just a thought I had today. nothing I'm planning for a project yet. just a random thought really.
how feasible is it to run 2 or 3 mosfets or bjt's on pwm? basically when 1 or 2 are "off/low" then 1 is "on/HIGH"... and have them all on a common Vout so that it read as a steady HIGH signal.
almost like 3phase but not really.
my thinking for that would be to keep heat down on the individual components while maintaining a steady output.
I'm sure its been done before somewhere...
I'm really just curious on what the code would look like for something like that. or if anybody could lend me extra theory on the topic.
But the main source of heat is the non-zero time that the MOSFET spends switching between on and off and the second source of heat is the time switching off to on. If you turn it on and leave it on, then there is less heating.
If you have too much current for one MOSFET to handle then you can put many in parallel. (Note that BJT transistors can't be simply paralleled.) Or you buy a bigger MOSFET.
OK. One without much of a background would think that on time would create the heat. I've seen some mosfets that are rated at 23amps and 100volts and still relatively small in size....it's just hard to believe something that small can support those numbers
You don't go by the current rating, you go by the on-resistance rating and calculate the heat
dissipation. Heat dissipation is the limiting factor for power MOSFETs, and unless you are using
liquid cooled heatsink you can just ignore the max continuous current rating!!
A modern low on-resistance device might be as low as 1 milli-ohm on-resistance. That could handle
30A with a minimal heatsink.
how feasible is it to run 2 or 3 mosfets or bjt's on pwm? basically when 1 or 2 are "off/low" then 1 is "on/HIGH"... and have them all on a common Vout so that it read as a steady HIGH signal.
almost like 3phase but not really.
Feasible, but completely pointless since that would have much higher losses than switching them
all on together as the combined on-resistance is less and you don't have any PWM switching losses either.