开关电源仿真问题 附图和波形

如下图所示,推挽升压仿真.变压器用电感耦合,变比1:9,输入电压36V,拟输出240V,在仿真的时候发现上面的IGBT好像没导通.查看电流通过情况,实际是导通的,但是它的CE极电压不变,这是为什么呢?请达人指导
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