Searching \ for '[EE]: Reverse Phase Dimming' in subject line. ()
Make payments with PayPal - it's fast, free and secure! Help us get a faster server
FAQ page: www.piclist.com/techref/index.htm?key=reverse+phase+dimming
Search entire site for: 'Reverse Phase Dimming'.

Exact match. Not showing close matches.
PICList Thread
'[EE]: Reverse Phase Dimming'
2003\04\25@050804 by Mirko Bakocevic

flavicon
face
Reverse Phase Dimming or Reverse Phase control, does anyone has some
references?
I would use it for light control. I would be glad to see IGBT in such
circuit.
Thanks

--
http://www.piclist.com#nomail Going offline? Don't AutoReply us!
email spam_OUTlistservTakeThisOuTspammitvma.mit.edu with SET PICList DIGEST in the body

2003\04\25@091619 by Chris Loiacono

flavicon
face
Do you mean phase control with GTO thyristors? This is the only 'reverse'
method I have seen done successfully. I spoke with someone who was thinking
about doing so with transistors, but I don't rmember the outcome. I will
re-check to see what I may have saved on the subject.
Chris

> {Original Message removed}

2003\04\25@235914 by Michael Reid

picon face
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.



An IGBT driver turns the output ON at the zero cross point and turns

the output OFF part way through the cycle - this has really low

EMI properties and is one of the few methods allowed for phase control

in European countrys (i.e complies with EN55015 EMI standard).

Other countries are following suit for example New Zealand and Austrailia

are almost there (See AS/NZS 4051 and CISPR15 EMI Standards )

This method of dimming is audibly quiet, does not require extra filter

componets (If designed properly).It also has a better lamp life and can

control a wider range of lamps than the TRIAC method of dimming.









Reverse Phase Dimming or Reverse Phase control, does anyone has some
references?
I would use it for light control. I would be glad to see IGBT in such
circuit.
Thanks

--
http://www.piclist.com#nomail Going offline? Don't AutoReply us!
email .....listservKILLspamspam@spam@mitvma.mit.edu with SET PICList DIGEST in the body

--
http://www.piclist.com#nomail Going offline? Don't AutoReply us!
email listservspamKILLspammitvma.mit.edu with SET PICList DIGEST in the body

2003\04\26@024633 by Harold Hallikainen

picon face
    Is there any reason a reverse phase control dimmer would have less conducted emissions than a forward phase control dimmer if the rise (or fall) times are the same? It seems the conducted EMI spectrum is entirely a function of the speed of the on/off transition.
    I understand that non-triac dimmers have low conducted EMI because of slow transitions in the turn on/off. This slow edge reduces EMI and efficiency. However, chokes used in triac dimmers also have some losses. It'd be interesting to compare efficiencies between choke and non-choke dimmers.
    My (perhaps wrong) understanding of IGBTs is that they are kinda like a BJT with a FET between the base and the collector. This limits the saturation voltage to Vbe, typically about 700mV. A regular BJT would have  a saturation voltage of 300mV or so, and an FET would be even lower.
    Of course the IGBT, BJT, or FET are DC devices. You could add a diode bridge or another device and steering diodes to handle AC. This adds complexity and increases the saturation voltage further.
    Then there's the problem of driving this device. You want to have isolation between the PIC and the power device (like the good ol' MOC3020), but there's no simple way to do it.
    So, it's an interesting problem. For now, I'm using triacs (or SCR pairs).

Harold


________________________________________________________________
The best thing to hit the internet in years - Juno SpeedBand!
Surf the web up to FIVE TIMES FASTER!
Only $14.95/ month - visit http://www.juno.com to sign up today!

--
http://www.piclist.com hint: To leave the PICList
.....piclist-unsubscribe-requestKILLspamspam.....mitvma.mit.edu>

2003\04\26@101827 by Michael Reid

picon face
For the foreseeable future all of our dimmers will also be TRIAC based.  The
IGBT defenders claim that without the need for snubbers and chokes, etc.
they are cost competitive.  However, I can purchase a 40 Amp TRIAC (800V)
for about $2.00  Try that with an IGBT, and the fact that you have to use 2
of them.

