On Mon, 23 Nov 2015 10:40:11 -0700, Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote:>On Mon, 23 Nov 2015 09:19:02 -0800 (PST), habib.bouaziz@gmail.com >wrote: > >>Le lundi 23 novembre 2015 17:57:39 UTC+1, Winfield Hill a �crit�: >>> habib.bouaziz@gmail.com wrote... >>> > >>> >--> Vgs becomes smaller when current is increasing through >>> > 100 Ohm resistor >>> > --> then vgs becomes smaller ... There it may have needs >>> > some math or Spice simulation isn't it ? >>> >>> This is likely intentional, because it effectively creates >>> a current limit, which is desirable. Of course the FETs >>> have to be able to handle this. Ultimately the 1.5kV >>> supply will sag and shut down. The current limit would >>> act until the HV byass capacitors are drained. >>> >>> >>> -- >>> Thanks, >>> - Win >> >>Of course as you say "1.5kV supply will sag and shut down". >>E(capacitors) = 1/2 * C * V *V = 0.5J >>P max admissible for th MOSFET = 80W >> >>Let's say the discharge time is about Td = 10ms >> >>E = P.t then P = 50W --> Ok for the MOSFET >> >>But if Td = 1ms the P = 500W --> The MOSFET should blow >> >>May be i missed something ... >> >>Habib. > >If there's no photo current in either input loop, the 2SK4177's are >OFF... though I'm not sure how well-behaved they are with an >essentially floating source.They have gate zeners, so a bit of d-s leakage won't blow them up. I don't think that will affect my application, either.> >Needs some kind of shut-down means to ensure no photo-current.Not sure what you mean by that. Only one opto can be on at a time. There is a 1G resistor load to ground, so the upper fet always conducts a bit. I guess I could add a big resistor or a zener to clamp the source voltage, but it probably doesn't need it. Some mosfets are surprisingly leaky, so a zener option might be prudent.
ping Win LND150 avalanche
Started by ●November 21, 2015
Reply by ●November 23, 20152015-11-23
Reply by ●November 23, 20152015-11-23
On 23/11/2015 18:49, John Larkin wrote:> On Mon, 23 Nov 2015 09:19:02 -0800 (PST), habib.bouaziz@gmail.com > wrote: > >> Le lundi 23 novembre 2015 17:57:39 UTC+1, Winfield Hill a �crit : >>> habib.bouaziz@gmail.com wrote... >>>> >>>> --> Vgs becomes smaller when current is increasing through >>>> 100 Ohm resistor >>>> --> then vgs becomes smaller ... There it may have needs >>>> some math or Spice simulation isn't it ? >>> >>> This is likely intentional, because it effectively creates >>> a current limit, which is desirable. Of course the FETs >>> have to be able to handle this. Ultimately the 1.5kV >>> supply will sag and shut down. The current limit would >>> act until the HV byass capacitors are drained. >>> >>> >>> -- >>> Thanks, >>> - Win >> >> Of course as you say "1.5kV supply will sag and shut down". >> E(capacitors) = 1/2 * C * V *V = 0.5J >> P max admissible for th MOSFET = 80W >> >> Let's say the discharge time is about Td = 10ms >> >> E = P.t then P = 50W --> Ok for the MOSFET >> >> But if Td = 1ms the P = 500W --> The MOSFET should blow >> >> May be i missed something ... >> >> Habib. > > The 100 ohm resistors and the opto CTR limit the mosfet currents. > That's not so much to protect the fets as to limit power supply dip. > > One 2SK4177 can dissipate about a kilowatt for one millisecond, and > around 3KW for 100 us. It could easily discharge all the energy that I > have available.Ok i missed the fig. ASO on page p.4/7 http://www.onsemi.com/pub_link/Collateral/ENA0869-D.PDF Since it is a one shot overload, it's ok. Apologies. Habib> >
Reply by ●November 23, 20152015-11-23
On Mon, 23 Nov 2015 20:15:49 +0100, Habib Bouaziz-Viallet <habib@nowhere.com> wrote:>On 23/11/2015 18:49, John Larkin wrote: >> On Mon, 23 Nov 2015 09:19:02 -0800 (PST), habib.bouaziz@gmail.com >> wrote: >> >>> Le lundi 23 novembre 2015 17:57:39 UTC+1, Winfield Hill a �crit : >>>> habib.bouaziz@gmail.com wrote... >>>>> >>>>> --> Vgs becomes smaller when current is increasing through >>>>> 100 Ohm resistor >>>>> --> then vgs becomes smaller ... There it may have needs >>>>> some math or Spice simulation isn't it ? >>>> >>>> This is likely intentional, because it effectively creates >>>> a current limit, which is desirable. Of