UCC256302: ＵＣＣ２５６３０２

Hello Bob,

I would recommend first that you double check your design with the excel design tool.  The excel design tool can be found at the following link. 

Second there is an application note that discusses typical design guidelines for LLC converters.  It reviews the most common design problems and how to resolve them.  The following link will get you to an application note.  I suggest you review this.

To ensure the LLC converter works correctly requires properly selecting the primary magnetization inductance.  The following link will bring you to an application note that describes how to do this. 

I would also suggest ordering the evaluation module that can be found at the following link.   You can use is as a reference to see what the signals should look like for all of the pins of the UCC25302 and compare it to your design.

If this information does not help you resolve your issue.  Please respond with your input and output power requirements.  Schematic and completed Excel tool for review.

Regards,

I think the LLC part is ok and tried with 400Vdc input to LLC part , the result is positive.

the problem is plus PFC(UCC28180), and UCC28180 VCC is from UCC256302 VCC with a linear circuit.

do you have the similar application? perhaps the LLC　ＩＣ　ｓｔａｒｔｕｐ　ｃｕｒｒｅｎｔ　ｉｓ　ｎｏｔ　ｅｎｏｕｇｈ． 

Hello,

I would suggest evaluating the PFC stage separately as well just to make sure it is O.K.  If it does not function correctly there is an excel tool at the following link that you can use to check your design.

Regards,

another issue VCR wave form is abnormal when no load while others load is normal.  do you have comments?