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2.2 Start-up circuit<br />As already mentioned in the introduction section, the controller is located on the secondary side of the power<br />transformer, and for this reason, a start-up circuit has to be provided for a correct system activation.<br />The start-up circuit is based on a diac sending a train of controlled pulses to the low side drive section; the floating<br />drive section is energised by the second secondary gate drive transformer winding .<br />As soon as the L5991a wakes-up, it generates a pwm signal enabling the start-up circuit.<br /><br />大概翻译为：前面已经介绍控制器放在二次侧，因此启动电路就必须提供合适的方法令IC工作，本设计基于采用二端交流开关送出一触发脉冲给低边驱动部分，高变MOS再由二次侧供电，L5991即刻唤醒，即产生PWM信号从而完成启动。<br /><br />问：此说明中的二端交流开关是怎么一回事？这个启动的描述，我没弄懂、、
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<br /> 相关链接:<a href='https://bbs.21ic.com/upfiles/img/20095/2009519212819610.pdf'>https://bbs.21ic.com/upfiles/img/20095/2009519212819610.pdf</a>
