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UCC28070: Several questions

Hirotaka Matsumoto
Guru 27585 points
Part Number: UCC28070
Other Parts Discussed in Thread: LM5032

Hi all

Would you mind if we ask UCC28070?

<Question1>
Does UCC28070 allow to input DC-input?
There is the description on the datesheet P4 as follows;
VINAC : Scaled AC Line Input Voltage～

<Question2>
In relation to <Question1>, if it is possible to use DC-input, does it have any caution for DC-input?  

<Question3>
About Qvff architecture, does Zero-cross(VINAX<0.7V) require to operate UCC28070 normally?
And does it require every cycle?


As the background of these questions, our customer would like to use UCC28070 as Interleaved Boost Converter with DC-input.
We assume that it is better to use LM5032 instead of UCC28070.
If you have  some advice, please let us know.

Kind regards,

Hirotaka Matsumoto

  • 0
    TI__Mastermind 34465 points
    Hello Matsumoto-san,
    The multiplier section of the UCC28070 relies on detecting zero crossing to accurately set the QVFF level of of the multiplier.
    Zero crossing is defined as VINAC falling below 0.7V for at least 50 uS.
    So with a DC input the multiplier will be stuck in one of the levels shown in Table 1 of the data sheet.
    The UCC28070 will work but it will not accurately control power over the full input voltage range.
    If the input DC drops then the controller may be unable to provide the full load power and if the input rises the controller may provide more power than the system can support.
    The zero crossing does not need to be detected every line cycle but the faster it detects zero crossings the faster is its response to changes in the line voltage.
    For a DC input it is best to consider using the LM5032 device.
    I hope this answers all of your questions.
    Regards
    John