两级LC滤波器设计

?两级滤波器设计的一些注意事项，以前都没有关注过，写得非常好。两级LC滤波器的Design Rules 抄下翻译，详细看原版。
?Design Rule #1:Don't think of the filter as “Main filter followed by Noise filter”, that can get your design in trouble. It's an integral filter which you won't separate that way when you design it properly.
?规则1：不要将滤波器看成是“一个主滤波器后跟随一个噪声滤波器”，这会给你的设计带来麻烦。你想正确设计就不能将滤波器前后级分开看待，它是一个完整的滤波器。
?Design Rule #2: Make the first capacitor the smaller of the two.Then you'll have a second filter resonance which is fixed— it won't be affected by capacitive loading. Typically, the first capacitor will be 2-20 times smaller than the output capacitor.
?规则2：前级电容比后级电容小。这样的滤波器两个谐振点固定，而不会被容性负载改变。前级电容的典型值比输出电容小2-20倍。
?Design Rule #3: Make the second inductor much smaller than the first— typically about 10% of the main inductor value.
?规则3：使第二个电感比第一个电感小很多，典型值为前级主电感的10%。
?Design Rule #4: Put the second filter resonance about 3 times higher than the loop crossover frequency.
?规则4：是第二级滤波器谐振频率大概为环路穿越频率的3倍。
?Design Rule #5: Damp the second filter resonance properly. That means carefully choosing the ESR of the second inductor and the filter capacitors.
?规则5：次级滤波器谐振阻尼适当。这意味着需要小心选取次级电感和两个电容的等效串联阻抗(ESR)值。