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mosfet gate driving problem

E

exxos

Jan 1, 1970
0
Hi all,

I have a problem when driving a mosfet via gate driver IC's. The input wave
has some noise on it and its causing the gate drive IC to turn on when its
not supposed to. This is happending on the rise and fall of the drive wave.
Such as on the rise its switching on and off very fast (probably in the mhz
range) before actually staying on with the input wave. . The only half
solution is to use very slow gate driver IC's which seem not to be able to
react fast enough to this oscilation and thus smoothing it out a bit. Though
its by far a cure.... anyone any ideas what I can do to filter out this
noise and stop the mosfets from turning on when they are not supposed to ?

thanks,
Chris
 
C

CWatters

Jan 1, 1970
0
exxos said:
Hi all,

I have a problem when driving a mosfet via gate driver IC's. The input wave
has some noise on it and its causing the gate drive IC to turn on when its
not supposed to. This is happending on the rise and fall of the drive wave.
Such as on the rise its switching on and off very fast (probably in the mhz
range) before actually staying on with the input wave. . The only half
solution is to use very slow gate driver IC's which seem not to be able to
react fast enough to this oscilation and thus smoothing it out a bit. Though
its by far a cure.... anyone any ideas what I can do to filter out this
noise and stop the mosfets from turning on when they are not supposed to ?

Lots of ways.. anything from a simple RC low pass filter and a gate with
some hysterisis to a single chip microprocessor (code would be similar to
that used to debounce a keyboard).
 
E

exxos

Jan 1, 1970
0
CWatters said:
Lots of ways.. anything from a simple RC low pass filter and a gate with
some hysterisis to a single chip microprocessor (code would be similar to
that used to debounce a keyboard).

mmmm, there are debounce Ic's though these are for switches, they operate
around 25ms, my bounce time is 0.1uS, a LP filter may work....

Chris
 
C

CWatters

Jan 1, 1970
0
exxos said:
found this one also, looks good aswell...

http://www.ee.ttu.edu/lab/robot/hyster.htm

If your source is digital the unwanted spikes are probably rail to rail and
would go right through the circuit on that page. You need the RC filter to
eliminate short spikes AND the Schmitt to eliminate noise introduced by the
slower rise/fall times after the RC.

Sorry if you know this stuff.
 
K

Ken

Jan 1, 1970
0
I have a problem when driving a mosfet via gate driver IC's. The input wave
has some noise on it and its causing the gate drive IC to turn on when its
not supposed to. This is happending on the rise and fall of the drive wave.
Such as on the rise its switching on and off very fast (probably in the mhz
range) before actually staying on with the input wave. . The only half
solution is to use very slow gate driver IC's which seem not to be able to
react fast enough to this oscilation and thus smoothing it out a bit. Though
its by far a cure.... anyone any ideas what I can do to filter out this
noise and stop the mosfets from turning on when they are not supposed to ?


http://www.avxcorp.com/docs/techinfo/mlcbypas.pdf
 
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