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LM5176-Q1: Issue in Buck-Boost output

Shubham Singhal
Prodigy 95 points
Part Number: LM5176-Q1
Other Parts Discussed in Thread: LM5176

Hi,

We ave designed one buck-boost power supply circuit using LM5176 to charge 6 capacitors in series of 100F each.

The below schematic has been used as a reference for our circuit.

https://www.ti.com/lit/df/tidrvc1/tidrvc1.pdf?ts=1593405259384&ref_url=https%253A%252F%252Fwww.ti.com%252Ftool%252FPMP21278

The output voltage is set to be 14.5V

The output current limit is set to 25A.

Input operating voltage range: 9-16V

Now when the input voltage is 15V then the circuit is working fine and the capacitors are getting charged properly. 

But when the input voltage is around 13V or 14V, there are some fluctuations in the output and also there is audible noise in the circuit.

As per my understanding, the Buck mode is working fine but Boost mode is having some issues.

Please suggest the possible reason and solution for the same as it is quite urgent for us.

Thanks in advance.

Regards

Shubham

  • 0
    TI__Guru 66350 points

    Hello Shubham,

    Would you please check the output voltage ripple while reducing the input voltage slowly?

    Please share your schematic (if you do not want to post it hear, please send me a friendship request).

    The audible noise can be caused by the inductor or the capacitors. Please check if the audible noise is gone when you remove the inductor and connect it through short wires.