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  1. Replies
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    Closed: Re: Half Bridge LLC Transformer

    what are you potting in? does the potting compound have high thermal conductivity ? or is it more of a thermal insulator?
  2. Closed: Re: Size of the LCL filter damper resistor

    It will be exactly 0.2% of the total kVA of the GCI .....
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    Closed: Re: Pulse power dissipation in a BJT

    Sot-223 ...
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    Closed: Re: Half Bridge LLC Transformer

    PQ5050 N97 = 3.5W 100kHz, 100mT peak ...

    make sure the freq can go high enough fast enough when a short is applied to the o/p. This is the biggest killer of LLC designs ...

    - - -...
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    Closed: Re: Half Bridge LLC Transformer

    The graphs are somewhat useful, remember you must control Fmin, such that you do not attempt to go too low in freq, i.e. in an attempt to get more current at 60V.

    everything above the peak...
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    Closed: Re: Transformer winding, how to?

    Yes, using 2 x toroids is possible - just a bit untidy looking ...
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    Closed: Re: Half Bridge LLC Transformer

    If you are in ZVS, then by definition you are above the resonant freq of the ckt at that operating point ...

    - - - Updated - - -

    Also if you go over the gain hump to cap mode your regulation...
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    Closed: Re: Half Bridge LLC Transformer

    you are evidently un-aware of the hard switching failure mode of almost all mosfets in hard switched capacitive mode - let alone the losses and voltage spiking under these conditions ....
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    Closed: Re: LT3083 lab PSU question

    It's a fair bet you have inadvertently built something wrong - or blown a part or parts up thus far ...
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    Closed: Re: Half Bridge LLC Transformer

    below resonance operation is inviting your mosfets to go bang all the time - redesign for always above resonance ....
  11. Closed: Re: Best topology for a 5kW DC-DC 48V input

    Dear Draytek, if you really require 400V 12.5A out, AND, at another time, 40V 125A, you will need either a serious tap on the transformer or some very thick windings on the 400V winding, ...
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    Closed: Re: Transformer winding, how to?

    you need an EI core at least with wdgs on the outer legs - as well as the central leg ...
  13. Closed: Re: Where to get schematics about SCRs full-wave triggering circuits ?

    A diac is in fact a triac, with internal resistors such that it breaks down to a volt or so ( as long as there is sufficient current to keep it on ) once the off state firing voltage is reached
  14. Closed: Re: 12kW power supply spec with vin = 1000v to 880v?

    We would do this with 3 x H-bridges in series, 600V devices on each - giving 1800V input max

    84A o/p per H bridge @ 48VDC ...

    Automatic input voltage sharing due to topology and control...
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    Closed: Re: UC3845 ETD29 transformer PWM signal

    The ringing is normal for light load - the overshoot is not too bad either - try higher loads ....
  16. Closed: Re: Is a snubber circuit required with zero-cross optocoupler

    A snubber is a good idea if the load is unknown, these drivers switch the triac on soon after zero crossing, so the load current will start from zero too ( although will go up quickly for some...
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    Closed: Re: Dimmer lamp 220v ac (resistor values)

    if you want to limit the max gate current to 1A say, then R1 + R2 = 325 ohm, note they must be rated for >200V each to avoid them breaking down ...
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    Closed: Re: UC3845 ETD29 transformer PWM signal

    Faulty scope probes or "open ckt" gnd connections will not help in fault finding, hopefully your fet and driver and associated cktry have survived and you can check the transformer phasing

    you...
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    Closed: Re: UC3845 ETD29 transformer PWM signal

    A flyback transformer needs a gap in the core ( unless for VERY low power ) to store the energy, It is essentially a well coupled inductor.

    With no gap the transformer will saturate ( Bpk ) and...
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    Closed: Re: UC3845 ETD29 transformer PWM signal

    the fet might well be dead ...

    - - - Updated - - -

    or the transformer phasing or gap may be wrong ...
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    Closed: Re: how to make diy inverter

    the above modified sine wave will power a lap top charger as will even cruder modified sine system of a single step - mainly because the laptop adapter has a bridge rectifier from which it operates...
  22. Closed: Re: thought experiment to understand measuring equipment.

    I think you guys have properly scared him off this thread/site now ...
  23. Closed: Re: Inductor question. Why current goes up then down instead of decreasing with frequ

    yes opposite effect described - apologies - either a typo or there is a series cap causing a min resonance in Z.
  24. Closed: Re: Inductor question. Why current goes up then down instead of decreasing with frequ

    You are seeing parallel resonance of the inductor - at a certain frequency it will look hi Z - it will then support all the volts from the source, at other frequencies it is lower Z and pulls...
  25. Closed: Re: Current sensor upstream of Bulk of output capacitance in DCDC converter?

    Some of your caps might be a bit iffy - this used to be a prime source of noise once - which was hard to find ...
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