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UCD3138ACCEVM149: Failure in Open Loop Operation of PSFB

Nishant S
Prodigy 51 points
Part Number: UCD3138ACCEVM149

Hello,

I am working on 2.5kW with 400 Vdc input and 48V PSFB DC-DC Converter.


For Open Loop Operation of PSFB converter, UCD3138ACCEVM-149 EVM is used to generate 6 PWM pulses (viz., GATE A, B, C, D, E and F).

First, the 12V auxiliary supply (for both the primary and secondary MOSFETs) is separately provided using a dc source. Then, while gradually increasing the input voltage from 0 to 100V, the output voltages were as expected (12Vdc output @ 100Vdc input).

But as we increase the input voltage beyond 100V, the auxiliary supply draws higher current (up to 0.600 A) and simultaneously, heavy ringing is observed across Vds of Synchronous MOSFETs.

Ultimately, one of the Synchronous MOSFETs was damaged (out of the two paralleled MOSFETs). Also, as observed, the heatsinks of the damaged synchronous MOSFETs had a significant temperature rise than that compared to the other synchronous MOSFETs of the center-tapped configuration. A similar nature is observed during multiple test instances now. 

Could you please suggest the reason for such a failure and how can I bring the input voltage up to 400V?

Regards, 

Nishant

  • 0
    TI__Genius 14580 points

    Hello,

    How do you configure open loop in your code? Can you take VGS of SR and primary side MOSFET? 

    Make sure enough blanking time is used, and the voltage spike on the current sensing may trigger the protection. 

    Also you may turn off SR gate signals during open loop test to identify if SR is normally controlled.

    Thanks,
    Sean