双管正激PC电源的驱动波形(附图)

请帮忙看下此电源的驱动波形,上管的MOS关断后,会出现一个很大的反向的电压,我试过更正不同的驱动方式,但都没有效果,请帮忙分析一下,急!!!
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接地的MOS的驱动
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变压器输出波形
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上管MOS的驱动