The lower emissions from reverse phase dimming come from turning off in the
middle of the cycle vs. turning on in the middle like a TRIAC.

I was in a CE testing lab a few years ago in England where we were testing
our US designed dimmer to pass. It was a standard 2 SCR design with a
snubber and 68 uh small choke on the output.  A very standard text book
design.  It failed miserably on the conducted emissions test. To pass we
added a complex LRC filter on the circuit.  It would not be a practical
design from a cost perspective.

One of the biggest pushes for reverse phase dimming is pushed by
manufacturers of electronic low voltage transformers.  Many of these only
work with reverse phase dimming. With the growing popularity of low voltage
lighting systems (12 and 24 vdc) there are more and more of these types of
transformers on the market.  Most are 50-100 watt electronic switching
supplies.  Some manufactures have designed them to work with standard
TRIAC/SCR based dimmers as they see the price difference in the dimmers and
the lack of reverse phase dimmers from many manufacturers

Here are some links on IGBT dimming:

http://www.lolcontrols.com/products/Compli_ILS/compli_ILSroadshow.asp

http://www.rosco-et.com/capio_press.htm

http://www.etnow.com/news/features/generationgame.htm



{Original Message removed}

2003\04\26@135827 by Oliver Broad

flavicon
face
I can't figure this one out at all.
Either something switches fast and noisy, slow and quiet (and hot) or it
employs some kind of filtering.

The only explanation I can think of for reverse phase dimming is it could
function with a large parallel capacitor to soften the switch-off losslessly
and I suppose capacitors are cheaper than chokes.

A triac requires a series choke to soften it's switch-on current spike.
Since the voltage across the triac will collapse rapidly and may ring a
substantial RC snubber (not just a capacitor) will be needed in parallel
with the triac.

Also I notice a number of mains filters are capacitor-ended rather than
choke-ended which is completely wrong for a triac, and I suppose that in the
worst instance with a filter between line in and neutral then RFI would be
dumped into the lamp leads leading to a common mode current that would be
very hard to filter.

I was asked to advise on a low noise heater control system for a specialist
application. After prolonged discussions on the unfeasibility of phase angle
we decided on a variable output DC supply as the power controller, with
either the current or voltage being controlled by the PID temperature
controller. Expensive option though.

Oliver.

{Original Message removed}

2003\04\26@170041 by Wagner Lipnharski

flavicon
face
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.


I always wanted to do an AC-PWM type of dimmer.
Never read anything against, nor in favor.

The PWM is based on the 60Hz from the AC power, a simply microcontroller or
even a counter controls a Zero Crossing Detector to fire a TRIAC, keeps it
on for one, two, n cycles, turn it off, keeps it off for one, two, n
cycles, like a PWM, with the pulse resolution to be exactly 16.66ms
synchronized by the street AC.

For a large incandescent lamp, it doesn't matter to receive 2 whole AC
cycles ON and 1 cycle OFF, to run at 66.6% of the power. The heavy
incandescent filament will not blink or cintilate since it takes almost one
second (or more) to get fully bright and more than that to cool down, so,
the filament itself will serve as a cintilation filter.

Cycles ON   Cycles OFF    % Power  Status
---------   ----------    -------  ------
  1          0            100       a
  9          1             90       b
  8          1             88       c
  7          1             87       d
  6          1             85       e
  5          1             83       f
  4          1             80       g
  3          1             75       h
  5          2             71       i
  4          2             66       j
  5          3             62       k
  3          2             60       l
  5          4             55       m
  1          1             50       n
  ...       ...            ...      ..

Other than the load will receive an interrupted rate of whole sinewaves,
everything else should be fine.
Even at 50% power (1x1), the load will receive 30 whole sinewaves per
second, no noise, no EMI, I suppose.

The software algorithm for such thing should be quite easy.
The Zero Cross Detector interrupts the microcontroller each time it crosses
zero.
The microcontroller divide it by two so it gets a whole sinewave period
(16.66ms).
The uC inserts a 14ms delay after the "even" interruption (even delayed
interrupt), and decides that at the next interrupt (zero crossing) the
power should be;

x) Removed
y) Applied

Once the user set the Status desired (a-n) the microcontroller loads the
relative PWM values and start operating. Suppose the selecetd was "d", 87%,
values loaded would be 7=ON, 1=OFF.

