Boost Converter Circuit From 5V to 12V using Transistors

Many electronic projects need 12V power, but sometimes only 5V supply is available, for example from USB, logic board or microcontroller.

So, here this Boost Converter Circuit From 5V to 12V using Transistors is useful which converts 5V DC to 12V DC.

It uses simple components like transistors and inductor, it is with low cost and easy to build.

Therefore, beginners can also try this circuit and it is good for learning switching circuits.

Circuit Working:

Parts List:

First, the circuit starts when 5V is given, after that transistor Q3 starts oscillation and then Q2 helps in switching process.

Now the signal goes to transistor Q1 and this Q1 works as main switching transistor, so Q1 turns ON and OFF very fast.

When Q1 is ON the current flows through inductor L1, so inductor stores energy.

Next, when Q1 is OFF the stored energy is released, because of this voltage of inductor increases.

Then diode D1 becomes ON, and energy moves to output capacitor C1, so output voltage goes higher.

At the same time Zener diode works, it controls the output voltage and it limits voltage near 12V.

As a result stable 12V DC output is obtained.

Formula with Calculation:

Inductor current formula and calculation:

IL = Vin / L × Ton

where,

• Vin is 5V
• L is 330uH

Switching frequency estimation:

f = 1 / (Ton + Toff)

Output voltage formula for boost converter is:

Vout = Vin / (1 – D)

where D is duty cycle for 12V output:

12 = 5 / (1 – D)
1 – D = 5 / 12
D = 1 – 0.416
D = 0.584

So the duty cycle is roughly around 58 to 60 percent depending on load and component values.

How to Build:

To build a Boost Converter Circuit From 5V to 12V using Transistors we need to follow the below connections steps:

• Start, the circuit by gathering all the components as shown in circuit diagram above.
• Transistor Q1 2N2222 emitter pin connects to resistor R1 and ground.
• Base pin connects to collector of transistor Q3.
• Collector pin connects to junction of inductor L1, diode D1 and resistor R5.
• Transistor Q2 BC547 emitter pin connects to ground.
• Base pin connects to anode of Zener diode.
• Collector pin connects between base of Q1 and collector of Q3..
• Transistor Q3 BC557 emitter pin connects to Vin 5V supply through resistor R4.
• Base pin connects to the junction of one end of resistor R3 and capacitor C2 and resistor R5.
• Collector connects to C2 and R5 network.
• Inductor L1 one end connects to Vin 5V and other end connects to the junction of collector of Q1, inductor L1, diode D1 and resistor R5.
• Diode D1 1N5819 anode connects to inductor L1 and cathode connects to the junction of 12V output, cathode of Zener diode and positive of capacitor C1 .
• Zener Diode ZD1 12V cathode connects to the junction of output 12V, D1 diode cathode and positive of capacitor C1 .
• Anode connects between base of Q2 and resistor R2.
• Capacitor C3 positive side connects to Vin 5V and negative to ground.

Conclusion:

This Boost Converter Circuit From 5V to 12V using Transistors is simple and useful project.

It uses easily available components and also it does not need any IC.

Therefore, it is with low cost and is helpful in educational projects.

Moreover, it is suitable for beginners and so this circuit is a good for practicing project.

References:

easiest way of driving amplifying from 5v to 12v