Electronics > Projects, Designs, and Technical Stuff
Overvoltage protection circuit w/ TVS diode and resettable fuse?
thinkfat:
This is what I ended up building.
PCB:
What I learned about PTC fuses: You need to select them very carefully. In particular, you need to be sure that your power supply can provide enough current to trip the fuse reliably and quickly. Otherwise, you'll have a heating match between the mosfet, the SRC and the fuse. It might not be the fuse that looses. If you're unlucky, the SRC will fail open, or something will start burning.
Zero999:
That looks like it should work. You might want to consider another resistor, about 1k, in series with D1 to slow it down to avoid nuisance tripping and a higher voltage, around 33V, transient suppressor diode in parallel with the whole thing to to clamp, brief high voltage spikes.
Now it may seem like I'm being a little picky, but the schematic is drawn backwards. The convention is power in on the left and out on the right. My first thoughts were it won't work, then I realised the power in is from J3. Mirror the top, so J3 is on the left and it will be much clearer.
thinkfat:
Quote from: Zero999 on Today at 00:23:38
That looks like it should work. You might want to consider another resistor, about 1k, in series with D1 to slow it down to avoid nuisance tripping and a higher voltage, around 33V, transient suppressor diode in parallel with the whole thing to to clamp, brief high voltage spikes.
Now it may seem like I'm being a little picky, but the schematic is drawn backwards. The convention is power in on the left and out on the right. My first thoughts were it won't work, then I realised the power in is from J3. Mirror the top, so J3 is on the left and it will be much clearer.
--- End quote ---
Understood your remark regarding the drawing flow of the schematic.
I actually considered putting a resistor in series with D2 for current limiting, D3 might create an interesting region where Vgs drops into the linear region of the mosfet and that'll make it burn up real quick, I think. But a resistor for that would be seriously big. I also should have put more copper around the mosfet to help cooling it, but I'm a bit size constrained here, I cannot make the board any larger as it has to fit onto a 100x150 mm heatsink together with the LPRO. What I might do is put a thermal plane on the bottom side of the PCB under the mosfet and connect it with some thermal vias. And maybe choose a different type with less than 60 milliohms. Rds_on.
thinkfat:
Here's a photo of the adapter mounted to the LPRO.
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