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  1. Closed: Re: Adding an LC post filter can make an SMPS unstable....use RC filter instead?

    Thanks, and by damped C's i take thats C's with "added ESR" (series resistors added)?
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    Closed: Re: Flyback Airgap Doubts?

    Thats probably the only other one.....the zener or TVS clamp.....there is the RCDZ clamp which reduces rcd clamp dissipation in light or no load.
    Power integrations used to have app notes on it....
  3. Closed: Re: Adding an LC post filter can make an SMPS unstable....use RC filter instead?

    Thanks, I am speaking of cases where the output feedback is taken upstream of the RC filter. Though I believe we would say that the reduced phase shift of an RC post filter means that its not so...
  4. Closed: Re: Adding an LC post filter can make an SMPS unstable....use RC filter instead?

    Thanks, i am thinking , the straight RC second-stage output filter may offer good enough filtration, and has no problem with any instability like the LC second stage filter.....the problem with LC...
  5. Closed: Adding an LC post filter can make an SMPS unstable....use RC filter instead?

    As per page 32 of the attached….
    “Switch Mode power converter compensation made easy “ by Robert Sheehan

    ….if you design an SMPS, and you compensate its feedback loop such that it is stable with...
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    Closed: Re: Flyback Airgap Doubts?

    its a flyback so you cant avoid the RCD clamp....if you dont like it you could do a two transistor forward instead.
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    Closed: Re: uc3842/3843 Vcc problem in smps.

    I wonder of the trxformer is wrongly phased, and the bias outputs into vcc when your fet is on, and the turns are higher than should be also, hence the high voltage on your vcc?

    ...i think remove...
  8. Closed: Re: Calculating capacitor ripple current in output filter of DCDC module?

    Thanks, with tan d being proprotional to Freq , that makes the ESR readings a lot lower.......taking the vishay 038 series electros...
    http://www.vishay.com/docs/28309/038rsu.pdf

    ...the 220uF ,...
  9. Closed: Re: Need to ensure SMPS output filter has at least 10mR of ESR...use "ESR resistor"?

    thanks, at 20khz, I get ESR = "tan d" * Xc = 637microohms for a 1000uF cap and tan d = 0.08 and 20khz
  10. Closed: Re: Need to ensure SMPS output filter has at least 10mR of ESR...use "ESR resistor"?

    thanks, im obviously missing something here, but wouldnt the cap with no esr placed in series with it, partially short out the esr that had been placed in series with the other one?
  11. Closed: Re: Calculating capacitor ripple current in output filter of DCDC module?

    thanks, i was wanting to do the calculation with the "tan d" figure for 20khz...but its not available......though i believe "tan d" will be less at 20khz than at 120hz......which means the esr at...
  12. Closed: Re: Calculating capacitor ripple current in output filter of DCDC module?

    Thanks, the Fsw is not stated , i agree, but i found the figure hidden on page 14 which shows the vout ripple scope shot...which looks to be about 750kHz.
    Yes i agree the electro's will look like...
  13. Closed: Impedance vs frequency plot of input filter of SMPS?

    Hi,
    How do I get the impedance vs frequency (fig 2.32a) plot of page 33 of the attached in LTspice?
    http://www.vicorpower.com/documents/design_guides/DG-DCM-Design-Guide-VICOR.pdf

    The LTspice...
  14. Closed: Re: Need to ensure SMPS output filter has at least 10mR of ESR...use "ESR resistor"?

    In fact, In order to ensure that the DCDC module always effectively “sees” at least 10millOhms of ESR…could we add a series resistor into the output as in the attached pdf file called “SMPS output...
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    Closed: Re: uc3842/3843 Vcc problem in smps.

    it sounds like the light bulb is maybe messing things up...not leaving enough voltage for the flyback startup circuit.

    Can you just get rid of the light bulb, and power the uc3xxx chip with an...
  16. Closed: Calculating capacitor ripple current in output filter of DCDC module?

    Hello,
    We are doing an SMPS using the DCM3623T50M53C2T00 Vicor DCDC module.

    We need to know what is the ripple current in the external output capacitors that we must fit.

    Please either...
  17. Closed: Need to ensure SMPS output filter has at least 10mR of ESR...use "ESR resistor"?

    Hello,
    We are doing an SMPS using the DCM3623T50M53C2T00 Vicor DCDC module.
    Please assist us in getting at least 10mR of ESR in our external output filter.
    What we currently have is as attached....
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    Closed: Re: Smps design with UC3844 for 300V /0.5A

    You probably know the next suggestion......get rid of the isolation, implement resistor divider feedback straight to the uc3844, power the uc3844 with an isolated bench psu and remove the bias coil...
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    Closed: Re: Why dooes offtheshelf DCDC module limit the numbr of parallel units?

    Thanks, the routing situation is what i first thought, but the DCM3623T50M53C2T00 module uses "droop" sharing....(its vout decreases by some 5%, from 10% load to full load)......so routing...
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    Closed: Re: uc3842/3843 Vcc problem in smps.

    but you seemed to say that you had 84v on a 21v zener?
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    Closed: Re: Smps design with UC3844 for 300V /0.5A

    R7, at 12k, is way too low ohmic value.
    Please tell what is R7?...what package and power rating?


    Also, what is your Z4 value....you could be overvoltageing your TL431 if its too low

    Also,...
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    Closed: Re: uc3842/3843 Vcc problem in smps.

    So you put a 21V zener in the circuit, and the voltage at the cathode of the zener went to 84v?..........something is very wrong here....the zener has blown up for a start.....then you put the chip...
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    Closed: Why dooes offtheshelf DCDC module limit the numbr of parallel units?

    Hello
    Page 1 of the DCM3623T50M53C2T00 datasheet states that only up to 8 modules can be placed in parallel.
    Why is this? Why not say, 40 in parallel?

    DCM3623T50M53C2T00 datasheet......
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    Closed: Re: uc3842/3843 Vcc problem in smps.

    esd damage to your uc3843?

    If a 150k resistor is connected to a >47uF cap at the vcc pin, it shoudl simply not be possible for the vcc voltage to rise to anywhere near 270v...because the bias...
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    Closed: Re: uc3842/3843 Vcc problem in smps.

    Yes all the points above are valid, and especially from Klaus who has given me and many many others some fantastic electronics info in the past.
    But anyway……its interesting that you have 80v on your...
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