EFT 61000-4-4 test issue in PS with INN3165C
Hello everyone,
We have designed a power supply for USB charger with de IC INN3165C and we found some problems in burst test (ETF) at 1kV (2kV also) when we apply the test through AC input port. Once we apply the voltage burst the power supply starts to fail and reset the device, constantly. After the test (once all the pulses have been applied) the device recovers the functionality and it works again.
We have a MOV at the input and we are using several snubber networks (primary and secundary) and we follow the recommendation from the datasheet and application notes from PI.
However, I would like to highlight that this issue doesn't occur at maximum current output. So, it seems depends on the output current we demand.
Best Regards.
Comments
Thank you so much for the reply.
The H code of the IC is AH401.
Regarding UV/OV, we haven't added any resistor to V pin because we wanted to have OV/UV disabled so, we have tied that pin to Source.
In fact, we have a previous product version with OV/UV enable, however it has the same problem.
We also don't have any OV output declare at BPS. In BPS pin we only have a 2.2nF capacitor (we don't have any resistor nor zener).
Unfortunately I could say how much time it takes befor recovering.
Best Regards.
Can you please confirm if the capacitor in the BPS pin is really 2.2 nF?
We recommend using 2.2 µF for the secondary bypass capacitor as values lower than 1.5 µF can cause unpredictable operation, mentioned in Page 16 of AN-72 InnoSwitch3 Family Design Guide.
Best Regards.
Sorry, my fault. I meant 2.2uF rather than 2.2nF. Sorry for misundertanding.
Regards!
Would you be able to provide a schematic and layout? We can assist you better if we can have more context on your design.
Best regards.
Yes, I would but due to confidenciality, I prefer sending you by email rather than make it public in this chat. Could you provide me an email to send the schematic and layout?
Unfortunately, we cannot provide our own email in this forum.
What we can do instead is this:
- You can provide us an email which we can reach out to
- We will contact that email and you can send us the files through that channel
Best Regards.
You can contact me using this email. Then I will delete it from the post.
Hi Guillermb,
To start troubleshooting the issue, we need to know the fault that is being triggered during the application of EFT.
Multiple faults can trigger an Auto-Restart response.
For the primary, the faults that can trigger this response are Line Overvoltage or BPP overvoltage, depending on the H-Code of the InnoSwitch3 IC.
While for the secondary, some of the possible causes are output overvoltage, output undervoltage, output short circuit.
One common cause of restart during line transient events is line overvoltage.
The bulk capacitor voltage can get charged during EFT especially during light load conditions and may trigger the line OV protection.
Even if the energy in an EFT pulse train is not enough to raise the input bulk capacitor level to trigger an overvoltage, the high slew rate of the voltage applied may get capacitively coupled to the UNDER/OVER INPUT VOLTAGE (V) pin.
For this reason we recommend placing the line voltage sensing resistors close to the V pin. Can you please verify if that is the case in your design?
It would also be helpful to know the following:
-Value of the line voltage sensing resistors
-How much time it takes before the unit recovers
-H Code (Feature code) of the device that you are using
These information can help us narrow down the cause of this unwanted response.
Best Regards.