course the FETs >>>> have to be able to handle this. Ultimately the 1.5kV >>>> supply will sag and shut down. The current limit would >>>> act until the HV byass capacitors are drained. >>>> >>>> >>>> -- >>>> Thanks, >>>> - Win >>> >>> Of course as you say "1.5kV supply will sag and shut down". >>> E(capacitors) = 1/2 * C * V *V = 0.5J >>> P max admissible for th MOSFET = 80W >>> >>> Let's say the discharge time is about Td = 10ms >>> >>> E = P.t then P = 50W --> Ok for the MOSFET >>> >>> But if Td = 1ms the P = 500W --> The MOSFET should blow >>> >>> May be i missed something ... >>> >>> Habib. >> >> The 100 ohm resistors and the opto CTR limit the mosfet currents. >> That's not so much to protect the fets as to limit power supply dip. >> >> One 2SK4177 can dissipate about a kilowatt for one millisecond, and >> around 3KW for 100 us. It could easily discharge all the energy that I >> have available. >Ok i missed the fig. ASO on page p.4/7 >http://www.onsemi.com/pub_link/Collateral/ENA0869-D.PDF > >Since it is a one shot overload, it's ok. Apologies. > >Habib >> >>Oh, don't apologize, we all keep learning stuff. I just did this, to better understand the mosfet. https://dl.dropboxusercontent.com/u/53724080/Parts/Fets/2SK4177_Measurements.JPG They don't guardband that 1500 volt rating much! -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Reply by ●November 23, 20152015-11-23
It looks downright readable with a simple inversion! http://seventransistorlabs.com/Images/JL_Pulser.png Guess your layout guy has their eyes upside down ;) Whoever encoded it in a JPEG, I can't help that much though. Can't quite tell if the image was antialiased to begin with, or the JPEG was just that shitty. The fine print is almost Panteltje level readability. Tim -- Seven Transistor Labs, LLC Electrical Engineering Consultation and Contract Design Website: http://seventransistorlabs.com "John Larkin" wrote in message news:ttk45blitrkc6n40rjd5g572cvcd20n8jl@4ax.com... On Sun, 22 Nov 2015 16:10:49 -0700, Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote:>On 22 Nov 2015 14:29:55 -0800, Winfield Hill ><hill@rowland.harvard.edu> wrote: > >>John Larkin wrote... >>> >>> Here's my HV regulator. It has almost zero quiescent dissipation >>> and fast programmable rise/fall times, about 1KV/ms up or down. >>> >>>https://dl.dropboxusercontent.com/u/53724080/Circuits/Power/HV_Reg_T840.jpg >> >> Why are there two opto-couplers in parallel? What's the >> output current spec? Lots of load capacitance? > >Gawd-awful schematic color choices :-( > > ...Jim ThompsonMy layout guy likes those colors. I don't.
Reply by ●November 23, 20152015-11-23
On Mon, 23 Nov 2015 15:24:12 -0600, "Tim Williams" <tiwill@seventransistorlabs.com> wrote:>It looks downright readable with a simple inversion! >http://seventransistorlabs.com/Images/JL_Pulser.pngYep. I inverted it with Paint Shop Pro... came out much better than yours ;-)>Guess your layout guy has their eyes upside down ;) > >Whoever encoded it in a JPEG, I can't help that much though. Can't quite >tell if the image was antialiased to begin with, or the JPEG was just that >shitty. The fine print is almost Panteltje level readability.Sno-o-o-ort >:-}> >Tim...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 Skype: skypeanalog | | | 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.
Reply by ●November 23, 20152015-11-23
"Jim Thompson" wrote in message news:93175bpcji7vblpmuek4ip60edi697o2vc@4ax.com...>Yep. I inverted it with Paint Shop Pro... came out much better than >yours ;-)A peculiar thing to say as I use PSP7 ;-) Tim -- Seven Transistor Labs, LLC Electrical Engineering Consultation and Contract Design Website: http://seventransistorlabs.com
Reply by ●November 23, 20152015-11-23
On Mon, 23 Nov 2015 15:48:16 -0600, "Tim Williams" <tiwill@seventransistorlabs.com> wrote:>"Jim Thompson" wrote in message >news:93175bpcji7vblpmuek4ip60edi697o2vc@4ax.com... >>Yep. I inverted it with Paint Shop Pro... came out much better than >>yours ;-) > >A peculiar thing to say as I use PSP7 ;-) > >TimPSP8 ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 Skype: skypeanalog | | | 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.
