Buck Converter Based Regulator – Design and Implementation

It would appear that the answer to "how to make a buck converter not suck up tons of power when subjected to no-load condition" has already been answered by manufacturers who have greatly improved buck converter no load current consumption over the years.

If you dig for long enough, you will eventually come across buck converter data sheets that specify the no-load current consumption of the converter. Some converters have pretty darn low current consumption at no load, such as the TPS562200 which consumes ~22 mA at no load

The term LDO has come to be misused -- I see folks calling plain old high dropout linear regulators "LDO".

• LDO -- a linear regulator that is capable of operating with a low dropout. But they can still work just fine with a large difference between \$V_{in}\$ and \$V_{out}\$
• Linear regulator -- any regulator that works by burning up power; i.e., a regulator whose input current is substantially the same as its output current.
• Switcher -- any regulator that works by switching power through an inductor (I'm purposely ignoring charge pumps here). Generally more efficient than a linear regulator when \$V_{in}\$ is substantially higher than \$V_{out}\$

You can use a linear regulator, LDO or not. But at worst case it'll burn up (13V - 3.3V) * (output current + regulator current). That means that (A), you have to supply that power, and (B) you need to pay attention to thermal issues. That regulator will be the hottest part of your board, and it's heat sink may be the biggest feature of your board. They will have problems if they get too hot, and thermal issues can get very un-trivial. Maybe you can stand that, maybe not.

You could also buy a switching regulator module -- they make them to be pin-compatible replacements for the popular linear regulators. It's not at all a bad way to go if you don't have the circuits chops for a switcher, or if you just don't want to bother.