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H-bridge with 4 N-ch FETs

BlackMelon

Aug 7, 2012
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I want to design H-bridge to drive 12V DC Motor at rate of 12A with Pulse Width Modulation
but the problems is the FETs which can drive the motor with that high current are N-ch (The P-ch is so expensive because it's extremely rare in my area) so I have to put 4 N-ch FETs in the H-bridge and 12V battery to drive the motors
But the problems is how to drive the gates of FETs correctly? and how the circuit will be?
(I've got a Microcontroller which can give me only 5-0V pulse,and one 12V battery)
 

BobK

Jan 5, 2010
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You need a high-side driver. They use a bootstrap capacitor to raise the voltage above V+ in order to turn on the gate even though the source is at a high voltage.

The are often packaged as a high and low in one package to drive half a bridge. There might even be full bridge drivers.

Bob
 

BlackMelon

Aug 7, 2012
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Yes,There are full bridge drivers... but they can't withstand such a high current that I'm gonna use T___T
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Jan 21, 2010
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They're not designed to drive the motor, they're designed to drive the mosfets which drive the motor.

And yes, a mosfet can have a gate current measured in amps!
 

BobK

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They're not designed to drive the motor, they're designed to drive the mosfets which drive the motor.

And yes, a mosfet can have a gate current measured in amps!
But, hopefully, only for microseconds.

Bob
 

BlackMelon

Aug 7, 2012
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Sorry I can't get your idea about using Full bridge drivers to drive 4FETs in h-bridge...
Plz. explain me more with the circuit diagram
Thank you
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Give me a part number. I will find the datasheet for you and show you (unless we're talking bout different things)
 

BobK

Jan 5, 2010
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A full bridge driver usually means an IC that drives the motor directly. What you need is a MOSFET gate driver with high-side and low-side drivers. I think most of these come with one of each per package. I don't seem to be able to find any that have 2 of each in a package, so you will need 2 high-side + low-side driver chips to drive a full bridge.

Bob
 

BlackMelon

Aug 7, 2012
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ok sorry for making confusions..
I think I'm gonna use chips that BobK has spoken of
but how the circuit will be?
 

BobK

Jan 5, 2010
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Pick out a chip and it will have examples in the datasheet. The high-side and low-side drivers will go between your signals from the microcontroller and the gates of your power MOSFETs.

Bob
 
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