• State Resolved
  • Locked Locked
  • Replies 2 replies
  • Subscribers 30 subscribers
  • Views 146 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.

UCC15241-Q1: Output Shuts Down When Switching 300VDC BLDC Thrusters (Relay or switch -Like Control)

Nafiul Joy
Prodigy 20 points
Part Number: UCC15241-Q1

Tool/software:

Dear TI Support,

We are using the UCC15241-Q1 isolated DC-DC converter in a thruster control system to power gate driver circuitry that switches 300 VDC BLDC motors. The application uses the DC-DC converter to support relay-style switching, i.e., turning motor power on/off—not for high-frequency PWM control.

Application Summary:

  • A total of 8 isolated gate driver switches (each powered by UCC15241-Q1, gate driver, and SiC Mosfet) control high-side power to BLDC thrusters. For now, we have only connected 5 of these thrusters. 

  • The remaining 3 switches are unconnected, but all 8 share the same 300 VDC bus.

  • Each switch turns on/off the 300 VDC supply to the motor—used as a simple on/off control, not high-speed switching. The ON/OFF is controlled from a microcontroller. 

Problem Observed:

  • At system power-up, all UCC15241-Q1 outputs are healthy.

  • Once one or more thrusters are switched on, the UCC15241-Q1 converters powering unconnected channels shut down.

  • These affected channels lose gate driver power and fail to switch. The issue only resolves after a full power cycle.

  • Thruster-connected channels remain functional.

Additional Notes:

  • We've added flyback diodes across the thruster connections to suppress potential back-EMF — no improvement.

Please kindly let me know if you have any suggestions.

Thank you!

I’ve attached a simplified block diagram (not our actual schematic) for your reference to understand the setup.

  • +1
    TI__Mastermind 32775 points

    Check:

    1. Measure VIN directly at the input pins of the UCC15241-Q1 ICs that are shutting down. Trigger on falling edge then rising edge and try to capture any transient  below/above VIN OVLO/UVLO. This will verify the input voltage is within the valid range but VIN below UVLO then recovering is a non-latching, auto-recovery fault, so this is likely not the cause of the shutdown.
    2. Probe FBVDD, FBVEE during the shutdown and try to capture output UVLO latching fault
    3. Check capacitor placement and value and make sure caps are properly routed at/near the gate driver
    4. Check to verify your component values are correct according to the UCC15241 Excel Design Tool.
    5. Schematic you attached seems like gate/source connections are crossed - are the gate source connections correct in the real schematic?

    Steve

  • +1 in reply to Steven Mappus1
    Prodigy 20 points

    Hi Steve, 

    Thanks for getting back to me.

    You're absolutely right — the gate/source connections are crossed in the simplified schematic I shared earlier, but that’s not the case in the actual design. I’ve attached UCC15241 circuit for your reference. 

    I’ll go ahead and probe to see if I can catch any transients.

    Really appreciate your help — I’ll share the scope captures once I have them.

    Regards,

    Joy