PMP10350: Question About Schematics

Derui Kong

Part Number: PMP10350

Dear TI Engineer,

As a college student, I ran into this puzzling problem with the PMP10350 reference design. As shown in the schematic of reference design PMP10350, Why is the HV pin of UCC28710D connected to the drain of the MOS instead of the positive pin of capacitor C2. In UCC28710D data sheet, the HV pin is connected to the positive pin of the capacitor.

I would appreciate any insight or explanation on this matter.

Sincerely,

Derui Kong

over 1 year ago

0 Robert Taylor1 11 months ago

TI__Expert 5425 points

Hi Derui,

I have asked to original designer to comment.

My thought is that pin is used for HV startup so it doesn't really matter which side of the transformer it is connected to, once the converter starts up, the HV switch inside the part is turned off.

Thanks,

Robert

0 Derui Kong 11 months ago in reply to Robert Taylor1

Prodigy 20 points

Hi Robert,

Thank you very much for your reply.

But in the case shown in Figure 1, the HV pin will withstand additional reflected voltage after start up,is that OK?

Thanks,

Derui Kong

0 Sheng-yang Yu1 11 months ago in reply to Derui Kong

TI__Expert 3640 points

Derui,

The only reason I connect HV pin to MOSFET drain is it's easy for layout on this particular board. As HV pin is rated for 700V while MOSFET drain voltage is less than 650V, it is okay to do so.

But I have to admit by connecting HV pin to MOSFET drain has a negative impact to EMI.

Regards,

Sheng-Yang Yu

0 Derui Kong 11 months ago in reply to Sheng-yang Yu1

Prodigy 20 points

Hi Shengyang,

Thanks for reply in your busy business.

Best regards,

Derui Kong

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PMP10350: Question About Schematics