EMC scan in DER538

Posted by: treez on 11/07/2024

Hi
I noticed in the DER538, details about the conducted EMC scans.
On page 41, the setup shows a small green wire coming to the LISN.
Please advise what is this? Is it the earth bonding? We thought that
had to be done with a short thick connection?

Also, in the scan pf page 43, why is MT set to 1s? Also, why is
Attenuation set to 10dB? Also, what is the step? It says "TD scan" though
please advise what step time is that?

Also, we wish to do an innoswitch design, but first wish to check our conducted EMC measurement setup.

So we will build one of the SMPSs in one of the DERXXX files, and then check if our EMC scan corresponds to Power.com

scan.

Which DERXXX file is best for this?.....we want something where we can be sure if getting the sane result as the

DERXXX one...so that we can check if our EMC Conducted measurement lab is good.

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Hi, to continue this, Sorry ot bother with this....but we have just spent the last two hours searching for a DERXXX or RDRXXX report for which i can source the transformer core set in qtys of less than 10.

I cannot find the core set of any DERXXX or RDRXXX report on digikey, farnell, RS or mouser. Do you know where eg we could source a PQ2620 core set with AL=400 for the DER535?...nowhere has it in stock. The big ferrite manufacs have it but they only sell in qtys of 1000+.

I appreciate this nil-providion of small qtys is not power.com fault....its just that these things are things only found in PRC these days.

_____________________________________________________________________

The following ferrite cores are the only "flyback size" ferrite cores that I can find in stock
at the moment..........................

ETD29/16/10 with AL = approx 383
ETD34/17/11 with AL = APPROX 482
ETD34/17/11 with AL = APPROX 251
EFD30/15/9 with AL = APPROX 251
EFD20/10/7 with AL = APPROX 100
PQ3230 with AL = APPROX 150

May I please ask do you have any DERXXX or RDRXXX reports that contain any of these?

Comments

Hi treez,

Thank you for posting a new question to our public forum.

The green wire you see in the image is the earth connection wire of one of our equipment. Rest assured that we comply international standards for testing. It is better that you reach out to the manufacturer of your preferred test equipment to ensure that the test setup and the results of the test are aligned with international standards.

It will be better to get power supplies with prefix RDR-XXXX. This can be purchased through our distributors. Here is one we can recommend: RDK-747 - 65 W Charger Using InnoSwitch3-EP (750 V PowiGaN Switch) | Power Integrations

Have you tried using our RTSS service? We here at Power Integrations can help you with your prototype. Please see this link on how to proceed: Rapid Transformer Sample Service (RTSS) | Power Integrations.

You may also reach out to our suppliers in this link: Component Suppliers | Power Integrations.

We hope this helps you.

Regards, Gavin

Thanks for your reply. Please advise how we should connect the secondary of RDK747 to earth (as mentioned in the 2nd lot of EMC scan plots). Presumably the earth connection to secondary must be from an earth wire which comes pretty directly from the mains cable that also brings line and neutral to the RDK747 inputs?.....if not done like this, then presumably there will be bad earth loops?

Hi treez,

Thank you for your response. The Earth wire is connected to the return path (negative terminal) of the secondary circuit. You are correct, the earth terminal of the system will create direct loops to the secondary circuit. In effect, you will see that the noise level is higher compared to the floating output scans in higher frequencies.

It must be ensured that the layout follow our guidelines to help mitigate this. Please refer to our design guide: AN-72 - InnoSwitch3 Family Design Guide | Power Integrations

Attached is our general document for EMI that we made for Topswitch. Since Innoswitch is also a flyback power supply, you may still find this applicable.

Regards, Gavin

Attachment	Size
an15 - Power Supply Design Techniques for EMI and Safety.pdf (462.19 KB)	462.19 KB

Hi Thanks very much. I would be very grateful if you had a photograph or description of the exact setup that was used for the conducted EMC scans in the RDK747 document?

ie length of cables, Length/thickness of earthing cables/Any torroids used on the cabling/Any extra filters used upstream of the LISN/etc/etc/distance from ground planes/size and shape and orientation of metal ground planes and exactly where and how many times they are connected to mains Earth, etc etc?

Hi treez,

Thanks for your response. The typical setup can be found on page 3 of application note AN15, and everything surrounds it should be earth grounded. There should be no requirement about type of wire used, as long as it can handle the operating currents of your power supply.

Please reach out to your test equipment supplier to confirm proper set up. They should be able to assist you.

Regards, Gavin