CIRCUIT · ADJUSTABLE DC POWER SUPPLY

Adjustable DC Power Supply Circuit Examples

Whether you're prototyping a bench power supply or designing a variable voltage regulator, adjustable DC power supply circuits are essential for electronics projects. This collection showcases practical circuit examples to help you get started.

4 EXAMPLES· UPDATED 2026-08-02
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ABOUT

About these examples.

Browse the gallery below for schematics featuring LM317, LM338, and other popular regulators, with details on voltage adjustment, current limiting, and protection features.

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HOW TO

Make one yourself.

  1. 1

    Select a base circuit

    Start with a common regulator like LM317 or LM338, or pick a template from our library.

  2. 2

    Add power input and filtering

    Include a transformer, rectifier, and smoothing capacitors to provide clean DC input.

  3. 3

    Wire the voltage adjustment network

    Connect a potentiometer and fixed resistor to set the output voltage range.

  4. 4

    Include protection features

    Add diodes for reverse polarity protection, fuses for overcurrent, and heat sinks for thermal management.

  5. 5

    Test and refine

    Simulate or prototype your circuit, measure output under load, and adjust component values as needed.

FAQ

Frequently asked questions

What is an adjustable DC power supply?01
An adjustable DC power supply is a circuit that converts AC mains or a DC source into a variable DC output voltage, typically used for testing, prototyping, or powering electronic devices.
What components are essential for a basic adjustable power supply?02
A basic design includes a voltage regulator (e.g., LM317), a potentiometer for voltage adjustment, input and output filtering capacitors, and a few resistors. For higher currents, you may add pass transistors and heat sinks.
Can I build a high-current adjustable power supply?03
Yes, by adding external pass transistors to a regulator like LM317, or using higher-current regulators like LM338, you can achieve output currents of several amperes.
How do I calculate the output voltage for an LM317 circuit?04
The output voltage is given by Vout = 1.25 * (1 + R2/R1) + Iadj*R2, where R1 is typically 240 ohms, R2 is a variable resistor, and Iadj is negligible. It's approximately 1.25*(1+R2/R1).
Is it safe to build my own power supply?05
Yes, if you follow proper safety practices: use a fused input, isolate high-voltage AC sections, ensure adequate cooling, and test with a current-limited supply first.
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