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Hbridge design

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Hi , i wanna your opinion on this design before doing it on a PCB, whethere it has something wrong or not , also i added the 2n2222 to make an ENABLE like pin to use it for PWM ..
 

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Hayato

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It makes no sense to me.
Those NAND gates, they will do nothing.

And the 2n2222? Will you ground the ground with that? Or, try to control the power side of the mosfets with a very low power transistor?
 

Hayato

Member
IRF540 can handle up to 33A.
A 2N2222 cannot handle more than 500mA, your circuit will not work.

And I cannot understant how the NAND are supposed to "protect" the H-BRIDGE.
 
So what is the subistiute for the 2n2222 ?
for the nand gate when there are two high inputs , the h-bridge will be short circuited
 

Hayato

Member
But your design will never have 2 high inputs. Your H-Bridge is just dynamic as a statue.

And you must control it with the NAND gates, you don't need to add a 2N2222.
 

Hayato

Member
Just configure the NAND gates the way that when you have a HIGH input, one optocoupler is driven HIGH and another LOW, and vice-versa.
 

Hayato

Member
Take a look:
nands.GIF

When A = 0, then #Q = 1 and Q = 0
When A = 1, then #Q = 0 and Q = 1

A is where your signal comes from.

Then you know what you should do.
 

Hayato

Member
Still not right.
The A from my schematic is the direction. If you just connect PWM where it should be VCC it will malfunction.
You should add 2 more NAND gates to make some sort of MUX, with the Outputs and "PWM".

Then, in your power section, probably the MOSFETs gates capacitances will interfere your output waveform, you should drive them with push-pull or totem-pole drivers.
 
Thanks hayato,
well how about the other problem you said , i couldnt understand it ??
why i need to drive the mosfets in totem pole form ?
 
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