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Topic: can someone please confirm if this mosfet will work? (Read 1 time) previous topic - next topic

jameshutton

Hi there.
I have a 120v 10a DC power supply that I need to regulate with a mosfet.
I realize this is a bizarr request.

I have come across this mosfet: IPP320N20N3 G-ND
which seems to meet my needs.

Can someone please simply confirm if a pwm signal from the arduino to the gate of the mosfet modulate it properly?

I have tested the circuit with the irfp250 which has all the same specs except being able to use logic level. So I am regulating it with 0-12v instead of pwm from the arduino. It works perfectly in this way, now I just want to control it with the arduino instead.

thanks

knut_ny

Datasheet says that its fully open at max 4V, so the Arduino will open it properly.
I guess your next challange it to speed up PWM to at least 20kHz .. then some filtering.

Ny

MarkT


Datasheet says that its fully open at max 4V, so the Arduino will open it properly.
I guess your next challange it to speed up PWM to at least 20kHz .. then some filtering.




NO NO NO!!

Firstly in English "open" for a switch means "off" or "no connection" as in "open circuit",
its not like a water tap at all.  I presume you mean "fully on at max 4V".

That MOSFET is not logic level and certainly is not switched on at 4V.

Perhaps you think threshold voltage is when the device is on?  Its not, its the point
at which the device switches OFF, or more precisely conducts only a few microamps.

The voltage at which the device is guaranteed to be fully _on_ is given in the Rds(on)
spec as the Vgs value - here its given as 10V for a Rds(on) of 32 milliohms max.

That means you need at least 10V between gate and source to guarantee the on resistance
is at or below 32 milliohms.

In general a logic level device will have Rds(on) quoted for Vgs = 4.5V.  It will also
likely have a threshold voltage of 0.5 to 1.0V.


Anyway, back to the original question.

Yes you can use that MOSFET but you will need a MOSFET driver chip to drive the
gate and a 10 to 12V supply to power the MOSFET driver.

With high voltage high power switching you cannot safely drive the gate directly from
an Arduino anyway as the drain-gate capacitance can back-drive the gate and burn
out the Arduino - you need a beefy driver chip to hold the gate voltage steady, something
like the MIC4422 will do nicely.

Again with that big load voltage you need to think about protection circuitry really -
a TVS diode to protect the 12V rail from over voltage, a 15V zener on gate-source
to protect gate oxide layer, a 10k resistor between Arduino and MOSFET driver to
protect Arduino.

But also we need to establish why you are trying to use low-side switching in the first place,
is seems unrelated to "regulating a power supply" - that would imply high side switching
if anything, which at 120V is rather more complex.
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

jameshutton



Datasheet says that its fully open at max 4V, so the Arduino will open it properly.
I guess your next challange it to speed up PWM to at least 20kHz .. then some filtering.




NO NO NO!!

Firstly in English "open" for a switch means "off" or "no connection" as in "open circuit",
its not like a water tap at all.  I presume you mean "fully on at max 4V".

That MOSFET is not logic level and certainly is not switched on at 4V.

Perhaps you think threshold voltage is when the device is on?  Its not, its the point
at which the device switches OFF, or more precisely conducts only a few microamps.

The voltage at which the device is guaranteed to be fully _on_ is given in the Rds(on)
spec as the Vgs value - here its given as 10V for a Rds(on) of 32 milliohms max.

That means you need at least 10V between gate and source to guarantee the on resistance
is at or below 32 milliohms.

In general a logic level device will have Rds(on) quoted for Vgs = 4.5V.  It will also
likely have a threshold voltage of 0.5 to 1.0V.


Anyway, back to the original question.

Yes you can use that MOSFET but you will need a MOSFET driver chip to drive the
gate and a 10 to 12V supply to power the MOSFET driver.

With high voltage high power switching you cannot safely drive the gate directly from
an Arduino anyway as the drain-gate capacitance can back-drive the gate and burn
out the Arduino - you need a beefy driver chip to hold the gate voltage steady, something
like the MIC4422 will do nicely.

Again with that big load voltage you need to think about protection circuitry really -
a TVS diode to protect the 12V rail from over voltage, a 15V zener on gate-source
to protect gate oxide layer, a 10k resistor between Arduino and MOSFET driver to
protect Arduino.

But also we need to establish why you are trying to use low-side switching in the first place,
is seems unrelated to "regulating a power supply" - that would imply high side switching
if anything, which at 120V is rather more complex.


Wow, ok this is great information. I will try using this mosfet with the mosfet driver you suggested. Would you mind possibly keeping in contact with me if I have any questions when I receive the ordered pieces? This project is very important to me, however it would be nice to have some guidance and you seem to really know what your talking about.

fungus

#4
Jan 04, 2014, 03:13 pm Last Edit: Jan 04, 2014, 03:16 pm by fungus Reason: 1


Datasheet says that its fully open at max 4V, so the Arduino will open it properly.
I guess your next challange it to speed up PWM to at least 20kHz .. then some filtering.

NO NO NO!!

Firstly in English "open" for a switch means "off" or "no connection" as in "open circuit",
its not like a water tap at all.  I presume you mean "fully on at max 4V".


NO NO NO NO NO NO!!

Neither way is correct for a transistor.

An electronics engineer would say "fully saturated at 4V"

(which that transistor isn't, 4V is where things start to happen, as you correctly point out)
No, I don't answer questions sent in private messages (but I do accept thank-you notes...)

MarkT

For MOSFETs "saturation" is completely different from BJTs - for MOSFETs the
saturation region is when the current saturates as the drain voltage is increased and the device leaves the ohmic region.

A switching MOSFET in the saturation region is overloaded (this
either happens when the device is asked to handle more current than it is
rated for, or if the gate-source voltage is too low to turn it fully on.

A switching MOSFET is either off (sub-threshold) or on (ohmic region)
and only enters saturation briefly during transitions.
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

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