A simple way to make a PWM with a 50% of duty cycle input you two outputs 1)from50% up to 92%,2)50% down to 8%.Left pot control frequency right pot adjust Pulse Width.IC you can use any buffer NOT GATE I use CMOS 4049 on my projects.If you change values on capacitors resistor and IC's delay you get higher or lower frequencies.Cmos 4049 have 7.34Volts threshold input at 12 Volts power on it.
