UCC28950: Senkron rectf question

mehmet özdemir

Prodigy 120 points

Part Number: UCC28950

Hello,

Does canceling the "DCM" mode cause synchronous rectf burning in no-load operation ?

over 3 years ago

+1 Harish Ramakrishnan5 over 3 years ago

TI__Mastermind 24375 points

Hi Mehmet,

Thank you for the query.

Not Cancelling the DCM mode (disabling the SRs) at light loads will most likely allow a negative current to develop in your output input inductor and your SRs. This negative current will most likely cause excessive voltage on the SRs and damage the FETs during SR turnoff.

With the SR drive disabled, the rectification happens through the SR MOSFET body diodes, in this case the body diodes will not conduct negative current and will result in discontinuous (DCM) operation. Cancelling this could potentially lead to damages.

Please let us know if you require any clarifications.

Regards,

Harish

0 mehmet özdemir over 3 years ago in reply to Harish Ramakrishnan5

Prodigy 120 points

Hi Harish,

Can you recommend a document that explains this subject in detail?

Regards,

Mehmet

0 Harish Ramakrishnan5 over 3 years ago in reply to mehmet özdemir

TI__Mastermind 24375 points

Hi Mehmet,

The following app note Section 14 briefly describes how it is done.

https://www.ti.com/lit/an/slua560d/slua560d.pdf?ts=1662442564254&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FUCC28950

It might not be a detailed one, but a good starting point for your query.

Thank you

Regards,

Harish

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UCC28950: Senkron rectf question