LM5185EVM-SIO: Most Power on PSR Flyback DC/DC Controller

Michele Bonollo

Part Number: LM5185EVM-SIO
Other Parts Discussed in Thread: LM5185,

Good evening at all;

I would like to create a simple PSR Flyback DC/DC Controller for example with the LM5185 features approximately: Vin 30 to 65 Volts and Vout of 30 Volts 3A. Without Auxiliary winding on the T1 transformer.
An architetture similar to the LM5185EVM-SIO schematics.

Obviously by sizing the components and protections much more powerful example; Q1 200 Volt 80A, D2 200 Volt 20 etc...

I also need to replace a much larger and more powerful RF T1 transformer for example the Wurth 749196540 with all the windings in parallel I obtain approximately > 10 A rated and saturation current.

Is it possible that I can obtain similar powers with a simple flyback with the LM5185 controller, or do you recommend other controllers or other configurations that are simple and have few components??

NB: My important degree of freedom of mine; my 30 Volt output voltage does not have to be perfectly regulated and stabilized, it can also have a high ripple, and also vary from 25 V to 35 Volt

Thank you very much

3 months ago

0 Youhao Xi 3 months ago

TI__Guru 71675 points

Hi Michele,

Thank you for reaching out and consider TI products. I think the Wurth part that you referred to is not suitable. I searched Wurth website, and you may consider 750319021 to deliver your 90W power. You can leave the aux winding open. https://www.we-online.com/components/products/datasheet/750319021_valid_from_2024-06-13.pdf

Please use our design calculator to help you design. https://dr-download.ti.com/design-tools-simulation/calculation-tool/MD-L5I2HJNedi/REV-3.1/LM5185-DESIGN-CALC.xlsx

Good luck in your project.

Best Regards,

Youhao

0 Michele Bonollo 3 months ago in reply to Youhao Xi

Prodigy 170 points

Hi Youhao,

Thanks for your analysis and help, yes you are right these PoE++ transformers suitable for flyback seem the best, I hadn't seen them immediately on the Wurth site thanks.
I found two family 750319021 # 750319032; perhaps for my application where I want to increase the output voltage up to around 30 Volt,
the best might be  750319032  24V out 4A ~90W  N1:N2:N3 2.4:2:1  what you think ??

Yes the N3 Aux i leave it open or with large resistor~100K and small capacitor~10 pF in parallel for RF EMI disturbance...
Or the last, i can use another TI chip similar to PSR LM5185 with No optocoupler but with auxiliary winding...,
but I don't know if it's worth looking into...

Thank you for your suggest 

Michele

0 Youhao Xi 3 months ago in reply to Michele Bonollo

TI__Guru 71675 points

Michele,

I would not suggest the 750319032, because its 1.2:1 turns ratio would lead to higher primary current which can easily exceeds the transformer's Isat rating. However, you may try both once you have a PCB, because they look to be pin-to-pin compatible.

TI does have other devices that implements PSR flyback with an aux winding, but the LM5185 can achieve better Vout regulation, and you also save a diode and some capacitors if you don't have to use the aux winding.

Again, please use our design calculator to help you design.

Best Regards,

Youhao

0 Michele Bonollo 3 months ago in reply to Youhao Xi

Prodigy 170 points

Thank you!

Ok i can try 750319021 and possibly later the 750319032 by modifying the LM5185EVM-SIO

comparing the values with the LM5185-DESIGN-CALC_MyMod.xlsx

I'll let you know later, thank you very much

Michele

+1 Youhao Xi 3 months ago in reply to Michele Bonollo

TI__Guru 71675 points

Hi Michele,

Looking forward to your progress. Good luck!

Regards,

Youhao

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LM5185EVM-SIO: Most Power on PSR Flyback DC/DC Controller