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Search for Proven Regulated Power Supply Schematic

Discussion in 'Power Electronics' started by Electromotive, Jun 19, 2019.

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  1. Electromotive


    Feb 14, 2018
    I am looking for a proven working schematic for a 4-5 Amp 0-16Volt DC regulated power supply. I have LM338T regulators purchased from Newark (a TI product) to avoid the Chinese knock-off's with poor reputations.

    I have 2-3 of the various TI spec. sheets but they leave a lot of detail out. I have a collection of schematics and they vary greatly. For example, I have ones that specify 1 -200 mf electrolytic capacitors. All of the non-data sheet circuits vary greatly.

    The data sheets don't specify electrolytic or tantalum nature of the caps.
    I have built successfully two 1 Amp power supplies but need more current flow for my O-Scale 2-Rail model railroad.

    Thanks... Tom
  2. Harald Kapp

    Harald Kapp Moderator Moderator

    Nov 17, 2011
    Small wonder. As the saying goes "All Roads Lead to Rome" - may be not all circuits lead to a working power supply, but many do. You select the circuit that has parameters (voltage, current, components) that fit your expectations best.

    If it isn't specified, it isn't important. Mostly the type of capacitor will easily be recognizable from the capacity (e.g. 1000 µF electrolytic: yes, tantalum: no)

    Application circuits in a datasheet usually show the basic functionality. In many cases these circuits are meant to lay the ground for your own development.
    One example of a complete circuit is here.
    Note that a linear regulator such as the LM338 will require a big heat sink when used with low output voltages. The LM338 has a dropout voltage of up to 3 V at 5 A current. If you want a max. output voltage of 16 V this requires an input voltage of 19 V.
    If the output voltage is turned down (lowest value 1.25 V), the voltage drop across the LM338 will be 17.75 V. Multiplied with an output currrent of 5 A this results in a power dissipation of 88W! You'll need a really big heatsink.
    Of course, if your load is resistive, output current will drop with lower output voltage and so will power dissipation. It's up to you to calculate this parameter depending on your load.

    A much less power dissipating voltage regulator is of the switch mode type. You can buy complete modules using e.g. an LM2596 for little more than a $ in China. or buy a 5A module for 9$ on Amazon.
    hevans1944 and stspringer like this.
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