John Larkin said:
On 8 Feb 2005 16:51:22 -0800, "Paul Mathews" <
[email protected]>
wrote:
As I told Speff, we have NTC surge limiters and TT fuzes, so that
seems to be under control.
John
Hi John:
I hit this problem (too) many years ago on a switcher - no toroid, but
serious
issues on inrush current "burning" switch contacts. Even back then the
NTC thermistor was an often used solution, but had a major problem
with time constant - there always seemed to be some timing of the user
"mis-hitting" the power switch that would bypass the protection.
What I did was to put a high voltage power MOSFET inside a bridge
rectifier in series with the input, arranged to always turn on, with a real
simple
R/transistor current sense to turn it off when the instantaneous current
exceeded a set point (together with gate protection). Worked a treat.
No idea if this would now fall foul of CE harmonics legislation, ask
John Woodgate. There may now be easier ways to do this, but it was
pretty cheap even back then.