Would this H-Bridge Work?

My main convern is whether the transistor pairs (top right, bottom left / top left, bottom right) will be able to react to the PWM signal. Also, whether the logic for the braking works or not.

Assume that when brake is on, there will be no PWM signal.

Thanks.

Updated Other than that, would the circuit work?

your top tow PNP darlington pair BJT's are the wrong way up

Are they? I would say they're not - the top ones are PNP's.

Exo said:

Are they? I would say they're not - the top ones are PNP's.

Click to expand...

He's edited the diagram since then!.

It was only that he'd accidently used the wrong symbol, it was reasonably obvious what he meant.

Exo said:

Are they? I would say they're not - the top ones are PNP's.

Click to expand...

They were!!! Honest.
Must of been an edit. Just a small thing I know


EDIT
you have no free-wheel diodes across the darlingtons of the H-Bridge.


give me a bit of time, just going through the logic


EDIT
you have a slow turn-off of the top PNP's with no interlock logic. High
chance of switching shoot-throughs esp during PNP-off and NPN-on

EDIT
This will not work.
The direction pin (fwd/rev) feeds two AND gates, the output of the AND gates then feeds teh relevant BJT's. When the direction bit is LOW, no PWM can get through.

This is more of a disable than a direction

Sorry, I had the NOT gate placed incorrectly. This is what I meant. About the slow turn off of the pnp/npn at the top. I actually got my idea from this site:

http://www.mcmanis.com/chuck/robotics/tutorial/h-bridge/bjt-circuit.html

If this transistor configuration won't work, is there another way to turn on only the top two transistors of the H-Bridge when I need to brake and assume normal operation of the bridge when I don't?

Here's the updated diagram:

It will work, you will just have to carefull IF you change the direction at a PWM HIGH.

best be in the software is to only make it change the direction bit when the PWM is LOW

Ok, I will add an on/off input too then. Thanks a lot for all the help.