What is exactly happening when AC power is being converted to DC energy?
In: Technology
A simple explanation using water as an example.
One cycle of the pump will put some water in a bucket, and then stop flowing. Each cycle of the pump will dump some water in the bucket.
The bucket has a hole in it that can allow water to flow out of it at a certain rate based on the gravity and the pressure of the water accumulating in the bucket.
If the pump can provide enough water to the bucket so that a steady flow of water exits the hole, we have achieved the goal.
The pump keeps pumping in water each cycle (AC), the bucket (capacitor and inductance) accumulates it and allows it to flow out at a steady rate and pressure (DC)
There are different ways to achieve this with components.
There’s a few steps
Usually the first step is an AC/AC transformer which reduces the voltage closer to the final voltage.
Then some one-way valves (diodes or rectifiers) are wired in such a way as to change the electrons from moving both ways to moving one way only. However it’s still pulsing on and off.
Then there is usually a filter which smooths out the pulsing. This usually consists of one or more capacitors, which are kind of like batteries, or an electron-balloon.
Finally there is usually a regulator which acts like an automatically adjusting variable resistor designed to maintain a constant output voltage. This is much more important for electronics than, say, a fan.
Some of the fancier regulators (switching regulators) actually convert the DC back to AC and then back to DC again; this is more efficient, because instead of acting like a variable resistor, it’s merely turning on and off very fast, which has the same effect, but without heating up the resistor. (although it can heat up the switching transistors)
This is one of those things that’s much harder to explain with just words, so I’m going to invest about a hundred seconds in MSpaint to make some bad images that will help a great deal.
First off, DC, or direct current, is electricity that flows in one direction.
AC, or alternating current is simply electricity that switches directions on a regular basis. Household AC switches 60 times per second.
AC starts out looking like this on a device called an oscilloscope. You can see it smoothly changes from one direction (positive, or +) to the other (negative, or -):
Using a pretty simple circuit, you can ‘cut off’ one side and send it all in one direction, so that it looks like this:
That circuit just uses a few components called diodes, which only allow electricity to flow in one direction through it.
The problem is that it isn’t very smooth. It’s more like very fast bursts of DC current, so we need to try and fill in those gaps.
To do that, we use a component called a capacitor. That device is like a tiny battery. When there is current going through it, it charges up. When there isn’t, it discharges. We can use these to sort of fill in those gaps, like so:
The better a job done by the capacitors, the more it looks like a straight line, the closer to pure DC it gets.
There are more modern ways of converting AC to DC with much more accurate results using transistors, but this classic way has been around for a very long time.
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