Hello,
To add a little to what Claude was saying...
Another point of interest is the peak diode current. Here are some estimates of the diode average current and the diode peak current:
Iavg=(1-DC)*Iout
Ipk=(2*Iout*L+Tp*Vout*(1-DC))/(2*L)
where
Iavg is the average diode current
DC is the duty cycle
Iout is the average output current to the load
Ipk is the peak diode current
L is the inductance of the inductor in Henries
Tp is the total switching period, Ton+Toff
Vout is the average output dc voltage
Note that if you had an error condition where the output resistance went very low, the regulator circuit would increase the duty cycle and this would increase the peak diode current to some fairly high level. The limit of the duty cycle is usually determined by the nature of the ic used as the controller. Most have some limit such as 0.95 and can not get to a full 1.00, which is nice for an overload but usually still isnt enough.
To guarantee proper operation for fault currents usually a second loop has to be used to sense current and cut back if needed, because the output voltage will try to go up to the set point voltage even with a short and this will cause a huge current in the switching transistor. Some controllers already have this built in in the form of peak inductor current sensing.