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UCC28180: PFC MOSFET FAIL

SENATLA IN
Prodigy 140 points
Part Number: UCC28180

Tool/software:

Dear TI team,

Greetings of the day...

We found PFC mosfet getting fail at initial switch ON condition. we found at input 90degree phase angle mosfet current rising to >30A but at 0 or 10 degree phase angle <10A only. 

Please look into problem and give us solution. please let me know if any details required.

0 Degree                                                                                 90 Degree

0 Degree              90 Degree

Design details:

2.4KW

400V@6A

two mosfets in parallel(STW48N60M2)

820uH inductor

60KHz

Regards,

Prathap M

  • 0
    TI__Mastermind 40350 points

    Hello Prathap, 

    There is not enough information here about your system and the failure conditions to be able to diagnose the problem. 

    In the two photographs provided, I assume that the yellow trace (CH1) is AC input current.  What is the input voltage and the output load power at these captures?
    What are the initial conditions of the PFC at the moment that you turn ON AC power? 
    How is that power turned on?  Can you provide a diagram of your test set up?  

    Do you have inrush current limiting for power up?  I think I will need to see a PDF file (preferably) of your PFC schematic, please.

    Please identify the signal in the blue trace (CH2).  

    Regards,
    Ulrich

  • 0 in reply to Ulrich Goerke
    Prodigy 140 points

    Hi Expert,

    PLease find below details.

    In the two photographs provided, I assume that the yellow trace (CH1) is AC input current.  What is the input voltage and the output load power at these captures?

    Input - 230Vac, Output - No load condition.
    What are the initial conditions of the PFC at the moment that you turn ON AC power? 

    Switched ON at 230Vac and wait 3 sec for pre-charge and battery hand shake, than charger ON(at this moment PFC getting fails rare time. 
    How is that power turned on?  Can you provide a diagram of your test set up?  

    DC link is ready(325Vdc) and lease +12V supply to UCC28180 whenever output is required.

    Do you have inrush current limiting for power up?  I think I will need to see a PDF file (preferably) of your PFC schematic, please.

    Yes, we provided inrush limiter(12E/25Dia), Attached schematic please go throught it.

    Please identify the signal in the blue trace (CH2).  

    That is PFC shutdown signal(Active high), if it is low than PFC will turn ON.

    Regards,

    Prathap M

  • 0 in reply to SENATLA IN
    TI__Mastermind 40350 points

    Hello Prathap, 

    Thank you for the information and the schematic diagrams.

    I don't see anything obviously wrong in the schematics, and I don't think there are hidden problems. 

    I think the turn-on peak may be due to your power-on sequencing.  From your waveforms and description I conclude this scenario:
    1.  When 230V is applied, PFC output cap charges up to 325Vpk through inrush NTC, +12_PRI comes up and closes the relay, and "SD_PRI" signal is high until battery control causes SD_PRI to go low to turn on the PFC.
    2.  While PFC is off, PFC output has no load, input current is zero (except for some X-cap current in EMI filter).
    3.  When SD_PRI goes low, VCC is applied to PFC controller UCC28180 and it begins to regulate PFC Vout from 325V to 400V.
    4.  Not shown, but I think a load is applied to PFC Vout at the same time that SD_PRI goes low.   Please verify if this is true.
    5.  Because a load is applied, AC input current increases to 6A pk-pk which = 2.12Arms = ~488W input power, maybe ~460W load?
    6.  Because a load is applied when SD_PRI goes low, PFC has not been able to provide much output boost to 400V yet, so applied load actually pulls Vout below 325V briefly before PFC can boost Vout > 325V.  
    7.  When SD_PRI going low occurs at 0-degree phase angle of Vin, there is very little voltage amplitude so input current from PFC boosting is low and input "spike" < 10Apk.  
    8. When SD_PRI going low occurs at 90-degree phase angle of Vin, there is maximum voltage amplitude so input current goes directly through bypass diode D1 to peak charge Cout back up to the peak of 230Vrms (325V) which results in the 30A+ peak current.  Since relay is closed, only stray series resistance and small voltage difference limits the peak current. 
    9.  After the peak charge surge, the PFC input current settles at about 2.12Arms to support the load.  
    10.  Since PFC starts switching at the same time that the 2nd inrush surge occurs, I think the inductor current builds up beyond the saturation point because there is not enough reverse voltage to discharge the current.  At saturation, the current through the MOSFET may be higher than it can withstand and it fails from excess drain current overstress. 

    Assuming that everything from point 4-10 is true, then to avoid the 30A surge at 90-degrees turn-on and possible inductor saturation, I suggest to delay applying the PFC load until after the PFC voltage has increased from 325V to at least 375V or higher.  This will allow the PFC to boost the output so that the inductor current can discharge during the MOSFET off times and avoid saturation. 

    Please check into this possible sequence of events, and alternative sequencing.   

    Regards,
    Ulrich