菜鸟求助!~开关电源启动

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附图为现一开关电源的启动电路,启动MOS管Q10后,通过VCC1启动Q55,通过Q8来控制Q10的通断.Q10漏极输入为交流半桥输入,输入范围85VAC-265VAC.
Q10为什么不串入VCC1一路?Z2的具体作用是什么呢?