Planar Magnetics

Hello everyone,

Planar magnetics in general are better than conventional magnetics, it gives a better heat disipation, it covers better every surface needed and it minimize AC resistance and leakage inductance. The usage of high frequency magnetics  and higher power densities have increased and it is needed the design of smaller and more efficient devices is necessary. 

Also in planar magnetics, turns are flat foil patterns on a printed cicuit board and it results in a high degree of consistency in spacing between turns and layers. This reduce AC losses. There are a lot of advantages referred to planar devices, so i want to know why are conventional magnetics used more than planar magnetics if planars usually are better? 

Regards!

Edited by zhihao sun on 9 months before

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Llukes says:

Hello Zhihao,

Planar magnetics are the best solution in some applications, but they could be much worse than conventional magnetics in some cases. You are right in some of your statements, but you must also look at the some of the drawbacks of planar magnetics.

The low leakage inductance is not for free and significant parasitic capacitance appears there which might give isolation and noise problems.

It is true that the AC resistance can be minimized if you have perfectly interleaved your windings and your currents in the primary and the secondary side are somewhere similar. Now put and LLC at light load with high magnetizing current and low secondary current and figure out what would happen. We must also consider the fringing effects which can destroy the “good” AC resistance of a planar magnetic.

So, the answer is not straightforward and each application needs a clear understanding of the requirements.

Published: 9 months ago

Llukes said:

Hello Zhihao, Planar magnetics are the best solution in some applications, but they could be much worse than conventional magnetics in some cases. You are right in some of your statements, but you must also look at the some of the drawbacks of planar magnetics. The low leakage inductance is not for free and significant parasitic capacitance appears there which might give isolation and noise problems. It is true that the AC resistance can be minimized if you have perfectly interleaved your windings and your currents in the primary and the secondary side are somewhere similar. Now put and LLC at light load with high magnetizing current and low secondary current and figure out what would happen. We must also consider the fringing effects which can destroy the “good” AC resistance of a planar magnetic. So, the answer is not straightforward and each application needs a clear understanding of the requirements.

Hello Llukes,

Thank you for answering. What you say makes a lot of sense, I understand that there are better applications for planar and better applications for conventional magnetics. Could you tell me some application where a planar is better for? An example of an application in which a conventional one is worse, I mean. And on the other hand?

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Published: 9 months ago

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zhihao sun said:

Hello Llukes, Thank you for answering. What you say makes a lot of sense, I understand that there are better applications for planar and better applications for conventional magnetics. Could you tell me some application where a planar is better for? An example of an application in which a conventional one is worse, I mean. And on the other hand?

Hi guys, I saw this post just when I wanted to comment about planar magnetics. I work designing power supplies and of course designing the magnetics on them.

Since some years a go I see a lot of hype around the planar magnetics as them seem or used to seem like the future

However, I have implemented them in some of my projects and I can affirm that, although some advantages are provided, planar are mainly viable for high frequency , high current and low turns magnetics. Also due to its shape, planars tend to take more space out of the boards. Furthermore, planars are considerably more expensive than normal ferrite shapes.

So my question, why are they sold as a big thing?

I have seen LLukes that you have experience in differentiating in the applications of planars or "conventional" as you call them, and I think you agree with me that they are not that bad.

What do you guys think?

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Published: 8 months ago

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