Just wondering cus like wouldn’t it be more convenient to just plug your phone into the wall without a brick, or like cheaper to build a pc without a power supply? why do these devices need DC but lamps, fridges, fans, most household appliances can run off AC?
In: Other
Motors and heating elements run fine with AC. Transistor based circuits tend to explode when their supply is AC. Processors designed so small that 2V already risks internally arcing across wiring really don’t like 230V. If your device is more complex than a motor with a switch, it starts making sense to have a DC power supply.
Most of those household appliances are also converting some AC to DC to run the internal electronics.
Electrical motor and heaters can run on AC but complex electronics wilt logic circuits can’t.
Monolithic large appliances that just use DC will have the AC to DC converter built in. Som small like LED lamps often convert the power to AC internally.
You could have AC to DC conversion in a phone. The problem is that it significantly increase the size. It is simply more practical to have it externally when it is not needed all the time.
DC is easier to work with. Most “fine detail” electronics have an AC-to-DC transformer either inside them or in a separate power supply. As for convenience, there are USB wall sockets available for USB powered devices. PC power supplies aren’t sufficiently standardised to replace them that way.
Anything using transistors (so pretty much all electronics) and / or batteries will use DC, because both of those elements fundamentally work on DC. It’s part of how they physically function.
It’s possible to create a sort of imitation AC out of the DC supplied by batteries, but it’s rarely necessary. It’s kinda sorta done with brushless DC motors.
Other things, like electric motors, incandescent bulbs, heaters etc. run on AC because they can, that’s what’s in the wall. In case of electric motors, AC are actually simpler than DC motors. So are transformers. Other things could run just as well off of DC, but why bother.
Phone’s would run on dc for the battery anyway circuit board’s require small voltage and have internal battery to store things like time ect so it makes sense to run on dc
If you wanted to plug your phone into the wall “without a brick”, your phone would have to include the electronics that are inside the brick inside the phone itself. This means your phone would be 20% bigger, and that 20% biggerness would be with you all the time, even if you only need them for a couple of hours when you charge your battery.
If you tried to put the electricity from your wall directly into a piece of electronics without going through a power supply, the device would in the best case stop functioning, in the worst case literally catch on fire. The circuits that make these devices function are too delicate to be able to handle the much high voltages that the power grid operates on, and the circuits would literally disintegrate from the very high temperatures that would be caused by squeezing a very high voltage through a very very *very* thin wire.
Typically speaking, the thinner a wire is, the less electricity can pass through it. The wires in a computer chip are so thin that you can’t even see them with a magnifying glass, so the amount of power that can fit through them is very little.
You might ask why this is fine in a light bulb, as that’s also a very thin wire but still hooked up to mains voltage. Well, old-school lightbulbs are made from tungsten, which is a very heat-resistant metal. You can’t really make electronics from this material because it’s not a semiconductor. Furthermore, this wire is encased in an oxygen-free gas, which means even if it gets hot, it can’t burn up because there’s no oxygen available to burn in. Had the light bulb not had this, the glowing wire would burn up in less than a second. Also, that tungsten wire in a light bulb is still over a thousand times thicker than the wires inside in a computer chip.
Why they want DC instead of AC is a completely different topic. Whether you want to run a digital or an analog system, you want the input voltage to be stable. AC means the intensity of the electricity goes up and down 60 times (in some regions, 50 in other) a second, and this will severely interfere with the work that the circuit is trying to do. For example, if you have an analog speaker amplifier and some of the mains voltage gets into places it’s not supposed to be, you might get a 60 hz humming in the speakers, which wouldn’t sound very nice.
The explanation is really outside the house; in the power grid.
To carry power a long distance (from power station to your home), the power needs to be a very high voltage otherwise it would just heat up the wires instead, wasting almost all of the power generated.
But that high voltage is too dangerous to enter your home – it can create arcs that leap several feet from the wires and kill you. So the voltage has to be lowered. The only realistic way to change voltage at grid scale is a transformer, and a transformer only works with AC. Conveniently, AC is also what a generator generators, so the whole grid works better and cheaper on AC
Most home appliances could be made for either AC or DC or would prefer DC, but a bunch of small adaptors in the house is easier to manage than the massive consequences and expenses of a last-mile DC grid
imagine ac power is like a wiggly line that goes up and down, while dc power is like a straight line. Household things like fridges are okay with wiggly power but phones and computers prefer straight power to work there best
AC is basically the biggest strongest athlete you know, UFC/WWE/NFL/etc. DC is like a 5 year old. AC is typically between 120 and 240V, while DC is between 3 and 12V (or less). Put that AC into a DC circuit and its like letting that big-bad athlete fight a 5 year old, it won’t end well for the 5 year old.
Devices with an LED/LCD display, connect to wifi, or are ‘smart’ will all internally convert AC to DC. Simpler devices that are basically just a motor and switch may just be AC.
AC is used because it can be distributed over long distances with little loss. DC is needed more modern electronics, and where storage (a battery) is used.
Latest Answers