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I have been extensively testing the board recently and as you say, under the load whole thing collapses, although it can output over 3A with ease I think you are right and so the revised schematic was born:
Long story short, new elements marked with arrows:
R28 R9 that forms a divider that...
10V is reached pretty much immediately. I have tested this circuit many many many times. I don't see much happening for first 10-80ms simply because of soft start. Previous version starts immediately. And it was bad, sof start already helps a lot.
Another difference between pcb V1 and V2 is...
I have added D component do PI making it PID (just a cap 100nF parallel to R14) and that managed to reduce overshoot significantly.
160V with 16V zener, no flare (meaning there isn't much energy dissipated on it):
blue = VIN
green = STARTUP node
yellow = VOUT
160V thermal boot...
I may be wrong on this one but i don't think this is the real issue. Or to be precise, why that overshoot was caused.
From what scope tells me, it has evertything to do with initial jump of chip supply voltage. I am not sure how to explain it properly but i will try:
at the startup both driver...
Yes but problem was visible on all voltage ranges, it just so happened that above certain threshold driver or Zener (D5) died. Removing the D5 revealed nature of the problem.
Today i will test this new idea against higher voltages.
Ah sorry, yellow = output
Green = input
blue = mosfet gate vs gnd
repeatedly turns on and off.
I have also tried one more thing that came to my mind. clamping just the "STARTUP" node with zener and limiting current with resistor:
D5 is currently replaced with 1k resistor
As a result, there...
Components replaced, going again, only on power supply at 55V, no zener on the output.
First control (no changes to pcb):
Now second test with those values. Whole dcdc bootloops
Control PCB but with C20 = 22uF (biggest longest softstart possible)
Driver is definitely not ON all the time, if you take a look at first pic here is what is happening.
for first 10ms absolutely nothing, then during next 10ms driver is outputting PWM on mos gate but slope is too steep and TL494 doesn't get change to react fast enough.
Which can be probably...
I have tried 13V 3W zener and 15V 1W zener, both died at same voltage levels.
I had some bedtime thoughts to debug it more in depth and here is what I came up with, measuring overshoot at different VIN levels. Starting up from 43V
Legend:
yellow - main mosfet gate (just sanity check if it gets...
I have made version 3 of this circuit and I have some good and bad news.
Bad:
First of all Zener diode on the output dies no matter what at VIN > 130V.
Good:
Even if zener dies, both Mosfet Q5 and diode D2 survives
Without zener diode this circuit is able to withstand sudden turn on at 184V...
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.
Short run, it will be too slow to react to 0.1s internal...
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.
EDIT:
Ok its doable, may need some leg bending but should fit with some small changes
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.
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