Dot convention of transformer in flyback topology

Harshal Pawar17

Other Parts Discussed in Thread: UCC28700

Hello,

I am designing DC-DC converter. In the typical application circuit of the datasheet (Page No. 17) Primary & Auxiliary side of transformer are out of phase (as per dot conventions) but in attached design ( even in WEBBENCH design also) they are in phase.

1.So what should be the status of auxiliary?

2.What precautions should be taken while constructing transformer with out of phase output ?in terms of start & end of winding, direction of winding etc.

3. Ground on Primary side and Auxiliary side (i.e Aux winding,RS2,CDD,RCBC,IC GND & RCS) is same or different?

over 6 years ago

0 Sonal Singh over 6 years ago

TI__Expert 6080 points

Please do not duplicate the posts.
e2e.ti.com/.../2784694

Regards
Sonal

0 Harshal Pawar17 over 6 years ago in reply to Sonal Singh

Intellectual 260 points

1. Ground on Primary side and Auxiliary side (i.e Aux winding,RS2,CDD,RCBC,IC GND & RCS) is same or different?

2. What precautions should be taken while constructing transformer with out of phase output ?in terms of start & end of winding, winding direction etc.

0 Sonal Singh over 6 years ago in reply to Harshal Pawar17

TI__Expert 6080 points

Hello Harshal,

UCC28700 is a Primary side regulation flyback controller; given that the isolation is between the secondary and primary side and the voltage sensing is done via the Aux winding of the transformer on the primary side. the Aux GND will have to be same as the primary GND.

On tips for winding the transformer please visit a transformer vendor like wruth electronics with the mag inductance and turns ratio of your transformer and they can better suggest you on moving forward.

Regards,

Sonal

0 Harshal Pawar17 over 6 years ago in reply to Sonal Singh

Intellectual 260 points

Thanks for the help.

Because of the holidays, TI E2E™ design support forum responses will be delayed from Dec. 25 through Jan. 2. Thank you for your patience.

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Dot convention of transformer in flyback topology