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  1. Closed: Re: Will this ceramic capacitor be damaged by overvoltage spikes?

    hello Treez, that engineer was a bit ill informed himself - even X7R MLCC's have a characteristic of falling effective capacitance with DC bias voltage - at 1.5 x Vrated the cap will be about...
  2. Closed: Re: Will this ceramic capacitor be damaged by overvoltage spikes?

    MLCC are good for quite a bit of over-volts - the acid test is the leakage current at rated volts - when this starts going up - you have damaged it ...
  3. Closed: Re: Differential amplifier measure -32V to +32V with single 3.V supply

    for negative input voltages you need a neg supply for the op-amp unless you level shift the op-amp or the input.

    assuming the CM i/p range of the op-amp is nearly 3V, you have to divide down...
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    Closed: Re: current-mode boost converter UC3845

    turn on your fets slower to reduce radiated noise - try 33 ohm for starters ...
  5. Closed: Re: Scoping the post rectifier DC bus in a 240VAC , 100W PFC'd flyback

    it is not a constant thing - certainly for a flyback entering CCM - high mains and full load will be an issue - the most stress on the o/p diode ...
  6. Closed: Re: Scoping the post rectifier DC bus in a 240VAC , 100W PFC'd flyback

    X7R has a worst case dissipation factor ( tan delta ) of 2.5% for HV caps

    The rms voltage during the noisy periods is about 42V rms at sw freq, the current at sw freq is 730mA rms thus the...
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    Closed: Re: inverter output Vhigh voltage

    Wow - so much helpful supporting information - ckt diagram, part numbers, type of chips used ...

    don't forget only if an output line is low ohms say 1 ohm - will a 50 ohm load not drop...
  8. Closed: Re: Scoping the post rectifier DC bus in a 240VAC , 100W PFC'd flyback

    Yup - emc is always measured at worst case - so min AC line max current & max AC line - max load both cases ....
  9. Closed: Re: Scoping the post rectifier DC bus in a 240VAC , 100W PFC'd flyback

    running CCM is a bad idea for RFI noise, as the o/p diode gets quite the hit - this explains the band of noise in pic #1 ...
  10. Closed: Re: Scoping the post rectifier DC bus in a 240VAC , 100W PFC'd flyback

    The first picture is a bit odd, it is almost as if you are going from DCM to CCM for the middle (noisy) part - CCM makes the o/p diodes reverse recover and causes noise - which might be what...
  11. Closed: Re: Scoping the post rectifier DC bus in a 240VAC , 100W PFC'd flyback

    sorry - brain fade - of course the ferrite Tx is the boost choke - actually flyback Tx performing same function...

    your constant off control is part of the issue - the waveforms are...
  12. Closed: Re: Scoping the post rectifier DC bus in a 240VAC , 100W PFC'd flyback

    What is the boost choke --- ?

    the PFC flyback is obviously doing more work at higher loads / higher mains, the associated volt ripple on the nearest filter cap will likely see its demise...
  13. Closed: Re: Scoping the post rectifier DC bus in a 240VAC , 100W PFC'd flyback

    it appears the PFC is somehow going to a lower sw freq once it passes a certain voltage ( or current ) and this is causing the increase in Vripple observed - can you post the PFC schematic? ...
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    Closed: Re: 2SC1971 Amplifier problem

    try running off 6V initially - this xtor does not have a high Vce, class E will ring the collector up to 2 x Vin...
  15. Closed: Re: NPN having its VBE protected against reverse voltage....but unecessary?

    I have never seen a BJT fall to un-useable levels of gain through being OCCASIONALLY used as a zener, when it is used as a zener - the gain is often irrelevant.

    Fluke use 2 x npn in an AC...
  16. Closed: Re: NPN having its VBE protected against reverse voltage....but unecessary?

    you seem to be allowing my point - which is - by far most of the B-E junction is buried - away from any oxides ... ?
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    Closed: Re: IFC TG179 TO-92 (transistor)

    likely npn - as the base is in the middle, Collector on the left ( flat down, pins towards you ) emitter on right - but this is just best guess
  18. Closed: Re: NPN having its VBE protected against reverse voltage....but unecessary?

    surely in a BJT the metallisation goes straight onto the Si, then if you want to protect the Al metal, you form an oxide on that, any non metallised Si can be oxidised - on the surface - but ...
  19. Closed: Re: Symmetric Source + 10V and -10V - help me !!

    the 12V to +9V could be done with a TLC555 IC and a sepic power stage ( to allow for dips when starting ) - easy for 800mA

    the 12V to -9VDC could be done with a TLC555 and a buck-boost ...
  20. Closed: Re: Longer deadtime or blanking time between two mosfets of one leg phase U or v or w

    Can the longer dead time cause distortion in output waveforms? YES

    And as a result torque ripple?? YES - but usually quite small

    And can we perform the operation also without giving...
  21. Closed: Re: Reverse recovery losses in synchronous rectifier

    Dear smazzer, you asked several questions, which in particular do you consider was not answered ?

    - - - Updated - - -

    surely this was the main question : recovery losses in this...
  22. Closed: Re: Reverse recovery losses in synchronous rectifier

    Well, yes, as you must have a finite dead time - the losses in the bottom fet are related to the dead time - too long a dead time and the current will commute to the body diode and you will...
  23. Closed: Re: NPN having its VBE protected against reverse voltage....but unecessary?

    Are there many oxides in a BJT ...? I would have thought not - in CMOS maybe ...
  24. Closed: Re: NPN having its VBE protected against reverse voltage....but unecessary?

    Dear std_match, assuming the junction remains below 115 deg C how EXACTLY does zener operation reduce the gain of the device? natural drift or osmosis of dopants is generally temp dependent...
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    Closed: Re: Dc/Dc controller LT8316 power limit

    above ~ 100 watt, layout, RFI, and transformer construction issues tend to dominate and need an experienced power electronics designer - the RFI especially can upset the control, the leakage...
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