Is MOSFET in series is possible?

Status
Not open for further replies.
M

muhammadali_16

Full Member level 3
Joined
Jul 15, 2011
Messages
161
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,296
Activity points
2,335
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

 

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
 

Status
Not open for further replies.

Similar threads

Menu
Log in
Register
Cookies are required to use this site. You must accept them to continue using the site. Learn more…