It loads the values, waits for the first "even" delayed interrupt and turn
ON the TRIAC (at zero crossing) if the "ON" value is bigger than zero, and
decrement it.  If the ON value is zero than the operation is over OFF
counter, at this time turning OFF the TRIAC at zero crossing.  When both
counters are zero, they are reload with the table values, in the example, 7
and 1.

The example will results in a load receiving power in a train of 7
sinewaves (116ms) and skiping just one sinewave (16.6ms), cycle repeating
itself.

Some loads require 60Hz, others don't.
What about not-sync motors? how they would react?

Is this solution already exist?

Wagner

--
http://www.piclist.com hint: To leave the PICList
EraseMEpiclist-unsubscribe-requestspam_OUTspamTakeThisOuTmitvma.mit.edu>

2003\04\26@173110 by erholm (QAC)

flavicon
face
Wagner Lipnharski wrote:
[about only switching TRACS'at the zero crossing pont]

Sounds interesting !
Just a minor point...

Take this setting as an example :

> Cycles ON   Cycles OFF    % Power  Status
> ---------   ----------    -------  ------
>    5          4             55       m

Here, we have a "blink" frequency of 1 / (9 * 0.20) =
aprox 5.5 Hz. Now, I don't know if this is visible,
but, as having a son with epilepsy, I know the *some* people
are very sensistive to flickering lights, even those
not *visible* to us "others".

As an example, when taking out money at the automatic
teller machine, my son can't look at the screen, just
becuse someone selected to use a "low cost" CRT with a low
scan freq in the unit.
And he can't look at a 50Hz TV set, it have to be a 100Hz set.
On his computer we have installed a LCD screen, and so on.

Anyway, what I ment was that we should be easy with
flickering lights, because there are many "out there"
that has big problems with them...

Jan-Erik Soderholm.

--
http://www.piclist.com hint: To leave the PICList
piclist-unsubscribe-requestspamspam_OUTmitvma.mit.edu>

2003\04\27@085831 by Chris Loiacono

flavicon
face
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.
{Quote hidden}

--
http://www.piclist.com hint: PICList Posts must start with ONE topic:
[PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

2003\04\27@125425 by Wagner Lipnharski

flavicon
face
Jan-erik Soderholm (QAC) wrote:
{Quote hidden}

I agree with you, but there is a difference in response time from a CRT and
an incandescent lamp.
The CRT phosphor should react very fast, well, at least for our eyes, its
"persistance" should be enough to allow the trace to scan all the image and
get back, I guess it is no more than 1/20 of a second.  The persistance of
a incandescent lamp is a little bit higher, I guess more than 1/2 of a
second, mostly for lamps 100W or more.

The 1/9 blink "off" rate would be 60/9 = 6.66 per second, with a "off" time
of only 16.66ms.

Recently I built a SMT soldering oven with a 800ms PWM rate.  When the
thermal elements are bright red, and reach the desired temperature, the
electronics (an AVR and a solid state relay) keeps the temperature floating
via a glass NTC sensor into the oven.  Even with a 50% power applied under
a gross power control (zero crossing at the relay), you can only notice the
neon lamp blinking at the front of the oven, the elements just reduce the
red bright, but no cintilation at all, even with 800ms of on/off.  Of
course, that is not a lamp, and the persistance is much bigger than a
regular incandescent lamp.  The oven control is not in sync with the power
lines single sinewaves, just a crude PWM with a resolution of 800ms.

<out of control brainstorming>

I wonder why, up to now, nobody produced any kind of glasses using lenses
made from some kind of translucid fluorescent polymer with a capacity to
store photons energy for some milliseconds.  Even being a very difficult
task, including wide spread light wash (all over the lens) and monochrome
lag, in time and technology, it could help somehow the epilepsy people who
suffer with light cintilation.  Even gel contact lenses (with or without
correction degrees) could be produced for this purpose.  The counter effect
is the viewed image turns to be a little greenish, but in time the brain
compensantes it.

