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UCC25600: 500W DCDC

Dhananjay Yadav
Prodigy 75 points
Part Number: UCC25600
Other Parts Discussed in Thread: UCC28180, , UCC256404, UCC256301, UCC256403, UCC25640, UCC25660, UCC256402, UCC25661

Tool/software:

Hello,

I am working on 500W DCDC design. Input is three phase AC and output is 24V/21A. This will be completely HW based design with no MCU.

Output over current, Output overvoltage, Output undervoltage, DC link over and undervoltage, these protections shall be implemented using discrete circuit. 

PFC:  There will be three phase AC rectification using six diodes. UCC28180 will be used to boost input AC to 800V. 

LLC:  760V- 840V. Output is 24V/21A. 

Resonance frequency is ~200KHz, max. operation frequency: 250KHz at maximum input voltage. Since bus voltage is ~800V, if PWM controller has integrated gate driver then it needs to be rated >>600V. 

I found below few options in TI, for PWM controller:

1. UCC25660x

2. UCC25600

3. UCC25640x

Considering above requirements, I am planning to use, UCC25600 with external gate driver for DCDC and discrete circuit to implement above mentioned protections.

Please let me know if this IC is ok for this or do you suggest any other part.

Thanks

Regards

Please let me know if this IC is ok for this. 

  • 0
    TI__Guru 50170 points

    Hi Dhananjay,

    TIDA-010015 looks like a close match to what you are trying to do. This is based on the UCC256301 (NRND) but can be replaced with the UCC256404 or our latest UCC256611.

    You can create a simulated design with the UCC256611 in WEBENCH. 

    I hope this answers your question.

  • 0 in reply to JCHK
    Prodigy 75 points

    Hello,

    Why are you not recommending UCC25600?

    Regards

  • 0 in reply to Dhananjay Yadav
    TI__Guru 50170 points

    HI Dhananjay,

    That can work as well, but the newer devices tend to be easier to make work in a given application as they have more integrated features and protection.

  • 0 in reply to JCHK
    Prodigy 75 points

    Hello

    Thanks for response. How about UCC256403. We have dedicated flyback based auxiliary supply generation for PFC, LLC PWM ICs and gate driver. 

    Regards 

  • 0 in reply to Dhananjay Yadav
    TI__Guru 50170 points

    Hi Dhananhay,

    That can work. the UCC256403 and UCC256613 both have integrated gate drivers. The key features that the newer UCC256613 has over the UCC256403 is as follows:

    1. Much higher resonant frequency capability - Can help to maximize power density

    2. Self -adaptive soft start - quickly gets into resonance and won't prematurely exist due to noisy layout

    3, Active capacitive region avoidance - will detect and prevent the controller from hard switching

    4. New dual frequency burst mode - operates above and below human hearing range to minimize audible noise. 

    5. Wide Vin/Vout support via IPPC

    Regards,

  • 0 in reply to JCHK
    Prodigy 75 points

    Hello,

    Thanks for the response. 

    Considering system level features required, I am planning to use UCC256402A.  But this IC has integrated HV start up feature and we have dedicated flyback auxiliary supply. Is it possible to use this IC without HV start up feature and provide VCC from flyback directly?


    Few comments against what you mentioned about new features:

    1. In our case, max. switching frequency is 250KHz. No need to have PWM controller with 750KHz capability.

    2. This I need to study against UCC256613.

    3. Operation in capacitive region feature is also available in UCC256402A. 

    4. UCC256402A has soft burst on and soft burst off to minimize audible noise. 

    5. Since LLC power stage input is from PFC and this is DC-DC application where Vin and Vout variation is minimal, So IPPC feature is not required.

    Thanks

    Regards

  • 0 in reply to Dhananjay Yadav
    TI__Guru 50170 points

    HI Dhananhay,

    I just wanted to make a few clarifications:

    1. In our case, max. switching frequency is 250KHz. No need to have PWM controller with 750KHz capability. Noted.

    2. This I need to study against UCC256613. Please let me know if you have any questions. 

    3. Operation in capacitive region feature is also available in UCC256402A.  Yes the UCC25640 series also tries to avoid capacitive region operation, but the UCC25660 series does a better job, especially in soft start. 

    4. UCC256402A has soft burst on and soft burst off to minimize audible noise. Yes. the UCC256402 has soft in.out of burst mode. The UCC25661 series has a dual band burst mode to avoid the audible region. There is also an option with soft in/out of burst mode as well with an option to force it to stay in burst mode which can be tricky with the older part. 

