Power Supply Circuit Diagram & Basic Principles for Beginners

Not just a diagram—this page teaches how linear power supply circuits actually work. Designed for those who want to learn electronics from the inside out.

What is a power supply circuit?

A power supply basically takes the power input from a power source and converts it into a suitable current and voltage for the electrical load; hence the name “power supply,” which means supplying power to the load. However, it also has other additional benefits, such as being able to cut power in case of a short circuit, filtering out unwanted noise or sudden changes in voltage from the input, setting the current limits for the load, and maintaining a constant amount of power going to the load even when the source is disrupted momentarily.

A power supply comes in many shapes and forms, ranging from a stand-alone power supply that is used in small electrical experiments to a form of power converter found integrated in our electrical appliances. However, regardless of the type of power supply, it still requires an electric current from a power source, which could include a home outlet, electrical generators, or a cleaner alternative such as solar and wind power.

Some power supplies offer other functions as well, such as power usage monitoring or variable control over their output. Generally, power supplies provide us with greater control over the delivery of electric power to a load, thus increasing both the safety and efficiency of the electronics. 

3 Power Source for Electronic Devices

Let’s look at the three most used types of Power Supplies.

Types 1# Battery—A lot of circuits use a little power. So, it can be powered by batteries. The battery is small and easy to use anywhere. But normally they are low voltage. Thus, they are best used for low current loads. But for a heavier load, what should we do? Rechargeable batteries are a better answer. Can be reused many times to save a lot of money.

Type 2# Solar—We can use the solar cell to power our circuit directly. But usually, we like to use it as a battery charger for a rechargeable battery. For example, a battery charger inside a solar light, etc.

Type 3# AC Line—Often through an AC Adapter as a power supply. They are more compact and easy to use than the battery. We can adjust its output to various voltages and currents. At home, we should use them instead of batteries and solar. Because it will save our money replacing our batteries when it is dead and convenient, no need to wait for sunlight when using a solar cell.

Learn power supply circuits for beginners

If you are a beginner, I know that you do not want to waste time learning principles, and want to create a power supply circuit quickly. But you should learn its working principles at least once. To reduce mistakes and select the circuit appropriately for your usage. It will make your life easier.

Unregulated Power Supply Circuit

Almost all circuits are based on this principle. So, you should read it beforehand. Learn more: Unregulated Power Supply Circuit works

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Fixed Voltage Regulator Circuit

Even though we do not like complexity. But every project needs good stability. So, this is necessary! Let’s learn how a Fixed Voltage Regulator works

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Series Voltage Regulator Circuit Diagram with Overload Protection

Let’s learn about the transistor series voltage regulator with short circuits and overload protection. And how it reduces ripple.
Find out more: Series Voltage Regulator Circuit with Overload Protection

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Op-amp Voltage Regulator Circuit

Learn an error voltage sensor using transistors circuit work inside of variable voltage regulator using 741 and 2N3055.
Discover how a voltage regulator using OP-AMP works

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The current booster circuit for 7805

Learn how to increase/boost up current of 7805 (or 78xx) regulators with helping the 2N3055 and others transistors. Learn more about the current booster circuit for IC7805

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Simple Designing 12V 5A Linear Power Supply

Here is a 12V 5A linear power supply. Use a series of 7812 regulator ICs. Using a power PNP transistor booster with short circuit protection. Learn more about the 12V 5A DC Power Supply design

Next, let’s try building a real working circuit.

Top 8 power supply circuits

On our site have a lot of power supply circuits. We can not show it all to you. Thus, to save you time, please see the lists below.

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LM317 Variable DC Power Supply

You can adjust an output voltage from 1.25V to 30V at 1.5A.  I like this one.  Because… It is easy and cheap. For example,  You can use it instead of a 1.5V battery. Let’s build an LM317 Power Supply

Read also: LM317 pinout and how to use, Calculator Datasheet

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Simple Fixed voltage DC regulator

We often found this circuit in many appliances. They are quite old circuits but still have many uses. It is very simple with just one transistor, Zener diode, and resistor. The output voltage depends on the Zener diode.
Discover the Fixed Voltage DC Regulator.

