Power Supplies

A DC linear power supply is an electric circuit that converts AC voltage to a stable regulated DC voltage – without any switching or digital circuitry. This makes the circuit both simple to understand and easy to build.

In this guide, you will learn how DC linear power supplies work and how to build your own.

In this guide, I’ll show you how to build a dual +5V -5V power supply from a standard USB outlet.

Dual power supplies with a negative output taken from the positive output can be a little tricky. It’s not a matter of difficulty, but about the low availability of support for easier ways to do this kind of power supply.

So I’ll show you one of the easiest ways to make a dual power supply (also known as bipolar power supply) using a simple USB connection.

It is fair to mention, that this will be for low-power projects since the IC used for this is not capable of outputting much power.

The difference between Alternating Current (AC) and Direct Current (DC) is simple: AC vs DC comes down to how the current flows. AC is a current that alternates its direction. It goes back and forth continuously. DC is a current that flows in one direction.

Current flow in a DC circuit:

For example, a battery provides direct current. The current only flows one way out of a battery.

I’m going to show you what negative voltage is by putting John into a hole. As you’ll quickly learn, it’s nothing weird or mystical.

Meet John. He is 1.8 meters (6 feet) tall.

What does it mean that John is 1.8 m tall? Could you find his height by only looking at his head?

No. You have to compare the top of his head to the ground he is standing on to be able to find his height. That John is 1.8 m tall really means that the top of his head is 1.8 m higher than the ground that he stands on.

It’s the same thing with voltage. You can’t say anything about the voltage without comparing it to another point.

Build this portable USB charger circuit, and you’ll always have access to a charger.

Imagine a beautiful summer day. You’re on your way to meet friends for a picnic in the park. But, the park is huge and full of people. Since you don’t know where exactly your friends are, you pick up your phone to call them.

But as you dial the number, the battery on your phone dies…

Ahhh!

With this portable USB charger circuit, there’s no need to worry. Just drop by a supermarket nearby and pick up some standard batteries to recharge your phone on-the-go.

This power supply circuit is easy to build and cheap. And it requires only 5 components.

I have built many circuits in my life, but this is actually the first time I’ve built a power supply circuit from scratch.

The final project I wanted to build was a wall adapter with a USB socket to charge my iPhone. But first I wanted to start by creating a simple circuit that converts from the main power voltage, 220V or 110V, to 5V.

As I’m in Australia while writing this, and the voltage here is 220V, I built this with 220V in mind. But it’s very easy to convert to 110V instead by switching one connection (or one component).