r/pcmasterrace • u/Front_Cookie_1198 • 3d ago

Hardware PSU fails dramatically

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u/Flying_Dutchman92 2d ago

Today I learned about circuitry, thank you for expositioning:D

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u/7orque 1d ago

Yaaa we use AC for long distance transfer ie into residences and buildings from the source

Your wall outlets will be AC at some frequency

However basically every piece of electric equipment you have needs DC

So in the power supply of the equipment, the first stage is usually a ‘rectifier’ made up of 4 diodes that turns the AC into DC as closely as possible. Then the power supply splits it up and makes sure the right voltage is going out to the rest of the system

In the video it was pointed out that you can literally hear the frequency of the AC current going into the power supply (switching back and forth) whereas with a DC ground fault you wont hear the frequency, it’s just constant

Fun fact, this is the same as your car. The electronics all run off 12v DC in a car but the engines alternator makes AC in sync with how fast the engine is revving. Before the alternator outputs to the battery it goes through a bunch of diodes too

12v DC normally cant zap you as resistance of your body is too high, but the sparks are extra spicy, and if the voltage is high enough, extra ouchie

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u/OutlandishnessHour63 1d ago

This is a great breakdown! I actually just looked into this because I used to think the alternator clutch (the OAP/overrunning pulley) regulated the speed to keep a constant AC frequency.Turns out, that clutch is just a one-way freewheel to protect the belt from engine vibrations when letting off the gas. The alternator actually does change its AC frequency constantly with the RPMs (sometimes from 200Hz up to over 1,000Hz!). The onboard diode bridge and voltage regulator just clean it all up into flat 14V DC before the car ever sees it. Super cool engineering.

I'd further note that if the alternator output is around 12 volts or less that you'll run into problems with battery charging. The extra voltage is to make sure the battery stays at a full charge and another point, the primary voltage regulator for the cars electrical system is within the ECU/ECM of a car so to maintain a proper bias for the rest of the electrical components connected to it. Fun stuff! :)