Buffers

[Tamim]

Hi every1,
I have designed a high side gate drive cct for a power mosfet(450V
11amps). The finaly component in my gate drive is a JK flip-flop that
is directly connected to my mosfet. Everytime I power the circuit it
blows my JK. The only reason i can think that this is happening is
becuase the too much current is going in the output of my JK. So i
need A buffer. The buffer should have no Voltage swing at the
output(very important) as i want the mosfet to be either fully on or
off.I cannot find one anywhere. Does anybody know a website that will
sell buffers suitable for my application i.e. supply voltage of about
12 V and no voltage swing at the output. I know there are many other
things in buffer but dont worry about that! I would really appreciate
any help. Thanks!

Regards,
Tamim

 

[Tim Dicus]

"Tamim" <tazizi@yahoo.com> wrote in message news:3a4d075e.0403030506.6722add7@posting.google.com...

Hi every1,
I have designed a high side gate drive cct for a power mosfet(450V
11amps). The finaly component in my gate drive is a JK flip-flop that
is directly connected to my mosfet. Everytime I power the circuit it
blows my JK. The only reason i can think that this is happening is
becuase the too much current is going in the output of my JK.

***
I can think of a couple others. How about incorrect voltage supply? How about incorrect setup of the JK?
***

So i need A buffer. The buffer should have no Voltage swing at the
output(very important) as i want the mosfet to be either fully on or
off.I cannot find one anywhere. Does anybody know a website that will
sell buffers suitable for my application i.e. supply voltage of about
12 V and no voltage swing at the output. I know there are many other
things in buffer but dont worry about that! I would really appreciate
any help. Thanks!

Regards,
Tamim

If you could be a little more complete, it would be easier to help you with your circuit. ID of the JK and the MOSFET, and how they
are connected, would be helpful.

Tim

 

[Tim Wescott]

"Tim Dicus" <tim@prolectron.com> wrote in message
news:%7l1c.22830$UU.578@lakeread01...

"Tamim" <tazizi@yahoo.com> wrote in message
news:3a4d075e.0403030506.6722add7@posting.google.com...
Hi every1,
I have designed a high side gate drive cct for a power mosfet(450V
11amps). The finaly component in my gate drive is a JK flip-flop that
is directly connected to my mosfet. Everytime I power the circuit it
blows my JK. The only reason i can think that this is happening is
becuase the too much current is going in the output of my JK.

***
I can think of a couple others. How about incorrect voltage supply? How
about incorrect setup of the JK?
***

So i need A buffer. The buffer should have no Voltage swing at the
output(very important) as i want the mosfet to be either fully on or
off.I cannot find one anywhere. Does anybody know a website that will
sell buffers suitable for my application i.e. supply voltage of about
12 V and no voltage swing at the output. I know there are many other
things in buffer but dont worry about that! I would really appreciate
any help. Thanks!

Regards,
Tamim

If you could be a little more complete, it would be easier to help you
with your circuit. ID of the JK and the MOSFET, and how they
are connected, would be helpful.

Tim

There are special chips out there to drive MOSFETs. While I may not use
one, I'd hesitate to use an innocent little CMOS logic chip for the job.

If its excess current from the flip-flop you can use a series resistor.
This'll slow down the gate drive.

When you try to switch your MOSFET it will cause large voltage swings on the
drain. This will couple into the gate, which may very well exceed the
ratings of your flip-flop.

Give us more detail, and we'll give you more than guesses.