I am familiar with the CE requirements and several other standards. The
Problem is primarily one of insufficient information. I have found (with the
help of others) ways to phase angle control some large loads with all kinds
of thyristor devices and combinations with EMI levels that would satisfy
most standards. Low voltage can be done extremely well without filters if
the transformation is carefully planned. None of them are very standardized
however. There is too little taught on the subject and even less documented.
For example, a simple increase in resistance between the gate and the
properly polarized main terminal makes a tremendous reduction in noise.
Capacitance changes between layers hs similar effects. Different
manufacturer's devices range the full spectrum in these characteristics and
the standards have been written to not favor one manufacturer or another. I
have collected information that keeps my forward-phase angle circuits quiet
only because of having figured out internal device characteristics.
Can someone explain more clearly why reverse control is supposed to be
quieter? all the rules say that when you open a controlling device's circuit
at high voltage that there will be a large spike. There must be a reason
this doesn't happen when reverse controlling???


BTW, Here's another interesting one to try - One of my newer controller
designs does both zero-cross firing or phase angle on the same board. The ZC
firing proportion can be set to take advantage of combinations of 1/2 waves
instead of full-waves, thus doubling the resolution of a standard ZC
controller and giving the user control in roughly 1% increments. Although
it's normally thought of for heater loads rather than lighting, this baby
runs lamps down to the 20 - 30% range before flicker is noticeable (to
someone without epilepsy, that is.) It has found allication in short-wave-IR
industrial applications and is OK for US or Europe.
> Michael Reid wrote:
> > I work for a manufacturer of home lighting control systems and the
> > TRIAC vs. reverse phase dimming (or lagging edge dimming) has heated
> > up in the past few years.  CE approvals in Europe and other parts of
> > the world test for emmitted emissions and conducted
> emissions.  TRIAC
> > dimmers need massive amounts of filtering to pass CE.  Some of my
> > clients claim that TRIAC dimming is against code in some countries
> > due to the high EMI output as they turn on part way through the
> > cycle. My previous company, Vantage Lighting has a reverse phase
> > dimmer that uses MOSFETS.  It is expensive and limited to 6 amps per
> > channel, and is very easily blown.  Of course they use 2 MOSFETs per
> > dimmer. There are a number of commercial IBGT dimmers on the market.
> > We've done some testing of IGBT's for dimming and they do run a
> > little hotter than TRIAC's and cost more.
> >
> > Here is some info from a document I found on my computer.
> I think it
> > is from an engineer in New Zealand by the name of Mike Pearce.  He
> > has a PIC design for a dimmer with code for both types of dimming.
> > If anyone wants the files I can send them to you.

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