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UCC28070: Over current protection.

KIM Andy
Expert 2530 points
Part Number: UCC28070
Other Parts Discussed in Thread: UCC256303, , UCC27324

HI

Currently, my client is developing 800W SIGNAGE using UCC28070, UCC256303, UC29002, UCC27324.

There is a problem with the overcurrent protection of UCC28070.

If the output load is increased from the input voltage of 90V to the interval of 1A, there is a phenomenon that the fet is damaged at about 1kW.

We have changed RIMO from 24kohm to 16kohm as an improvement.

At about 840W, the output voltage gradually dropped and the output current rose. 840W was maintained.

At the moment, the customer wants to adjust the OC standard to about 1000W as the initial input current instantaneously rises when LLC starts.

In contrast, RIMO and RPKLMT were adjusted, but 840W was maintained or the FET was dead as before.

Is there a way to improve this?

I will attach the corresponding circuit diagram.

18Y_LED SIGNAGE_IT800P_S_Rev0r2_180307.pdf

  • 0
    TI__Mastermind 34465 points

    Hello Andy Kim,
    It is not clear how this test is being done.
    Which FET is being damaged ?

    You need to test the pfc section of the power supply by itself in order to isolate the issue to the pfc.
    Please complete the calculator tool for the UCC28070 and use the recommended value for RIMO and all of the other components associated with this part.
    The value of RIMO sets the power capability of the pfc. With the proper design values the  pfc should be capable of delivering the set output voltage at its rated power over the full input voltage range. That is why its is important to use the calculator and check first the pfc section.

    Regards

    John

  • 0 in reply to John Griffin1
    TI__Mastermind 31580 points
    Hi Andy,

    its over two weeks since the last repsonse, we will close this post and if you have further information please start a new post.

    Thanks

    Peter