LM5155-Q1: Mistake in Excel calculator

Jass Jin

Part Number: LM5155-Q1

Hi expert,

I found that the secondary side turn ratio of Load 2/3 doesn't change as input voltage and max duty circle varies? Is that right?

9 months ago

0 Niklas Schwarz 9 months ago

TI__Mastermind 21810 points

Hi Jass,

Thanks for using the e2e forum.
If I understand your observations correctly, this should not be an error.

The winding ratios and output voltage results of load 2 & 3 are depending on the regulated rail, which is load 1.
The flyback controller can only regulate one rail actively (load 1), the other two (or any additional winding) will be indirectly regulated via the winding ratio of the transformer.
We have a lot of resources on flyback design in general. One example would be this app note:
https://www.ti.com/seclit/ml/slup261/slup261.pdf

I hope this explanation is helpful.

Best regards,
Niklas