Basic Power Supply Circuit & Theory

In this project I will show you how to make your own power supply using basic components. I will cover the basic theory on Transformers, rectification smoothing and regulation.

The voltage in the UK and European countries is 230v. This voltage is too high to use for many applications so it needs to be reduced. You use a transformer to reduce the voltage. I have included the input and output wave for the transformer. In this case the transformer reduces the 240V down to 40V.

Once you have reduced your AC voltage by the use of a transformer you will be left with a lower voltage AC power supply. Most circuits use DC (direct current) in order to get DC from an AC supply you will need to rectify it. I have included a example of the waves so you can better understand what it looks like.

Rectification is done using diodes. You can use a single diode rectifier or a full bridge rectifier. A single diode rectifier is half wave rectification this means that it will only have the positive parts of wave but it will be missing the negative parts of the wave.

Full wave rectification uses 4 diodes and will 'flip' the negative part of the wave so you will end up with a positive wave with no gaps between the original positive wave like the half wave rectifier would.

For half wave rectification you use 1 diode and for the full wave rectifier you use 4 diodes. The configuration for the half bridge and full bridge rectifier are shown below.

Now that you have you have rectified your AC it now needs to be smoothed. Smoothing refers to taking the rectified wave and holding the output to the highest point of the wave.

To smooth a rectified AC signal you use a capacitor. I have included a circuit diagram to show how you would place the capacitor in the circuit.

Now that you have a DC voltage it needs to be stepped down to a precise voltage. You can use a regulator to reduce a DC voltage. Voltage regulators can come in many variants from fixed voltage to variable voltage.

Now just combine all the parts and you will have a DC power supply.

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