DIY studio strobe
in [Design]
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From: Jim Thompson on 29 Jan 2010 19:44 On Fri, 29 Jan 2010 18:31:33 -0600, John Fields <jfields(a)austininstruments.com> wrote: >On Sat, 30 Jan 2010 00:10:06 +0100, El Loco Mateo <ellocomateo(a)free.fr> >wrote: > >>On 2010-01-29 15:19, MooseFET wrote: >>> If you know about MOSFETs and bipolar transistors, you and think of an >>> IGBT as an N channel MOSFET feeding a PNP transistor. >>> >>> You need to apply a pulse to the gate of the IGBT that is about 10V >>> tall and lasts for as long as you want the current to flow. The gate >>> of the IGBT must be moved from near zero to the near 10V and back >>> quickly. Holding it high and low is the easy part. >>> >>> The IGBT must be in the path of the current through the tube. You >>> can't control the tube via the trigger electrode once it is fired. >>> The plasma inside the tube is a short circuit. You need to open one >>> end connection of the tube by turning off the IGBT in that path. >> >>Thank you both for your comments! Is an IGBT the only solution to >>achieve my goal? What other alternative do I have, should I want to >>reach currents higher than say 150A? > >--- >Not trying to be difficult, but are you sure you understand the comments >stating that in order to stop the discharge through the tube you must >interpose a switch between either the high or the low end of the tube >and what that end is connected to? > >JF One of my early patents... 3,496,411 Timing Circuit for a Flash Camera (PDF on my website) One of those rare and amazing situations where an engineer in another department at Motorola came by and asked a lot of questions. He went away and tried my suggestions... they worked... and he told the patent attorney I was the inventor :-) ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
From: John Fields on 29 Jan 2010 20:05 On Fri, 29 Jan 2010 17:44:06 -0700, Jim Thompson <To-Email-Use-The-Envelope-Icon(a)My-Web-Site.com> wrote: >On Fri, 29 Jan 2010 18:31:33 -0600, John Fields ><jfields(a)austininstruments.com> wrote: > >>On Sat, 30 Jan 2010 00:10:06 +0100, El Loco Mateo <ellocomateo(a)free.fr> >>wrote: >> >>>On 2010-01-29 15:19, MooseFET wrote: >>>> If you know about MOSFETs and bipolar transistors, you and think of an >>>> IGBT as an N channel MOSFET feeding a PNP transistor. >>>> >>>> You need to apply a pulse to the gate of the IGBT that is about 10V >>>> tall and lasts for as long as you want the current to flow. The gate >>>> of the IGBT must be moved from near zero to the near 10V and back >>>> quickly. Holding it high and low is the easy part. >>>> >>>> The IGBT must be in the path of the current through the tube. You >>>> can't control the tube via the trigger electrode once it is fired. >>>> The plasma inside the tube is a short circuit. You need to open one >>>> end connection of the tube by turning off the IGBT in that path. >>> >>>Thank you both for your comments! Is an IGBT the only solution to >>>achieve my goal? What other alternative do I have, should I want to >>>reach currents higher than say 150A? >> >>--- >>Not trying to be difficult, but are you sure you understand the comments >>stating that in order to stop the discharge through the tube you must >>interpose a switch between either the high or the low end of the tube >>and what that end is connected to? >> >>JF > >One of my early patents... > > 3,496,411 Timing Circuit for a Flash Camera (PDF on my website) > >One of those rare and amazing situations where an engineer in another >department at Motorola came by and asked a lot of questions. He went >away and tried my suggestions... they worked... and he told the patent >attorney I was the inventor :-) > > ...Jim Thompson --- I've always liked Motorola. ISTM they've always been pretty straight-up kind of folks and your experience adds credence to my belief. Do you remember when they used to make capacitors? JF
From: Jim Thompson on 29 Jan 2010 21:06 On Fri, 29 Jan 2010 19:05:37 -0600, John Fields <jfields(a)austininstruments.com> wrote: >On Fri, 29 Jan 2010 17:44:06 -0700, Jim Thompson ><To-Email-Use-The-Envelope-Icon(a)My-Web-Site.com> wrote: > >>On Fri, 29 Jan 2010 18:31:33 -0600, John Fields >><jfields(a)austininstruments.com> wrote: >> >>>On Sat, 30 Jan 2010 00:10:06 +0100, El Loco Mateo <ellocomateo(a)free.fr> >>>wrote: >>> >>>>On 2010-01-29 15:19, MooseFET wrote: >>>>> If you know about MOSFETs and bipolar transistors, you and think of an >>>>> IGBT as an N channel MOSFET feeding a PNP transistor. >>>>> >>>>> You need to apply a pulse to the gate of the IGBT that is about 10V >>>>> tall and lasts for as long as you want the current to flow. The gate >>>>> of the IGBT must be moved from near zero to the near 10V and back >>>>> quickly. Holding it high and low is the easy part. >>>>> >>>>> The IGBT must be in the path of the current through the