The circuit above is a buck converter which can boost or buck(decrease the voltage). This circuit uses the Ne555 timer and is the same circuit as the pwm dimmer circuit but modified with a inductor, extra diode and a 7812 linear regulator. The inductor rating is a trial and error, i would est a 40 to 60 uH cored inductor. To use the circuit you would turn the potentiometer on the top left either left or right so that it either increases the voltage or decreases the voltage.
As the voltage decreases, the current output should be higher and as voltage increases, current output should increase. The input voltage of the circuit should be at least 13-30v as long as you have the 7812 regulator.On the left shows which the gate, drain and source of the n-channel mosfet diagram. Below shows the pinouts of a IRF540 n-channel mosfet.
Note: The output wattage will never exceed the input wattage.
