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Recent content by cupoftea

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    What is difference between Sync Buck chips?

    Hi, We wish to use either the LTC7803, or the LM25148 as a synch buck controller. Vin=24v, vout=15v, iout=3A. LTC7803 is three times the price of LM25148, but appears to have no obvious advantages over it?....do you know why it costs so much more? LM25148...
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    Why is Two Transistor forward snubber so villified?

    Hi, Why is it that the attached output diode snubber (.PNG and LTspice) for the two transistor forward is so villified? Its just a basic RCD clamp style snubber, and even recycles some of the snubber energy back to the output.
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    LLC Resonant Converter

    What control chip are you using, or is it a micro? I think LLC sounds best for you, as there is no overvoltage ringing in the output rectifiers. Scrub the Phase shift full bridge. PSFB usually needs an output inductor, but i guess your leakage L is kind of doing that job. There is something...
  4. C

    LLC Resonant Converter

    Sorry but you often say "phase shift"...do you mean the gate drives?...phase shifted operation?..as you know, in LLC, the drive is always 49% 49%..and the frequency changes.
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    Control chips for Two Transistor Forward?

    Thanks, the LM5021-2 doesnt have slope comp so we'll have to add a rcd off the gate drive....but the magnetising current may just do it for us. Also, ill try and get time to test it tomorrow...but say we have 20 turn pri giving 2.08mH (with no gap)...then if we kapton gap the cores, what do you...
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    Flyback with Parallel diodes or parallel secondary_and_diodes?

    Thanks, to be honest it looks gimmicky to me now....i mean, why dont they just use one coil and one diode, or one coil one diode and a heatsink....or one coil, and a sync rect on the diode. They have the hassle of 2 coils and each to be equally coupled to the pri.
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    Flyback with Parallel diodes or parallel secondary_and_diodes?

    Hi, LM5021 datasheet page 19 shows flyback with two output diodes. What is the percentage sharing improvement like with this method, compared to just paralleling the secondaries directly and paralleling the diodes directly ? LM5021...
  8. C

    Control chips for Two Transistor Forward?

    Thanks, also , as you know, if using a 50% chip like LM5021-2 for a two tran forward, one can simply drive the lower fet through a gate drive IC, and RC filter the LM5021 's gate output into the gate drive ic.....then you deffo get below 50% duty cycle.....also, this advantageously ensures that...
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    Control chips for Two Transistor Forward?

    Hi, When you do a 2 tran forward, as you know, in CCM, once your duty cycle gets up to 50%, then you cannot produce vout from the given vin, if vin is too low for that....however, if the load is light enough, that it goes DCM then you can still squeeze some juice out of it (and at nom vout) even...
  10. C

    Testing an SMPS for stability

    Thanks, would agree...the drain pulses need viewing over all the conditions you kindly describe....and over the widest possible variation of the time base wherein the drain pulses can actually be seen...obviously as you know, at say 1s/div you just get a big blurb.....so not useful at that...
  11. C

    Testing an SMPS for stability

    When you are testing a 400kHz 20vin 60W, 30Vout DCDC Boost SMPS for stability, you obviously look at Vout over multiple time bases.....say 2us/div to 50ms/div....why not look over that range?...all you have to do is turn the timebase dial...might as well view it over that full range. You...
  12. C

    Are top copper gerbers the same?

    Thanks, we wish to check if the actual overall top copper shape is the exact same or not.
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    Are top copper gerbers the same?

    Hi, We have two Altium Projects, with similar PCBs. If we get the gerber files from them..then how can we check that the top copper gerber file for one project, is the same as the top copper gerber for the other project? Open both in notepad++ and do a comparison?
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    Transient load testing with AC coupled scope to view Vout?

    Yes, I see the benefits of AC coupling, though as you know, it depends on the size of the coupling capacitor etc etc. Do you think the attached is a good rendition of the circuit that you end up with when doing an AC coupled transient test? As you know, the capacitor value affects it.....too...
  15. C

    Transient load testing with AC coupled scope to view Vout?

    Hi, We need to do transient load testing on a 9Vin, 20Vout , 60W boost converter. There is no need for any great transient response, since the 20V rail is just supplying some battery chargers. We just want to check that the Boost doesn't become unstable after the transient. Also, for the full...
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