Summary： This content involves a complete guide on how you can design a 5V DC power supply where all the components have been discussed including computing their values and a step-by-step design.
Hello all! Welcome on board. Here we are going to focus on designing a 5V power supply. We will design the power supply and carry out and explain how to do various calculations including all the necessary steps. The main objective of this article is to share know-how and ensure that at the end of the project tutorial, you have enough lessons to allow you the ability to design your power supply according to your specifications and requirements. This project guide will take you through every design step including the design mathematics for example if we have a capacitor in our schematic, we should end up knowing why it exists where it is and how we sized it.
At the end of this project guide, we shall be able to:
Let us start with the complete design guide.
In general, the block diagram of a power supply is made up of
Let us have a look at the block diagram and what each element in the block diagram does before doing the actual design.
Figure 1: Power Supply General Block Diagram
Each section of the block diagram has a specific function and we have to go deeper into that so that we can know why the sections exist.
Transformers have the function of stepping up or stepping down the circuit voltages and this is guided by the energy conservation law.
In our circuit, we shall be employing a step-down transformer so that depending on your country we can lower the input voltage from 220V to something closer to 5V which is our project requirement.
The transformer stepped-down voltage remains to be AC. To convert the voltage to DC, the rectifier circuit is employed in converting the AC to DC, and without it becomes very impossible to have our 5V DC output.
The rectifier does the conversion of AC to DC but this conversion does not give a purely DC output. The rectifier output is in pulsation. This is known as pulsating DC.
The pulsating DC is never good for powering most sensitive electronic devices since it is noisy, and corrupted with ripples.
A filter is used in the circuit to remove the pulses and ripples, making the voltage compatible with the voltage regulator.
A good filter should reduce the ripples to lower than 10% for perfect voltage regulation and the best filter we can use for the project is the capacitor which is a charge-storing.
A voltage regulator is a perfect device that is used when a regulated constant output voltage is required. This ensures that the output voltage does not change even if the load or line voltages change.
Figure two below summarizes the happenings in the block diagram in Figure 1.
Figure 2: Power Supply Block Diagram and Graphical Analysis
Figure 3: 5V DC Power Supply Schematic Using KiCAD EDA
Figure 3 above shows the circuit diagram for our project. The main power supply is 220 Vrms at a frequency of 50Hz but this depends on your country’s regulations. The fuse is used to protect the circuit, the transformer for stepping down voltage, the rectifier, the filter capacitor, the LED used as an indicator, and the voltage regulation IC.
The circuit is implemented and simulated using KiCAD EDA, open-source software good for professional and educational PCB design.
From the circuit, we shift to a step-by-step power supply design.
At this stage, we shall design every stage mentioned above and assemble them to have a complete design at the end.
At this stage, we shall design every stage mentioned above and assemble them to have a complete design at the end.
Let us calculate the values of the capacitor mathematically;
Since we are using a full wave rectifying circuit, the frequency is 120Hz
From the table of standard capacitors, we cannot find 397 uF, and therefore, a good practice is to settle for a standard value close to this.
Hence in our design, we shall settle for 470 uF as our filter capacitor.
Step 5: Securing the Power Supply
Every electronic design has protective features which protect it against burning. Our circuit will have an input fuse that secures it against overloading.
For our simple power supply, the maximum current to be handled should be 1A and hence our fuse should not exceed the rating of 1A.
After designing the circuit and showing how we arrived at all the component ratings through our calculations, below is the 3-D output of the 5V power supply
Figure 6: 5V Power Supply 3D Design Output
Summary
If you love being an electronic expert, you should start by designing your power supply system. It is the greatest test to learn about electronic design and how electronic components work, why they are used, and how to value and use them. As you do design, you can go ahead and manufacture such boards through PCBWay so that you can use the prototypes to carry out more tests to ascertain that for sure you have achieved the goal of your project.