Reply by ●November 23, 20152015-11-23
On Mon, 23 Nov 2015 15:04:38 -0700, Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote:>On Mon, 23 Nov 2015 15:48:16 -0600, "Tim Williams" ><tiwill@seventransistorlabs.com> wrote: > >>"Jim Thompson" wrote in message >>news:93175bpcji7vblpmuek4ip60edi697o2vc@4ax.com... >>>Yep. I inverted it with Paint Shop Pro... came out much better than >>>yours ;-) >> >>A peculiar thing to say as I use PSP7 ;-) >> >>Tim > >PSP8 > > ...Jim ThompsonForgot to say... I converted black background to white and all other colors to black. Since the bottom of that output totem-pole is tied to ground I'd not use a photocoupler there, thus giving me a nice handle for a controlled shutdown. ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 Skype: skypeanalog | | | 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.
Reply by ●November 23, 20152015-11-23
On Mon, 23 Nov 2015 15:24:12 -0600, "Tim Williams" <tiwill@seventransistorlabs.com> wrote:>It looks downright readable with a simple inversion! >http://seventransistorlabs.com/Images/JL_Pulser.png >Guess your layout guy has their eyes upside down ;) > >Whoever encoded it in a JPEG, I can't help that much though. Can't quite >tell if the image was antialiased to begin with, or the JPEG was just that >shitty. The fine print is almost Panteltje level readability. > >TimThat was just a screen capture. It's readable enough to show the idea. -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Reply by ●November 24, 20152015-11-24
Le lundi 23 novembre 2015 21:09:11 UTC+1, John Larkin a �crit�:> On Mon, 23 Nov 2015 20:15:49 +0100, Habib Bouaziz-Viallet > <habib@nowhere.com> wrote: > > >On 23/11/2015 18:49, John Larkin wrote: > >> On Mon, 23 Nov 2015 09:19:02 -0800 (PST), habib.bouaziz@gmail.com > >> wrote: > >> > >>> Le lundi 23 novembre 2015 17:57:39 UTC+1, Winfield Hill a �crit : > >>>> habib.bouaziz@gmail.com wrote... > >>>>> > >>>>> --> Vgs becomes smaller when current is increasing through > >>>>> 100 Ohm resistor > >>>>> --> then vgs becomes smaller ... There it may have needs > >>>>> some math or Spice simulation isn't it ? > >>>> > >>>> This is likely intentional, because it effectively creates > >>>> a current limit, which is desirable. Of course the FETs > >>>> have to be able to handle this. Ultimately the 1.5kV > >>>> supply will sag and shut down. The current limit would > >>>> act until the HV byass capacitors are drained. > >>>> > >>>> > >>>> -- > >>>> Thanks, > >>>> - Win > >>> > >>> Of course as you say "1.5kV supply will sag and shut down". > >>> E(capacitors) = 1/2 * C * V *V = 0.5J > >>> P max admissible for th MOSFET = 80W > >>> > >>> Let's say the discharge time is about Td = 10ms > >>> > >>> E = P.t then P = 50W --> Ok for the MOSFET > >>> > >>> But if Td = 1ms the P = 500W --> The MOSFET should blow > >>> > >>> May be i missed something ... > >>> > >>> Habib. > >> > >> The 100 ohm resistors and the opto CTR limit the mosfet currents. > >> That's not so much to protect the fets as to limit power supply dip. > >> > >> One 2SK4177 can dissipate about a kilowatt for one millisecond, and > >> around 3KW for 100 us. It could easily discharge all the energy that I > >> have available. > >Ok i missed the fig. ASO on page p.4/7 > >http://www.onsemi.com/pub_link/Collateral/ENA0869-D.PDF > > > >Since it is a one shot overload, it's ok. Apologies. > > > >Habib > >> > >> > > Oh, don't apologize, we all keep learning stuff. > > I just did this, to better understand the mosfet. > > https://dl.dropboxusercontent.com/u/53724080/Parts/Fets/2SK4177_Measurements.JPG > > They don't guardband that 1500 volt rating much! > > > > > > > -- > > John Larkin Highland Technology, Inc > picosecond timing precision measurement > > jlarkin att highlandtechnology dott com > http://www.highlandtechnology.comJohn, You measure VGss = +-42V ! OnSemi gives absolute VGss = +-20V Strange ! Habib.
