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H BRIDGE, driver for a dc motor

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nuttaphong191

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h-bridge driver with dc motor

i am designing a 6 amps h bridge bidirectional dc motor driver ckt.

the current rating is 4amps @ 12v..

i m using a pmos on top and nmos on bottom.

the prob is that the upper pmos is getting hot like anything.
i used a transisitor to drive the upper mosfet and a logic level +5v for the lower one.
i even tried connecting one cap(i microfarad) and one resistor(one kiloohm) b/w
gate and gnd,but in vain.

can anyone suggest some tested soln to this prob please...
 

Is the on resistance higher for the pmos fets?
If it is, you may do better putting 2 devices in parallel in each pmaos position in the bridge.

Is the turn on voltage for the pmos devices less than your voltage rail?
If these devices are not being turned on sufficiently, you may want to substitute a fet with a lower turn on voltage.
 

yet check that gate voltage transition for upper mosfet is not too long .
You can also substitute upper mosfet with n channel and use half bridge mosfet driver from IR to get better performance .
 

Getting too hot because of too much power dissipation. Something is wrong with the switching of your PMOS. Are you sure there is no short circuit in the switching times? Did you arrange deadtime good so never PMOS and NMOS are switched on for very short time together?

BR
 

you must use some kind of level translation for the upper part of the bridge like bootstrap or similar. The upper mosfets will be hot if they are not opened completely but working in linear region

Greetings
Dragan
 

dragan said:
you must use some kind of level translation for the upper part of the bridge like bootstrap or similar. The upper mosfets will be hot if they are not opened completely but working in linear region

Greetings
Dragan
Click to expand...

he uses pmos on upper site so no bootstrap is needed, just shift down .
 

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