https://www.dropbox.com/s/s6nfu30ldyzvpqy/Fet_String.jpg?raw=1 This is to test four fets on a heat sink for power dissipation. -- If a man will begin with certainties, he shall end with doubts, but if he will be content to begin with doubts he shall end in certainties. Francis Bacon
mosfet strings
Started by ●April 20, 2022
Reply by ●April 20, 20222022-04-20
On a sunny day (Wed, 20 Apr 2022 10:09:53 -0700) it happened John Larkin <jlarkin@highland_atwork_technology.com> wrote in <26f06hdar70hcvasi9l7m29agpafd9ui1o@4ax.com>:>https://www.dropbox.com/s/s6nfu30ldyzvpqy/Fet_String.jpg?raw=1 > >This is to test four fets on a heat sink for power dissipation.Just wondering is it not simpler to use them all in parallel and connect the drains directly to the metal of the heatsink? Washers decrease thermal resistance
Reply by ●April 20, 20222022-04-20
On a sunny day (Wed, 20 Apr 2022 17:41:17 GMT) it happened Jan Panteltje <pNaonStpealmtje@yahoo.com> wrote in <t3pgoe$el$1@dont-email.me>:>On a sunny day (Wed, 20 Apr 2022 10:09:53 -0700) it happened John Larkin ><jlarkin@highland_atwork_technology.com> wrote in ><26f06hdar70hcvasi9l7m29agpafd9ui1o@4ax.com>: > >>https://www.dropbox.com/s/s6nfu30ldyzvpqy/Fet_String.jpg?raw=1 >> >>This is to test four fets on a heat sink for power dissipation. > >Just wondering >is it not simpler to use them all in parallel and connect the drains directly to the metal of the heatsink? >Washers decrease thermal resistanceoops increase I mean, and then insulate the heatsink.
Reply by ●April 20, 20222022-04-20
20.04.22 20:09, John Larkin wrote:>https://www.dropbox.com/s/s6nfu30ldyzvpqy/Fet_String.jpg?raw=1 > >This is to test four fets on a heat sink for power dissipation. >MOSFET strings are prone to problems. Dynamic switching can be solved with adding capacitors in the divider string -- Klaus
Reply by ●April 20, 20222022-04-20
On Wed, 20 Apr 2022 22:41:14 +0300, Klaus Kragelund <klauskvik@hotmail.com> wrote:>20.04.22 20:09, John Larkin wrote: >>https://www.dropbox.com/s/s6nfu30ldyzvpqy/Fet_String.jpg?raw=1 >> >>This is to test four fets on a heat sink for power dissipation. >> >MOSFET strings are prone to problems. Dynamic switching can be solved with adding capacitors in the divider stringI just want to burn watts to test the thermals. I do want the dissipations to be about equal among the fets. -- If a man will begin with certainties, he shall end with doubts, but if he will be content to begin with doubts he shall end in certainties. Francis Bacon
Reply by ●April 20, 20222022-04-20
John Larkin <jlarkin@highland_atwork_technology.com> Wrote in message:r> https://www.dropbox.com/s/s6nfu30ldyzvpqy/Fet_String.jpg?raw=1This is to test four fets on a heat sink for power dissipation.-- If a man will begin with certainties, he shall end with doubts, but if he will be content to begin with doubts he shall end in certainties.Francis BaconI've seen the zener version used in a HV power supply about 20 years ago. Cheers -- ----Android NewsGroup Reader---- https://piaohong.s3-us-west-2.amazonaws.com/usenet/index.html
Reply by ●April 20, 20222022-04-20
On Wed, 20 Apr 2022 22:41:14 +0300, Klaus Kragelund <klauskvik@hotmail.com> wrote:>20.04.22 20:09, John Larkin wrote: >>https://www.dropbox.com/s/s6nfu30ldyzvpqy/Fet_String.jpg?raw=1 >> >>This is to test four fets on a heat sink for power dissipation. >> >MOSFET strings are prone to problems. Dynamic switching can be solved with adding capacitors in the divider stringIn this case, I just want the fets to get hot, to test a heat sink. -- If a man will begin with certainties, he shall end with doubts, but if he will be content to begin with doubts he shall end in certainties. Francis Bacon
