Gapping the Transformer in Two Transistor Forward converter (DER-472)....why the gap?
This concerns gapping a Transformer for a Two Transistor Forward SMPS. -And why a gap is needed!
Page 21 of DER-472 shows that a gap is needed in a 300W Two Transistor Forward. The second picture down (pg21) shows a gap being made with 0.02mm tape. The reason for the gap is given at the bottom of page 31. It says that the gap must be present so that the “no_load resonant frequency Between L_PRI and C_PRI does not get too low”. -Presumably , there is a problem if this resonant frequency becomes the same as the switching frequency (??)
Does anybody know why the primary resonant frequency, as discussed above, is so important, such that a gap is needed?