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78xx voltage regulator circuits

78xx is a popular 1A fixed DC Regulator. Because of easy to use and cheap. And the output depends on the IC. If you need a 6V 1A output for a digital circuit, then the LM7806 is your pick. Builds this: 78xx voltage regulator circuits

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Also Learn: 7805 voltage regulator circuit, pinout, and more

LM350 Adjustable Regulator circuit

I sometimes need to use 3A variable voltage source. But… LM317 cannot help me, easily. In a short time, we used the LM350 Variable regulator. It is the best linear IC@3A. The output is 1.25V to 25V.
Build it yourself → LM350 Adjustable Regulator Circuit

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0-30V Variable Power Supply Circuit at 3A

We seldom use 3A Current that can adjust 0V to 30V output. This is a better choice. It uses LM723 as the famous regulator IC and Power transistor, TIP3055. Let’s build 0-30V Variable Power Supply Circuit

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0-50V Variable supply @3A

Build a powerful adjustable lab power supply (0–50V, 3A) with overcurrent protection. Designed with UA723 and 2SD5200, this circuit supports up to 70V and 5A for demanding DIY electronics projects.
Build it yourself → 0-50V Variable supply @3A

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Build 12V 2A Power Supply with a Hammer

Learn to build a 12V 2A power supply without IC regulators. Uses bridge diodes and capacitors. Full schematic and design guide included.
Check out the full guide → 12V 2A Power Supply Circuit with Bridge Rectifier & Filter Design 

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15V Dual Power Supply circuits

If you need to use many circuits using OP-AMP. For example, Preamplifier with tone control and more. They need to use +/- 15V regulated supply. We have 3 circuits using 7815-7915 and transistors.
Explore the project → 15V Dual Power Supply Circuits

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Other Linear Power Supply Circuit Diagram

If you do not like the above circuits, check out others below. I have grouped them into three main categories: Fixed Voltage, DC Variable, and Dual Power Supply Circuits.

Fixed Volts regulator

Let’s look at fixed-voltage regulator circuits at various voltage levels. To provide an idea for choosing a variety of uses.

5V 1A Regulator circuit

Using 7805 chip and recycling electronic circuit boards

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Variable Voltage Power Supply Circuits

Imagine you need 1.65 V to test an electronic circuit powered by an all-aluminum battery. Oh, that is perplexing, is it not? We do not use this voltage very often, right? But that problem is solved with a variable power supply.

These are just some examples from a total of 17 Variable Power Supply Circuit.

For example, with an LM350, I can choose any output voltage I want—from just over 1V up to 37V at 3A.

And take a look below. We have several options that might be suitable for your application.

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0-12V 3A Variable Power Supply Circuits

In a normal circuit, the general LM350 regulator has a start voltage of 1.25V. But this circuit is special that start of 0-volts. We use only one IC and a few other components. So cheap and easy for you. Read more: 0-12V Variable Power Supply.

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7805 Adjustable voltage regulator, 5V to 25V

Did you know you can also use the 7805 as an adjustable voltage regulator? It’s simple and inexpensive. You probably already have one in your parts box—it’s that popular. In my experience, it’s perfect for loads under 500 mA, which covers most small DIY projects, right? So let’s try modifying it into a 5V to 22V variable power supply.

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LM338 Variable Supply, 5A

When you’re using a load that draws around 5A, there are several options to choose from. But if you want a simple circuit like the LM317, with the same adjustable output voltage, I think you should go with the LM338. It handles higher current, so you’ll need a larger heatsink, transformer, and filter capacitors. If you’re interested, take a look at the LM338 variable supply circuit — it can make your life a lot easier.

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Dual Power Supply Circuits

You can use these circuits to power op-amps, audio amplifiers, or DIY electronics. This guide shows you different ways to create ± voltage from simple parts in your home.

• 0-60V Dual Variable power supply circuit using LM317&LM337
• 7805 and 7905 Dual Adjustable Power Supply Circuit

Want to dive deeper? Check out our Dual Power Supply page for a full range of DIY ideas.

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Other circuit list

• 1.5V,  3V,  4.5V, 6V,  9V at 1.5A Selector Voltage regulator

• Digital DC Regulator If you are looking for a 5V power supply for the digital circuit. But you have a 12V source and battery. I will show you, a 12V to 5V converter step-down regulator. In many ways for using, it depends on the parts you have and other suitability.  Recommend
• Small Uninterruptible UPS

• 6V Power Supply Circuit diagrams
• 12V to 6V Converter circuits —Your load is too hot. It will be damaged. Why? You connect it to a 12V battery. It can get 6V only. If you do not want this to you. You should read 10 ways to make a 12v to 6v step-down circuit.
• Experiment Variable Zener diode
• 24V 2A Supply Circuit Diagram

• 0-30V, 5A DC Adjustable Regulator using IC-723, 2N3055x2
• Simple DC regulator, 12V, 15V,  30V
• Power Supply Splitter circuit using op-amp +New

Constant Current Source Circuits Ideas for DIY Projects

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