LM5185: Auxilary winding feedback

Ponkamali P

Prodigy 100 points

Part Number: LM5185
Other Parts Discussed in Thread: LM5022, LM5020, LM5155, UCC28700

Hi,

Can I use auxiliary winding from the flyback transformer to power and provide voltage feedback to LM5185 controller?

I am looking for newer versions of LM5020, LM5022 for my application and came across this part.

Thanks

over 1 year ago

0 Ponkamali P over 1 year ago

Prodigy 100 points

The datasheet suggests that there is "No Need" for an auxilary winding, But will there be any issue by using a 3rd winding from the transformer?

0 Richard Fu22 over 1 year ago

TI__Mastermind 31015 points

Hi Ponkamali,

The responsible engineer for this part is OOO and will respond after May 15th.

Thanks,

Richard

0 Ponkamali P over 1 year ago

Prodigy 100 points

Hi,

Can anyone respond to this

Thanks

0 Youhao Xi over 1 year ago in reply to Ponkamali P

TI__Guru* 78070 points

Hi Ponkamaili,

Sorry for the delay. There is no problem to use a 3rd winding to generate 2nd output rail. Actually you should use N+1 windings to generate N number of output rails. "1" here represent the primary winding.

The "third winding" in the context is an extra winding necessary to use by the conventional flyback. Namely, it would have to use N+1+1 to save the opto for the same job. Saving 1 winding saves the cost in making the transformer.

Hope this clarifies.

Best Regards,

Youhao

0 Ponkamali P over 1 year ago in reply to Youhao Xi

Prodigy 100 points

Hi Youhao,

So, I CAN proceed using LM5185 with voltage regulation through feedback from auxiliary winding as well as power LM5185 from it.

Right?

Thanks

0 Youhao Xi over 1 year ago in reply to Ponkamali P

TI__Guru* 78070 points

Hi Ponkamali,

Sorry to ask, could you show me a simple diagram for what you want to do? The LM5185 uses the Primary Winding itself for the feedback, not the aux winding, if I get your point.

Thanks,

Youhao

0 Ponkamali P over 1 year ago in reply to Youhao Xi

Prodigy 100 points

HI Youhao,

My question is, even though the datasheet suggests using feedback from primary winding, Can I use auxiliary winding for feedback?

The reason being my application has very high input voltage (>1000V) and as LM5185 is not rated for such higher voltages, Can I use auxiliary winding feedback?

Thanks

Ponkamali

0 Ponkamali P over 1 year ago in reply to Ponkamali P

Prodigy 100 points

This is what I mean by feedback from aux winding.

Dot convention of transformer in flyback topology - Power management ...

+1 Youhao Xi over 1 year ago in reply to Ponkamali P

TI__Guru* 78070 points

Hi Ponkamali,

I see. The max input voltage operated with the LM5185 is 100 V. It works in a different operating principle than the conventional flyback does in the example you showed. In this case, the LM5185 is not a right part.

Thanks,

Youhao

0 Ponkamali P over 1 year ago in reply to Youhao Xi

Prodigy 100 points

Ok, Thanks Youhao.

Can you please suggest some parts in the line of LM5020 and LM5022? I am looking for some part that is newer and has minimum operating frequency in range of 30khz.

0 Youhao Xi over 1 year ago in reply to Ponkamali P

TI__Guru* 78070 points

Hi Ponkamali,

Thank you for considering TI product! We have many new parts but to my knowledge they all operate at a min freq of 100 to 200kHz. Parts that I am familiar with include the LM5155/56, but I understand that you do not want to operate too fast with 1000Vin.

I can pass this to our high voltage group, but if you do a new post with the subject of UCC28700 and showing the example circuit, and ask if there is part to support 30kHz operation, then you should get a faster response. Please let me know if you want me to reach the high voltage group or you can post in e2e under a new subject.

Let me know.

Thanks,

Youhao

0 Ponkamali P over 1 year ago in reply to Youhao Xi

Prodigy 100 points

Hi Youhao,

I can post in e2e under UCC28700.

Thanks

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LM5185: Auxilary winding feedback