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UCC25630-1EVM-291: modified to use of UCC256302 OCP detail

Hiroshi Doi35
Expert 2845 points
Part Number: UCC25630-1EVM-291

Hi Ben-san,

My customer want OVP latch and OCP auto restart.

OVP is ok by adding zener Di BLCC to FB.  But OCP restart by gradually current decrease is not good.

Please answer to below.

① Output overcurrent protection It seems that it enters the repetition operation (hiccup mode?) Of 1 second pause after operating about 100 ms when entering detection, but is this time ratio fixed?
Also, what is determined by this time?
 
② If the load is gradually returned to the rated load from the overload protection operation in the previous section ①, what condition change can be captured (what inputs can be monitored) and can be restored?
 
③ What are the points (caution points) for restoring the output voltage with no problem at rated load from the overload protection operation due to each overload assuming 2 output control (closed loop control output and unregulated output)? Especially in case of large capacity load etc.
 
④ Overcurrent protection function has OCP 1, 2, 3 and 3 types of operation level, but how do you specifically protect each of them?
A. Since OCP 1 is a peak voltage detection, can it be thought that it can be protected by observation voltage of TP 16 by adjusting the R 13 constant of the evaluation board?
B. Although OCP 2 and OCP 3 are protective detection of average current,
Can this detection value be confirmed from the outside of the IC?
Also, please tell me about the observation method and setting method.
In case
The reason for this question is that static overload and recovery starting point are necessary because confirmation of static operation setting is necessary.

  • 0
    TI__Mastermind 27095 points
    Hi Doi-san,

    1. The controller is likely detecting either OCP2 or OCP3. There is likely some delay between hitting the OCP trip point and the converter shutting down. The time delay of OCP2 and OCP3 are fixed.

    2. You would see the controller auto-retry every 1s. You could monitor RVCC and check for when it returns to a steady 12V output. If the converter is having trouble recovering after the load has decreased try switching at a higher frequency during startup to avoid OCP1. You can do this by decreasing the capacitance of VCR.

    3. Do you need to be able to start up with both outputs under heavy load? This will ultimately drive your OCP set point. Because the controller is sensing the primary side resonant current, the loading on both outputs will affect the resonant current. If you need to support starting into heavy load on both output rails then keep in mind the OCP trip point will be higher if one rails is lightly loaded while the other is loaded beyond its rated output.

    4. OCP1, 2, and 3 all use the ISNS waveform for overcurrent protection. You can observe OCP1 at TP16. OCP2 and OCP3 are internally derived inside the IC and are not observable from outside. Adjusting R13 or C11 will change all 3 overcurrent thresholds.

    The OCP point can be set by adjusting the ISNS cap or resistor. For choosing the recovery point, this is essentially the same as starting up into heavy load. As such, you can choose the OCP recovery point by selecting an appropriate VCR setting.

    Best Regards,
    Ben Lough
  • 0 in reply to Benjamin Lough
    Expert 2845 points

    Hi Ben-san,

    No answer from customer.

    I think he will evaluate more about secondary circuit.

    And after the evaluation, next question will come.

    Please close this thread.