Reply by ●April 21, 20222022-04-21
On a sunny day (Wed, 20 Apr 2022 13:51:50 -0700) it happened John Larkin <jlarkin@highland_atwork_technology.com> wrote in <hhs06hpq06r1a50v8k6vknva5l34bp6vf0@4ax.com>:>On Wed, 20 Apr 2022 22:41:14 +0300, Klaus Kragelund ><klauskvik@hotmail.com> wrote: > >>20.04.22 20:09, John Larkin wrote: >>>https://www.dropbox.com/s/s6nfu30ldyzvpqy/Fet_String.jpg?raw=1 >>> >>>This is to test four fets on a heat sink for power dissipation. >>> >>MOSFET strings are prone to problems. Dynamic switching can be solved with adding capacitors in the divider string > >I just want to burn watts to test the thermals. I do want the >dissipations to be about equal among the fets.Use power resistirs? Much simpler. http://panteltje.com/pub/power_resistors_IMG_6291.JPG
Reply by ●April 21, 20222022-04-21
On Thu, 21 Apr 2022 05:28:27 GMT, Jan Panteltje <pNaonStpealmtje@yahoo.com> wrote:>On a sunny day (Wed, 20 Apr 2022 13:51:50 -0700) it happened John Larkin ><jlarkin@highland_atwork_technology.com> wrote in ><hhs06hpq06r1a50v8k6vknva5l34bp6vf0@4ax.com>: > >>On Wed, 20 Apr 2022 22:41:14 +0300, Klaus Kragelund >><klauskvik@hotmail.com> wrote: >> >>>20.04.22 20:09, John Larkin wrote: >>>>https://www.dropbox.com/s/s6nfu30ldyzvpqy/Fet_String.jpg?raw=1 >>>> >>>>This is to test four fets on a heat sink for power dissipation. >>>> >>>MOSFET strings are prone to problems. Dynamic switching can be solved with adding capacitors in the divider string >> >>I just want to burn watts to test the thermals. I do want the >>dissipations to be about equal among the fets. > >Use power resistirs? >Much simpler. > http://panteltje.com/pub/power_resistors_IMG_6291.JPG >The question is, how hot do these fets get on this heat sink? One issue with heat sinks is that the theta is usually/probably measured with heat uniformly applied to the baseplate. Real parts don't do that... they are usually a small number of hot spots. So footprints matter. My tests will use the real fets and the real insulators and we'll measure real fet temperatures. -- I yam what I yam - Popeye
Reply by ●April 21, 20222022-04-21
On a sunny day (Thu, 21 Apr 2022 07:01:19 -0700) it happened jlarkin@highlandsniptechnology.com wrote in <ilo26hlaqq7e711j4klot7ekc9oc5dgsng@4ax.com>:>On Thu, 21 Apr 2022 05:28:27 GMT, Jan Panteltje ><pNaonStpealmtje@yahoo.com> wrote: > >>On a sunny day (Wed, 20 Apr 2022 13:51:50 -0700) it happened John Larkin >><jlarkin@highland_atwork_technology.com> wrote in >><hhs06hpq06r1a50v8k6vknva5l34bp6vf0@4ax.com>: >> >>>On Wed, 20 Apr 2022 22:41:14 +0300, Klaus Kragelund >>><klauskvik@hotmail.com> wrote: >>> >>>>20.04.22 20:09, John Larkin wrote: >>>>>https://www.dropbox.com/s/s6nfu30ldyzvpqy/Fet_String.jpg?raw=1 >>>>> >>>>>This is to test four fets on a heat sink for power dissipation. >>>>> >>>>MOSFET strings are prone to problems. Dynamic switching can be solved with adding capacitors in the divider string >>> >>>I just want to burn watts to test the thermals. I do want the >>>dissipations to be about equal among the fets. >> >>Use power resistirs? >>Much simpler. >> http://panteltje.com/pub/power_resistors_IMG_6291.JPG >> > >The question is, how hot do these fets get on this heat sink? > >One issue with heat sinks is that the theta is usually/probably >measured with heat uniformly applied to the baseplate. Real parts >don't do that... they are usually a small number of hot spots. So >footprints matter. > >My tests will use the real fets and the real insulators and we'll >measure real fet temperatures.OK, if that is what you want to do, looks like a nice application for my FLIR camera recording. http://panteltje.com/panteltje/newsflex/download.html#xflir
