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UCC28180: Driving capacity of UCC28180 and UCC256403DDBR

Part Number: UCC28180
Other Parts Discussed in Thread: TIDA-010080, UCC256403

Hi TI Experts,

I have designed 500W charger using TIDA-010080 reference design. I am using UCC28180 for PFC and UCC256403DDBR for LLC. Currently i am driving my PFC and LLC MOSFETs without any gate driver Ics.

Now i want to upgrade my design to 1200W with same ICS. I have the following questions.

1. Can i drive my PFC MOSFET(STW24N60M2) directly with UCC28180 without any gate driver for 1200W design?. UCC28180 is having only 2A and 1.5A Sink and source capacity. Is it enough to drive?

2. Can i drive my LLC MOSFETs(STW26N65DM2) directly with UCC256403DDBR without any extra driver for 1200W design?. UCC256403 having only 1.2A and 0.6A  sink and source current. Is it enough to drive my LLC mosfets?

Regards

Aneesh

  • Hello,

    I am reviewing your inquiry and will get back to you shortly.

    Regards,

  • Hello Aneesh, 

    I am replying to the PFC MOSFET part of your question.  

    The TIDA-010080 design uses one IPW60R099CP MOSFET which has Rds(on) = 99mR max and uses 60nC gate charge, for a 500W application.
    You are uprating power to 1200W, but ask about a single STW24N60M2 which has Rds(on) = 190mR max and uses 29nC gate charge.

    The new STW24N60M2 is a smaller MOSFET and the UCC28180 can definitely drive one of them directly; it can even drive two of them in parallel. 
    Two in parallel will have roughly the same Rds(on) and slightly less Coss as a single IPW60R099CP.
    The UCC28180 can drive this, and even more but how much more depends on switching speed requirements. 

    I recommend for you to first assess how much MOSFET you need to reliably process 1200W (with acceptable conduction and switching losses), and then determine whether the UCC28180 gate-drive specs can accommodate the total gate charge at the turn-on and turn-off switching speeds that you require.   

    Regards,
    Ulrich

  • Hello,

    Based on the Vgs(th) and the miller plateau of the FETs and drive currents.  The STW24N60M2 will turn on in roughly 8 ns and turn on roughly 10 ns.  The STW26N65DM2 will turn off in roughly 35 ns and turn on in roughly 18 ns.  These should work for your application.

    Regards,

  • Hi Ulrich,

    Thanks for your reply. I am planning to use a single STW24N60M2 for my 1200W design. My switching frequency is 130KHz.

    Regards

    Aneesh

  • Hello Aneesh, 

    I suggest that you reconsider using only 1 MOSFET for your 1200W PFC application.  
    The TIDA-010080 design delivers 500W from 90Vac input.  Your upgrade to 1200W will more than double the input current if you plan to still operate down to 90Vac input.  The new MOSFET has 2X the Rds(on) of the TIDA design.  So conduction loss will go up by (2I^2)*2R = 8 times higher than the TIDA loss. 
    Switching loss will stay about the same, since Coss is ~1/2, but frequency is ~2X.   

    So a single MOSFET with 90Vac input will run extremely hot unless you provide massive cooling.  
    If you choose to run at high voltage only (>170Vac) then I^2 will be lower again, but Rds(on) is still 2X. 
    (Don't forget to account for increased Rds(on) at your target Tj(max) junction temperature.)

    That is why I recommended that you assess how many MOSFETs will be needed in parallel to achieve acceptable conduction and switching losses. 
    If your conclusion is still that a single MOSFET can do the PFC job with acceptable losses, then definitely no gate-driver IC is necessary.

    Regards,
    Ulrich