high_power_voltage_step-down.zip



Recently someone requested I post this, so here it is.



Be certain to read the enclosed .txt file.  This explains what you need to do.  Take proper safety and anti-static precautions.  This is the highest power device yet, as-is it can provide 20A current which is 150W at 7.5V and 240W at 12V.  I've verified that it can provide up to 27A, but not for a long period. 



It is perfectly possible to increase the current output to upward of 60A.  Again read the .txt file for my recommendations of how to do this.  The main thing that adds size and weight to this design is the inductor. 



I never really had classical RC racing in mind when I first build this device, the original application is the cap-car which can maybe run for 2 minutes 30 seconds on 6x 400F, 2.7V caps (in series).  This device steps down the ever-dropping capacitor voltage to a constant 5.4V, which is then used to power a Novak stock brushless motor with a 13.5 ESC.  2 min 30 sec hard driving in a parking lot is about the best I can do with the cap-car right now.  The tech still needs to advance a ways before this becomes preferable.  But for that particular application, the device works great. 



Note:  Certain brushless (and maybe even brushed) ESCs will channel braking energy back into the batteries.  This is bad.  If the output of this device rises too far above 16V, it will blow out the comparator in the LT1148 IC.  To prevent this, I put 3x 5.6V zeners in series across the output to clamp the voltage and stop it from rising too far above 16V.  This is critical if you are using one of these ESCs.