UCC2897A: schematic check

Tommy Tzeng

Genius 5885 points

Part Number: UCC2897A

Hi Sir,

MOSFET have damage situation, may we know the schematic is ok?

0 Sean Xu over 2 years ago

Hello,

1. Please make the loop is stable with good phase margin more than 45 degree; and gain margin more than 10db;

2. Decrease R27 and C31 so that CBC responds fast to protect over current.

Thanks,

0 Tommy Tzeng over 2 years ago in reply to Sean Xu

Genius 5885 points

Hi Sean,

Decrease R27 and C31 so that CBC responds fast to protect over current..<== got it, we will decrease value of R27&C31.

in addition, we want to know what is the purpose of Y-cap multiple connection?

is there any risk if we reduce the Y-cap?

0 Sean Xu over 2 years ago in reply to Tommy Tzeng

Hi, Tommy,

I guess you are talking about C25-C29 which are Y-cap. They help to pass EMI. How much cap is needed depends on EMI performance.

0 Tommy Tzeng over 2 years ago in reply to Sean Xu

Genius 5885 points

Hi Sean,

yes, we mean C25-C29. so Y-CAP will only help to pass EMI, is there any risk to remove c25/c26/c28? we will only put c29.

we reduce the value of C31 and find that there is hicup situation, should correct R31? avoid reach the current sense voltage?

0 Sean Xu over 2 years ago in reply to Tommy Tzeng

He, Tommy,

No risk to remove C25-C28 as long as EMI can be passed.

Small C31 may not filter out the switching spike and cause the OCP. Yes, you can increase R31 and reduce the current spike.

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