The importance of some components in switching power supplies

classd

The importance of some components in switching power supplies [Copy link]

 

 

I was recently exhausted by the CE and EFT of a project. I have worked on several projects with power adapters, but I have never encountered such a problem. I suspect that the power supply itself does not suppress interference well. After disassembling the power supply, I found that there is no X capacitor or common mode inductor at the AC input of the power adapter. Some even do not have a π-type filter at the output. I wonder if this is all due to cost? In addition, it is understood that the electronic load of such adapters is basically in constant current mode during factory testing, and the dynamic load is not tested. How can we ensure that the situation is consistent when the dynamic load suddenly changes?

The components saved on the switching power supply still have to be added to the subsequent products. Is this approach really scientific?

1231234从v

Cost

wangerxian

I think it is to control costs so that they can outperform their peers. As for the subsequent products, whether they have protection or not, I guess the power adapter manufacturers will not consider it.

蓝色天使

The first reason may be cost; it seems that this is a product of a small factory, and the engineers do not have the knowledge of safety regulations, EMC, loop stability, dynamic response, and design awareness, not to mention the various protection circuit designs.

qwqwqw2088

The left side is needed to obtain certification.

The actual product on the right is installed.

Many small manufacturers do this

okhxyyo

So I always feel that the current products are not as solid as the old ones. Maybe it is because of these reasons. I think it is mainly to save costs, so everything that can be saved and will not cause problems in the short term is saved, and only the components that must be required to achieve the necessary functions are retained.

classd

If some companies' products do not come with a power adapter, but they happen to have a good power adapter that has passed CE and EFT, they can save a lot of magnetic components on the product. If they use this rolled adapter, the cost of the components that need to be added to the subsequent products will not be a small amount for their own company.

1nnocent

[There is no X capacitor or common mode inductor at the AC input, and some even have no π-type filter at the output]

This is too much water, these are very important things

不亦心

1nnocent posted on 2024-3-13 16:46 [There is no X capacitor or common mode inductor at the AC input, and some even do not have a π-type filter at the output] This is too much, these are all very important things

Who said filtering is necessary? The low power in the picture can pass the certification without adding it. You can disassemble a 5V1A charger from Apple to see if there are any of the things you said. It is obvious that the author chose a power supply that is not suitable for his application. You can't blame others. Not mentioning the design indicators is just a hooligan.

maychang

Bu Yixin posted on 2024-3-13 18:38 Who said that filtering is necessary? With such a low power as the one in the picture, it can pass the certification without adding it. You can disassemble a 5V1A charger that has been passed down from generation to generation to see if it has what you said...

[With such a small power as shown in the picture, it can pass the certification without adding any power]

agree.

1nnocent

Bu Yixin posted on 2024-3-13 18:38 Who said that filtering is necessary? With such a low power as the one in the picture, it can pass the certification without adding it. You can disassemble a 5V1A charger that has been passed down from generation to generation to see if it has what you said...

I'll take a look if I get a chance to take it apart.

classd

The answer is basically the same as the previous great god's. Yesterday, I also asked the engineers of the power supply factory, and they replied that due to cost reasons, low-power power supplies below 15W basically do not add this component. As long as the test can pass the power supply standard, it is fine. Today, I took apart an Apple 5V1A charger, as shown in the attached picture, but it still has a common-mode inductor inside.