Dimming 120VAC Incandescent Light using IGBT rather than TRIAC or SCR

Ryan

Hi,
·· I'm doing a project where I would like to control a standard incandescent light bulb (like 60-100W, 120VAC, 60Hz) with the SX.· This would include on/off and dimming.· Traditionally, TRIACs or SCRs are used to dim lamps by use of "phase control".· This means you turn on the lamp during a certain phase of the AC sine, then back off when at the zero-crossing point.· This leads to high EMI and noisy light bulbs, as the current spike during the turn-on causes vibrations of the filament.· After doing a bit of research, I've discovered that IGBTs (Insulated Gate Bipolar Transistors) have the ability of being turned off anytime during the phase (TRIACs and SCRs·can only be turned off during the zero-crossing of the waveform).· Therefore, "reverse phase control" can be used, which greatly reduces the EMI of the circuit, along with quieting the light bulb.· This approach has just recently been used commercially.
·· My problem is that I don't know a thing about IGBTs, so I'm wondering if anybody else does.· More specifically, I'm wondering what the best way is to electrically·interface a SX to the gate of an IGBT (using an optocoupler).· I can't find any useful schematics on the net.· If I could get a good electrical interface working, then the code to detect zero-crossings and do "reverse phase control" should be no problem.· If anybody has any advice, I'd greatly appreciate it!

Thanks,
Ryan

PJMonty

Ryan,

I went to google and typed "IGBT dimmer schematic". On page two, the ninth entry was this (or mostly, I manually went up a page after going to actual link):

www.circuitcellar.com/zilogdtd2000/Third.htm

Go there. It's an entry to a CircuitCellar contest. The entry is called "DMX512 Dimmer". Here's a bit from the abstract:

Using IGBT drivers allows the dimmer to handle up to 500 W. By using IGBTs to control the lights, the dimming can start on the leading edge of the power cycle. This allows for a smooth turn on/off, thereby eliminating the rapid rise times that produce noise. This design eliminates costly noise filtering and extends the life of the lights by reducing thermal shock.

Sound good? The email address of the guy who designed it is on the page. Email him.

When you're done with that, go here:

www.st.com/stonline/prodpres/discrete/igbt/dimmer.htm

STMicroElectronics makes IGBTs specifically for lighting dimmers.

After that, go get this file:

www.microchipc.com/sourcecode/PIC_Hi-Tech_C_Mike_Pearces_phase_controller_TRIAC_or_IGBT_50-60Hz.zip

It has PIC code in C for dimming either a triac or an IGBT. It also has a schematic, although the schematic only has the triac portion of the circuit. However, the author's email is in the ZIP file. Email him.

Here's an URL to a different forum with a thread on this exact topic:

www.electronicshelp.net/ftopic60.html

I'm not sure if they ever got the topic answered completely, but I would try jumping in there as well.

Here's another forum where someone was trying to do the same thing. The person who started the topic has posted 376 times, and the most recent post was a few days ago, so you know he's active.

www.edaboard.com/ftopic81366.html

Join that board and send him a message to see if he ever got his circuit working. He said he would post it if he did, so it sounds like he's willing to share info.

That's what I found when I looked. You should definitely try and contact some of these people.

Thanks, PeterM

Ryan

PeterM,

Thanks so much for all of the info.

I've sent e-mails to people/forums you mentioned, and I'll post any information I get back here, in case anybody else has the same question.

I'm really hoping that Charles, the guy who did the Circuit Cellar project, replies, because that would be most useful.· It amazes me that there isn't more information out on the net about this topic... I guess nobody wants to move away from using TRIACs.

If anybody has any further info, please let me know.

Thanks for the help!

Ryan