Constant Current DC Power Supply Project Circuit — The Engineering Knowledge

Hello, readers welcome to new post. Today we will discuss Constant Current DC Power Supply Circuit. The constant current power supply is considered as 4 pins active device. Its input is denoted as dc volts source for basic current regulators and it denotes the AC line voltage for such supply that comes with rectifiers and filters. In the case of practical operation transformer, rectifiers and filters is used for every device to generate dc supply. In the end, the power controller is connected.

In a circuit of constant power supply, there is the dc power source that operates the series pass transformer that is regulated through the high-gain operational amplifier. The feedback signals get through the use of shunt resistance Rs. In this post, we will make a circuit of a constant dc power supply through the use of an LM317 regulator. In this project, we used PCB from JLCPCB over which the design of the project is created.

Introduction to LM317

  • The negative correspondent of LM317 is LM337 which varies volts less than a reference.
  • It comes with three pins structure used for voltage regulation.
  • Through the use of this component, we can get up to 37 volts regulation according to circuit design.
  • In this component circuit, there is no need for external resistance. Through this module line regulation value is about 0.01 percent and load regulation is about 0.1 percent.
  • Its common specification are protection from overload current

Features of LM317

  • Used to protect the overload thermal
  • It helps to sustain the inner short circuit current limiting area
  • It is used for floating operating in case of larger voltage circuits.
  • It comes with D2PAK-3 packaging

Constant Current DC Power Supply Circuit Specification

  • Features of this circuit are discussed here
  • Bridge circuit used for rectification
  • A transformer of a step-down type is used
  • Input volts for this circuit are 220 to 240
  • 125 mA current is getting at the output load
  • It gives the constant power at the load end

Component of Project

  • The main component of this circuit are listed here
  • Resistances
  • Capacitor
  • LM317
  • Transformer
  • JLCPCB is the most reliable and trustworthy with a high-quality experienced engineer team who supplies PCB and based in China.
    They have been serving their customers for 15 years, offering them high-quality printed circuit boards, assembly services, and fast delivery on time.
  • If you want to get a simple level of boards for small quantities to mass production, JLCPCB is considered to be the best choice for you.
  • Founded in 2006, it has been at the forefront of the PCB industry. With more than 15 years of continuous innovation and improvement based on customer needs, they have grown rapidly to become the world’s leading printed circuit board manufacturer, providing rapid production of highly reliable and cost-effective printed circuit boards and creating the best customer experience in the industry.
  • From JLCPCB you can get 1 to 2 layers PCB in five pieces in just 2$ with dimensions of 100 by 100 mm with FR4, aluminum, and lead-free features. Also, have $56/m2 for batch production
  • The material FR-4 Standard Tg 130–140/ Tg 155 can also get from JLCPCB. The dielectric constant used to JLCPCB is 7628 Prepreg 4.6 3313 Prepreg 4.05 2116 Prepreg 4.25.
  • You can also get the panels of your PCB from JLCPCB panelization services at good rates. Their advanced PCB technology makes sure to provide high-precision boards suitable for industrial, military, aerospace, and medical applications.

Circuit Explanation

  • To make a constant current dc power supply first of all make the rectifier circuit through the use of four diodes. Here we will use a bridge rectifier that will convert full ac into dc. This rectifier is linked to the output of the transformer.
  • In this circuit at input, 230V input is linked that will be converted into nine volts at the secondary side of the transformer that volts are given to rectifier connected to the transformer that will convert that volt to DC volts after that these volt passes through capacitors that will remove the ripples to make the pure DC. This DC is given to voltage regulator LM317
  • The LM317 is attached to the load through resistance denoted as Rx and operating as feedback of current
  • Here is the formula used for the calculation of the value of resistance RX on the basis of current for output.
  • In this circuit, we used 10ohm/5watt resistance and we get 125mA constant current output at our dc supply
  • Iout=Vref/Rx
  • If we put values of our components that are
  • Iout=1.25V/10
  • here Vref for LM317 is 1.25 volts
  • So our final result is
  • Iout = 125 mA


  • The constant current device is used to give the constant value of current as the output is varying. To work this power supply in constant mode adjust the power supply to a voltage value larger than the required volts for the circuit
  • It mostly used for laser and electroplating applications

That is all about the Constant Current DC Power Supply Project Circuit all details of this project has covered if you have any queries ask in the comments. Also not forget the PCB from the best PCB supplier JLCPCB at good rates and high quality

Author: Henry

I am a professional engineer and graduate from a reputed engineering university also have experience of working as an engineer in different famous industries. I am also a technical content writer my hobby is to explore new things and share with the world. Through this platform, I am also sharing my professional and technical knowledge to engineering students.

Originally published at on September 8, 2022.



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