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and what is the resistance between the sw node and the bottom rail when the bottom mosfet is ON ?
- how much time is spent in voltage transition ? ( either way )
- what is the voltage doing in this transition time ? ( either way )
- in a classic 2 fet buck, what are...
Short answer = yes - you will know if you ever get into the hard switching areas ( below resonance ) as the mosfets will get very hot and then go bang !
having said that, you still need just the right amount of dead time above resonance to get perfect ZVS and soft switching
why...
Plenty of our customers seem to be able to make 400kHz work at these low voltages and powers - laser drilled Cu filled vias for heat transfer to sinks,
resonant gate drive, really quite narrow dead times ( 30nS ), carefully designed low capacitance chokes, 4 layer ( or 6 ) boards to...
Welcome to the world of fast switching edges with associated high di/dt & dV/dt causing RFI and other effects ( e.g. ground bounce )
affecting your control circuits - most often due to poor layout, poor wiring and poor de-coupling.
The fuse will be largely un-affected by the 450kHz current ( as reasoned and shown above ) - not several times the DC resistance as you posited,
putting the fuse right by the fet drain allows a high speed fuse to be used - as the peak current in the fuse will only be that determined by...
Certainly - if there are low Z electro's feeding the converter in question - then there will be few issues
220uF - 470uF per amp drawn by the converter is a good guide.
these days you do not get 100's of mH in an upstream filter causing low frequency effects - which require...
skin depth ( mm ) is 0.066 / ( SQRT ( MHZ ) ), so for 35 um ( 0.035 mm ) pcb , at 450kHz the skin depth ( depth at which current density falls to 37% of surface value ) = 0.098 mm ( 98 um )
so anything similar in thickness to 1 Oz ( 35um / 0.035mm ) or 2 Oz ( 70 um / 0.07...
re the waveform - it s rare to have real world current spikes like that - it assumes the rest of the connected ( driving ) circuit has very little wiring or stray inductance.
If you can, slowly increase the current thru the fuse and note the surface temp - ideally you should stay below...
aah - damaged from the last blow up - it does seem more likely the new mosfet would have gone POOF ! too, with 56k drive and 15k pull down.
1714776838
Cp and Cz are way too small - in the FB loop
R3 is far too large
R2 is a bit big at 40 ohm
Hello - pretty simple - the C on the Vcc charges up - then the flyback starts - but there is insufficient time for the 1000uF output cap to charge ( hence not enough volts out of L3 ) before the cap on the control IC discharges to the point the IC latches out, then the...
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