In this article, we have discussed a 5V 3A power supply circuit for people who are trying to make a Microcontroller or power digital supply source.

This microcontroller is used in experiments such as logic circuit and/or Microprocessor types or even raspberry-pi. These circuits require 5 volts at a high current rate of up to 3A.

This circuit is very simple with the LM323K (or LM123 or LM223). But the thing to be kept in mind is that it can supply 5V fixed output voltage, and so it can be connected to the load current of up to 3 Amp.

If you are not able to buy this IC or want to design an easy circuit with LM350 or 7805, you must read below.

There are 3 circuits that are quite interesting and useful.

## Digital Power Supply Circuit Using LM323K

This setup is the easiest.

### How it works?

As shown in the figure of the circuit below, we can see that only one LM323K is used.

Microprocessor 5V 3A Digital power supply circuit using LM323K:

A step by step process is described below.
In the circuit, only a few pieces of equipment are used. These pieces include a transformer which reduces the voltage from AC main (230V or 117V) to AC 9V.

After that, the bridge diode of 4A 100V will convert the AC voltage into DC voltage. Next, we will use C1 as the current filter to make it smooth. Then, the IC1-LM323K regulator works to maintain a constant voltage of 5 volts.

In addition, let’s not forget the internal circuit’s overload protection. Due to the Short Circuit, output and the thermal protection system will also be determined.

The C2 works as a noise frequency filter while C3 is the output filter.

### The parts list

IC1: LM323K or LM323T (To-220) THREE-TERMINAL 3A-5V POSITIVE VOLTAGE REGULATORS
C1: 4,700uF 16V Electrolytic capacitor
C2: 0.1uF 63V Polyester Capacitor
C3: 470uF 16V Electrolytic capacitor
T1: Transformer primary 9V at 3A.
BD1: Bridge diode 4A 200V.

Construction:

All devices used are according to the circuit requirement except for the transformer which can be mounted on the PCB is shown in Figure 2. In installing the IC1, you must be careful about the input or an output short circuit with the heat sink as this is strictly prohibited.

## Using LM350 as a 5V 3A regulator:

I have heard it many times from people that they are unable to find LM323. I think we can use LM350 instead on its place, but before using it must be modified with a few additional devices. See the circuit diagram below.

### How it works?

This circuit requires the use of more equipment. This circuit works with unregulated power supply and is very similar to the circuit above.

But we have made a few changes. There is a 3 filter capacitor connected in parallel which resulting in combined capacitance of 6,600uF. According to the original principles, capacitance chosen must be 2,200 uF per 1A output current.

This is done because it is much cheaper than buying 10,000uF and it’s quite easy to find too.

See an LM350 Regulator. Normally, its output voltage of 1.25V to 30V can be adjusted. We can set this voltage by R1 and R2.

When we want a 5V output, we should use R1 = 270 ohms, R2 = 820 ohms. How do I know all that? Because I read…

### Diode protection:

As shown in the datasheet, we must add both diodes to protect the voltage going backwards from the output and others. It can cause damage to LM350.

### Transient noise filter

C4, C7 (0.01uF to 0.1uF) filter out the transient noise which can be transferred into the supply by stray magnetic fields. C5 and C6 keep voltage stable.

Other parts:

LED1 is the power on display like other circuits.

Parts lists

IC1: LM350 Three-Terminal 3A Positive voltage regulator
Electrolytic capacitor
C1-C3: 2,200uF 16V
C5: 22uF 16V Electrolytic
C6: 100uF 16V Electrolytic
C4,C7: 0.01uF 50V Polyester Capacitor
0.5W Resistor tolerance: 5%
R1: 270 ohms
R2: 820 ohms
Others
T1: Transformer, Primary 9V at 3A.
BD1: Bridge diode 4A 200V.

### Using 7805 and PNP transistor (cheapest option):

If you are unable to buy both LM323 and LM350, you can use normal IC-7805 and power transistors which can make you a 5V 4A power supply circuit.
It will turn out to be the cheapest circuit.

### How it works?

We have designed this circuit in a small size to save money.

5V 3A Power supply using 7805 and TIP2955

This circuit is very similar to the circuit above. Here is the step-by-step process.

It has unregulated power supply. We have used this circuit as a full-wave diode rectifier. In any circuit similar to this, we must use a center-tap transformer 9V-CT-9V.

We know that 7805 is a 1A 5V regulator IC so it runs nicely. But the current it provides is too low for us. We must add a helper that can be a little more kind.

So, the PNP power transistor, TIP2955 comes to our rescue. It will boost up the current to 4A max. When the current flow R1 at B-E of Q1 gets a bias current, it will conduct a current more than IC.

## Overvoltage protection

This circuit has a disadvantage. It does not provide overvoltage protection and short circuit protection.

This problem can be easily and effectively handled by using a fuse and Zener diode.

Fuse easy, but sure!

In normal circumstances, we do not connect a short circuit or use an overcurrent. Hence using just one fuse is quite economical. It definitely works better than complex electronic circuits.

Zener over-voltage protection
We already know that when the voltage reaches the VZ of Zener diode, it will have a high current flowing through it. But if we use a 5.6V Zener diode and the voltage exceeds 5.6V, this will be a safe voltage level of the digital circuit. There will be a lot of current causing the fuse to burn immediately

Learn: How Zener diode works

Is it simple?

Parts lists

IC1: LM7805, 3 Terminal 1A Positive voltage regulator
Q1: TIP2955, 15A 80V PNP transistor
ZD1: 5.6V 1W Zener Diode
Electrolytic capacitor
C1-C3: 2,200uF 16V
C4: 10uF 16V Electrolytic
C5: 100uF 16V Electrolytic
C6: 0.1uF 50V Polyester Capacitor
R1: 3.3 ohms, 1W Resistor tolerance 5%
Others
T1: Transformer, Primary 9V at 3A.
BD1: Bridge diode 4A 200V.
F2: 4A Fuse
F1: 1A Fuse

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