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LM5045EVAL: Feedback network design

Mia Ma
Intellectual 2515 points
Part Number: LM5045EVAL
Other Parts Discussed in Thread: TL431

Hi team,

Here is several confusing items of LM5045EVAL design. The feedback network is as following.

1.To simplify the design, could I replace the U4 and it's external compensation network by a TL431/LM4041 architecture? If any drawback if I use a TL431 with a TypeII compensation?

2. why we put a U5 LM4041 here, if not NC, what's the specific function?

Thanks.

Best regards

Mia Ma

  • 0
    TI__Intellectual 2515 points

    Hi team,

    Here is an additional question about LM5045EVM:

    why we choose a current sense transformer but not a current sense shunt resistor? 

    If the only consideration is better efficiency performance, any other benefits here?

    Thanks

    Best regards

    Mia Ma

  • 0 in reply to Mia Ma
    TI__Genius 14580 points

    Hi, Mia,

    1. Use TL431 to replace feedback loop, and it is feasible. A lot of applications actually use TL431 for compensator and reference. I think if you need very accurate reference, you may use very accurate external voltage divider and Opamp for feedback network.

    2. The current transformer dissipates less power than current shunt. To get a large current signal for CS/RAMP, the shunt need be big which reduces power efficiency. At higher output power, you try to avoid this. Meanwhile, the shunt couples higher switching spike.

    Hopefully, it helps,

    Sean