dc/dc converter

[owenhooker]

Can anyone explain to me the difference between a switching regulator and a dc/dc converter? I need to go from 24volts to 5v 500ma and don't have enugh experience to know the best rout. I'm trying to stay away from linear regulators to avoid heat build up. Any insight would be greatly appreciated.

Thanks,
Owen

[Chris Smith]

Most DC to DC units today are switching Power supplies.

Efficiency and loss are the main differences between to two types of systems as the old style takes DC, chops it into a standard transformer, then takes the AC coming out the other side, then converts it back to DC with a Diode bridge and caps. This is less efficient.

The newer types use the Buck /Boost method which is more efficient, same principal but no huge transformer is needed, just a small one because the frequencies and methods are much higher and different,... for starters.

It also depends on the voltage differences [In VS Out] as this can reduce the part count.

[MrAl]

Hi there,

As long as you dont need isolation you can use a buck converter,
also called a down converter.
The easiest route i can think of is the National Semiconductor line
of 'Simple Switchers", which with a few other components produces
a down converter. I've built a number of these circuits for various
things and i dont think it gets any easier than this.
Lets see, the parts are something like this:

LMxxxx simple switcher ic
input electro cap, maybe 1000uf
output electro cap, maybe 100uf
Schottky diode 1N5817 or better (for 500ma output)
100uH inductor (say 1 amp sat current rating)
fuse on input would be nice
two 1/4 watt resistors to set output voltage

[L. Daniel Rosa]

If cost is your primary concern, you can get some useful information at http://www.romanblack.com/smps/smps.htm

[bic]

For a step down converter you can check out the Texas Instrument series of switching regulators available at Digikey. One of them is: PT78HT205H-ND, which costs yoy $16. It goes from 9-28V down to 5V.
For step up circuit intergrated to a battery pack you can check out our products at:
www.bodhilabs.com

Good luck on your project,

Bic

[philba]

since you probably aren't a power supply designer, there are two great resources that you can use to design your DC to DC converter.

National Semi's web bench. plug in your parameters: Vin, Vout, Iout and a few other options and it will give you a list of chips that will do the job. Many of the chips have simulations built in - if you select one, it will put together the actual schematic and give you a list of parts. pretty cool. http://webench.national.com/appinfo/web ... ebench.cgi

Linear Tech's switcher CAD (a great general purpose simulator in its own right) does the same thing but a lot faster and much easier to play with. great free software! http://www.linear.com/company/software.jsp first entry on the page.

My only complaint about both is that they don't let you specify max acceptable ripple but it wouldn't be fun it they did it all for you.

Phil