tube. You >>>>> can't control the tube via the trigger electrode once it is fired. >>>>> The plasma inside the tube is a short circuit. You need to open one >>>>> end connection of the tube by turning off the IGBT in that path. >>>> >>>>Thank you both for your comments! Is an IGBT the only solution to >>>>achieve my goal? What other alternative do I have, should I want to >>>>reach currents higher than say 150A? >>> >>>--- >>>Not trying to be difficult, but are you sure you understand the comments >>>stating that in order to stop the discharge through the tube you must >>>interpose a switch between either the high or the low end of the tube >>>and what that end is connected to? >>> >>>JF >> >>One of my early patents... >> >> 3,496,411 Timing Circuit for a Flash Camera (PDF on my website) >> >>One of those rare and amazing situations where an engineer in another >>department at Motorola came by and asked a lot of questions. He went >>away and tried my suggestions... they worked... and he told the patent >>attorney I was the inventor :-) >> >> ...Jim Thompson > >--- >I've always liked Motorola. > >ISTM they've always been pretty straight-up kind of folks and your >experience adds credence to my belief. > >Do you remember when they used to make capacitors? > >JF I didn't know that. I was only at Motorola from 1962-1970. (Though I did do later chip designs for both Motorola and ON-Semi... as a contractor.)) ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
From: Don Klipstein on 30 Jan 2010 01:37 In article <4b636ad8$0$5384$426a34cc(a)news.free.fr>, El Loco Mateo wrote: >On 2010-01-29 15:19, MooseFET wrote: >> If you know about MOSFETs and bipolar transistors, you and think of an >> IGBT as an N channel MOSFET feeding a PNP transistor. >> >> You need to apply a pulse to the gate of the IGBT that is about 10V >> tall and lasts for as long as you want the current to flow. The gate >> of the IGBT must be moved from near zero to the near 10V and back >> quickly. Holding it high and low is the easy part. >> >> The IGBT must be in the path of the current through the tube. You >> can't control the tube via the trigger electrode once it is fired. >> The plasma inside the tube is a short circuit. You need to open one >> end connection of the tube by turning off the IGBT in that path. > >Thank you both for your comments! Is an IGBT the only solution to >achieve my goal? What other alternative do I have, should I want to >reach currents higher than say 150A? I have heard of GTO ("Gate TurnOff") SCRs being used in applications like these. I have also heard of MOSFETs and IGBTs being used for this. One fault of IGBTs that I have heard in a bit of older literature (mid 1980's or a few years older) is that they, "in my words", are "latched-conductive" when current exceeds some amount. MOSFETs have a different fault - their "on resistance" varying directly with temperature, to extent of being roughly or even over double that of Tj=25 C (which the nominal figure usually is) at the highest Tj at which they are rated to operate continuously. - Don Klipstein (don(a)misty.com)
From: Tim Williams on 30 Jan 2010 02:11
"Don Klipstein" <don(a)manx.misty.com> wrote in message news:slrnhm7kt3.b5b.don(a)manx.misty.com... > I have heard of GTO ("Gate TurnOff") SCRs being used in applications > like these. I have also heard of MOSFETs and IGBTs being used for this. Ever heard of MCT's? MOS triggered SCRs. Apparently important for big power, but I've never seen one for sale anywhere (and come on, I can buy a megawatt SCR from Digikey right now). > One fault of IGBTs that I have heard in a bit of older literature (mid > 1980's or a few years older) is that they, "in my words", are > "latched-conductive" when current exceeds some amount. All the manufacturers are saying that's fixed now. Collector characteristics often go up to 300A+ on a 50A device. Then again, I get concerned when they *don't*. Makes me wonder about this 1200V 50A IGBT module I have... it's kind of old, date code something in the 80s. Not sure I can trust it for actual duty, not in my hands... (Not that I have any 480V three phase in the house anyway!) > MOSFETs have a different fault - their "on resistance" varying directly > with temperature, to extent of being roughly or even over double that of > Tj=25 C (which the nominal figure usually is) at the highest Tj at which > they are rated to operate continuously. Plus being approximately resistive (and rising at higher currents), MOSFETs are quite poorly suited to a pulsed power application like this. In fact, the deliciously low Vce(sat) of an IGBT, even at high peak currents, makes them particularly well suited to this application. What else is there to reflect on... BJTs? Imagine the darlington you'd need to switch a flash tube. ;-) Tim -- Deep Friar: a very philosophical monk. Website: http://webpages.charter.net/dawill/tmoranwms |