Monday, July 2, 2012


Circuit diagram
A truly timeless circuit. LM317 is a versatile and highly efficient 1.2-37V voltage regulator that can provide up to 1.5A of current with a large heat sink. It's ideal for just about any application. This was my first workbench power supply and I still use it.
Since LM317 is protected against short-circuit, no fuse is necessary. Thanks to automatic thermal shutdown, it will turn off if heating excessively. All in all, a very powerful (and affordable!) package, indeed.
Although LM317 is capable of delivering up to 37V, the circuit pictured here is limited to 25V for the sake of safety and simplicity. Any higher output voltage would require additional components and a larger heat sink.
Make sure that the input voltage is at least a couple of Volts higher than the desired output. It's ok to use a trimmer if you're building a fixed-voltage supply.
Possible uses:
Variable workbench power supply, fixed-voltage supply... Just about any possible application when no more than 1.5A is necessary.

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  1. A variable regulated power supply, also called a variable bench power supply, is one where you can continuously adjust the output voltage to you requirements. Varying the output of the power supply is the recommended way to test a project after having double checked parts placement against circuit drawings and the parts placement guide.

    Computer Power Supplies

  2. A variable DC power supply can be more useful than a fixed supply, as you can use it to power a wider variety of projects. An adjustable voltage regulator such as the LM317 simplifies designing a variable supply. The supply follows a standard linear DC design, incorporating a step-down transformer, rectifier, capacitors and regulator. In this case, the regulator will have a control for voltage. Since the regulator does all the hard work, a variable supply design will be only slightly more involved than that for a fixed supply.

    Rackmount PC Case

  3. Nice post.. explain me workflow of LM317 VARIABLE POWER SUPPLY Electronic Components