need help on Mosfet design suggestions

[vvenky88]

Hi all,
I am new for designing analog circuits...
Actually i need to convert 5V to 110V with the load of 3A. The 5V input is coming from the Microcintroller and my design should convert that 5V into 110V using mosfet and the external load is 3A...

Can anyboody suggest me which mosfet is good for this design whether n-channel or p-channel mosfet and why???

Regards,
Venkat,8)

 

[yadavvlsi]

According to your specifications I think you wants to control a large load (like a motor) that works on 110V using microcontroller.
3 Amps is huge current.!! MOS cannot give that much current. MOS can source and sink few micro Amps of current.
You can use a BJT(CL 100, SL 100) and a relay for your project. You need a 110V external supply that is connected to relay and BJT can be used to control the relay switching.

 

[alexan_e]

3 Amps is huge current.!! MOS cannot give that much current. MOS can source and sink few micro Amps of current..

You are obviously talking about something different.
mosfets can control huge amounts of current, for example:
IRL2203 (30v/116A)

Alex

 

[hussain_kiet]

3 Amps is huge current.!! MOS cannot give that much current. MOS can source and sink few micro Amps of current.

goto International Rectifier Home Page - Flash Detection
where you can find MOSFETS with ratings in 100's of Ampere's 400A,500A etc...
look for IRF520N looks suitable for your application...

 

[yadavvlsi]

That's right.! But microcontroller can not give such a high voltage that can switch this MOSFET ON. Microcntroller gives output 0-5V so it always will be in OFF state.

 

[alexan_e]

That's right.! But microcontroller can not give such a high voltage that can switch this MOSFET ON. Microcntroller gives output 0-5V so it always will be in OFF state.

Check the datasheet of IRL2203, gate threshold is 1V, with 4.5v Vgs you get an Rds-on as low as 10mΩ.
This mosfet is not a suggestion for the above circuit but there are plenty others with low gate threshold.

Alex

 

[hussain_kiet]

for higher end MOSFET's you need some sophisticated driving circuitry with proper isolation but for a 3A load an optocoupler can do the trick....
i did it for my project in which i used 4 Mosfet's to drive a stepper motor with 2.5A ouput and i only added a optocoupler in between the micro controller and MOS

 

[vvenky88]

Hi hussain_kiet,
Yes...correct even i am also going to use on optocoupler in between the microcontroller and Mosfet....But now what i need is that whether n-channel mosfet is good or p-channel mosfet is good and why??

 

[hussain_kiet]

Usually N Mosfet's are preferred you can find articles on the internet that which one is better and why...
but since your load is AC 110V you should be careful because switching an AC load produces noise which cause micro controller to get hanged or malfunction
what do you want simple turn ON and OFF the AC load or continuous switching...?

 

[vvenky88]

hi hussian_kiet,
I am using 110V dc only and i want only ON/OFF function only....
Find the below schematic...

Actually i need to convert 5V to 110V using p-channel MOSFET.

input 5V is coming from the Microcontroller and Mosfet should generate 110V to drive the external relay with 3A.

here i have attached schematic which i have tried in simulation...

I am using IRF9640 p-channel Mosfet. In schematic the transistor collector is connected to the 110V and the output is taken from the drain of MOSFET...In this condition i can able to switch ON/OFF the MOSFET properly....
But actually my system have only 5V,12V and 110V power supply only...So in the transistor collector i should use only 12V...If i use with 12V i cant switch the MOSFET...I think the MOSFET is always ON...I cant switch OFF the MOSFET...

So can you suggest me in this design????


https://obrazki.elektroda.pl/54_1302088635.jpg

 

[hussain_kiet]

yes you are right to wouldn't be able to switch OFF the Mosfet. but in your circuit i see 110V supply on the transistor collector in this case you can turn it OFF and ON why not use why not usse in this config..?
all you need to do is to select a suitable transistor with enough Vce rating...

 

[vvenky88]

In this configuration i can switch ON/OFF the MOSFET but i should use only 12V only in the collector side.....this is sample schematic only instead of transistor i should use only optocoupler for isolation at that time i should use only 12V in the collector side...this is only my problem...

 

[hussain_kiet]

you can use optocoupler to switch the transistor in that case you can use 110V dc at transistors collector...

 

[alexan_e]

You can use level shifting so that the gate gets 110 or 100v (so that Vgs stays below 20v) using a voltage divider in the collector.



Alex

 

[hussain_kiet]

You can use level shifting so that the gate gets 110 or 100v (so that Vgs stays below 20v) using a voltage divider in the collector.

then again you have to use the optocoupler before the transistor....

 

[alexan_e]

then again you have to use the optocoupler before the transistor....

or the output (transistor) of the optocoupler instead of the transistor shown in the schematic (assuming that 110v can be used with the optocoupler transistor).

Alex

 

[hussain_kiet]

i agree you can use optocoupler in place of Transistor in the circuit suggested by alexan_e but the assumption is very critical

assuming that 110v can be used with the optocoupler transistor

 

[alexan_e]

Something like H11D1 datasheet could be used.

Alex

 

[vvenky88]

hi all,
my main problem is that, i should not use 110V in the collector transistor or optocoupler output....I should use only in the P-channel MOSFET itself only...i should use only the 12V in the collector of transistor or Optocoupler output.....

 

[hussain_kiet]

well the easiest way is to use n channel Mosfet rather P channel all of your problems will be resolved.....
try IRF640N....