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LM5022-Q1: LM5022-Q1 OUTPUT RIPPLE

Eric Long
Prodigy 190 points
Part Number: LM5022-Q1

Dear Sir

We used TI LM5022-Q1 in our new project. As a lfyback power,there is a issue happened,which we need you help to closed this issue.

As the attachment is my SCH and the ripple  waveform.

My issue is the output ripple is to high. The ripple Vp-p=3.3V.

Cloud you please help to give me some advice to solve this issue?

Many thanks!

MINI_ISO_Power supply.pdf

  • 0
    TI__Guru* 78190 points

    Hello Mr. Long,

    Thank you for using the LM4022-Q1. 

    Let me take a deeper look and respond to you later.

    Thanks,

    Youhao Xi

  • 0 in reply to Youhao Xi
    TI__Guru* 78190 points
    Hello Mr. Long,

    I am afraid the circuit is not set up correctly. Which rail voltage is the one showing 3V ripples?

    You circuit structure is primary side regulated flyback, and it should work well for +18VH and +18VH_I, because the two 18V rails are cross regulated by coupling to primarily regulated TP2 node voltage.

    However, for the rest of the output rails, none of them are coupled to a regulated rail, and regulation in those rails become lost. To correct, you should also connect all the pin 2s and 4s of the transformers, such that these secondary rails can also be coupled to the TP2 node voltage.

    Hope this clarifies.

    Thanks,
    Youhao Xi