Homebrew PCBs

On Tue, 21 Jun 2005 18:45:30 +0200, Phil <phil1960us@...> wrote:

>
> Also, I wasn't aware that the kickback waveform speed was related to
> the drive frequency.  I thought it was intrinsic to the driver and
> windings (and mechanical design) of the motor.  To be good enough, the
> diode needs to let less energy though than can damage the driver (er,
> shunt it off).  The reverse recovery time of the diode needs to be
> fast enough for that.  Some energy will get through so the issues are
> driving voltage and switching time.  I've heard that typical
> rectifiers have a Trr of about .5 uS.  Unfortunately, this isn't
> spec'd.  Schottkys are in the range of 10s of nS so there is a big
> gap.  Unfortunately no one seems to document Trr on the spec sheets
> for barrier schottkys, either.  sigh.


Hmm, interesting theory, i would still think there is some relation to  
drive speed.

For example, if you look at a relay, most wouldn't argue that a 400x is  
not ok.

But your point makes sense.
Well, hopefully the diodes in the FETs will catch the mess (if FETs are  
used)

ST