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Type: Posts; User: mtwieg

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    Closed: Re: Reflections when conjugately matched

    There's a subtle distinction between travelling waves (aka voltage waves) and power waves. For travelling waves, the reflection coefficient is defined as Gamma=(ZL-Zs)/(ZL+Zs). For power waves,...
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    Closed: Re: SMPS Switching transistor getting too hot

    By itself that circuit does absolutely nothing, and therefore can't heat up. Can't help you if that's all you can show.
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    Closed: Re: SMPS Switching transistor getting too hot

    That schematic doesn't show a functional power supply circuit. Show the whole thing.
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    Closed: Re: SMPS power stage bode plot

    I was addressing the original question, not any particular post...

    When I do control analysis, my attention is always on the pole/zero locations. If I make a mistake estimating the magnitude of...
  5. Closed: Re: Voltage spikes on the Gate-source of upper H-Bridge MOSFETs (for LLC converter)

    Wait, you see a 30V spike on the Vds of the upper FETs, or their Vgs?

    Your layout definitely has excess inductance in the gate drive loops. But I don't think that alone can explain 30V showing up...
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    [SOLVED]Closed: Re: Need help to add GaN Transistor on OrCAD

    EPC2010C is the successor to the 1010. Same footprint, same Rds and Vdss. Only major differences are the significantly reduced junction capacitance and thermal impedances.

    EPC2019 and EPC2012C...
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    Closed: Re: SMPS power stage bode plot

    "Power stage" isn't really standard terminology, but I would expect a bode plot to include the effect of the PWM modulator on the transfer function. Meaning that it should account for whether it's...
  8. Closed: Re: Which transformers can pass approvals testing rergarding isolation voltage testin

    I'm assuming the TIW insulation didn't fail, unless it was damaged during handling (as FvM suggests). Was insulating tubing used to protect the windings as they terminate to the pins?

    What was the...
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    Closed: Re: LTSpice Noise Analyis

    Just look at the datasheet. The AD8429 is based on the typical three-amp circuit, so it basically has two cascaded amp stages. When the gain of the first stage is high, its noise dominates the...
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    Closed: Re: Class D amplifier simulation

    Well if the load really is just a capacitance, then no the flywheel diodes don't matter.

    Capacitive loads have their own problems though, mainly large current spikes and switching losses. I assume...
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    Closed: Re: Class D amplifier simulation

    I wouldn't even bother using real FET models, at least to start. Just use voltage controlled switches in place of the FETs (if your load is inductive, make sure to put diodes across the switches)....
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    Closed: Re: Integrated planar transformer

    I did come across that same app note, lots of good rules of thumb, but nothing really specific :/

    I would definitely need some sort of jig to apply pressure between the two halves while...
  13. Closed: Re: Type one compensator...why is everybody giving it a phase of -90 degreees

    Often the 180 contributed by the opamp is left out during analysis. It's then accounted for by calculating phase margin relative to -180 degrees, rather than -360.

    So long as it's done...
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    Closed: Re: Integrated planar transformer

    Yeah I know if I made my own clamp, I'd have to put some sort of cushion, maybe like a soft thermal pad. But I was hoping to minimize the number of manually assembled custom parts. That's why simply...
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    Closed: Integrated planar transformer

    Anyone here done an integrated planar transformer before? By integrated, I mean that all the windings are on your main PCB, instead of having a separate PCB for windings. My PCB is already going to...
  16. Closed: Re: Reducing radiated emissions in an offline flyback SMPS transformer

    Agreed, it's most likely a conducted EMC (probably common mode) which is being radiated via long interconnects. So it needs to be treated like a conducted EMC issue. Increase common mode filtering,...
  17. Closed: Re: Offline flyback SMPS with bigger core generally has less transformer loss

    Keep in mind the number of turns will likely be different, especially if you optimize the gap. It's certainly not impossible for the smaller core to yield less losses, but that requires more info...
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    Closed: Re: Switching regulator peak current

    They can, especially with very high switching frequencies, but usually if this is the case the design hasn't been properly optimized. A good engineer will estimate both DC and AC losses for the...
  19. Closed: Re: Measuring leakage inductance of flyback transformer

    Measuring open circuit impedances will be much more susceptible to parasitic capacitances, I think.

    And accurate LCR meters aren't expensive anymore. I use this and it works fine for hundreds of...
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    Closed: Re: H-Bridge heating without load

    I think you've eliminated shoot-through as a possible cause. That really leaves the Eoss losses. This is why soft switching is important at high voltages. Depending on what your load is, getting ZVS...
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    Closed: Re: H-Bridge heating without load

    Yeah, I just realized this, see above. Also confirmed it with a simple SPICE simulation.
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    Closed: Re: H-Bridge heating without load

    Eoss is energy stored in Coss, the drain source capacitance. It is always dissipated by the FETs, unless some amount of soft switching occurs.

    - - - Updated - - -


    Interesting. Note that in...
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    Closed: Re: H-Bridge heating without load

    The device datasheet gives a plot of Eoss vs Vds, it's about 1.6uJ at 250V. So with no load and 100kHz, you should see about 0.32W per FET of dissipation. Not enough to account for what you're...
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    Closed: Re: Totem pole pfc challenges

    Yes, the peak to peak Vout_cm is not very different between the two circuits. But leakage is measured in RMS, and as you mentioned, the leakage current from the totem pole comes in sharp pulses. This...
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    Closed: Re: Synchronous Buck Converter FET selection

    Sounds like switching losses are the likely culprit. There are several components to switching loss worth considering.
    1. Cross conduction. Obviously this is the most important one to rule out...
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