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UCC28180: IC getting damaged

A M
Prodigy 115 points
Part Number: UCC28180
Other Parts Discussed in Thread: UCC256402

Hi
we are using ucc28180 as pfc controller for LLC converter 200W(28V,7A)
input :115Vac(85-125V),frequency=400Hz
we have first used input frequency of 50Hz.Converter is working fine.Now we increased the frequency to 400Hz. it is working fine but at higher loads we have oscillations at pfc output voltage.So we changed the compensation values. But ic is getting damaged on turn on. Gate pin is getting short to ground(20-100 ohms between gate and ground).
At 50Hz vcomp values are Cvcomp=5uF,Rvcomp=22.4k,Cparallel=0.5uF.


At 400Hz              Cvcomp=2.2uF,Rvcomp=100k,Cparallel=0.1uF,
another iteration   Cvcomp=1uF,Rvcomp=224k,Cparallel=5.6nF.
Gate resistor turn on 10ohms, turn off 5ohms. Gate pulses are clean and no spikes are present. Please help how to remove these oscillations.

 

Channel 1 : LLC Output Voltage

Channel 2 : PFC Output Voltage at 7A(input 85V)


Excel sheet attached.UCC28180 Design Calculator@400Hz.xls

  • 0
    TI__Mastermind 24245 points

    Hi A M,

    Thank you for the query on UCC28180.

    The design calculator looks good for the design at 400hz. But unfortunately 80Hz could be too high crossover limit for UCC28180. The Rcomp value of 225kohm is too aggressive and can lead to instability.

    We would recommend reducing this resistor and eventually try reducing the banwidth (to 20hz) of the voltage loop even though it is targetted application is for 400hz, but it will have consequence of affecting pf/thd.

    You could also check out this reference design which i meant for aerospace frequencies:

    https://www.ti.com/lit/ug/tidt169/tidt169.pdf?ts=1690007042384&ref_url=https%253A%252F%252Fwww.google.com%252F

    Please let us know if you have questions.

    Regards,

    Harish

  • 0 in reply to Harish Ramakrishnan5
    Prodigy 115 points

    Hello,

    For 50Hz also issue is same. Observed vsense has noise at high load. Upto 6A it is ok but above 6A noise is present. Increased vsense capacitor,same issue but if it is decreased from 820pF to 200pF it improved. But on further testing ic again got damaged.I think supply from RVCC is causing damage(Observed waveform it is clean) so I supplied Vcc from external rather than LLC RVCC(UCC256402) now no issue observed at full load, waveform is clean.

    Channel-1 : PFC Output Voltage @ 7A load

    Channel-2 : Vsense

    Channel-1 : Vsense @ 6A Load

    Channel-2 : Vcomp

    After decreasing Vsense Cap value from 820pF to 200pF @ 6A load

    Channel-1 : PFC output voltage @ 6A Load

    Channel-2 : Vsense

    Regards

    AM

  • 0 in reply to A M
    TI__Mastermind 24245 points

    Hi A M

    Thank you for the reply.

    Since the PFC section runs fine without the RVcc from LLC, I feel the PFC section should as such be ok and signal is probably getting corrupted from noise from LLC stage as you suggested. You might to check the layout of the design and ensure the power and signal paths are clear and switching noise does not couple into the controller ground. Please probe the Vcc signal to see if there is any GND bound or there is any abs. max violation in this pin. The effectiveness of the filter capacitors on the signal pins depends upon the integrity of the ground return. Please ensure the VSENSE cap is returned directly to the portion of the ground plane that is the quiet signal GND and not in high-current return path of the converter Please let us know if you have further questions. 

    Regards,

    Harish

  • 0 in reply to Harish Ramakrishnan5
    Prodigy 115 points

    Hello,

    PCB track is the issue. we bypassed the track through a wire and it is now working.

    Thanks

    AM

  • 0 in reply to A M
    TI__Mastermind 24245 points

    Hi,

    Glad to know the you were able to solve the issue and let us know your feedback. Please let us know if you have further questions. I will close the thread for now.

    Thank you

    Regards,

    Harish