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UCC28910: Need lowest power at no-load

Thomas Kofoed-Hansen
Prodigy 90 points
Part Number: UCC28910
Other Parts Discussed in Thread: UCC28730, UCC28610, UCC28631

Tool/software:

Hi,

I need to design a flyback converter with 2 isolated outputs (12V 10mA, 6V 350mA).

Input 18V - 70Vdc

The most important requirement is the no-load consumption, preferably < 10mW.

To me this indicates a PSR converter where there is no optocoupler current.

UCC28910 looks good but only mentions a possible no-load of < 30mW.

Price is off course also a major factor.

Does TI have another more suitable solution?

  • 0
    TI__Guru 60785 points

    Hi,

    An expert will reply to you.

  • 0 in reply to Hong Huang
    TI__Mastermind 24365 points

    Hi Thomas,

    Thank you for reaching out.

    UCC28910 should be able to work for this solution.

    But you might want to check the startup at 18V as the drain/HV node is only operation beyond 24V. A depletion mode startup could be used for this purpose as shown below.

    https://www.ti.com/lit/df/tidrs78a/tidrs78a.pdf?ts=1730302122110&ref_url=https%253A%252F%252Fwww.ti.com%252Freference-designs%252Findex.html

    Regards,

    Harish

  • 0 in reply to Harish Ramakrishnan5
    Prodigy 90 points

    Hi Harish,

    Thanks for your reply.

    I can easily make sure that VDD does not get above max rating using a solution as shown in your answer and the startup is specified as 10V which is fine. The question is how low a no-load consumption do you think I can achieve?

    I need to get below 10mW.

  • 0 in reply to Thomas Kofoed-Hansen
    TI__Mastermind 24365 points

    Hi Thomas,

    10mW overall standby power is going to depend on how effectively we can operate at close to minimum switching frequency of 360Hz. UCC28730 on the other hand can offer 10x reduction in the minimum switching frequency at 30Hz which can account for more variation in the component parameters. So practically UCC28730 looks a better choice here to meet this requirement.

    Regards,

    Harish

  • 0 in reply to Harish Ramakrishnan5
    Prodigy 90 points

    Hi Harish,

    you are right that the UCC28730 is a much better if not the perfect choice except that it won't startup below 23V and I need minimum 20V preferably lower.

    Right now I'm considering either the UCC28610 (cheapest thus preferred) or the UCC28631. Both seem to fit my requirements.

    UCC28610 does not have a calculator/design tool but does support Webench designer although it can't be simulated.

    UCC28631 does have a calculator/design tool but this does not seem to work for low dc voltages (15 - 70V).

    Do you know of any other tolls that can be used for the calculations for either of these two?

    I guess the no-load current mainly is defined from the IC supply current and the input voltage. I assume that the specified <30mW is for the high/maximum input voltage. If this is correct it should not be a problem getting down to <10mW with my low input voltage.

  • 0 in reply to Thomas Kofoed-Hansen
    TI__Mastermind 24365 points

    Hi Thomas,

    I have little experience using UCC28610, but UCC28631 I would not advise for this as it primarily suited for universal line voltage applications.

    Also when I check the calculator of UCC28610 it also seems less optimal for this voltage range.

    Yes, you are correct at high line, the no load current will also be affected by leakage current in bulk capacitors. At low voltages (especially DC as in your case), this is going to be very less. Secondly (in addition to IC supply current), snubber dissipation can also affect no load power consumption. Instead of RCD snubber, a diode and zener clamp can be used for this purpose.

    I think we may need to stick to UCC28730 or UCC28730.

    Regards,

    Harish