The basic equation of the regulation is shown at the top of this slide for VOUT2, relative to VOUT1 and the turns ratio. When the switch goes high, it creates a ramping inductor current signal. This can be seen in the two inductor current ramp waveforms in blue and black, as shown in the lower right. The blue one is IL1, which ramps up when the switch turns on. Then when the high-side buck switch turns off, the diode D1 becomes forward biased, and that in turn provides a charge to the output voltage. The gray line is the sum of the two other waveforms. The sum of the two acts like a single winding inductor.