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LM5180-Q1: Inquire about the output voltage of lm5180

jing.yin
Prodigy 10 points
Part Number: LM5180-Q1
Other Parts Discussed in Thread: LM5180

May I ask if the output voltage of lm5180 is solely determined by the FB resistor?

The transformer ratio I used in actual testing was 1.11:1, and the FB resistor used was 240k. The test showed an output voltage of 23V, but according to the above formula, the Vout should be around 21V.

  • 0
    TI__Mastermind 18986 points

    Hi

    Can you please share the schematic? Also, what's the test condition, The Vout can be higher than the set value under no load.

    Thanks and best regards.

  • 0 in reply to Gui He
    Prodigy 10 points

    The following is the schematic diagram used in the test, which uses an lm5180 chip with three transformer structures. The diagram only shows one transformer structure. In actual testing, a 1W load was connected between each output terminal VCC and VEE.

  • 0 in reply to jing.yin
    TI__Mastermind 18986 points

    Hi Jing

    Let me check and get back later.

    Thank you

  • 0 in reply to Gui He
    Prodigy 10 points

    Hi Gui

    I would like to add some information for your analysis. Firstly, the transformer used in the test has a primary inductance of 130uH and a leakage inductance of 2uH, which I believe is too large. Therefore, in the subsequent simulation, I changed the parameters of the transformer to 40uH self inductance and 100nH leakage inductance. However, the simulation results show that there is a power outage when the output voltage is 50ms. I would like to inquire about the reason for this situation. The following is a simulation diagram, which also uses a structure of an LM5180 chip with three transformers.

    thank you

  • 0 in reply to jing.yin
    TI__Expert 3400 points

    Hi Jing,

    Thank you for providing more information for us to help resolve your issue. Can you please share the input voltage waveform as well as SW node voltage and output current in your simulation?

    The product expert is out of office now. TI responses may be delayed during the year end holiday season until Jan 2nd, 2024. Thank you for your patience and happy holidays.

    Best wishes,

    Ryan

  • 0 in reply to Ryan
    Prodigy 10 points

    Hi Gui,

    The following are the input voltage waveform V (V10), SW pin voltage waveform V (SW), and output current waveform I (R14). In addition, a transformer primary current waveform I (T1:1) and a clearer simulation schematic have been added.

    I'm looking forward to your prompt reply. 

  • 0 in reply to jing.yin
    TI__Mastermind 18986 points

    Hi jing

    we are on holiday and sorry for the late reaponse，will get back later，thank you