FAQ: Switching Regulators vs LDOs

Document created by LWong on Aug 9, 2011Last modified by AndyR on Jan 31, 2012
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Q.

Is efficiency the only advantage of switching regulators over LDOs?

 

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A.

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.

 

This FAQ was generated from the following discussion: Switching Regulators vs LDOs

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