I hope this message finds you well. I am currently working on a 90V power supply design and would like to ensure that it meets the necessary EMI and EMC standards. Given the importance of these aspects for compliance and optimal performance, I am seeking feedback from the community to verify my design and suggest any potential improvements.
I would appreciate it if any members could review my design and provide insights on possible improvements to minimize electromagnetic interference and ensure electromagnetic compatibility. If needed, I can share the schematics and layout for further review.
Thank you in advance for your valuable time and expertise. I look forward to your feedback.
Thanks for posting such a well-described question and schematic.
I'd remove R32 + R39 and simply tie EN and DIM together, but not connect them to any external net, as per the MP9486 datasheet.
The rest seems to quite closely follow the datasheet, with the exception of an extra 100nF cap on the output as well as a 220uF buffer cap. The latter you may not actually need, but it depends a bit on what this is going to power. It likely doesn't hurt much either.
Dear @jim-p
First of all, I would like to sincerely thank you for your prompt response. I am seeking certification for AIS004 in India, as well as the following standards:
ISO 7637-2:2004 ā A voltage spike of 123V, 8 Ohms, 200ms pulse-5a.
Shock Test as per IS 9000, Part 7, 2006 ā Severity Level: 15g, Impact duration: 11ms, Impact Type: Half sine, Total number of impacts: 9 (3 on each axis).
International Standards ā CE and FCC certifications.
Kindly let me know the next steps in the certification process. I appreciate your assistance and look forward to your guidance.
So, you have never contacted a lab that could do the testing for your device. I suspect you need to do that and get their feedback and requirements,
In the US, the testers will want you to supply test devices from a production run of your product. Is that also the case in India?
No idea about India, but certification in Europe is pretty expensive (if you do not make a large series).
As already said: the layout of your board is also pretty important...
Ground pour, coils at 90 degrees instead of parallel, sufficient separation, sufficient track width.
Where is this 90V coming from? That is already a dangerous voltage level... Your schematic does not have galvanic separation.
Cannot comment on your circuit nor the required compliance for your market.
I will say you will need to put a 0.01Āµf on the input and output positioned as close to the connector pins as possible. This helps High freq performance.
Even with a larger series it will be - it's just that you can spread it out over a larger number so it doesn't hurt as much.
Also, involving a 3rd party in certification is expensive, but sticking a CE 'certification' on your device can often be entirely 'free' if the device doesn't fall in one of the categories that requires an external assessor to validate the certification. Btw, I doubt that a device that works with a 90V input can ever be categorized as a 'low risk, cat I' device, so it would likely require external validation by default.
If you get a copy of the relevant standard it will tell you what you need to do .
Layout of PCB , the housing etc has a big effect on EMC performance .
EMC testing usually requires testing by a third party who can confirm compliance .
The equipment used is specialised and very expensive .
There will be other standards to which you must comply , if you are selling a product , to get for example a CE or ULA mark..
Just re reading - if you are going for CE certification , there is a host of stuff you have to comply with - look for the appropriate Directive , which will give you the appropriate standards you must meet .
Some things you may be able to do yourself , some not.
Youāll need technical file with drawings , material data and so on. need to be competent to do it too ā¦.
No idea about India, but certification in Europe is pretty expensive (if you do not make a large series).
Answer : We are planning to make in large series. Thanks for telling the certification is expensive in europe
As already said, the layout of your board is also pretty important
Answer : Okay, i'm sharing it
Ground pour, coils at 90 degrees instead of parallel, sufficient separation, sufficient track width.
answer: okay, i keep it in mind
Where is this 90V coming from? That is already a dangerous voltage level... Your schematic does not have galvanic separation.
Answer : Its used in EV BMS power is coming from BMS 72V, but I take its provision to 90V. so i need to add galvanic and any other isolation Please suggest what are different options for isolations
I do not know the exact rules in europe and I know nothing about rules in India.
I guess it will also depend if this will be a consumer good or an industrial thing. And how it is housed and the type of connectors used.
Galvanic separation is reached with a transformer and sufficient trace separation.
Since an EV is also part of the equation, part of the rules will likely even be country-specific. I have a feelin this may be about electric bikes/mopeds (90V is a common electric moped battery pack voltage), and legislation per country is quite different and also in flux. What regulation applies also depends on what the subsystem/add-on is supposed to do and how it affects overall performance of the vehicle.
It's a tricky situation, possibly extremely complex and not something within the scope of a forum to solve.
Conclusion
As per my understanding after testing, we should work on filter and choke to make more effective and also add the zener diode protection to clip the extra voltage spikes at output 5V
Setup with 12V Input Yellow line SMPS and output line blue 5.1v
as per above waveforms i have some question and hoping that you guys answer
i was expecting that i will get smooth dc 5.1v at output of mp9486IC BUT it has some noise is it normal or i need to work on this if yes then what techniques i should use.
as you can see i already added pi and choke on input but i didn't see the better and filtered output
and this much noise can pass the EMC/EMI if possible please suggest or any setup that i can diy to test my this circuit in lab.
below i try some experiment on the output side to change the output capacitor
using tantalum cap 100uf 6.3v 1206 (MPN ā TMCMACJ107MTRF)
Below Results
input 66V yellow line smps and output blue line 5.1v
Without Load
Whether it's normal is not really the question. The first question is how much noise your application will tolerate. If the present performance is sufficient, forget it and move on. If it's not, then you need to identify the sources of the noise and deal with them.
Did you analyze the sources of the noise you're seeing? How did you conclude that a CLC filter on the input was the way forward? If that is indeed the correct approach, did you model the performance of the filter over a relevant frequency range (e.g. spice sim)? If so, have you verified that the simulation parameters are representative of the real-world components and circuit layout including parasitic capacitances, inductances and resistances?
I don't know what the regulations are that apply to this product and the regions it is supposed to be sold in. I also don't see any measurements of the EMI behavior of this circuit; you've only shown us plots of power supply line noise. That doesn't say much about EMI/EMC performance at all. Note that this also involves testing in the actual housing/physical setup of the end product. I see you're presently working with a prototype PCB that's only populated in part. I don't see how you could do a final EMI assessment of this setup.
Please refer to page 13 of the datasheet and the instructions provided for the selection of the output cap etc.
Capacitors are not created equal. ESR can differ from type to type. Parasitic inductance and parallel parasitic resistance also differ, and moreover can vary according to PCB layout.