    5. Since LLC power stage input is from PFC and this is DC-DC application where Vin and Vout variation is minimal, So IPPC feature is not required.True, just keep in mind with IPPC, the only advantage you would see is if you disable the PFC, the burst mode threshold and over-load power threshold will not move.

    At the end of the day, please choose the controller you feel is right for your application. 

    Thank you,

    John

  • 0 in reply to JCHK
    Prodigy 75 points

    Hello,

    Below screenshot is from UCC26650. I am not able to understand how PFC DC link voltage is ramping up before LLC switching starts. Auxiliary winding supply from LLC stage is not available as LLC switching is not started but still PFC soft start is shown well before LLC.

    In case of UCC25640x, RVCC is supplied to PFC controller. How this is happening in case of UCC25660x?

    Thanks

    Regards

    Dhananjay 

    Thanks for the response

  • 0 in reply to Dhananjay Yadav
    TI__Genius 16155 points

    Hi Dhananjay,

    In UCC2566xx, The HV startup of the LLC controller charges both the LLC VCC capacitor and PFC VCC capacitors. So, thats the reason you see PFC output voltage ramps up even before LLC starts switching.

    Regards

    Manikanta P

  • 0 in reply to Manikanta Pallantla
    Prodigy 75 points

    Hello ,

    UCC25660x or UCC25661x has integrated gate driver circuit rated at 600V. Can this IC be used for 800V bus application with additional circuit?

    Can you recommend the circuit? is this IC being used by others for 800V DCDC with additional circuit?

    Thanks

    Regards

  • 0 in reply to Dhananjay Yadav
    TI__Guru 50170 points

    Hi Dhananjay,

    Yes. Here is a proposed circuit that supports up to 1000V:

    UCC25661 High Voltage Sensing Proposal.pdf

    I hope this gets you started.

  • 0 in reply to JCHK
    Prodigy 75 points

    Hello,

    thanks for quick response. Same circuit can be used for ucc25640x and ucc25660x family controllers ?

    ucc25661x family is latest one? This also charges PFC supply capacitor ? 

    ucc28180 and ucc25661x combinely can eliminate additional auxiliary flyback supply?  In fault conditions like PFC dc link OV/UV, OCP, Output OV/UV, how does this combine solution will behave? Will it restart itself without need of MCU.

    regards

  • 0 in reply to Dhananjay Yadav
    TI__Guru 50170 points

    Hi Dhananjay,

    The pdf I shared was simulated for the UCC25660/1 only. We would have to look to see what changes if any would be required to work with the UCC25640.

    Yes the UCC25661x is the latest and is pin to pin with the UCC25660 with the following improvements:

    • Faster startup up to 4.5 times faster and can enable <300ms startup times

    • Faster load transient response with a 60% reduction in undershoot and overshoot

    • Options to balance between output ripple and burst mode efficiency

    • Widened burst mode hysteresis to prevent oscillating in and out of burst mode

    • Added option for soft in and out of burst mode to further minimize audible noise

    • Also added ability to force controller to stay in burst mode

    • Improved noise immunity by adding 80ns de-glitch filter on ISNS pin.

    As for the PFC, that is the input stage to the LLC. The advantage of the UCC25661x is that we are less sensitive to input ripple so you can potentially use a smaller filter capacitor at the output of your PFC stage.

    As for fault conditions we have options for latch off or restart:

    I hope this answers your question.

  • 0 in reply to JCHK
    Prodigy 75 points

    Hello, 

    thanks for the response. I will explain again the requirements of the application: 

    input AC voltage: 3 phase, 480V L-L max

    PFC DC link voltage: 800V

    LLC output voltage: 24V/21A ~ 500W

    MCU is not used and standalone power supply shall protect itself and restart in below  fault conditions: 

    additional flyback to supply gate driver / pwm ICs need to be avoided. 

    1. PFC dc link OV/UV

    2. 24V output overcurrent and short circuit 

    3. 24 output OV/UV

    A. based on the previous discussion, ucc28180 and ucc256602 looks to be good option. please confirm this combination of controllers as a standalone power supply unit without need of additional flyback and MCU as explained above.

    B. Rectified input three phase AC is rectified using six diodes, same will be provided to H V pin of controller. And we have selected 02 option of controller without integrated X discharge feature as rectified AC will have DC component and won’t cross zero. 

    thanks

    regards

  • 0 in reply to Dhananjay Yadav
    TI__Guru 50170 points

    Hi Dhananjay,

    Sounds good. The UCC28180 and UCC256612 would be a good option. Please keep in mind that we have released the UCC256612 now which is P2P with the UCC256602. We have no plans to officially release the UCC256602.

    Regards,

    John