One of my MOSFET source-drain shorted after I connect them in parallel?
So I was making an ARC speaker yesterday, and I used one MOSFET ( irf540), and it got really hot, but it did not blow up, so I decided to put another MOSFET connected in parallel, and before I connected them I have tested both MOSFET and both of them worked normally, but when I connected them in parallel, the whole setup shutdown immediately due to overloading, and I found that one of my MOSFET was source-drain shorted that's why the power supply shut down to protect itself.
How do you connect the MOSFETs?
Just normal parallel circuit gate to gate, drain to drain, source to source, .connected with a piece of wire
PWM controller?
TL494CN, powered by a battery, completely isolated from the MOSFET side
MOSFETs?
IRF540 from IR
As you can see in this video there are two MOSFETs on the heat sink but the lead was disconnected because it was shorted.
By the way this video is not specially made to show the setup so it would be more focused on the fly-back.
Here is the full schematic and the PWM board.
Best Answer
A pretty normal explanation for this is as follows: -
You said the first MOSFET (on its own) got hot but continued working and my 1st observation is that you may not have been driving the gate "hard" enough. This would have caused some switching losses and possibly some conduction losses causing the device to get hot but it still worked.
So then you put another device in parallel and in doing so you have "shared" the gate drive current - the gate capacitance has effectively doubled and the rise time and fall time of the gate signal has doubled increasing switching losses for the device that begins to turn on first (not all FETs are identical). It rapidly overheats, melts and short circuits.
If you want this confirming, produce a circuit diagram of what you actually did.