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UCC28180: How to enable and disable UCC28180.

Kazuya Nakai59
Guru 22025 points

Part Number: UCC28180

Hello guys,

One of my customers is considering using UCC28180 for their new products.

At this moment, they have the following questions.
Could you please give me your reply?

Q1.
They are trying to turn on/off the UCC28180 by connecting an NMOSFET between VSENSE and GND. Is this method no problem?

Q2.
They are concerned that when VSENSE is pulled down with the NMOS, it will take time for OLP/STANDBY detection to occur, causing the output voltage to rise. The OLP/STANDBY detection time is very short, so won't this happen?

Q3.
Are there any pin that can be used to turn the UCC28180 on/off except VSENSE pin?

Your reply would be appreciated.

Best regards,
Kazuya.

  • 0
    TI__Prodigy 580 points

    Hi Kazuya,

    I am looking into your query.  I will get back to you with solution/response soon.

    Regards

    Sagar

  • 0 in reply to Sagar Rothe
    Guru 22025 points

    Hi Sagar,

    Thank you very much for your reply.

    I will wait for your next reply.

    Thank you again and best regards,
    Kazuya.

  • 0 in reply to Kazuya Nakai59
    TI__Prodigy 580 points

    Hi Kazuya,

    The UCC28180 can enabled or disabled by pulling the VSENSE pin voltage below the open loop protection limit (OLP) of 0.82V. Once the VSENSE voltage falls below 0.82V the controller enters into standby mode, where the PWM switching is halted but the device is still ON.

    Please refer to the following thread for more details: How to control ON/OFF operation of UCC28180.

    Do let me know if this answer your questions.

    Regards

    Sagar

  • 0 in reply to Sagar Rothe
    Guru 22025 points

    Hi Sagar,

    Thank you very much for your reply.

    I understood that UCC28180 can enabled or disabled by pulling the VSENSE pin voltage to GND.

    Could you please give me your answer to the remained following questions?

    Q2.
    They are concerned that when VSENSE is pulled down with the NMOS,
    it will take time for OLP/STANDBY detection to occur, causing the output voltage to rise.

    Is this concern not correct?

    UCC28180 OLP/STANDBY detection time is very short, so won't this occur?

    Q3.
    Are there any pin that can be used to turn the UCC28180 on/off except VSENSE pin?

    Thank you again and best regards,
    Kazuya. 

  • 0 in reply to Kazuya Nakai59
    TI__Prodigy 580 points

    Hi Kazuya,

    Kazuya Nakai59 said:

    Q2.
    They are concerned that when VSENSE is pulled down with the NMOS,
    it will take time for OLP/STANDBY detection to occur, causing the output voltage to rise.

    Is this concern not correct?

    UCC28180 OLP/STANDBY detection time is very short, so won't this occur?

    The voltage loop bandwidth in PFC is very slow, so in the duration OLP/STANDBY detection occurs, the voltage loop will not respond fast enough to increase the duty and shoot up the output voltage. So this should not be a concern.

    Kazuya Nakai59 said:
    Q3.
    Are there any pin that can be used to turn the UCC28180 on/off except VSENSE pin?

    I would like to understand here, whether you want completely disable the PFC? or keep it in standby mode where the PWM pulses only will be shut down but controller will still be running drawing a minimum standby current.

    Regards

    Sagar

  • 0 in reply to Sagar Rothe
    Guru 22025 points

    Hi Sagar,

    Thank you very much for your support.

    Could I ask you one more question?

    Q.
    They'd like know how to go into both standby mode.

    If they want completely disable the PFC device, I think they need to stop
    VCC power supplying to VCC terminal.
    Is this correct?

    If they want to disable PWM switching only, I think one of way to shutdown(Standby)
    is ICOMP pulling to GND except VSENSE pulling to GND.
    Is this correct? Is there any disadvantage compare with VSENSE using case?  

    Your reply would be much appreciated.

    Thank you again and best regards,
    Kazuya. 

  • 0 in reply to Kazuya Nakai59
    TI__Prodigy 580 points

    Hi Kazuya,

    Kazuya Nakai59 said:
    If they want completely disable the PFC device, I think they need to stop
    VCC power supplying to VCC terminal.
    Is this correct?

    Yes, the device will turn off if the VCC falls below 9.5V (UVLO) which the disable threshold.

    Kazuya Nakai59 said:
    If they want to disable PWM switching only, I think one of way to shutdown(Standby)
    is ICOMP pulling to GND except VSENSE pulling to GND.
    Is this correct? Is there any disadvantage compare with VSENSE using case?  

    The controller is disabled when the voltage on the ICOMP pin drops below 0.2V, triggering the ICOMPP protection. However, compared to the VSENSE pull-down method, the disadvantage here will be: if the ICOMP voltage decreases, the duty cycle will increase, resulting in a higher output voltage, since the UCC28180 operates using leading-edge modulation.

    Regards
    Sagar

  • 0 in reply to Sagar Rothe
    Guru 22025 points

    Hi Sagar,

    Thank you very much for your reply.

    Your replies are helpful for the customer and me.

    Thank you again and best regards,
    Kazuya.