MPS电源芯片的输出电容发现问题，请教选型问题。

banyai

最近有一个产品，用的是MP1591，电路是推荐的电路，5V输出，输出电容是22uF/10V的贴片陶瓷电容X5R，开始都正常，运行半年多以后，陆续发现个别输出电压降到3V左右，更换这个电容后又好了。请问是不是就是这个电容的问题。有什么性价比好的品牌和销售商推荐？

浮生莫若闲

据你的描述，我猜你的万用表电池快没电了的可能性大点

sunicecream

换成独石电容试试

again

把电容拆下来测下，换电容好的话应该是这个电容不行，你确定电容是X5R正品，我一般多并几个

wye11083

电容不好的可能性比较高。另外查查有没有焊接不良。万用表查不出纹波，如果电容有问题，纹波会变大。

chen057399

可以用钽电容呀！

reflecter

可有LCR表，测测下降到3V的22uF瓷片电容容值有改变？

reflecter

http://www.monolithicpower.com/D ... /GetDocument?id=246
Stable with Low ESR Output Ceramic Capacitors

Output Capacitor (C5)
The output capacitor is required to maintain the DC output voltage. Low ESR capacitors are preferred to keep the output voltage ripple low.
The characteristics of the output capacitor also affect the stability of the regulation control system. Ceramic, tantalum or low ESR electrolytic capacitors are recommended.
In the case of ceramic capacitors, the impedance at the switching frequency is dominated by the capacitance, and so the output voltage ripple is mostly independent of the ESR. The output voltage ripple is estimated to be:
Where VRIPPLE is the output ripple voltage, fLC is the resonant frequency of the LC filter, fSW is the switching frequency.
In the case of tantalum or low-ESR electrolytic capacitors, the ESR dominates the impedance at the switching frequency, and so the output ripple is calculated as:
Where VRIPPLE is the output voltage ripple and RESR is the equivalent series resistance of the output capacitors.

reflecter

chen057399 发表于 2016-7-10 10:46
可以用钽电容呀！

赞同
建议解决：
A 确认MPS电源，以及MLCC的采购渠道，是否为正品
B 22uF/10V 的钽电解，不会比MLCC的贵太多吧？

http://www.szlcsc.com/search/global.html

banyai

谢谢楼上各位，我再试一下。