Viewing 8 posts - 1 through 8 (of 15 total)
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  • #10081
    Giuseppe
    Participant

    Hello everyone
    I'm trying to charge a capacitor from 20 uF a 500Vpp circa , in less than 1,5 seconds starting from a voltage of 12-15 Vdc . Once uploaded, I need to download it via short .
    I managed to load it using the diagram I show you below .
    The problem that arises is at the moment of the discharge of the capacitor C4 . The mos-fet Q1 remains in an anomalous condition that I show you via an uploaded image .
    It does not get out of this condition until I turn off the power and then give it back again .
    Maintaining the capacity of C3 at 22nF this anomalous condition does not present itself but , increasing this capacitance consequently reduces the capacitance reactance and therefore I can charge the capacitor C4 in the time required by me ; doing so though , the problem of the abnormal mos-fet condition comes up.
    How could I solve this problem ?
    Elevator scheme 34063
    Mos-fet drain source condition after discharge

    #10084
    Amilcare
    Keymaster

    #10086
    Amilcare
    Keymaster

    #10088
    Amilcare
    Keymaster

    Correct images in size

    #10092
    Picmicro675
    Moderator

    What can happen if you delete the 7808?

    #10094
    Giuseppe
    Participant

    The 7808 I need it to keep the voltage stable 34063 even if there are variations at the entrance

    #10097
    Amilcare
    Keymaster

    Delete the 7808, it internally has a short-circuit protection that limits the current delivered to max 1.5A and you need at least six peak.
    The limiting resistance must be much lower, I propose two resistances from 0,1 in parallel.
    The 22nF capacitance used as the electrolytic charge current limiter seems excessive at the switching frequency. You need a reactance of about 10k to have a complete recharge in about a second without excessive current peaks.
    One thing you haven't specified is whether the coil core can withstand current spikes of at least 6A without saturating.

    #10099
    Giuseppe
    Participant

    hello Amilcare
    For proof I deleted the 7808 and short-circuited the current limiting resistor that is R1.
    With 22nF at a frequency of about 45Khz I have a reactance of 160 ohm if I'm not mistaken .
    The above problem occurs if I increase the capacity of the 22 nF .
    I needed to increase the capacitance of C3 to charge the capacitor C4 in 1.5 S circa
    Only IDC = data is shown on the coil date 2.2 (max) A

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