I have been trying to find a switching DC power supply that outputs a constant voltage of 12VDC, given a variable input between 4V and 25V. It's to my understanding I'd need a buck-boost converter, but many of the buck-boost converters I find on Digikey seem to show only a single application circuit for buck, and one for boost for the same chip (ie: no circuit that can do both simultaneously).
I am currently using the LM2577, and interestingly enough, it can accept a 12.5V input from a wall wart, as well as a 9V battery, and still has a constant 12V output. I don't know if for this type of chip though, if it makes sense for the input voltage to be greater than the output voltage, because it is a boost/flyback regulator.
So the first part of my question is: can someone recommend a good simple through-hole DC-DC converter that can take an input on the range [4V, 25V] DC and output a constant 12V DC output?
Second, I'm a bit confused on the terminology on Digikey, and Google has only gotten me so far. Could someone point my in the direction of a description of the various topologies? I get what a buck, boost, and buck-boost chip is, but the multiple combinations of boost/buck/forward-converter/flyback/inverting is somewhat daunting. Does flyback imply it is a buck-boost, even if the title is
"Step down (buck), flyback", etc? Some such examples are:
- Step down (buck)
- Step down, flyback
- Step down (buck), step up (boost), flyback
- Step down (buck), step up (boost), flyback, inverting
- Step up (boost), Cuk, Sepic
- Switched capacitor (charge pump), flyback