Re: SSTC Related: Shottky Diodes Unnecessary!!

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "by way of Terry Fritz <teslalist-at-qwest-dot-net>" <dhmccauley-at-spacecatlighting-dot-com>


The big deal is that is depends on how exactly you are driving your FETs.
Remember when you are switching an any type of complex load (i.e.
inductance), there is always a reverse current produced when the current is
turned off.  You need to provide
a path for this current during the duration that neither FET is carrying any
load current.  Typically, the internal MOSFET diode can handle except the
reverse recovey time of this diode is
very poor.   It basically has a slow turn-off time and will continue to
conduct when the opposite FET starts conducting.

My current SSTC coil is running between 1-2kW depending on whether is half,
full, or DC input and the FETs usually fail without these hefty
free-wheeling diodes in place.
Sure, you can take your chances and eliminate them (as in your case - your
design doesn't seem to require them), but when you are using FETs that are
over $50.00 apiece, every
bit of protection is good.

Dan