I am working on a charge controller circuit idea I had. The circuit 'works' meaning it achieved desired output voltage but the fet doesn't seem to be turning all the way on so lots of heat is generated.
I am using an LM393 dual comparator to measure the voltage at the junction of the zener and series resistor R1, compare it to the voltage at the - pin of the capacitor, and switch the enhancement mode FET on and off accordingly. I built the circuit on a breadboard and was elated when I measured the output and was able to connect a solar panel and battery. The fet needs about 5v at the gate. For some reason i only measure 2 or 3 v at the gate. Can you drive this FET direct from the output pin of the LM393 directly or will I have to amplify the output somehow to make sure the fet turns all the way off and on? Also, I am powering the LM393 directly from the input. I wonder if that could be a problem. Am I going about this all wrong? Any help would be much appreciated. It 'works' but wastes power by the fet presenting resistance. Please take a look.
Input is 16.5 v PV panel
zener is 12V
output is 12v lead acid battery
R1 is 1k, R2 has been 3k and 10k
The FET is a typical enhancement mode N channel, RL2203N or RFP50N06