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Simple USB Battery Charger Circuit

Last updated on 20 April 2026 by Admin-Lavi Leave a Comment

Nowadays, phones, headphones and many more things we use in our every day life, do they use battery? then the answer is yes they do need charging.

Hence, this small and Simple USB Battery Charger Circuit which is easy to make as it charges phone or other devices, uses few parts only and is good for learning and for home uses.

However, so many chargers are there in market but in this article we will show how to make one simple USB charger at home.

What is a USB Battery Charger Circuit:

This USB battery charger circuit is small device it takes power from USB to charge the battery.

Also, we see this circuit in many portable things like camera, tablet, phone and more, where it charges from USB wall charger, computer or power bank and it uses normal USB plug which are small in size, works good and easy to use.

Circuit Diagram:

Simple USB Battery Charger Circuit Diagram

Parts List:

ComponentsQuantity
Resistors
1k 1/4 watt1
560Ω 1/4 watt1
Capacitors
Electrolytic 100µF 16V2
Semiconductors
Zener Diode 4.7V 400mW1
Rectifier Diode 1N40071
Transistor TIP35C1
LED Red LED1

How to Build:

  • First, collect all parts as per the circuit diagram.
  • Next, Zener diode anode connects to USB positive (+) pin.
  • And, Zener diode cathode connects to base of TIP35 transistor.
  • Then, Battery positive (+) connect to transistor collector.
  • After that, USB ground (-) connect to transistor emitter.
  • Lastly, use R1 and R2 resistors to control current and voltage.

Calculate Zener Diode Voltage (Vz):

  • First, choose Zener diode with voltage same like battery needs this will give good charging.
  • Also, right Vz Zener voltage is important for mobile battery.

Formulas:

Formulas for USB Battery Charger:

Vz = Vbattery + Vdrop

where:

  • Vz is the Zener voltage
  • Vbattery is the battery voltage
  • Vdrop is the voltage loss across diode

How it Works:

  • USB port gives DC power.
  • Then, Zener diode ZD controls voltage by its Vz.
  • Output give near about 4.7V to charge the battery.
  • So, to charge just connect phone or other device to circuit.

Advantages of USB Battery Charger Circuit:

  • Firstly, it is very easy to use, just connect USB and charging start.
  • Also, USB power source is easily available (laptop, adapter, power bank).
  • Moreover, circuit is small and portable.
  • In addition, it consume less power.
  • Furthermore, good for charging small devices like mobile, gadgets.

Disadvantages of USB Battery Charger Circuit:

  • However, this charger charges slowly compared to a normal charger.
  • Also, limited current output, so not suitable for big batteries.
  • Moreover, sometimes voltage fluctuation can affect charging.
  • In addition, not all USB ports give same power.
  • Finally, no proper protection in simple circuit, so battery damage possible.

Conclusion:

To conclude, this Simple USB charger circuit is small, easy and useful as it charges phone and other device using USB power.

Also, the circuit is good for learning and home uses and there is no need for big tools or hard parts to build it.

References:

Datasheet Transistor TIP35C

Filed Under: Battery Charger Circuits, DIY Projects, Power Supply Circuits

About Admin-Lavi

Lavi is a B.Tech electronics engineer with a passion for designing new electronic circuits. Do you have questions regarding the circuit diagrams presented on this blog? Feel free to comment and solve your queries with quick replies

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