dc/dc converter: faq

[burningman]

I was wondering if anyone has any experience using dc/dc converters and where people use them.

[frequencycentral]

Do you mean like these: http://www.diystompboxes.com/smfforum/index.php?topic=74088.0

[Cliff Schecht]

Switchers (another term for DC-DC converter) can be used anywhere that extremely stable and efficient power is needed! Also, if you have a widely varying input voltage and/or a widely varying load, a switcher is your best friend. The current-mode controllers that do peak-by-peak monitoring of the power switching currents also have great transient response time; this means they gives you near instant corrections for any changes in input voltage or output load. If you need to change a lower voltage to a higher one (boost converter), a higher voltage to a lower one (buck converter) or output multiple voltages with better than 1% accuracy then again, a switcher is your friend.

Unfortunately, the non-cookbook design of a good switching power supply is not anything near a walk in the park. My last original switcher design took me months to get right and a LOT of scratch paper. But most every switcher IC has an extensive applications section in the datasheet to make starting from scratch an exercise in futility. Many of the modern parts are merely updates of designs from the 70's and 80's and are usually drop in replacements, so it's no big deal to use "older" application notes at least for ideas. A lot of the IC manufacturers also have tools that you can use to do all of the design for you and, typically, all of the parts they recommend can be found on Mouser or Digikey. It just doesn't get any easier than this, nor should it be very hard. A lot of great minds have tackled (and still are tackling!) the problem of designing a good switcher and have made it very very easy.

Also, you'll see a lot of 555 timer based DC-DC converters. These are simple devices though and while they work well for some home applications, they typically lack any sort of output voltage monitoring and if something goes awry (inductor saturates, power switch overheats, etc..) then you're going to release the hidden white puff of magic contained in every IC.

[burningman]

Thank you for your detailed replies - I'm starting to understand their application a bit more. THanks.