PMOsfet Overheating, help please?

[quantrug]

The Circuit below(Courtesy of SgtWookie) works just fine with the exception of the detail that the Pmosfet(an IRF 9540N) overheats excessively after about only 1 second of usage!

Any suggestion/solutions please?

thanks

 

[hameeds01]

use Half-Bridge MOSFET Driver ICs with the MOSFETs

 

[quantrug]

Hi Hameed,
Thanks for your suggestion. My IRFZ44N the NMosfet is fine and no overheating at all so what Half Bridge IC Driver do you recommend for the PMosfet?
In general does the circuit looks OK to you? Any ther suggestions/improvements recommendations?

thanks again

Cy

Added after 52 minutes:

Also please note some data below to help with the troubleshooting:

 

[quantrug]

Well, did some more tests and found that the heating problem is associated with the type of solenoid I use. There was one that was not heating too much and was a Sol. that was wound with a 0.35 mm wire and the one overheating is a same size Sol. but wound with 0.5 mm wire!
How can possibly the thickness of the wire be related to the problem?
Below the data on the .5mm Sol., Pmos Loaded & Opto ON:
Source* Drain* Gate
19* 3* 15

As can be noted, the wire thickness drastically affects the Drain voltage!!!?

 

[quantrug]

Well, this has led me to check for shortage within the Sol. itself and indeed the .5mm wire coil had a short with it's Aluminium core...which explains the heavy draw!

 

[Audioguru]

Like I said on all the other websites, a high current in a Mosfet that is not turned on enough produces a lot of heat.

Why is this simple circuit posted on so many websites?

 

[quantrug]

Different forums, different audience and contributors hence more coverage and greater brainstorming of minds(like the news media, same news different broadcasters with different views and audiences!). You'd be surprised how experts' opinions differ even on simple matters!

Back to the Mosfet issue, so how can one assure a Mosfet receives the correct voltage at it's gate?
Also, what is the relationship of the GDS voltages in reference to each other? Say you have a 10v power supply, then what should the followings be:

1- Source Vs. Drain
2- Source Vs. Gate
3- Drain Vs. Gate
4- Gate Vs. Power supply?

thanks

 

[dick_freebird]

If you want rated RDS(on) you have to give it rated gate drive.
With only 5V applied, that had better be a "logic level" FET.

The solenoid is the only current limiting element in the case
that FETs are well driven. So there's your wire gauge
influence. If the limited current is below what the FET can
pass at low RDS(on) then the power dissipation will be elsewhere
(in the solenoid). A soft-driven FER can have an abrupt
transition from linear to saturated (dissipative) with current as
it acts pretty much like a current source.

Their data sheet has ID-VD curves for various VGS but they
rate at 10V, which you are well short of. You can tell by the
curve what ID can be supported by a gate drive voltage
though this should be no more than a rule of thumb and want
more care at the corners.

A purpose designed power MOSFET or bridge driver would do
you a lot of good, I think. If you need the optos for isolation,
put them in the signal path and don't make them do heavy
lifting.

 

[nashwan]

hi
i dont know why u use that p mos u can drive ur solenoid with just Q2

 

[quantrug]

nashwan,
This will be a Matrix whereby PMoses will drive the rows and the NMoses the columns.

Added after 11 minutes:

dick_freebird,
Thank you for your comprehensive response although technically a little too advanced for me.
Generally, I am using 5v just for my PC817 Optos.
It makes a lot of sense as you have pointed out to separate the power for the Gate and the rest of the circuit.