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2007 Fairchild Semiconductor Corporation www.fairchildsemi.com Rev. 1.0.4 ? 12/9/13 AN-6069 低端门极驱动器的应用和比较评价 摘要 功率MOSFET需要一个门极驱动电路,将来自模拟或者 数字控制器的开通/关断信号转换为控制MOSFET所必需 的功率信号.本文给出了当用作次级同步整流器以及驱 动脉冲/门极驱动变压器时,在钳位感性负载应用中 MOSFET的开关动作详解.探讨了潜在的驱动器方案, 包括分立驱动器和集成驱动器设计.MOSFET驱动器数 据表中的电流额定值已校验过,并给出了在实验室可以 辅助评估驱动器性能的电路. 引言 在许多中小功率的应用中,在PWM控制IC的输出驱动 下,低端(参考地)MOSFET用来开关一个感性负载. 如果PWM输出电路可以在一个令人满意的开关时间上 驱动MOSFET而不会浪费过多的功率,则该方案是令人 满意的.随着系统功率需求的增长,开关的数量以及相 关的驱动电路也随之增加.随着控制电路复杂性的增 加,由于接地和噪音问题,IC制造商越来越普遍地省略 IC内置驱动器. 当提高效率和增加功率密度变得重要时,越来越多的同 步整流器(SR)用来取代标准整流器.传递数十安培电 流隔离的功率级,在每个整流器桥臂上需要并联两个或 多个低电阻的MOSFET,这是很常见的.这些MOSFET 器件需要在低于100ns时间内具有高达几安培的电流脉 冲,才能正常开关.外部驱动器可以提供这些大电流脉 冲,确定时序防止直通,并优化效率来控制SR的工作. 此外,驱动器可以将逻辑控制电压转换为最有效的 MOSFET驱动电平. 低端驱动器也用于驱动变压器,能够给电源隔离的两边 提供隔离的MOSFET门极驱动电路或通信.在这些应用 中,要求驱动器能够处理变压器驱动中特有的问题,随 后进行讨论. 低端驱动器看似一个平凡的课题;