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发表于 2009-1-3 22:36:43
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It's just the bode plot of the plant stage, seeing from the negative gain of the low frequency. Actually, you need to add the control circuit which will give enough gain at low frequency (for example, 80db or greater) and model the pwm block ( if you use such method, that means you need to model the switch and diode). After including the control circuit, the whole loop gain will be changed into positive, and you can measure the loop stablity. For system design, you need to get the model of the control IC(normally, can model it as OTA, and adding the compensation component).
原帖由 analoger 于 2008-12-2 16:36 发表
下面的图是一个BOOST converter（开关频率=1*e6）的整体环路的频域响应图（还没加补偿电路）
这幅图怎么看啊？一般情况下都是看增益等于0时的相位裕度来说明系统是否稳定。
可是这幅图怎么看啊？相位裕度为多少？为 ...
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