• State TI Thinks Resolved
  • Locked Locked
  • Replies 7 replies
  • Answers 1 answer
  • Subscribers 62 subscribers
  • Views 397 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

UCC27714: UCC27714 VCC seems short circuitcharg

Faiz Majeed
Prodigy 115 points
Part Number: UCC27714


Hi!

I designed a schematics and PCB for a charger. in which I used PFC and then phase shift full wave bridge rectifier. In this PCB, PFC is working perfectly but for the H-bridge I am using UCC27714 for controlling MOSFETs of h-bridge. when I have the VCC_PFC and PWM signals, I the VCC_PFC (which is 12V) is dropped to few mV while checking the short test do not give any short circuit in VCC_PFC and GND. as this same VCC_PFC is going to PFC and PFC work but when I connect the H-bridge board, PFC also stop working

Can you review and my design and give me suggestions? 

 While testing, I am not giving any power on P1. I am first checking the pulses on the gates of MOSFETs.5557.PCB_Project.pdf

  • 0
    TI__Mastermind 23215 points

    Hello Faiz,

    Its not quite clear what is going on in the testing, but it sounds like when you connect the halfbridge bias for VDD that the bias supply is overloaded. There may be a fault in the half bridge VDD circuit.

    Are you doing this testing with the low voltage bias in place only, or is there high voltage applied to the power train? I see that there is a digital isolator prioviding signals to the UCC27714 driver inputs. One thing to be aware of is that during power up sequencing, some digital isolators do not guarantee a low while the bias(s) to the isolator are starting up. This can lead to unexpected high inputs to the gate driver and of course, serious stress to the power train.

    Confirm the control signals and gate drive signals, if possible with the controller and drivers powered by the bias only, and not high voltage to confirm correct operation.

    Regards,

  • 0 in reply to Richard Herring
    Prodigy 115 points

    Thanks for getting back to me.

    First of all I am using RDK-840Q module for generating VCC_PFC. I am doing testing with low voltage bias only, I didn't applied high voltage on connector P1 which is getting 395V. currently I have Enable control pin of isolator to my MCU. but VCC_PFC is not controlled. It is directly going to the UCC27714 IC.

  • 0 in reply to Faiz Majeed
    TI__Mastermind 23215 points

    Hello Faiz,

    It is not clear what would make the UCC27714 fail with only the low voltage bias and control signals applied. Is there a way you could share schematics of the design? If you do not want to show on the public forum, you can request to friend which will allow private conversation and file sharing. If you highlight my name, and option should show up for contact, or friendship request.

    Regards,

  • 0 in reply to Richard Herring
    Prodigy 115 points

    I attached pdf in the first message. please check it using this link 

    /cfs-file/__key/communityserver-discussions-components-files/196/5557.PCB_5F00_Project.pdf

    I sent you friendship request as well. 

  • 0 in reply to Faiz Majeed
    TI__Mastermind 23215 points

    Hello Faiz,

    If the VDD to the UCC27714 is overloaded or shorted, there is a fault on one of the devices on the PFC VDD or there may be a short on the board assembly.

    Try replacing the UCC27714 devices, in case one was damaged in some way during power up. After removing the UCC27714 devices, go ahead and apply tthe bias again to see if the UCC27714 drivers were causing the issue, or something else on the board.

    Regards,

  • 0 in reply to Richard Herring
    Prodigy 115 points

    I removed UCC27714 devices and tested it, there is no short circuit on the board. also 12V remains good even when UCC27714 ICs are connected but 12V is overloaded when pulses start going to it. it instantly reduce the 12V

  • 0 in reply to Faiz Majeed
    TI__Mastermind 23215 points

    Hello Faiz,

    It sounds like there could be a damaged UCC27714 which results in excessive current when the outputs start switching, or there is a low resistance fault on the Mosfet gate to source, which results in excessive average current from the driver outputs.

    Confirm that the Mosfet gate to source is not a low resistance, and also replace the UCC27714. Can you provide scope plots of the behavior you are seeing?

    Plot VDD, driver inputs and the driver outputs when you try to start up, to see if there are any driver outputs before the VDD drops completely.

    Regards,