• State Resolved
  • +1 person also asked this people also asked this
  • Replies 7 replies
  • Subscribers 64 subscribers
  • Views 94 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

UCC25600: UCC25660 Boost Mode Operation

Mustafa Yildiz
Prodigy 50 points
Part Number: UCC25600
Other Parts Discussed in Thread: UCC25660

Tool/software:

Hi,

I am trying to design an LLC converter by using UCC25660 IC. In the LLC operation, if input voltage is lower than output voltage, i.e. boost operation, then LLC goes into capacitive region and ZVS is disrupted, isn't it? 

In the IC's datasheet, it says that it includes ZCS protection property. What happens if I want to force IC to work as a boost converter in some input voltage intervals? Does it just face with the efficiency drop, or will there be an operational problem? 

  • 0
    TI__Guru 70115 points

    Hello,

    The ZCS protection will not allow the LLC to operate in the capacitive region.  It controller will force the design to operate at a frequency just above the capacitor region.  This is to prevent feedback control latch up that older LLC controller would face.

    It is not recommend to design LLC converters for more than a 2 to 1 input range.  What is your input voltage range intervals?

    Regards,

  • 0 in reply to Mike O'
    Prodigy 50 points

    Hi,

    Our input voltage range is 20-36V and output voltage is 28V. Will it create a problem? If there will be a problem, then adjusting input voltage to 28-36V and output still stands at 28V solve this case?

  • +1 in reply to Mustafa Yildiz
    TI__Guru 70115 points

    Hello,

    Your inquiry is under review and I will get back to you shortly.

    Regards,

  • 0 in reply to Mike O'
    TI__Guru 70115 points

    Hello,

    That should not be a problem.  You just need to design the transformer of the minimum input.

    Regards,

  • 0 in reply to Mike O'
    Prodigy 50 points

    Hi, 

    I have one more question related to this issue. In the Texas Instruments UCC2566x Design Calculator Tool, turns ratio is calculated based on nominal input voltage not the minimum input voltage. How should we proceed in this case? 

  • 0 in reply to Mustafa Yildiz
    TI__Guru 70115 points

    Hello,

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

    Regards,

  • +1 in reply to Mike O'
    TI__Guru 70115 points

    Hello,

    I would calculate the transformer turns ratio by hand and enter it in the tool.  I am not sure why the author chose to use nominal.

    The option would be to fake out the tool by make the min and maximum the minimum voltage.  This way the tool will calculate the transformer turns ratio to the minimum.  After you get the correct turns ratio then return the input to your real input range and hand enter the turns ratio into the tool.

    Regards,