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  • November 19, 2016 at 9:38 pm in reply to: KIT1 Feedback #3757
    Emmanuel_Fuste
    Participant

    Hello, I’m back.
    1kV C0G caps in place.
    Duty cycle is now 5% lower in same temp conditions. As C0G is not subject to derating or aging at high voltage (as X5R/X7R) and is more stable across temp variation, the inductor should now be the only/dominant cause of mean duty cycle variations with temperature variation.
    Duty is very stable.
    Hiss is lower.
    Direct on screen voltage readout seems to be more stable too. Need to be monitored on a longer period.
    I have stronger VHBCC-222J-01 too, will try later for fun.
    My unit is online for near six months. I’m very happy with the overall result.
    It’s time to add a Bosch sensor to it !

    August 28, 2016 at 6:24 pm in reply to: KIT1 Feedback #3354
    Emmanuel_Fuste
    Participant

    The Bourns inductor is in place.
    It is worse. Voltage is very unstable, duty cycle is ~70%. And the hiss is still there.
    The weather is very hot.
    I have anticipated the result : I have an bigger inductor to try, but I think the culprits are the capacitor. For some dielectrics, the temperature sensitivity is way more important than the inductor permeability one, and the piezoelectric effect could explain the hiss more effectively (and the Brouns inductor is supposed to be shielded).
    I have ordered some (expensive) 10nf 1Kv C0G capacitors to try. They were not in stock, estimated shipping mid november…
    The next days are suppose to be colder. Will see the result.

    You could follow the results on the website : unit 5100005F

    August 18, 2016 at 8:53 pm in reply to: KIT1 Feedback #3277
    Emmanuel_Fuste
    Participant

    Ok
    What about this one ?
    Bourns PartNo. Inductance(μH) Tol.(%) QMin. TestFrequency(MHz) SRF(MHz) Min.DCR(Ω) Max.Idc(mA) Isat(mA)
    9250A-225-RC 2200 ±10 45 0.25 0.97 33.8 50 27

    If ok I will include it in my next batch of component order (end of this week or beginning of next one).

    August 17, 2016 at 1:25 pm in reply to: KIT1 Feedback #3265
    Emmanuel_Fuste
    Participant

    Hi Radu,
    I’m back online.
    Thank you for your reply.
    I think that I’m hitting some parameter limits of the soldered inductor or capacitors. There is a temperature related limit after which there is a big step in the duty cycle and the voltage regulation become very noisy.
    Is it possible to have the exact models or parameters of the inductor and 1kv 10nf capacitors included in the kit ?
    I would like to try NP0 capacitors and better rated inductor to try to get less noise an better regulation under temperature stress.
    I would like to try this before pushing up the inverter frequency which could lower it yeld.

    Other than this minor nit (I’m a little bit perfectionist ….), the unit is up for more than ten day now and it work beautifully.

    Emmanuel.

    August 7, 2016 at 9:26 pm in reply to: KIT1 Feedback #3215
    Emmanuel_Fuste
    Participant

    The converter is making very powerful high frequency noise (after one hour near the kit close the the computer, it hurts my ears badly).
    Any idea to reduce the noise ? Is the inductance responsible for it ?
    I don’t know if this is related, but my duty cycle suddenly jumped from very stable 65.4% to 69.6%. Perhaps temperature related.

    Edit : the duty cycle variation is clearly temperature related. Blowing air on the converter parts get me back to 65%.

    August 6, 2016 at 8:29 pm in reply to: KIT1 Feedback #3212
    Emmanuel_Fuste
    Participant

    My unit is finally online !!
    Very simple to build, great design !
    My only last-minute difficulty was to get another usb power source. The one in my kit was for US plugs.
    Now dreaming of a A3 kit ! (pcb+enclosure+difficult to source sensors ?)

    Attachments:

    1. IMG_1.jpg

    2. IMG_2.jpg

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