This inverter circuit ... 12V about 3A current. The 555 timer IC is operated in astable mode, generates about 29Khz frequency of about 54% duty cycle drives the input of TIP41C transistor.1000uF ...

Seen in the accompanying schematic, the 555 square wave generator drives an MPF102 FET, which in turn drives a D718 power transistor that provides a “pulsed” 12V variable duty cycle driving the LED ...