Big crowbar module for <4VDC?
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From: Joerg on 18 Dec 2008 16:40 Jim Thompson wrote: > On Thu, 18 Dec 2008 12:48:54 -0800, Joerg > <notthisjoergsch(a)removethispacbell.net> wrote: > >> Jim Thompson wrote: >>> On Thu, 18 Dec 2008 11:16:38 -0800, Joerg >>> <notthisjoergsch(a)removethispacbell.net> wrote: >>> [...] >>>> I have here various schematics of OEM linears from reputable US >>>> manufacturers (unfortunately not at liberty to post on the web). All >>>> have the SCR connected to the output rails, just like I always did. Now >>>> all those manufacturers can't be wrong, can they? >>> They're probably all Democrats ;-) >>> >> I hope none of them read that ;-) > > I guess there's no convincing you that the crowbar goes (properly) > before the linear, all the energy to blow the fuse (between capacitor > bank and linear) comes from the capacitor bank, with properly sized > fuse (fuseI^2*t << scrI^*2t), SCR doesn't even flinch. > No, not convinced. Since you don't do system level designs you probably won't have any: There is a sizeable stash of various linear supplies here, at the ready when a prototype needs to be lashed up. All from very reputable manufacturers, in business for decades. _None_ have fuses between caps and pass devices, and _all_ that are crowbar-equipped have the crowbar short the output. > I personally consider crow-barring output, with no fuses except > primary, to be down-right stupid. > I consider it the correct method of choice. > But it's not my problem... > > My finished designs ALWAYS work ;-) > Mine, too. If you have fuses after the caps your crowbar solution is (probably) going to be ok. If not you better have good PL coverage and warning labels in English and Spanish ;-) -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
From: Jim Thompson on 18 Dec 2008 16:56 On Thu, 18 Dec 2008 13:40:56 -0800, Joerg <notthisjoergsch(a)removethispacbell.net> wrote: >Jim Thompson wrote: >> On Thu, 18 Dec 2008 12:48:54 -0800, Joerg >> <notthisjoergsch(a)removethispacbell.net> wrote: >> >>> Jim Thompson wrote: >>>> On Thu, 18 Dec 2008 11:16:38 -0800, Joerg >>>> <notthisjoergsch(a)removethispacbell.net> wrote: >>>> > > >[...] > > >>>>> I have here various schematics of OEM linears from reputable US >>>>> manufacturers (unfortunately not at liberty to post on the web). All >>>>> have the SCR connected to the output rails, just like I always did. Now >>>>> all those manufacturers can't be wrong, can they? >>>> They're probably all Democrats ;-) >>>> >>> I hope none of them read that ;-) >> >> I guess there's no convincing you that the crowbar goes (properly) >> before the linear, all the energy to blow the fuse (between capacitor >> bank and linear) comes from the capacitor bank, with properly sized >> fuse (fuseI^2*t << scrI^*2t), SCR doesn't even flinch. >> > >No, not convinced. Since you don't do system level designs you probably >won't have any: I was doing system level stuff before you were born ;-) >There is a sizeable stash of various linear supplies >here, at the ready when a prototype needs to be lashed up. All from very >reputable manufacturers, in business for decades. _None_ have fuses >between caps and pass devices, and _all_ that are crowbar-equipped have >the crowbar short the output. > > >> I personally consider crow-barring output, with no fuses except >> primary, to be down-right stupid. >> > >I consider it the correct method of choice. > > >> But it's not my problem... >> >> My finished designs ALWAYS work ;-) >> > >Mine, too. If you have fuses after the caps your crowbar solution is >(probably) going to be ok. That's where they belong. >If not you better have good PL coverage and >warning labels in English and Spanish ;-) ...Jim Thompson -- | James E.Thompson, P.E. | 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: Joerg on 18 Dec 2008 18:39 Jim Thompson wrote: > On Thu, 18 Dec 2008 13:40:56 -0800, Joerg > <notthisjoergsch(a)removethispacbell.net> wrote: > >> Jim Thompson wrote: >>> On Thu, 18 Dec 2008 12:48:54 -0800, Joerg >>> <notthisjoergsch(a)removethispacbell.net> wrote: >>> >>>> Jim Thompson wrote: >>>>> On Thu, 18 Dec 2008 11:16:38 -0800, Joerg >>>>> <notthisjoergsch(a)removethispacbell.net> wrote: >>>>> >> >> [...] >> >> >>>>>> I have here various schematics of OEM linears from reputable US >>>>>> manufacturers (unfortunately not at liberty to post on the web). All >>>>>> have the SCR connected to the output rails, just like I always did. Now >>>>>> all those manufacturers can't be wrong, can they? >>>>> They're probably all Democrats ;-) >>>>> >>>> I hope none of them read that ;-) >>> I guess there's no convincing you that the crowbar goes (properly) >>> before the linear, all the energy to blow the fuse (between