According to InnoSwitch3-EP datasheet, at start-up, the primary MOSFET current is limited to 75% of the programmed "ILIMIT" at 100 kHz. Apart from that, I noticed the primary MOSFET "Ton" during start-up is limited to a maximum value of ~7 μs...
I was surprised by that since this information is not in the datasheet and I hadn't expected the maximum MOSFET ON time should be so short at start-up, mainly because the switching frequency during it is only 25 kHz. In my case, this limits too much the initial power at low input voltages, which, by its turn, doesn't allow the power supply to start at full load.
Please confirm the information about the referred "Ton" limit at star-up and tell me if it will be changed in future silicon revisions.