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Switching Regulators vs LDOs

Is efficiency the only advantage of switching regulators over LDOs?

  • The primary reason for selecting a switching regulator is efficiency; but at high current/power levels, size and cooling becomes an issue for linear regulators.

    Let’s compare an example of using a switcher versus a linear regulator to produce a 3.3V output at 3A from a 12V input.  The linear regulator will dissipate a lot of power with a 3A load, Pd = (12V-3.3V) x 3A = 26.1W.  This will require a large, finned heatsink to dissipate the heat, probably around 6” x 6” x 1” which is too large to be mounted on a PCB.

    In contrast, a switching regulator with 90% efficiency at a 3A load will dissipate, Pd = (3.3V x 3A)/(1-0.9) = ~1W which may be cooled by the surrounding PCB copper or just a small heatsink.  So the tradeoff between switchers and linear regulators is really efficiency and size.

    Also, linear regulators are generally cheaper and easier to implement.

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    EZ Admin