If it's near the switcher, I would
reduce C1 in a first attempt to fight the inrush problem
[*QUOTE]
...My apologies, i am not sure what you mean by this, are you actually saying that you would adjust one of the compensation capacitors to counteract the inrush?
Trying to limit inrush with a FET and a resistor ends up needing far more components than i thought............................
....since this thing had to be operational from 8 to 17V i had to end up using the LTC1871's INTVcc output to turn the FET on and switch out the inrush resistor.
There is also an input which powers the converter down, which also is seen here, using an optocoupler.
I couldnt get the FET inrush circuit using any less components than this, and it was too much , so had to bin it.................and in the end used my C9, D6, D11 and D13 as in my secong diagram down.
Regarding the Scottky sensitivity to current spikes, if in the datasheet the "IFSM" figure is upwards of 12A, then i presume it is OK, would you say this is correct?
Also, are we in agreement that a surge of 400mA through some 350mA LEDs, even if only occurring for one millisecond per day (at switch on) would severely reduce the life expectancy of the LEDs?
Added after 3 minutes:
oh sorry, i forgot to say that in this simulation, the inrush FET is not much good, as its Drain-source capacitance passes virtually the entire inrush current even when the FET should be off !
here is the .asc file of the inrush FET version...
https://uploading.com/files/9ETW4EU... NFET _OVERSHOOT REDUCTION _080609.asc.html
FvM said:I assumed 8 - 10 A because of the 15 mohm inductor Rs in the simulation.
FvM said:If this isn't suitable or doesn't help, a softstart circuit with a series resistor and a FET switch to short it involves most likely the least effort.
FvM said:The 4.7 ohm resistor can protect the diode, but it also reduces the effectivity of preload, passes a larger current amount to the boost inductor.
eem2am said:Also max0412 circuit above did not use input EMC inductor, so you have obviously not suffered the same high level of resonant LC effects that i will suffer as in my top diagrams, also max0412 has not output inductor.
I will need all these components to pass EMC test
eem2am said:oh sorry, i forgot to say that in this simulation, the inrush FET is not much good, as its Drain-source capacitance passes virtually the entire inrush current even when the FET should be off !
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