MOSFET heating issue

Thread Starter

mohitarora

Joined Jul 3, 2019
3
upload_2019-7-3_17-17-33_mohitarora.jpg

Hello people,
I am working on this circuit and facing the following issues:
1) Mosfet is heating a lot.
2) some or the other component is droping too much voltage.
I used a 24v 20a PSU bt when I connect the PSU with the circuit the voltage drops to 3-4v


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danadak

Joined Mar 10, 2018
4,057
That circuit is a self oscillating circuit with virtually no design protections
in it. That being said I am guessing the load coil is too low impedance
so circuit not starting up, and leaves MOSFETs partially on operating them
in linear region thereby cooking.

Also power supply may be a little light in current capacity, cure is bigger supply
or smaller load (more turns on coil). Additionally leads from power supply to
circuit should be low R and short as possible.



Regards, Dana.
 
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Thread Starter

mohitarora

Joined Jul 3, 2019
3
That circuit is a self oscillating circuit with virtually no design protections
in it. That being said I am guessing the load coil is too low impedance
so circuit not starting up, and leaves MOSFETs partially on operating them
in linear region thereby cooking.

Also power supply may be a little light in current capacity, cure is bigger supply
or smaller load (more turns on coil). Additionally leads from power supply to
circuit should be low R and short as possible.



Regards, Dana.
Thanks Dana.
Currently I am using 6 turn coil and the wire is solid copper of 1.5 sq mm.
The supply is 24v 20A.
the mosfets are irpf260n.
the resistors are of 330 ohm.
the diodes are fast diodes FP309
Can you please guide me further for what changes I should do in my circuit.
 

danadak

Joined Mar 10, 2018
4,057
Do you have a scope that you can capture some waveforms ?
Like power up.

I tried spice sim of circuit, cannot get it to start oscillating, still
fooling around with sim.


Regards, Dana.
 

danadak

Joined Mar 10, 2018
4,057
Crutschow, can you get a sim to work on this ? I also tried
this topology, no luck. In this case L2 is in mH range, L1
uh. C1 same as posters original schematic. The transient
sim on either circuit produces no meaningful results. I
get no large signal behavior.



Regards, Dana.
 
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jjw

Joined Dec 24, 2013
542
Thanks Dana.
Currently I am using 6 turn coil and the wire is solid copper of 1.5 sq mm.
The supply is 24v 20A.
the mosfets are irpf260n.
the resistors are of 330 ohm.
the diodes are fast diodes FP309
Can you please guide me further for what changes I should do in my circuit.
The gate voltages of the mosfets are too high.
Absolute maximum is +- 20V
They may have been broken.
Use ~15V zeners to protect them.
Edit: Zener from gate to gnd.
 
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