo nerd turbo nerd is so hard to say
fast yeah you chucked it twice in the same sentence alex killing me
i'm done i'm out