LM317T Voltage Regulator with Pass Transistor

Motorcontroller_10-26-2011.mp4 I had designed a very high power motor controller that originally ran using a 555 timer that was setup for pulse width modulation. However; Problems where found with 0% and 100% duty cycles, and issues with reliability of the 555 under this kind of use. A pic18F26J11 8 bit microprocessor was used for the PWM drive and would also be leveraged for the additional features required for protection circuits and some miscellaneous other tasks. The ten Mostfets are 61-65 amps at 200V rating providing a 600-650 amp motorcontoller with a surge capability of 2500 amps for 10ms. Two high power fast diodes are incorporated on the ends of the mosfet strings to handle back EMF from a motor. I think these are 200 or 250 amp rated (will have to look later) so I am hoping this is enough to protect the mosfets. A single NPN transistor is used to setup up the 3.3v logic output of the microprocessor to 10-12 volts required to drive a 15 amp gate driver chip which does the fast switching to keep the mosfets cool. This gate driver needs only 5.5 volts minimum to switch the mosfets high. However this driver needs 10-12 volts in order to supply that voltage to the mosfets for a good strong switching affect with 10v being optimal to the gates. I burnt up a LM317 adjustable voltage regulator with some of the mosfet power oscillations which was used to drive the logic circuitry so in this video a 12v zener diode with voltage drop resistors was used to power the pic18 ...



http://www.youtube.com/watch?v=9THN3YrfckU&hl=en