This PWM regulator uses LM555 timer, P-channel MOSFET IRF4905 transistor and 1N4148 diodes. The configuration is very suitable for building of car's daytime running lights (DRL) based on standart headlight dipped beam or main beam of vehicle, running from 20% to 100% (usually 50%) of their power. Tested and proven in my own Audi 80 B4.
The main advantage of using P-channel MOSFET, unlike the N-channel MOSFET is easily installation in the automotive system, since the P-channel controls the + 12V line.
