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Is MOSFET in series is possible?

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muhammadali_16

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hiz to all
i want to switch 800v from microcontroller. for that purpose i want ot use p-channel MOSFET.

i am searching for mosfet of 800v - 1000v.
can anyone tell me a mosfet which can switch 800v to 1000v or tell me can i use two transistor in series to distribute the voltage in them???

i shall be greatful
 

Series connection of mosfets is described here (page 53)
https://www.scribd.com/doc/22238961/Power-Semiconductor-Applications-Philips-Semiconductors

The following are problems that have to be overcome for
successful operation of MOSFETs in series. If one device
turns off before another it may be asked to block a voltage
greater than its breakdown voltage. This will cause a
reduction in the lifetime of the MOSFET. Also there is a
requirement for twice as many isolated gate drive circuits
in many circuits.
Click to expand...
 

hiz to all
i want to switch 800v from microcontroller. for that purpose i want ot use p-channel MOSFET.

i am searching for mosfet of 800v - 1000v.
can anyone tell me a mosfet which can switch 800v to 1000v or tell me can i use two transistor in series to distribute the voltage in them???

i shall be greatful
Click to expand...
Hi Muhammad ali
Yes you can easily use some mosfets in series together but it depends on what kind of application you're referring to ? i think your aim is switching application . so what is your load ? LC load ? for how how current ? ( peak current )
A question : why you need to use a Pmosfet ? why not Nmosfet ? if you are able to use Nmosfet i can introduce you several mosfets .
And the other parameter that you forgot to mention is , how much is your switching frequency ?
Best Wishes
Goldsmith
 

i have 800V. there is not such frequency. i just want to turn on and off 800v by microcontroller. the current is <=100A but it is non-repititive. i have study IRF840 and other mosfets. those have PULSED Current parameter. i want to use that.

800v----------LOAD-----------GND. just a electronics switch between 800v and LOAD
 

Well is that 800 volts , AC ? or just a DC signal ?
If that is AC , you can use a simple triac .
If that is DC , you can use IGBT . because for 100 A mosfet isn't reasonable .
BTW : you can also use a thyristor with a chopper circuit to turn it off in DC current
Good luck
Goldsmith
 

n-mosfet can only be connect in ground reference and i want to switch positive side . so i have to use p-mosfet
 

n-mosfet can only be connect in ground reference and i want to switch positive side . so i have to use p-mosfet
Click to expand...
what ? i think you want control a positive voltage ( +800 volts ) so who told that you can't use N mosfet ? is your load between switch ad ground ?
If yes you can easily use a float driver .
 

can you little explain float driver???
Click to expand...
Certainly ! you can easily use two transistor , to drive your IGBT , floating ( create +15 volts across the GE to be sure about it's operation as a perfect switch )
By the way , a question : for such a high power , why you don't use contactors ? they are more suitable for your aim .
 

i think IGBT can do it. can you suggest me any IGBT which i can get easily in the market
 

i think IGBT can do it. can you suggest me any IGBT which i can get easily in the market
Click to expand...
Of course it can handle your aim but with higher price and higher dissipation in compare with a contactor ! because your current isn't pulsing ! ( 800 V 100 A is 80kVA ) so , i don't think that your interested to waste the power and waste you're money .
 

i have space issues. its just a small device which i want to make. the whole circuit is ready except this department
 

i have space issues. its just a small device which i want to make. the whole circuit is ready except this department
Click to expand...
space limitation ? i think if you use an IGBT with a large heat sink it will be larger than a simple contactor .
Anywhere if you've decided to do it with that method ( an IGBT ) , no problem ! ( however thats impossible that i use such a design ! ;-) ) you can easily do it with a float driver with two transistor ( HV transistors ) and an IGBT or some IGBTs
Best Wishes and Good luck
Goldsmith
 

can i connect two transistor in series to distribute voltage???

i mean that my voltage is 800V. can i use two 500v transistors in series to distribute voltage between them? if yes kindly refer some circuit?
 

can i connect two transistor in series to distribute voltage???

i mean that my voltage is 800V. can i use two 500v transistors in series to distribute voltage between them? if yes kindly refer some circuit?
Click to expand...
Yes you can , but you need a pretty precise driver ! because if both of them don't be on at the same time , both will born ! you'll need some feedback loops to be sure about on time and off time .
 

This is an example of a floating driver for a N-channel high side mosfet (or IGBT)
http://www.irf.com/product-info/datasheets/data/irs21850spbf.pdf
Although this only withstands 600v you may find a similar part for 800 or 1200v.
The dissipated power on the mosfets. Even with a Ron=0.06 will be high. If you are talking about 100A that will be 600W to warm the mosfet. Secondary breakdown reduces the voltage versus current that a mosfet can handle.
You will probably need to parallel transistors to handle such a current and to reduce the series resistance of the switch.
In that case series connection will need twice as many mosfets. snubbers and critical gate drivers. A contactor as goldsmith advice is a better solution.
 

series transistors
Click to expand...
Hi again
For series arrangement , you have to use choose values of each element according to the mosfet or IGBT that you've selected before .
Well , consider that you've two IGBT , collector of first one is connected to the +VDC and it's emitter is connected to the collector of the other one and emitter of the other one is connected to the load . ok ?
then you'll have to drive both of them with an overlapped signal ! ( two different signals will be one of the solutions ) however you can drive both of them with a main signal because you're not using a pulse train as your driving signal .
( because you're not using this composite element in a high speed circuit . )
Best Wishes and Good luck
Goldsmith

- - - Updated - - -

Hi Albert 22
I hope that you know a simple float driver won't do the best ! because each capacitor has a leakage resistance . hence it won't be able to keep it's stored charge for some seconds ! hence after a low time the composite element will be off !
So the best solution is a floated ground , PSU ( usually a transformer and a bridge diode and a capacitor and an opto coupler .

Best Wishes
Goldsmith
 

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