12V to 5V Buck Converter Circuit using Transistors

In todays world power supply plays a very important role, because most electronics need stable 5V DC.

But sometimes if the input voltage is high like for example 12V battery or adapter, then we must reduce voltage safely.

Therefore, a buck converter is useful, as it reduces voltage with high efficiency.

This 12V to 5V Buck Converter Circuit using Transistors uses only transistors and no IC is used here, so it is cheap and easy to learn.

Also, this circuit gives about 1A current and thus it is good for small projects.

Circuit Working:

The above circuit converts 12V DC to 5V DC as it works on switching principle and therefore, power loss is less.

First, input voltage of 12V DC is given which enters into the circuit.

Then capacitor C1 removes noise and it filters the input ripple.

After that TIP42 works as main switch and this switches ON and OFF very fast.

This switching is controlled by Q2 and Q3.

When TIP42 is ON the current starts flowing and energy is stored inside inductor L1.

At same time diode D1 is reverse biased and so it does not conduct.

Next, when TIP42 becomes OFF the inductor releases stored energy.

Current flows through diode D1 and so output voltage is maintained.

Meanwhile, capacitor C2 filters output and ripple becomes very low and output becomes smooth DC.

Then Zener diode checks output voltage, when voltage reaches 5.1V and Zener starts conducting little.

Because of this Q3 turns ON and then Q2 also turns ON and so base current of TIP42 reduces.

Switching action becomes less, with output voltage stays stable and so feedback loop works correctly.

To build a 12V to 5V Buck Converter Circuit using Transistors follow the below connection steps:

Start, the circuit first by collecting all the components as shown in circuit diagram.
Then start with Q1 TIP42 Transistor emitter pin connects to input 12V.
Collector connects to the junction of diode D1 and inductor L1.
Base connects to R2 and R3 junction.
Next, start with Q2 2N2222 transistor emitter connects to ground.
Base connects to collector of transistor Q3.
Collector connects to base of Q1 through resistor R3.
Q3 2N2222 transistor emitter connects to ground.
Base connects between Zener diode and R4.
Collector connects to Q2 base and resistor R1.
Capacitor C1 connects across input supply.
Inductor L1 one end connects to Q1 TIP42 collector and cathode of diode D1.
Other end connects to 5v output, positive of capacitor C2 and cathode of ZD1.
Zener Diode ZD1 cathode connects to output 5V.
Lastly, anode connects to base of Q3 and resistor R4 one end and other end of R4 connects to GND.

This 12V to 5V Buck Converter Circuit using Transistors is simple project to build.

It uses only basic components and so beginners can understand easily.

Moreover, it saves power, heat loss is also low and thus it is better than 7805 regulator IC.

Finally, this circuit is good and is best for learning switching supplies.

Also is useful in DIY electronics projects.