I think this can be done after I order PCB, right now i need to order asap to have something to play with.it needs to be speeded up / higher gain - until it becomes unstable - then back off a bit
I am sorry, i did not understand question? D3 after startup should see a max of 52micro amps.Why is the switcher driving high current into D3 even in steady state although the nominal output voltage is said to be 12V? There seems to be a problem with voltage feedback operation point.
Will do, right now i think i have complete PCB that should...As already stated, soft start time constant should be much higher, I'd test with 5 or 10 uF C5.
This is at 100VIn your sim - look at I_L1 or I_fet, M1 - this tells you real information about the start up !
Thanks for the link, i did replace my sub model. Didn't change much probably because i am using mosfet driver which doesn't really care about voltage on the output.For any one trying to run the TL494 model in LT spice - there are a host of issues with the model and LT spice's changing of internal workings
There is no minimum startup time requirement so i can make it as slow as I like. Even if it starts up after like 1 second.What is the max current your inductor and diode can handle at start up ? is it ok for the rest of the ckt if the start up is slow ?
if yes - make it slow !
Yes i understand that. Right now i have in sim like 1000 cycles do you suggest to make it even slower? (ie increase C5) or max dead time?The Duty cycle for 12V out and 190V in is 12/ 190 = 6.3 % allowing the Duty cycle to go way over this at start up from 190V is asking for trouble - hence a slow soft start that allows the control loop to " catch " the duty cycle and Vout before it overshoots too much is kind of a big deal !
I think this can be done after I order PCB, right now i need to order asap to have something to play with.it needs to be speeded up / higher gain - until it becomes unstable - then back off a bit
I am sorry, i did not understand question? D3 after startup should see a max of 52micro amps.Why is the switcher driving high current into D3 even in steady state although the nominal output voltage is said to be 12V? There seems to be a problem with voltage feedback operation point.
Will do, right now i think i have complete PCB that should be enough for testing.As already stated, soft start time constant should be much higher, I'd test with 5 or 10 uF C5.
Which ASC file? of entire SIM?You can zip the .asc file and attach next time.
Save schematic as ASC file. then zipI think this can be done after I order PCB, right now i need to order asap to have something to play with.
both soft start and/or dc gain can be adjusted with just cap/resistor values.
I am sorry, i did not understand question? D3 after startup should see a max of 52micro amps.
Will do, right now i think i have complete PCB that should be enough for testing.
Which ASC file? of entire SIM?
EDIT:
Just a quick question, does it make sense to add fuse between VBAT+ and entire DCDC + side?
I guess 1A would be enough or should I aim for something like 3A because of those initial spikes?Yes a fuse or Polyfuse.
I'm sure you can decide based on the thermal time constant.I guess 1A would be enough or should I aim for something like 3A because of those initial spikes?
Unfortunately i cannot decide because the moment we are talking about high voltages as well as (kinda) unknown current spikes I simply don't know which fuse to use.I'm sure you can decide based on the thermal time constant.
Resettable Fuses - PPTC LVR 240V 1A POLYSWITCH RESET |
Thanks, but that is what i was worried about... they are all THT. Either i will have to get really creative to mount them or completely redo the layout.mount near Q5
hold 1A trip 2A if that is enough
Yes I am aware of that, I was just wandering it it makes sense to add any kind of fuse in case some short happens or something.the PPTC won't trip or protect FET from inrush anyways, an NTC ICL helps with that but dissipates heat running.
I am bad with "three word shortcuts" so I'll assume you mean over temp protection but that is not going to ever be a problem in long run. According to my tests it never gets hotter than 32 deg in 23 ambient with no cooling whatsoever.perhaps OTP is more prudent. this can be a thermistor on a wire adhered to FET or SMD IC with latency.
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