H-Bridge COmplementary Transistors--Plz help in selecting them

[shaiqbashir]

hi guys!

following is the picture of the H-bridge i want to use. Please keep this thing in the mind that im ussing this H-bridge for some really powerful motors that will be requiring around 4-5 A of current each.  So. i will be using one circuit for each motor. But the problem is this that in the following circuit, they havenot written the model no of the MOSFETs. What should be ur suggestions?

Secondly, i know one MOSFET i.e. IRF540. Do u think it would be suitable as an N-channle power mosfet in the following circuit?

If yes then what P-channle mosfet should i use?

Please help me as soon as possible as i have a very short time left.

thanks in advance

 

[audioguru2]

Hi Shaiq,
I used an old IRF540 Mosfet to drive an 8A motor and it barely got warm. I don't know what you can buy in your country so just pick a matching 33A P-channel Mosfet.

 

[shaiqbashir]

Hi audioguru!

well! very very sorry for not putting up the diagram.

here is the diagram

Now this is the circuit which i want to use.

thanks for supporting IRF540. its available in our area. But i have read somewhere on a  website that IRF9540 is almost a complementary P-channel mOsfet of IRF540? so can i use it?

thanks in advance

 

[shaiqbashir]

one more thing audio guru.

dont u think that in the above diagram, there should be a 10K resistor on the right side of the left P channel Mosfet and there shoud be a 1K resistor with the left N-channel Mosfet?

plz tell me that what is the correct choice?

thanks

 

[Muhammad Abu Bakar]

Aslam O Alaikum  Shaiq Bashir!

If you see symmetry, R3 should equate R8 and R7 to R4.  However let's wait for audio guru to appear. 

 

[shaiqbashir]

One more thing that i want to ask here along with my previous questions is this that:


IF I USE MOSFET DRIVERS LIKE TC4424 OR TC4420 THEN DOES IT WILL IMPROVE THE PERFORMANCE. IF YES? THEN WHAT ADDITTION AND SUBTRACTION IN THE ABOVE CIRCUIT DO I HAVE TO MAKE?


One more thing that i want to ask is this that one of my friends said to me that IRF540 gets burned easily when used in an H-bridge. So it is not suitable for this application, Is this correct? if yes then what should be a suitable replacement for it?


thanks in advance
!

 

[audioguru2]

Hi Shaiq,
A Mosfet H-bridge driver IC is much better because it has dead-time when it switches to guarantee that an N-channel and a P-channel Mosfet that are in series across the supply are not both turned on at the same time.
It looks like your circuot doesn't have dead-time so will momentarily short the supply when it switches. The unbalance of the resistors helps because the 10k resistor turns on or off a Mosfet slower than a 1k resistor because it charges or discharges the high gate capacitance.

Another problem with your circuit is that it cannot use Pulse-Width-Modulation to control the speed of the motor because the gate resistors cause the Mosfets to switch slowly which causes heat.
Another problem is that the N-channel Mosfets get only 6V on their gates to turn on. They are spec'd with 10V on their gates.

 

[shaiqbashir]

Hi guys!

well! i tried to implement the above circuit on my breadboard. One problemt hat im facing here is this that my LEft IRF540(n-channel)  and Left IRF9540(p-channel) is getting very hot while the right transistors are both cool. And the motor is just not running. What might be the cause for this.

What i have done is to connect teh point A (forward ) with my 12V Vcc to make it logic 1. and the B is connected with ground.

im using a 12V 12Ah DC battery.

please help me as soon as possible,

 

[audioguru2]

Hi Shaiq,
You have the source leads of the P-channel Mosfets connected to the motor. The drains should connect to the motor and the sources should connect to +12V.

 

[shaiqbashir]

Hi audioguru!

thanks a lot for ur help. Now u see, i forgot to tell u about a bit update that im using the following circuit.

Now here u can see that sources of P-channel Mosfets are connected with 12V and drains with the motor. But again im facing the very same problem that motor is not running. However two important results i have observed:

1) The status LED Blinks with a very small intensity
2) When i connect a DC motor with the circui, i can feel a very very small vibration in the motor when given forward or reverse rotations logics.

THis means to me that there is not a proper amount of current given to the motor?

what do u say/?

U said that the gates of IRF540 need 10V to turn on, while this circuit is providing just 6V. i have checked the datasheet and it really requires 10V to

 

[audioguru2]

Hi Shaiq,
Now the circuit is connected correctly. The gates of the Mosfets now have 10.9V and 11.9V.
Make certain that the logic inputs are a steady DC and are not pulses.

Since the LED blinks and is dim and the motor vibrates and doesn't run then your power supply can't provide enough current. Measure its voltage when the motor is trying to run.