What is exactly happening when AC power is being converted to DC energy?

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What is exactly happening when AC power is being converted to DC energy?

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13 Answers

Anonymous 0 Comments

Imagine the energy as some water. Now imagine a big glass of water – something like a water tank full of water with a hole in the bottom with a continuous output flow. This is your D.C. current. Now, imagine that you bury this water tank in the sand on a beach and that each wave that arrives fill it a little bit (and you still have a the water going out of this tank). Well, the waves are you A.C. current entering in pulses in your tank. When an A.C. to D.C convertet is designed, its basically a calculation on how much you can bury your tank in the and the size of your tank (voltage and capacitance value for the capacitors) in order to have a more or less stable output flow out of the tank – also depending on the frequency of the waves arriving.

Anonymous 0 Comments

It always bothered me that devices that used batteries require them to be installed with the correct polarity. Just a couple diodes and that would allow the battery to be installed in any direction. Especcially things that only need one battery.

Anonymous 0 Comments

The most important part is the bridge rectifier. We use little electrical one way valves (diodes) so that no matter the input voltage (+ on top or on the bottom) you always get positive voltage on one wire and negative on the other, [the wiki has a nice GIF showing this](https://upload.wikimedia.org/wikipedia/commons/3/34/Diodebridge-eng.gif)

Generally we will put a big capacitor on the output to store the energy. This capacitor takes the ups and downs that are coming into it and stores the energy so it just sits at the peak voltage.

Now you’ve got a constant voltage that you can use to power things or can step down to a low voltage using a DC-DC converter so you can get 5V for your phone or 3V for a little micro controller.

Old style boxes, the really heavy ones, used to put a step down transformer in the front to bring the peak voltage down from 170V (on US 120V power) to the 12 or 24V that they were needing in the end and then they ran that lower voltage through the rectifier and into the capacitor. These are simple and don’t require any fancy electronics but they do require about 5 pounds of iron in the transformer core. Electronics are wayyyy cheaper these days than they used to be so its now cheaper to use the fancy electronics for the DC-DC converter than a big transformer meant for stepping down line voltage at just 50/60 Hz

Anonymous 0 Comments

You use some diodes and a capacitor to “rectify” the signal. They are arranged in such a way that when the voltage is positive, current flows, but current is blocked by the diode when your AC voltage is negative. The capacitor then starts discharging some stored energy it got when the signal was positive, and that keeps your DC voltage constant.

Anonymous 0 Comments

There are electronic components called diodes. These are sort of like one-way streets for electricity. If you try to pass AC through one of these, only half the wave will get through, say the positive half. This is called a *half-wave rectifier*.

Now, if you do two of these, one in each direction, you can have one stream that gets the positive halves of the waves and a second that takes the negative half. You can then combine these together using some more diodes so that you basically get the full wave, but with all the negative bumps flipped to positive. This is a *full-wave rectifier*.

Sometimes, your circuit uses 3-phase power. There are 3 wires running AC, but ⅓ of a cycle out of step with each other. If you fully rectify this, you get a signal that’s just a slightly bumpy version of DC.

Regardless of single or 3 phase, the next step is to smooth things out as best you can. This can be done using a *low-pass filter*. LP filters let through signals that don’t vary much, and are resistant to quickly changing signals. If you’ve got a sound system with a woofer and a tweeter (low and high speakers), there’s an LP filter making sure the woofer only gets the bass.

A simple LP filter is just a coil of wire, known as an inductor. When you pass a current through it, it generates a magnetic field. This field is resistant to changes in the current. It store energy, and when the supply drops, it gives off some of the stored energy to stabilise it. When the current tries to increase, the inductor takes in some of that energy to ‘charge up’ the magnet. This means the current coming out the inductor will be smoother than what went in.

Anonymous 0 Comments

AC – electrons moving back and forth in the circuit
DC – electrons moving in one direction
AC-DC – using a circuit made of diodes (which function as a one way street for current) you make a circuit, where both the positive and negative phase of the AC is contributed to positive part of DC. (Effectively making an abs(ac) funtion. Then you just smooth this output using filter (capacitor and resistor) and you get a DC

Anonymous 0 Comments

AC power is like a kid on a swing going back and forth. A diode is like a zip tie that can only go in one way but with electricity instead of the plastic rope. Imagine the swinger uses their feet to push the zip tie rope along, but the zip tie rope is up high a little ways, so the swinger has to swing really high to reach it. This turns the back and forth power(AC) into pulling power(DC).

Anonymous 0 Comments

The first step is to step it down to the right voltage, using a transformer to go from 120V AC, to 12V AC. Then, AC power goes back and forth, 60 times a second, So you take a bridge rectifier to make all the AC power go forward. Then you add a capacitor to smooth out the humps in the voltage, and you have 12V DC power

Anonymous 0 Comments

I think your question can be answered by studying the physics behind AC and DC, it will be a more complete answer that what we could write in such short time.

Anonymous 0 Comments

AC is electricity that goes from positive voltage to negative voltage over and over again. Each time it does this, we call that a cycle. The number of cycles per second are called hertz.

DC is electricity that is always a positive voltage.

There are 2 components you need to know about to converting AC to DC. The first is called a diode. A diode only allows electricity to flow one direction through it. Since AC voltage goes positive to negative, the current flows backward and forward. We want to stop that. The second component is a capacitor. More on that later.

So, imagine a sine wave of electricity, that is AC. The diode chops off the bottom half of the wave, or the negative part. What you have now is like hills of positive voltage with 0 volts between them. This is called pulsing DC. We want to make the pulses smooth, so that the voltage is constant.

This is where the capacitor comes in. The capacitor charges and then slowly releases that charge. So it charges up from the pulse of DC and the releases a longer slowly decreasing voltage that bridges the gap between the hills. Its still not perfectly constant, but its much closer to a constant voltage and most DC items don’t really care about the noise.

Extra credit: there are circuits you can build called full-bridge rectifiers that flip the negative part of the wave to positive and add it to the positive wave so that there is no time when the voltage is at zero and the hills are closer together. This is both more efficient and has less noise. These are made with 4 diodes in a clever arrangement.