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TIDA-00779: NTC Resistor, Temperature

jaeyup jung
Intellectual 570 points
Part Number: TIDA-00779

Hello, This is jaeyup

Currently, we are experimenting without using Boost Follower Circuit (Q4, R14).

When AC input voltage was applied, 390V operation (no load 0A) was operated without any problem.
However, the temperature of NTC did not decrease, but continued to increase. So the load could not be increased.
I would like to find an alternative to the phenomenon that NTC's temperature continues to rise.

Thank you..

Best regard

  • 0
    TI__Intellectual 755 points

    Dear customer,

    We will check and get back to you soon.

    Thanks

  • 0
    TI__Prodigy 420 points

    Hi jaeyup,

    NTC you mentioned is R2? if so, R2 is PTC, it seems the bypass circuit for R2 does not work.

    please check:

    • Bias supply is enough or not, it should be 12V/60mA at least.
    • Please check the working status of circuit related with relay(K1), the relay should be closed after power-on 0.2s.

    Thanks.

    Felix He

  • 0 in reply to Felix He
    Intellectual 570 points

    Hi Felix He

    I can't find the RTC part number in the BOM, can you tell me the replacement product in MOUSER or DIGIKEY?

    And there is a relay circuit, I would like to know the reason why not using NTC and using PTC.

    Thanks

    Jaeyup

  • 0 in reply to jaeyup jung
    TI__Prodigy 420 points

    Hi Jaeyup,

    The PTC part number is B470 from TDK, you can get it directly from TIDA-00779 BOM file.

    To limit the inrush current, NTC or PTC is popular method for most of applications, but in such case, it is much better to use PTC:

    • You need to turn ON/OFF your system frequently, means there has not enough time to cool the NTC.
    • The ambient temperature is always very high before turn ON your system, then the current limit performance should be down by NTC.
    • Another advantage of PTC is, when the relay in parallel with PTC is fail to turn ON, PTC becomes a breaker, just like your case.

    By the way, are you sure it is caused by PTC damage?

    Felix

  • 0 in reply to Felix He
    Intellectual 570 points

    I didn't know it was a PTC, I bought NTC and haven't bought it yet.

    I searched for the word B470 in the BOM and the photo below is correct ??

    Please tell me whether it is above or below.


    If it is not this part, we would appreciate it if you could tell us the part number of MOUSER or DIGIKEY.

  • 0 in reply to jaeyup jung
    TI__Prodigy 420 points

    Hi Jaeyup,

    It seems difficult to order B470, you can replace it with this one:

    Ordering code: B59213J0130A020, you can find it from MOUSER.

    Felix

  • 0 in reply to Felix He
    Intellectual 570 points

    Thanks for your kind response.
    There is one thing I want to ask.

    When I experimented, I tied the BIAS voltage and the PFC ON pin and supplied 12V voltage for the experiment.
    If you experiment in this state, the relay will not turn off after 0.2 seconds. Is there a circuit problem ?? (must the relay turn off after 0.2 seconds ...?)

    Or can I continue the experiment as it is ??

    Jaeyup

  • 0 in reply to jaeyup jung
    TI__Prodigy 420 points

    After power-on 0.2s, we should close(here close means turn-on the relay, not turn-off) the relay, it is normal state, no problem.

    The purpose of close-relay is to bypass the PTC after finishing inrush current limiting, otherwise the PTC should be a breaker.

    Felix