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InnoSwitch3-EP problem in multiple output power supply.

Posted by: Christos on

Hi.

It's about an InnoSwitch3-EP use in a three isolated outputs power supply. (As these outputs are isolated from each other, I suppose InnoSwitch3-MX + InnoMux pair cannot be used.)

A specific problem occurs when one of the secondary outputs has a heavier load than the main one: under this condition and at low input voltage, all of the three output voltages drop below the expected limits. The feedback voltage lowers as well and, unexplained at first, the frequency doesn't rise to compensate it.

After a careful analysis, I suppose this occurs because of the InnoSwitch3 QR mode operation combined with the leakage inductance between the outputs. In the above mentioned load condition, all of the energy consumed by the main output is provided by the correspondent leakage inductance and so the current across the rectifier falls to zero prematurely, making the InnoSwitch secondary control block detect the discontinuous conduction mode wrongly. (I said wrongly because, in truth, the transformer still has energy being transferred to the secondary output). The DCM detection, in its turn, enables the QR switching mode and imposes a 20 us waiting time for the magnetizing ring valley. Finally, this waiting time delays new switching pulse requests and doesn't allow the frequency to increase.

Does it make sense ? If so, what do you suggest to address the problem?

Regards.



Christos

评论

Submitted by PI-Enderman on 04/04/2022

Hello Christos,

Thanks for your inquiry.

We have received and online support request with the same inquiry and we need more information regarding your request. Please check your email for an update and let us proceed with the resolution offline.

Best Regards,

PI-enderman

Submitted by Christos on 04/05/2022

Thank you, PI-enderman!



Yesterday I received an e-mail from Kit (Applications Engineer). Let me make sure, please: you suggested me to proceed the support by this e-mai with Kit, right?

Submitted by PI-Enderman on 04/05/2022

Hi Christos,

That is correct. The technical support through email is well underway at this moment.

Regards,

PI-enderman