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[SOLVED] Why doesn't this simple circuit work in simulation?

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AlienCircuits

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I expect the switch to turn on and conduct when Vgs = 15V, which is the pulse I'm sending to the gate. However, the switch seems to always be off.

circuit.jpg
plot.jpg
 

goldsmith

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Hi Alien
At first why 100 k ohms in drain ? it is too high for switching applications ! decrease it as 1 k ohms or 560 ohms . how much is frequency of your pulses ?
Best Wishes
Goldsmith
 

AlienCircuits

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Hi Alien
At first why 100 k ohms in drain ? it is too high for switching applications ! decrease it as 1 k ohms or 560 ohms . how much is frequency of your pulses ?
Best Wishes
Goldsmith

The 100k ohms is because the supply voltage is 1000V and the MOSFET is only rated for .2A.

The frequency is 50Hz.

I tried your suggestions, changing the resistor to 560 Ohm, and I get the same simulation plot. So it still does not switch.
 

goldsmith

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Tell me your frequency , thus i can simulate it , perhaps i could earn success !
 

AlienCircuits

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My pulses are 50Hz.

Here is the model:
* PSpice Model Editor - Version 9.2.1
*$
.SUBCKT IXTP02N120P G D S
*********************************************************************
*Note: *
* Althought models can be a useful tool in evaluating device *
* performance, they cannot model exact device performance *
* under all conditions, nor are they intended to replace *
* bread boarding for final verification. Therefore IXYS does *
* not assume any liability arsing from their use. IXYS reserves *
* the right to change models without prior notice. The Pspice model *
* does not constitute product data sheet. Designer should refer to *
* the data sheet to guranteed the limit and specification. *
*********************************************************************
** model generated on August 31, 2012
* Node 1 -> Drain
* Node 2 -> Gate
* Node 3 -> Source
M110 D G S1 S1 MM111
L_s S S1 1n
.MODEL MM111 NMOS
+ LEVEL=3
+ L=2.0000E-6
+ W=.33
+ KP=1.0331E-6
+ RS=10.000E-3
+ RD=59.148
+ VTO=2.9879
+ RDS=1.2000E9
+ TOX=2.0000E-6
+ CGSO=191.89E-12
+ CGDO=16.167E-12
+ CBD=191.99E-12
+ MJ=1.4624
+ PB=1.5310
+ RG=10.000E-3
+ RB=1.0000E-3
+ GAMMA=0
+ KAPPA=0
*
L_bd S2 S 1n
D_1 S2 D BD
.MODEL BD D
+ IS=3.0108E-16
+ N=2.7849
+ RS=1.0000E-3
+ CJO=1.0000E-12
+ M=.3333
+ VJ=.75
+ ISR=10.010E-21
+ BV=1.1999E3
+ IBV=25.890E-3
+ TT=28.793E-6
.ENDS
*$
 

goldsmith

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I have simulated it with another mosfet and 500 volts ! see below , please : ( i think you didn't measure voltage of drain ! perhaps you have putted the probe on VDC ?)

Good luck
Goldsmith
 

AlienCircuits

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I have simulated it with another mosfet and 500 volts ! see below , please : ( i think you didn't measure voltage of drain ! perhaps you have putted the probe on VDC ?)

Good luck
Goldsmith

No, I have measured the voltage at the drain. The netname shows up in my first circuit picture, and that is the name in the simulation plot too. Your simulation shows what I expected to see with my circuit, but my circuit doesn't do this :/

Perhaps my MOSFET model is incorrect? I had to request it in email from the manufacturer.
 

keith1200rs

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It is a defective Spice model. Edit the first line of the model to be

.SUBCKT IXTP02N120P D G S

then it works.

Keith.
 

AlienCircuits

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I figured out the problem! Thanks goldsmith, you helped me because I am not confident with MOSFETs yet and I wasn't sure if what I saw was incorrect. You verified my thoughts, and so I checked the model.
They created the model non-standard, with the Drain and Gate order swapped. I fixed it and it simulations correctly.

Thank you.

- - - Updated - - -

It is a defective Spice model. Edit the first line of the model to be

.SUBCKT IXTP02N120P D G S

then it works.

Keith.

Hehe, I just found that out and came here to read this :D
 

keith1200rs

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You did well to find it. Fixing companies cr@ppy models is not easy. You always assume they have tested them and that you are making a mistake!

Keith.
 

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