Sizing AC fuse for a DC device
Littelfuse makes and distributes fuses (and numerous other overcurrent protection devices), and they also offer very good technical assistance. Their SWITCH MODE POWER SUPPLIES APPLICATION NOTE is a good place to start, and may just answer your question without further investigation. I have contacted them many times for assistance, and their application engineers have always been very helpful. It can be difficult to get the amount of protection you need while at the same time minimizing false trips, so don't hesitate to ask them for guidance.