When the switch is not activated, the load is powered only
by the primary dc power source. The output voltage is equal to
Vin1, and the primary dc power sources supply the load current
through the inductor and diode. On the other hand, the active
power switch with the inductor performs buck-boost
conversion from the second dc voltage source to the load by
turning the active power switch on and off periodically. As a
result, the output voltage is boosted up to be greater than Vin1,
and the load draws power from both two sources. The power
sharing between two sources as well as the output voltage
regulation can be made by adjusting the duty-ratio of the active
power switch.