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How can I easily step-down a DC voltage with out too much power dissipation?
I need to step down +45v DC to +12v DC, with as little amps dissipated as possible. I was thinking about using a simple voltage divider circuit, but this dissipates too much heat (thus too much mA). I also looked into some VRegs from Linear and National, however the +12v does not need to be superbly regulated and using a VReg would waste power, and needs too many external parts.
+42vDC IN to +12vDC OUT, with little Amps lost, it needs to ouput around 2.5 Amps. Hope that helps anyones confusion.
You'd probably want a switching power supply like this "Simple Switcher" from National Semiconductor. (You can get them at DigiKey)
Using resistors for a voltage divider is a very inefficient way to go about the voltage reduction. If you are dropping 33 volts at 2.5 amps, you are losing 82.5 watts to heat. Switching regulators use an inductor instead of a resistor and will probably be better than 75% efficient (losing 20 watts or less).