Alternative Flyback Transformer

Thread Starter

klm19

Joined Apr 13, 2018
3
Hi there I just started working on a PoE design. I am using the mEZS84801A as a reference design as shown below. It uses the MP8007 PoE chip. I have modified and tested this PoE system successfully and my camera can be powered and it can run at 1 Gigabit.

Now I am in the phase of selecting components for the schematics and layout. However, the T2 coil 750316206 Wurth Np:Ns:Na=22:10:6, Lp=47.4μH, Core=EE13 47.4uH, cannot be found anywhere. The flyback transformer seems very specific to the designs, and the topologies seem to vary depending on PoE controller chip. I am having a lot of trouble trying to find an alternative for the design. My system runs on 12V and consumes ~10W. Does anyone have a transformer that can be an alternative to this one? Ideally would like to order on Digikey/Mouser and test out.

I have read that it is a step-up transformer with very large ratios but another thought is, I am also wondering if there is a way to use the transformer to output 5V to the system instead of 12V since most of my circuitry runs off 5V. I currently have a step down converter but seems like a waste of space. If not, any help with a replacement transformer would be so helpful. I have reached out to MPS but gotten no reponse. Any help or suggestions would be very much appreciated! Thank you in advance!
 

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TeeKay6

Joined Apr 20, 2019
454
Hi there I just started working on a PoE design. I am using the mEZS84801A as a reference design as shown below. It uses the MP8007 PoE chip. I have modified and tested this PoE system successfully and my camera can be powered and it can run at 1 Gigabit.

Now I am in the phase of selecting components for the schematics and layout. However, the T2 coil 750316206 Wurth Np:Ns:Na=22:10:6, Lp=47.4μH, Core=EE13 47.4uH, cannot be found anywhere. The flyback transformer seems very specific to the designs, and the topologies seem to vary depending on PoE controller chip. I am having a lot of trouble trying to find an alternative for the design. My system runs on 12V and consumes ~10W. Does anyone have a transformer that can be an alternative to this one? Ideally would like to order on Digikey/Mouser and test out.

I have read that it is a step-up transformer with very large ratios but another thought is, I am also wondering if there is a way to use the transformer to output 5V to the system instead of 12V since most of my circuitry runs off 5V. I currently have a step down converter but seems like a waste of space. If not, any help with a replacement transformer would be so helpful. I have reached out to MPS but gotten no reponse. Any help or suggestions would be very much appreciated! Thank you in advance!
@klm19
Edit: I thought the part was at Digikey, but it was not the correct part. Sorry. (Also sorry to @be80be)
Update: I found a datasheet at Wurth-Midcom, but they do not offer the part for sale. That means, I think, that the part was custom made for the mEZS84801A module (that is for sale as I am sure that you know).

I am curious how you can say "I have modified and tested this PoE system successfully and my camera can be powered and it can run at 1 Gigabit" when you cannot obtain the parts.
 
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Thread Starter

klm19

Joined Apr 13, 2018
3
Hi TeeKay6, thank you for the response and finding the file!! Very helpful. I spent last night doing calculations to convert the output to 5V. It's a balance between R1, R2 and T2 with the formulas in the datasheet. When I said I tested it successfully with my camera, it was with their original 12V output design so the 750316206 that is currently on the board. I am looking to change it to either another flyback transformer that will output 12V since that one can't be sourced, or modify the design to 5V.

They don't mention anything about AUX voltage in their MP8007 datasheet being important in the design. But through transformers, I see various voltage and current values for AUX. The AUX pin is connected to a voltage divider with the output going to the feedback of MP8007. Does anyone know if this parameter is important in the design?
 
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Thread Starter

klm19

Joined Apr 13, 2018
3
I changed R1=379K and R2=50K using the 749119450 by Wurth (7:1:3, 5.2uH) and this is the waveform I get from VOUT. I am happy that my calculations does output 5V on the simulation but it seems like it fluctuates quite a bit. Does anyone have any suggestions on how to make it more stable? I can post my calculations if anyone is interested. I read that the switching frequency needs to around 200kHz or less in the datasheet so I had to find a transformer with winding ratios that would meet that requirement.
 

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