IRF540n

Status
Not open for further replies.
S

samarsingla

New Member
I using IRF540n for driving a dc motor in one directional only. I am controling speed by PWM. I tested initially without any protection diode.. and it worked fine. Please someone tel me is there any internal protection alreay there in IRF540n. If no, which diode should I use and how do I connect it?? I am a beginner and require it urgently, please help.
Thanx.
 
The diode in reverse parallel with the motor isn't for protection, it for efficiency. I strongly recommend you include it.
 
Hero999 said:
The diode in reverse parallel with the motor isn't for protection, it for efficiency. I strongly recommend you include it.
Click to expand...

err while protection isn't really the right word, it is kind of
the diode across the motor (which is essentially an inductor) provides a free-wheel path for the current that has build up in it via the controlled switch.

Without the diode across the motor/inductor when you goto turn the switch of (due to PWM) the inductor will develope a sufficient voltage to keep the current flowing (backEMF if you will) THAT will cause the FET/switch to hit is avalaunch voltage
 
Can you please post me a schematic for that and tell what kind of diode should i use? Are ultrafast diodes good for the purpose?
 
samarsingla said:
Can you please post me a schematic for that and tell what kind of diode should i use? Are ultrafast diodes good for the purpose?
Click to expand...

OMG!!! I am not cross-replying to a cross-post!!!
use your ORIGINAL thread WHERE I have posted the cct!!!

and next time
1) USE THE SEARCH
2) DO NOT CROSS-POST
 
Maybe his memory is failing so he forgot that this stuff was already discussed in his other post.
Maybe he wants another point of view from somebody else.
 
Styx said:
Without the diode across the motor/inductor when you goto turn the switch of (due to PWM) the inductor will develope a sufficient voltage to keep the current flowing (backEMF if you will) THAT will cause the FET/switch to hit is avalaunch voltage
Click to expand...
I know but even if this wasn't a problem a diode is still recommended. The diode allows the current to flow inbetween pulsses so the energy isn't wasted. Some effiecent PWM controllers use a P-channel MOSFET instead of a diode because it has a lower voltage drop.
 
Status
Not open for further replies.
Menu
Log in
Register
Cookies are required to use this site. You must accept them to continue using the site. Learn more…