</out of control brainstorming>

Wagner.

--
http://www.piclist.com hint: PICList Posts must start with ONE topic:
[PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

2003\04\27@173900 by Peter L. Peres

picon face
>I always wanted to do an AC-PWM type of dimmer.
>Never read anything against, nor in favor.

You can read about one, in this thread:

[PIC]: Squirrel cage fan motor or heater control (xfan1)

which implements it for an interrupt-less 12C508 (can use 16F84 oe 628 for
testing). The thread is from March 2002.

A simpler one can be built using a programmable CMOS counter.

Peter

--
http://www.piclist.com hint: PICList Posts must start with ONE topic:
[PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

2003\04\27@180044 by William Chops Westfield
face picon face
>> Cycles ON   Cycles OFF    % Power  Status
>> ---------   ----------    -------  ------
>>    5          4             55       m

So you should be able to do ON OFF ON OFF ON ON OFF ON OFF, and otherwise
distribute your on/off cycles so as to avoid MOST of the flicker, right?

BillW

--
http://www.piclist.com hint: PICList Posts must start with ONE topic:
[PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

2003\04\27@180659 by David Duffy

flavicon
face
Wagner Lipnharski wrote:
> Jan-erik Soderholm (QAC) wrote:
>
>>Wagner Lipnharski wrote:
>>[about only switching TRACS'at the zero crossing pont]
>>
>>Sounds interesting !
>>Just a minor point...
>>
>>Take this setting as an example :
>>
>>
>>>Cycles ON   Cycles OFF    % Power  Status
>>>---------   ----------    -------  ------
>>>   5          4             55       m
>>
>>Here, we have a "blink" frequency of 1 / (9 * 0.20) =
>>aprox 5.5 Hz. Now, I don't know if this is visible,
>>but, as having a son with epilepsy, I know the *some* people
>>are very sensistive to flickering lights, even those
>>not *visible* to us "others".
<snip>
> I agree with you, but there is a difference in response time from a CRT and
> an incandescent lamp.
> The CRT phosphor should react very fast, well, at least for our eyes, its
> "persistance" should be enough to allow the trace to scan all the image and
> get back, I guess it is no more than 1/20 of a second.  The persistance of
> a incandescent lamp is a little bit higher, I guess more than 1/2 of a
> second, mostly for lamps 100W or more.

Some theatrical dimmers use "dimmer doubling" where they control the
half cycles independently. The output from the dimmer is fed to two
lamps with a diode in series with each arranged so that one lamp gets
the +ve cycles and one gets the -ve cycles. The system uses 77V lamps
instead of 120V. (US based) The dimmer desk has two faders for each
dimmer output. From what I've heard, the lamps don't seem to suffer
from flicker but then again, they're higher wattage than usual being
in the range of 500W - 1000W usually.
David...

--
http://www.piclist.com hint: PICList Posts must start with ONE topic:
[PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

2003\04\27@183848 by

flavicon
face
Wagner Lipnharski wrote:
> The 1/9 blink "off" rate would be 60/9 = 6.66 per second, with a "off" time
> of only 16.66ms.

Yes, in *some* countries like Cuba, Guam and Panama. But in just about
every western, developed country it would be "50/9 = 5.55" and "20.00ms"...

:-)

Jan-Erik.

--
http://www.piclist.com hint: PICList Posts must start with ONE topic:
[PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

2003\04\27@222309 by Wagner Lipnharski

flavicon
face
William Chops Westfield wrote:
>>> Cycles ON   Cycles OFF    % Power  Status
>>> ---------   ----------    -------  ------
>>>    5          4             55       m
>
> So you should be able to do ON OFF ON OFF ON ON OFF ON OFF, and
> otherwise distribute your on/off cycles so as to avoid MOST of the
> flicker, right?
>
> BillW


That's right. The 5/4 doesn't mean exactly in sequence.

Wagner.

--
http://www.piclist.com hint: PICList Posts must start with ONE topic:
[PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

More... (looser matching)
- Last day of these posts
- In 2003 , 2004 only
- Today
- New search...