Very simple cost effective main AC (230V) converter, without transformer or PWM.
The 60 Ohm resistor (right) represents a (simplified) 12V / 0.2A PC fan.
The 3uF high voltage metallized capacitor (left) works as blind resistance to reduce the line power to roughly 30V. For US and other power lines different from 230V change capacitor value.
The 1M Ohm resistor (above 3uF capacitor) is a bleeding resistor to discharge the capacitor if the line power is cut.
The diodes are connected as bridge rectifier.
The zener diode is mainly for protection, to ensure the main AC is not above 12V, eg. when there is no load.
The 200uF filter capacitor is for rectifier output smoothing. For better smoothing increase the value.
The 50 Ohm resistor (bottom left) works as a current limiter, because the capacitor is short circuit for a tiny fraction of time at startup (instantaneous power)
To test the power-on behavior press the button (left) and release, to see the voltage spike.
Very simple to build, all parts except the 3uF polarity free capacitor everyone should have at hand. BUT BE VERY CAREFUL WHEN BUILDING IT's MAINS POWER