capacitor >>> bank and linear) comes from the capacitor bank, with properly sized >>> fuse (fuseI^2*t << scrI^*2t), SCR doesn't even flinch. >>> >> No, not convinced. Since you don't do system level designs you probably >> won't have any: > > I was doing system level stuff before you were born ;-) > But that doesn't mean us younger guys couldn't find a more cost efficient topology :-)) Hint: A decent fuse costs quite a bit and fuses always attract the scrutiny of the agency compliance inspector. More paperwork, more Dollars. And one likes to minimize scrutiny. >> There is a sizeable stash of various linear supplies >> here, at the ready when a prototype needs to be lashed up. All from very >> reputable manufacturers, in business for decades. _None_ have fuses >> between caps and pass devices, and _all_ that are crowbar-equipped have >> the crowbar short the output. >> >> >>> I personally consider crow-barring output, with no fuses except >>> primary, to be down-right stupid. >>> >> I consider it the correct method of choice. >> >> >>> But it's not my problem... >>> >>> My finished designs ALWAYS work ;-) >>> >> Mine, too. If you have fuses after the caps your crowbar solution is >> (probably) going to be ok. > > That's where they belong. > I guess this is an area where the two of us will never see eye to eye ... [...] -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
From: Jim Thompson on 18 Dec 2008 18:55 On Thu, 18 Dec 2008 15:39:20 -0800, Joerg <notthisjoergsch(a)removethispacbell.net> wrote: >Jim Thompson wrote: >> On Thu, 18 Dec 2008 13:40:56 -0800, Joerg >> <notthisjoergsch(a)removethispacbell.net> wrote: >> >>> Jim Thompson wrote: >>>> On Thu, 18 Dec 2008 12:48:54 -0800, Joerg >>>> <notthisjoergsch(a)removethispacbell.net> wrote: >>>> >>>>> Jim Thompson wrote: >>>>>> On Thu, 18 Dec 2008 11:16:38 -0800, Joerg >>>>>> <notthisjoergsch(a)removethispacbell.net> wrote: >>>>>> >>> >>> [...] >>> >>> >>>>>>> I have here various schematics of OEM linears from reputable US >>>>>>> manufacturers (unfortunately not at liberty to post on the web). All >>>>>>> have the SCR connected to the output rails, just like I always did. Now >>>>>>> all those manufacturers can't be wrong, can they? >>>>>> They're probably all Democrats ;-) >>>>>> >>>>> I hope none of them read that ;-) >>>> I guess there's no convincing you that the crowbar goes (properly) >>>> before the linear, all the energy to blow the fuse (between capacitor >>>> bank and linear) comes from the capacitor bank, with properly sized >>>> fuse (fuseI^2*t << scrI^*2t), SCR doesn't even flinch. >>>> >>> No, not convinced. Since you don't do system level designs you probably >>> won't have any: >> >> I was doing system level stuff before you were born ;-) >> > >But that doesn't mean us younger guys couldn't find a more cost >efficient topology :-)) > >Hint: A decent fuse costs quite a bit and fuses always attract the >scrutiny of the agency compliance inspector. More paperwork, more >Dollars. And one likes to minimize scrutiny. > > >>> There is a sizeable stash of various linear supplies >>> here, at the ready when a prototype needs to be lashed up. All from very >>> reputable manufacturers, in business for decades. _None_ have fuses >>> between caps and pass devices, and _all_ that are crowbar-equipped have >>> the crowbar short the output. >>> >>> >>>> I personally consider crow-barring output, with no fuses except >>>> primary, to be down-right stupid. >>>> >>> I consider it the correct method of choice. >>> >>> >>>> But it's not my problem... >>>> >>>> My finished designs ALWAYS work ;-) >>>> >>> Mine, too. If you have fuses after the caps your crowbar solution is >>> (probably) going to be ok. >> >> That's where they belong. >> > >I guess this is an area where the two of us will never see eye to eye ... > >[...] Aha! You don't care what burns up... as long as it's not the $BIG load ?:-) "...fuses always attract the scrutiny of the agency compliance inspector..." sounds like a business I don't want to play in. Fuses are for safety, n'est ce pas ?:-) And, done properly (aka "my way"), crowbars are _very_ fast at accomplishing disconnect. ...Jim Thompson -- | James E.Thompson, P.E. | 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: Tim Williams on 18 Dec 2008 19:10
On Dec 17, 7:12 pm, Jim Thompson <To-Email-Use-The-Envelope-I...(a)My- Web-Site.com> wrote: > Second question. You _are_ aware that the crowbar goes on the _input_ > side of the linear regulator, aren't you ?:-) Hey Jim, you respect AoE2 last I heard, right? Why, then, do they also recommend putting the crowbar at the output? Which is, incidentially, the logical place to put it when you want to protect $10k equipment powered by said supply anyway. Equipment >> supply, protect equipment. QED. Tim |