标签: 相位裕度

      It is easy to measure regulators’ stability and control loop behavior with vector network analyzer (such like PSM1700 ), The first element required for this method is to breaking the control loop and then inject a disturbance signal. To achieve this, it is necessary to insert a small resistor (10Ω to 100Ω) into the loop at a suitable point where the small resistance has negligible effect .        But many voltage regulators are of the fixed output variety and include the voltage divider internal to the regulator. for them aforementioned approach is not available.       According to fundamenal of power electronics,  we determined the relationship between phase margin and group delay Tg as:                  Omicron Bode100, together with Picotest current injector TJA2111A, allows direct measurement of the output impedance, group delay and Q of the system. Using this information the phase margin of the system can be calculated without breaking the feedback loop of the controller. This method is called "non-invasive.”        For example, Measure Low-dropout regulator L4949 in two cases: with and without 1 ohm resistor in series with buffer capacitor.              We get the result that: Phase Margin with 1 ohm resistor:      71° Phase Margin without 1 ohm resistor: 5.2°  

最近再次看了放大器的专业书籍，仍然有些还是不清楚，感觉进入新的境界，不过这几个点我仍是不明白？ 1：放大器的相位裕度 放大器的相位裕度我通过芯片资料提供图像知道了如何得出相位裕度； 不过相位裕度无载时在45°-60°属于正常，如若偏离参数范围过大，需要通过相位补偿补偿后可正常使用， 我不明白的是：如何补偿？有什么电路结构？参数如何确认？ 知识链接： 【相位裕度（phase margin，PM）在电路设计中是非常重要的一个指标，主要用来衡量负反馈系统的稳定性，并能用来预测闭环系统阶跃响应的过冲。经研究发现，相位裕度至少要45 ，最好是60 2：放大器的频率补偿（相位补偿） 放大器的补偿电容我暂时不知道如何求解出？求解中... 3：放大器的传递函数 相位裕度和相位补偿的问题均涉及到极点，我找了些资料发现极点的问题和 复函数与拉普拉斯变换 均有关联，但我无法将这些关联串接起来 以上是我遇到的问题，困惑很久了。。。万望有经验的高手赐教？