220V AC to 12V DC Converter Power Supply Using Diodes, Capacitors, Resistors, & Transformers

Summary

This video explains how to create a 12-volt DC power supply from a 220-volt AC source. It details the components required, such as a step-down transformer, diodes, and a capacitor. The process involves converting AC to DC using a full-wave bridge rectifier and filtering the output with a capacitor to produce a stable voltage. Additionally, it covers the use of a Zener diode as a voltage regulator, along with ways to limit surge current using resistors. By following these steps, viewers can build a reliable DC power supply.

Takeaways

• 🔌 The video explains how to create a 12V DC power supply from a 220V AC power source.
• 🔄 A step-down transformer with a 16.91 turn ratio is used to convert 220V AC into 13V AC.
• ⚡ The primary and secondary voltages of the transformer are related to the number of wire coils on each side.
• 🔀 A diode is introduced to convert AC to DC by allowing current to flow in only one direction.
• 🌀 The circuit in focus is a full-wave bridge rectifier, which uses four diodes to allow current flow during both positive and negative cycles of AC.
• 📉 Voltage drop across diodes is important; silicon diodes have a 0.6V drop, while germanium diodes drop 0.3V.
• 🔋 A capacitor is used to reduce voltage fluctuations (ripple voltage) in the output, making the DC output more stable.
• 🔧 A series current-limiting resistor can be added to manage surge current and protect the diodes from burning out.
• 🔍 A zener diode is added for voltage regulation, ensuring a steady 12V output by maintaining the correct zener current.
• 💡 The output is designed to provide a steady 12V DC supply by balancing components like diodes, capacitors, and resistors.

Q & A

What is the first component needed to build a 12V DC power supply from a 220V AC source?

The first component needed is a step-down transformer with a turn ratio of approximately 16.91.

What is the function of the step-down transformer in this circuit?

The step-down transformer reduces the 220V AC input to a 13V AC output, making it suitable for further conversion into DC.

How does a diode function in a power supply circuit?

A diode allows current to flow in one direction while blocking it in the other, enabling the conversion of AC to DC.

What is a full wave bridge rectifier and its purpose in the circuit?

A full wave bridge rectifier is a circuit configuration that uses four diodes to convert an AC input into a DC output by rectifying both halves of the AC wave.

Why would you choose a germanium diode over a silicon diode in this circuit?

A germanium diode has a lower voltage drop (about 0.3V) compared to a silicon diode (about 0.6-0.7V), resulting in a higher output voltage closer to the desired 12V.

What is the purpose of adding a capacitor in parallel with the load resistor?

Adding a capacitor in parallel with the load resistor reduces voltage fluctuations, or ripple, resulting in a smoother DC output.

What is ripple voltage and how can it be minimized?

Ripple voltage refers to the fluctuations in the output DC voltage. It can be minimized by increasing the capacitance of the capacitor used in the circuit.

How does a series current-limiting resistor protect the diodes in the circuit?

A series current-limiting resistor limits the surge current when the capacitor is charging, protecting the diodes from damage due to excessive current.

What is the role of a Zener diode in this circuit?

A Zener diode acts as a voltage regulator, maintaining a steady output voltage by drawing current to adjust the voltage to a desired level, such as 12V.

Why is it important to consider the worst-case scenario of a short circuit at the output?

In the event of a short circuit, the current through the series resistor could surge, potentially exceeding the current handling capacity of the diodes. Designing for this scenario prevents diode burnout.