LM5156H: Schematics Review

Matan Hershkovitz

Intellectual 905 points

Part Number: LM5156H

Tool/software:

Hi,

I designed flyback converter, based on the LM5156H.

Input Voltage = 12V

Output = 56V/600mA

Transformer:

Np/Ns/NAUX = 9T/30T/5T

Lp = 12uH

L,Leakage = 0.1uH

Freq.Sw = 250KHz

It will be great if you could review the schematics and give your comments/suggestions/modifications.

Please also review the snubbers & loop compensation values.

Thanks,

Matan

Flyback_For_Review_250125.pdf

7 months ago

0 Moritz 7 months ago

TI__Genius 15525 points

Hi Matan,

Thanks for reaching out.

The schematic looks good, i found only one point:

- The dutycycle will be more than 50%, so i recommend to use a value of~500 Ohms as a slope compensation resistor.

Best regards

Moritz

0 Matan Hershkovitz 7 months ago in reply to Moritz

Intellectual 905 points

Hi Moritz,

Thanks for your review.

Are you referring to R145, which is now 300Ohm?

Thanks,

Mata

0 Moritz 7 months ago in reply to Matan Hershkovitz

TI__Genius 15525 points

Hi Matan,

I am referring to R144. It is 0 Ohms now.

Best regards

Moritz

0 Matan Hershkovitz 7 months ago in reply to Moritz

Intellectual 905 points

Hi Moritz,

So R145 should stay 300Ohm and replace R144 with 500Ohm?

For BOM optimization, I guess 300Ohm for R144 as well, will work too...?

Thanks,

Matan

0 Moritz 7 months ago in reply to Matan Hershkovitz

TI__Genius 15525 points

Hi Matan,

Yes, 300Ohms for R144 should also work.

I think the your current sense filter is already quite big. You should not filter out too much of the current sense signal.

A goood starting point for the filter is 100Ohms+100pF (R145+C192).

Best regards

Moritz

0 Matan Hershkovitz 7 months ago in reply to Moritz

Intellectual 905 points

Hi Moritz,

OK. Will change according to your recommendation.

I wasn't sure about the loop compensation in the feedback/error amplifier circuits. Can you confirm the values are good?

Thanks,

Matan

0 Moritz 7 months ago in reply to Matan Hershkovitz

TI__Genius 15525 points

Hi Matan,

The compensation has to be finetuned in the lab anyway. But the values sees to be reasonable and you will achieve a sufficient phasemargin at the crossover frequency.

Best regards

Moritz

0 Matan Hershkovitz 7 months ago in reply to Moritz

Intellectual 905 points

Thanks, Moritz.

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LM5156H: Schematics Review