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发表于 2022-2-16 16:19:03
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其实一定范围内工作影响不大，最近刚看了一篇电感选取资料，分享下：
链接：https://pan.baidu.com/s/1E_azaFil0pY898nAOt5TYg
提取码：2222
总结一下这篇资料从3方面考虑：
1，从输出纹波：考虑输出纹波，现在电容ESR够小，可以不从这方面考虑。 It is almost always far lower than the high-frequency switching noise on the output.意思就是开关噪声有时甚至比ESR造成的纹波还大。
2，工作于CCM还是DCM：整个工作负载范围内，要保持在CCM模式。如果最小负载太小，那电感会很大！. In the early days of power supply design, this was an important factor to keep good transient performance under all conditions. With a modern power supply, using current-mode control, there is no reason at all to keep the converter in CCM operation.意思如果电流模式控制,CCM和DCM模式都可以很好响应。电流模式电感形成的二阶也消失了。
3，从损耗：Higher ripple current leads to higher RMS current in the inductor, plus greater AC currents and higher proximity losses. Core losses will also increase with larger ripple current. A higher value of inductor, with low ripple, has higher dc conduction loss.从后面的贴图看出在一定范围内磁损和铁损在一定范围内并不是很大。纹波电流大，开关管和整流管的RMS电流也增加，但是损耗并没有变化很大！！
结合文章中的图片损耗值看出来：
It is interesting to see that the big change in ripple from 10% to 200% (20 times) only incurred a relatively small increase in conduction loss of the power FET. The increase in the RMS current value does not change as dramatically as one might expect.Core losses were low for all designs, as would be expected when using a ferrite material.
最后看出来了文章中的例子最优的纹波系数是0.8，此时损耗最低，当然文中只对比了mosfet和电感的损耗，和常用的0.4还是有较大区别。 |
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