This power supply uses a bridge rectifier and smoothing capacitor, then a simulated inductor ( the two transistors, the 100 ohm resistor & the 1mF ( 1000uF ) capacitor ) and a final smoothing capacitor , 10mF ( 10000uF ) The simulated inductor and the 10mF ( 10000uF ) act as a low pass filter that attenuates ( makes lesser ) the 100 Hz ripple from the rectifier a capacitor circuit. Output ripple is under 10mV peak to peak, though in a real circuit would probably be a bit higher than this, due to practical limitations of the components. The two transistors can be replaced with a power Darlington.
