# Simultaneous Buck-Boost or Flyback Regulator - Help Selecting Chip [closed]

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

## closed as off-topic by Leon Heller, Daniel Grillo, Chetan Bhargava, Matt Young, Olin LathropOct 10 '14 at 17:04

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