Power Supplies

Adjustable Low-voltage Power Supply Schematic Circuit Diagram

Adjustable Low-voltage Power Supply

An adjustable low-voltage power supply is a device or circuit that provides a controllable and variable output voltage at low levels of electrical potential. These power supplies are commonly used in electronics, research, and educational settings to provide a stable and precise source of voltage for various applications. Here are some key features and uses of adjustable low-voltage power supplies:

Variable Output Voltage:

  • The primary feature of an adjustable low-voltage power supply is the ability to vary the output voltage within a specified range. This allows users to set the desired voltage level to match the requirements of their electronic circuits or devices.

Precision and Stability:

  • These power supplies are designed to offer stable and accurate voltage output, often with low levels of voltage ripple and noise. This precision is crucial for powering sensitive electronic components and ensuring reliable operation.

Current Limiting:

  • Many adjustable low-voltage power supplies also incorporate current limiting capabilities. This feature allows users to set a maximum current limit to protect their circuits from excessive current, which can help prevent damage to components or circuits.

Adjustable Current:

  • In addition to variable voltage, some models also provide adjustable current output, allowing users to control both voltage and current levels simultaneously.

Multiple Outputs:

  • Some power supplies offer multiple output channels, which can be independently adjusted. This can be useful for applications that require different voltage levels simultaneously.

Digital or Analog Control:

  • Adjustable low-voltage power supplies may have either digital or analog controls for setting the voltage and current levels. Digital controls often offer more precise adjustments and may include features like digital displays.

Overload and Short-Circuit Protection:

  • To protect against overloads and short circuits, many power supplies include built-in protection mechanisms that automatically shut down or limit the output current when such conditions occur.


  • Adjustable low-voltage power supplies are commonly used in electronics prototyping, testing and debugging circuits, powering microcontrollers, sensors, and other low-voltage electronic components, as well as in laboratory experiments and educational settings.

Laboratory and Benchtop Use:

  • They are often found in electronics laboratories and on engineers’ or technicians’ workbenches as essential tools for various tasks.

Voltage Range:

  • The specific voltage range and maximum current output capacity can vary from one power supply model to another, so it’s important to choose a power supply that matches the requirements of your particular application.

An adjustable low-voltage power supply can be a valuable tool for both electronics enthusiasts and professionals. It delivers a stable and customizable DC voltage output that can be tailored to meet the specific requirements of various electronic components and circuits. This diagram illustrates the construction of such a power supply.

At the heart of this power supply circuit lies a voltage regulator IC, such as the widely recognized LM317. The LM317 is a three-terminal adjustable regulator capable of producing a variable output voltage ranging from 1.25V to 37V. It boasts exceptional performance in terms of line and load regulation, along with built-in safeguards like thermal overload protection and current limiting.

Typically, this power supply circuit derives its input voltage from a transformer and rectifier arrangement, which converts AC mains voltage into DC voltage. Subsequently, the rectified DC voltage is smoothed by a capacitor to eliminate any voltage fluctuations.

Adjustable Low-voltage Power Supply Schematic Circuit Diagram

In a voltage regulator configuration, two resistors, R1 and R2, are linked to control the output voltage of the LM317. By selecting the appropriate values for these resistors, you can achieve the desired output voltage. The formula for calculating the output voltage is Vout = 1.25V * (1 + (R2/R1)).

To introduce programmability into the power source, you can replace R2 with a potentiometer (variable resistor). This allows users to adjust the resistance and, consequently, customize the output voltage as needed.

To ensure a stable output voltage, additional capacitors are used for further filtering and decoupling. Additionally, a heat sink is often required to dissipate the heat generated by the LM317, particularly when dealing with larger voltage differentials and currents.

When working with circuits connected to the mains voltage, it is imperative to adhere to safety protocols, including the use of fuses and ensuring adequate insulation.

By constructing this adjustable low-voltage power supply, you can create a versatile tool suitable for various electronics projects, testing and prototyping, as well as powering low-voltage devices.


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