DC/DC converter using transistors

Fairchild BC547

Sometimes, you may need to make a DC/DC converter with minor components that can handle small loads. In this article, we are going to make something like that. This DC/DC converter using transistor has only a few components and can handle small loads or higher voltages, suitable to use with a small AA battery. So let’s start!

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When do you need this type of DC/DC converters?

When I was working on a project, I found that I need to drive a buzzer of 12 V from a source of 3.7 V LiPo. But the circuit should not be costly and should be as small as possible. After looking at similar circuits over the net, I found several circuits but only one was satisfactory. After little modification, that circuit becomes very useful to me. That is why I’m sharing this circuit so that you may get some help.

When you need to drive a small load such as a sensor, or a buzzer, or a relay with a battery of 1.5 V, or such a source then you can use this type of DC/DC converters.

Circuit diagram

DC/DC converter using transistors
Figure 1.

Working principle

This is actually an Astable multi-vibrator using Transistors. With a small change in its configuration, this DC/DC converter is designed. The Q1 & Q2 are the same transistors. Once the power is up, the Q2 starts switching until C1 gets charged. Once C1 is charged, Q1 triggers as there is no pull down to its base through R3 & C1. This turns Q2 off. Once Q2 is off, as C1 was charged, it triggers Q2 through R2 and R3. This process keeps going until power is sufficient.

PCB

DC/DC converter using transistors
Figure 2.

Test result

DC/DC converter using transistors
Figure 3. DC input

 

DC/DC converter using transistors
Figure 4. Output

Conclusion

This article was a small one but can be helpful in the right situation. This DC/DC converter circuit is only suitable for small loads driving from low voltage sources. So when you use this keep that in mind.

Materials on the topic

  1. Datasheet Fairchild BC547
  2. Datasheet Vishay UF4007

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