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    Closed: Re: carbon arc modalities

    Correct, and current goes up as volts go down ( very counter intuitive ). Due to IR drop in the carbon rods - there will be a small element of V going up as I goes up - but swamped by the...
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    Closed: Re: carbon arc modalities

    The original carbon arcs used AC and a ballast choke to give an approx constant RMS current - the arc is a plasma in fact - and there were numerous mech systems to wind the carbon rods slowly...
  3. Closed: Re: LLC converter with F(sw) > upper resonant frequency

    it's simply wrong ...

    however you can get hard commutation of the o/p diodes for Fsw > Fres if the leakage is too high ...
  4. Closed: Re: Electronic Load Circuit for 380 Vdc (2A to 3A) Power Supply

    I'm just saying that due to extra "third breakdown" effect of fets run in linear fashion at high voltage ( they must be seriously de-rated ) - rather than the hassle of going through this learning...
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    Closed: Re: Single supply low-side shunt amplifier

    neg supply not needed for offset nulling ckt on LM358/324 ...
  6. Closed: Re: SMPS PFC+LLC/Flyback 24V 100W low THD cool thermals reference design?

    For 24V 100W try a FAN9611 running a dual interleaved flyback, low RFI , easy to build and test, just 2 x flyback Tx at 50W each, 2 x 800V fets, 2 x o/p diodes, automatic PFC with no...
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    Closed: Re: Single supply low-side shunt amplifier

    An LM324 / LM358 can be used to measure a neg shunt voltage - to 300mV below 0v on a single supply, because of offset etc need to add an offset pot running off a stable voltage then can trim...
  8. Closed: Re: Electronic Load Circuit for 380 Vdc (2A to 3A) Power Supply

    1200W, at 400V, beware the extra breakdown effect for mosfets above 60V, I expect you will need to use 250W fets, at 30W each, giving 40 mosfets min to avoid 3rd break down ... ...
  9. Closed: Re: Stacking diodes for high voltage rectification

    www.ppmpower.co.uk/products/diodes/axial-lead-low-current-diodes/

    are what you are seeking - a 1 min google search ...
  10. Closed: Re: Stacking diodes for high voltage rectification

    The problem is that for the diodes you seek to use - the source must supply a lot of reactive power as well as the real power to provide the DC to the unknown load.

    This is due to the...
  11. Closed: Re: Stacking diodes for high voltage rectification

    if you avalanche these diodes at 200kHz, the solder will melt ...
  12. Closed: Re: Center tapped transformer (forward converter)

    unfortunately there is a small chance (load dependent) that your ckt could end up operating in a linear mode and cook the series pass xtor ...
  13. Closed: Re: Center tapped transformer (forward converter)

    2nd way is flawed too - look closely at what other E-B can be zenered ...
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    Closed: Re: Bridge Rectifier won't Rectify

    To get the same RC time constant you put the smaller cap across the larger resistor ...
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    Closed: Re: Bridge Rectifier won't Rectify

    across EACH HV resistor - not across the outside of all of them ...

    - - - Updated - - -

    essentially you need to build a capacitive divider that matches the resistive divider, so smaller...
  16. Closed: Re: Center tapped transformer (forward converter)

    the xtor E-B will zener at approx 6V in reverse when the winding goes negative ... and thus there will be current flow in the buck diode and the wrong way through the main xtor ...
  17. Closed: Re: Stacking diodes for high voltage rectification

    without the snubbers and sharing resistors the diode with the lowest leakage current will break down in reverse first, then the next lowest leakage current, etc ...
  18. Closed: Re: Center tapped transformer (forward converter)

    For 2W on the 12V rail - its hard to beat the MC34063A - and its pretty cheap - remember you still need the diodes to rectify the Tx wdg and a choke and a cap to form the raw voltage - ...
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    Closed: Re: Bridge Rectifier won't Rectify

    you need a small HV cap across each high value resistor, and a compensating C across the 100k, same RC time constant for each I think ...
  20. Closed: Re: Stacking diodes for high voltage rectification

    The dv/dt of a 900Vpk sine wave at 200kHz, at the zero xing ( where it is maximum) is, I think , 1.13V/ns, or 282V in 250nS, so a little slower than my estimated 900V in 250nS for an...
  21. Closed: Re: Stacking diodes for high voltage rectification

    do you know the leakage inductance of your transformer?

    - - - Updated - - -

    Let us assume the low figure of 18pF per diode, at 200kHz this is 44k-ohm, lets say we have 900 volt reverse and 1V...
  22. Closed: Re: Stacking diodes for high voltage rectification

    You'll find out pretty quick if you try to rectify any thing greater than 1kV at 200kHz... do you have any wiring inductance, Tx leakage inductance, diode capacitance ....
  23. Closed: Re: Stacking diodes for high voltage rectification

    This is the first time you have mentioned 200kHz or higher, unless you have significant experience in this field - I would suggest abandoning this endeavour.

    There are no commercial products...
  24. Closed: Re: Stacking diodes for high voltage rectification

    I would suggest 220pF ( 2kV ) and 4k7 ( at least 600V rated ) for the RC snubber for 50/60Hz rectification
  25. Closed: Re: Stacking diodes for high voltage rectification

    you would need an RC snubber across each diode as well as voltage sharing resistors ( 1Meg-ohm - 4.7 Meg Ohm ) across each diode so that the voltage is shared when off.
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