最简单的电路,上电就烧MOS管,救急!(附图)

最近很忙,前一阵子做的300W正激电路经过改进,加了过流短路保护,重新设计了PCB,趁“五一”放假,赶制完成,却接连烧了6只9N90,很郁闷.请大侠支个招吧.
该电路只烧MOS管,其它都安然无恙.
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变压器参数:
EE40磁芯,AeAw=3cm4
f=95kHz
1-2:55T,0.3mm
3-4:45T,0.3mm*6
5-6:36T,0.9mm*2
7-8:8T,0.3mm
采用三明治绕法,从内至外:24:55:12+12+12:21:8
原边电感7mH,漏感0.023mH.