Timeline for P-Channel Mosfets in Series to Increase Max Drain-Source Breakdown Voltage
Current License: CC BY-SA 3.0
8 events
| when toggle format | what | by | license | comment | |
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| May 28, 2013 at 0:15 | comment | added | JamesHoux | Now that i reread your explanation, this just seems like a bad idea in general. It will be very complicated. If the first mosfet turns on first, then that will put all the voltage through it to the second mosfet, which could destroy it. Both of them would definitely need to turn on simultaneously or with the right delay. I don't think it's even worth trying to build it and get it to work reliably. | |
| May 28, 2013 at 0:12 | vote | accept | JamesHoux | ||
| May 28, 2013 at 0:11 | comment | added | JamesHoux | Wow. News to me. I haven't seen it happen but it does make sense. Great explanation! +5 :) | |
| May 28, 2013 at 0:08 | comment | added | Dave Tweed | If you haven't been putting resistors in parallel with your series diodes, then you haven't been doing it right. Different diodes (even if nominally "identical") can have very different amounts of reverse leakage current, which is equivalent to saying that they have very different values of resistance in the reverse direction. The reverse voltage distributes itself across the diodes in proportion to their resistance, and the "better" diodes (lower leakage) may get voltages that exceed their ratings. They'll break down, and the voltage will redistribute itself until the whole string fails. | |
| May 28, 2013 at 0:04 | comment | added | JamesHoux | Dave, would you mind looking at my other related question? You mentioned the use of other devices to let signals float. I asked about this particular issue using a single p channel and noone has answered yet: electronics.stackexchange.com/questions/70729/… | |
| May 27, 2013 at 23:59 | comment | added | JamesHoux | As far as the gate drive to each transistor... yes I see the problem there now that you point it out. It's because the source voltage on each transistor will be different which will entail a different necessary gate voltage when they're off. I'll have to puzzle over this and see if it's worth the trouble. | |
| May 27, 2013 at 23:55 | comment | added | JamesHoux | Thanks Dave, but I'm not totally following you. You said "Just like with diodes, you need high-value resistors in parallel"... I've never in my life seen a need for parallel resistors on series diodes. The diodes are in series so they must automatically share the same current. Did you mistakenly think of parallel mosfets instead of series mosfets? | |
| May 27, 2013 at 23:47 | history | answered | Dave Tweed | CC BY-SA 3.0 |