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Type: Posts; User: treez

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  1. Closed: When is power too high for BCM Boost PFC and CCM Boost PFC is more efficient?

    For 240VAC mains, what do you reckon is the transition point where you should change from BCM or DCM Boost PFC to CCM Boost PFC?... from the point of view of efficiency.
    As you know, the trade off...
  2. Closed: Re: Center tapped transformer (forward converter)

    RT6208 buck for the 12v output.
    In current mode forward, you need coupled inductors for good cross reg...but with your load difference, buck is best.............i find everywhere i work insist on...
  3. Closed: Re: Boost PFC controller must contain anti-distortion feature for zero crossings

    Thanks but that is in the mains input current , albeit the simulator....but it didnt get filtered out, and i find even increasding the fitration doesnt solve it......but as you say, it looks like it...
  4. Closed: Re: Power limitation using ic power integration topswitch

    either read the datasheet , do ctrl F search, or do a design in PI Expert from Power integrations.
    If you post the datasheet link i will help you search.
  5. Closed: Re: Boost PFC controller must contain anti-distortion feature for zero crossings

    Thanks… the attached (including LTspice sim) is a basic PWM controller that I’ve hacked to give average current mode power factor correction for a boost converter. I haven’t implemented the feature...
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    Closed: Re: Design of an isolated dc-dc power supply

    ..That kind of describes how its done in an LLC resonant converter.....
    A full bridge is a bit of a simpler way with square waves.
    Try my course, below...the "topologys -hard switched" folder...
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    Closed: Re: Switching power supply

    what is your vin?
    What are the powers of those rails?

    Kashke (kaschke?) , i think its German, do offtheshelf flyback trasnsformers, possibly for your application.

    If your power source is mains...
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    [SOLVED]Closed: Re: Transformer: current loss

    so they are mains transformers (ie 50Hz)?
    What is the coil resistance of each.
    Also, cheap mains transformers have loads of turns stuffed in a tight space, and resultant large interwinding...
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    Closed: Re: Design of an isolated dc-dc power supply

    i presume your power source is the mains.
    What is your output voltage?
    For you i would do a BCM Boost PFC followed by a two transistor forward converter....but it does depend on your vout
    ...power...
  10. Closed: Measuring leakage inductance of flyback transformer

    We all know that in say an offline flyback transformer, we measure the leakage inductance by shorting the secondary and measuring the inductance at the primary.

    However, the leakage inductance is...
  11. Closed: Boost PFC controller must contain anti-distortion feature for zero crossings

    Pages 22 and 23 of the L6564 datasheet show that Boost PFC controllers need to sense the instantaneous mains voltage, and then increase the FET current at the zero crossings. This is to reduce...
  12. Closed: LLC converter with F(sw) > upper resonant frequency

    Why does page 7 of the following say that in an LLC converter, operation with fs>fr results in hard commutation of the secondary diodes? This is not the case.

    ...
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    Closed: Re: BJT V(ce) ON in common emitter mode

    thanks , i appreciate that if a NPN in CommEm has <0.3v across its Collec-Emit (what we want), then it is going to be saturated......thing is, we find ourselves having to look at hfe, to see if it...
  14. Closed: Re: Passing radiated EMC with an SMPS involves an element of luck...how much agree?

    Thanks, sorry i mis-worded, i meant that whilst one is doing the design and PCB, there's no fixed way of caluclating what radiated emissions combating components are needed


    Thanks, I have worked...
  15. Closed: Passing radiated EMC with an SMPS involves an element of luck...how much agree?

    I once worked with one of the UK’s finest SMPS design engineers. They were working for the same company as myself at the time. They had already designed many of the SMPS PSU’s as used by the...
  16. Closed: Re: 1 minute vs 1 second isolation voltage test for isolated offline SMPS transform

    Thanks, is their any way for us to know how they did the hi-pot test on the mains transformer in the power supply?
    Ie what voltage time and current setting for the hi-pot test?

    We wish to remove...
  17. Closed: Small high voltage rated mains common mode chokes not available offTheShelf

    Hello,
    A contractor has provided us with a prototype product which is very good quality. It is an offline, non-isolated , SMPS LED driver of 10W. It has no metal shielding and is in a plastic...
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    Closed: Re: BJT V(ce) ON in common emitter mode

    thanks, we have BJTs with very very little base current in them (to save energy)....and we wonder if there Hfe will always be big enough to get them to turn on fully and have a vce(on) of <0.3v.
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    Closed: Re: BJT V(ce) ON in common emitter mode

    Is there any situation , where literally any SOT23 or SOT323 NPN with VCE voltage rating of <65V may suffer a drop in Hfe down to less than 15?...surely such a situation simply does not...
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    Closed: Package Marking for ST25DV04K-IER6S3

    Hi,
    Do you know what is the package marking for the SO8N version of this chip?
    The datasheet doesnt say...
    https://www.st.com/resource/en/datasheet/st25dv04k.pdf

    We have some with package...
  21. Closed: Re: 1 minute vs 1 second isolation voltage test for isolated offline SMPS transform

    thanks, all we want to do is repeat the same hi-pot test that Philips did for their approvals testing, to be sure that the power supply has sufficient isolation. But from the datasheet, there is no...
  22. Closed: Re: 1 minute vs 1 second isolation voltage test for isolated offline SMPS transform

    Thanks, but we notice that IEC61558 isnt mentioned in the datasheet
  23. Closed: Re: 1 minute vs 1 second isolation voltage test for isolated offline SMPS transform

    Thanks very much..

    We are wondering what kind of isolation test the following power supply is spec’d to?…..
    It’s the Philips Xitanium Xtreme 75W LED driver…..AKA…
    “Xitanium 75W 0.35-0.70A GL...
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    Closed: BJT V(ce) ON in common emitter mode

    Hello,

    For an FMMT491A BJT with 2.7mA flowing into its base and set up in common emitter mode….is there any set of circumstances (temperature, i(ce) etc etc) which might ever result in its...
  25. Closed: Re: 1 minute vs 1 second isolation voltage test for isolated offline SMPS transform

    Thanks.
    It is strange to me that power integrations, on their design software, only ever design the isolated flyback transformers to 3000vac for 1 second (thats for 200-265vac input).
    (screenshot...
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