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  1. Replies
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    839

    Closed: Re: current-mode boost converter UC3845

    Sorry no its temperature dependent.
  2. Closed: Re: Mains harmonic emissions for dimmable offline LED drivers.

    Thanks Volker…

    ..i hate to say it, but that is open to interpretation, and also, it says that it only concerns those conditions identified by the “manufacturer”, and not by the approvals body.
    ...
  3. Closed: Re: Mains harmonic emissions for dimmable offline LED drivers.

    Thanks, I would love to be able to afford these specs so i can read exactly what is said.
    The thing is, there is a question here which may remain unanswered, and that is the following....

    It is...
  4. Closed: Re: Mains harmonic emissions for dimmable offline LED drivers.

    Thanks for your quote. From the way that is worded, it does look to me that the mains harmonics are only to be tested at the maximum load. It talks about five equal dimming steps from min to max, but...
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    [SOLVED]Closed: Re: EMI reduction using GTO

    yes it sounds like you are doing leading edge dimming.
    I think trailing edge dimming may be slightly less EMC noisy.
    You can also make the switched egde slower to reduce emc.
    If its say a dimmer...
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    Closed: Re: Common mode choke DC circuit connections

    by the polarity dots on your CMC, i see that it is connected correctly....it is connected such that the field from the one coil, will cancel the field from the other coil, concerning diff mode...
  7. Closed: Mains harmonic emissions for dimmable offline LED drivers.

    Hi,
    As you know, its not difficult to design and build an offline SMPS LED driver that can run at 235W output, and also be dimmable down to 25W output. (eg, a Boost PFC followed by a 2...
  8. Closed: Re: Will this ceramic capacitor be damaged by overvoltage spikes?

    Thanks,
    I must admit, I once worked in a huge multinational aerospace company. I was doing a board where I needed more capacitance but didn’t have room. We weren’t allowed electrolytics, had to be...
  9. Closed: Will this ceramic capacitor be damaged by overvoltage spikes?

    Hi,
    I exposed a 630V rated ceramic capacitor (1812, X7R) to a spike voltage of 680Vpk. (the spike voltage as in the attached)
    It did not blow up. In spite of the fact that I exposed it to this...
  10. Replies
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    Closed: Re: current-mode boost converter UC3845

    pcb design as attached
  11. Replies
    24
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    839

    Closed: Re: current-mode boost converter UC3845

    did you kelvin connect the sense resistor?
    Did you put a gate series resistor to damp the fet switch on?
  12. Closed: Re: Regulating temperature of mains connected heating element: Skipping mains half cy

    thanks, yes because its an electric shower.
  13. Closed: Re: Scoping the post rectifier DC bus in a 240VAC , 100W PFC'd flyback

    Thanks, its only just creeping into CCM...so the reverse recovery of the output diode wont be as bad as it could be in hard CCM.
    But i guess you are pointing out that passing EMC will be much...
  14. Closed: Re: Regulating temperature of mains connected heating element: Skipping mains half cy

    Thanks, do you think the attached mains input current waveform would pass EN61000-3-11?
    Its 32ARMS.
    If this were the mains input current waveform to a device, would it fail regulations?
  15. Closed: Re: Regulating temperature of mains connected heating element: Skipping mains half cy

    OK Thanks very much, i now appreciate that we cant do 10ms "gaps".

    According to pg 12 of the following on EN61000-3-11, for the attached LTspice sim and schem, the difference in mains...
  16. Closed: Re: What is saturation current of ELC09D-221 (220uH) inductor?

    Thanks FvM, that's brilliant, we will change to the Wurth 7447452221

    - - - Updated - - -

    The RLB0914 is some five times cheaper though, and its difficult to say which has the higher...
  17. Closed: Re: Regulating temperature of mains connected heating element: Skipping mains half cy

    Thanks, it looks like electric showers are 7.5 to 10kW......this comes off single phase mains, but it has its own thicker wiring...and comes off its own breaker....
  18. Closed: Re: Scoping the post rectifier DC bus in a 240VAC , 100W PFC'd flyback

    Thanks yes, I believe you are right, the ripple seen is part real and part due to the noise of it edging into CCM at the peak. This flyback was designed for 60W, but we gave it a run at 100W.
    On...
  19. Closed: Re: Regulating temperature of mains connected heating element: Skipping mains half cy

    Thanks,
    Presumably the attached two mains input current waveforms to the heater are perfect, and would cause no problem in the mains supply system?

    - - - Updated - - -



    …Thanks...
  20. Replies
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    Closed: Re: current-mode boost converter UC3845

    always do a representative simulation before doing a power supply. LTspice is free and the LT124X series is the same almost as UC384X.

    - - - Updated - - -

    here is your simulation....in ltspice...
  21. Replies
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    Closed: Re: SMPS Switching transistor getting too hot

    Power supply repair is usually electrolytic capacitor replacement.
    Or maybe MOV and fuse replacement if it got taken out by a transient.
    Or maybe NTC replacement.
    Or fan replacement
    Or...
  22. Replies
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    Closed: Re: reason for 50 Hz ac current

    another reason for AC is it means relays get less damage from switching....eg, a relay for 250vac would only handle switching 30vdc

    >60hz means there is too much stray capacitve coupling from the...
  23. Closed: Re: Scoping the post rectifier DC bus in a 240VAC , 100W PFC'd flyback

    There is no boost choke. The flyback does pfc and outputs to the leds.
  24. Closed: What is saturation current of ELC09D-221 (220uH) inductor?

    Unfortunately , Datasheet only gives irms..
    http://industrial.panasonic.com/cdbs/www-data/pdf/AGB0000/AGB0000C1.pdf
  25. Closed: Re: Regulating temperature of mains connected heating element: Skipping mains half cy

    Thanks, if you look at the waveform of the top post, it skips only 10ms intervals, but the overall DC is zero......it skips a positive half cycle, then the next time a negative half cycle is skipped,...
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