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Need the topology for a current to current SMPS, not voltage to voltage SMPS

Started by RobertMacy October 16, 2013
On Mon, 21 Oct 2013 10:20:19 -0700, <krw@attt.bizz> wrote:

>>> ...snip... > In my last job I was the only one who wore long pants from April to > October. Everyone else in Engineering wore T-shirts year 'round. I > can't do that. I wear long-sleeved shirts (Oxfords, preferred) even > for mowing the lawn.
Me too! I paint in a long sleeved Oxford shirt! even in AZ My wife is still laughing about the time, on one of our sojourns including Santa Cruz Boardwalk; I went to get us hotdogs from the boardwalk vendors in a three piece suit, ...and was carrying my briefcase. In 70's while at Stanford's Chapel for Christmas obaservance, one of my colleagues wearing a rather worn sweatsuit [it WAS post hippy era] leaned over and in attempting to ridicule my dress suit asked, "Why do you want to dress like everyone else?" My reply, "Look around. I'm the ONLY suit here. Look at you. Why do YOU want to dress like everyone else." And, yes. EVERYBODY else was in totally casual attire.
krw@attt.bizz wrote:
> On Mon, 21 Oct 2013 06:52:46 -0700, Joerg <invalid@invalid.invalid> > wrote: > >> krw@attt.bizz wrote: >>> On Sun, 20 Oct 2013 12:51:26 -0700, Joerg <invalid@invalid.invalid> >>> wrote: >>> >>>> krw@attt.bizz wrote: >>>>> On Sun, 20 Oct 2013 09:33:54 -0700, Joerg <invalid@invalid.invalid> >>>>> wrote:
[...]
>>>>>> I work for numerous clients who are all in very different >>>>>> markets. This keeps our jobs interesting. But after talking to >>>>>> automotive designers I'd be bored stiff if I had to do their job for >>>>>> more than a year. >>>>> Perhaps but I think you have a pretty small view of that world. >>>> Nope. Medical devices for hospitals, low cost medical devices for >>>> consumers (over-the-counter), aircraft electronics, spacecraft stuff, >>>> chemical pump controllers, power generation, oil/gas exploration >>>> electronics, NDT, commercial automotive (trucks), and so on. >>> You have a very small view of the automotive market. That is for >>> sure. >>> >> I see it from two view points. One is the actual product and that often >> doesn't look very good, both from a quality point of view and sometimes >> also from an engineering point of view (flickering LED backlights >> anyone?). Then from a people perspective and here talking to folks who >> actually work in that field helps. Pretty much all of them reported >> extreme pressure to keep NRE and R&D schedules down, which explains a >> lot of the quality issues. To the point I wouldn't want to work there. >> As a consultant maybe but niot if they'd demansd unrealistic timelines >> like they often do from their employees. > > Cost is everything but it's still no excuse for designing junk. ...
Nobody seems to have told the executives that are ultimately responsible for automotive electronics. Nearly all quality issues have their root cause in upper management.
> ... In > that regard, it's not a lot different than what you've described that > you do. >
Except I do not cut corners. Ever. If a client wants me to do that I politely decline the whole assignment. It does happen but very rarely, and those companies then do not even become clients of mine.
>> There are automotive electronics that work quite well, mostly in >> Japanese cars. In the end it boils down to the reliability ratings of >> the various entities in the know. > > Things change. A lot! >
That's what Maxim kept telling people :-)
>>>>> However, I've been involved in many different markets at many >>>>> different levels, over the years. It's a *big* field. There is no >>>>> reason to do the same thing for forty years. Impossible, actually. >>>>> >>>> Not impossible. I met people who worked in one particular field such as >>>> engine control units for over 30 years. I'd have a hard time doing that, >>>> after being a consultant for this long. >>> ECUs have changed more than a little in 30 years. They will change >>> drastically, again, over the next ten. ... >> >> Sure, incremental change. Same in medical ultrasound which is my home >> turf. But ... after we built a flagship product in the late 80's and the >> satellite R&D location was closed afterwards I wasn't too unhappy that I >> could jump into consulting for the first time, and do something else. >> >> >>> ... Hell, you'd have a hard time >>> showing up for work with your pants on, after being a consultant that >>> long. ;-) >> >> As a consultant I get to wear shorts all summer long. When a web >> conference with bigshots is coming up I have a "dress shirt on duty" >> hanging in the lab closet :-) > > In my last job I was the only one who wore long pants from April to > October. Everyone else in Engineering wore T-shirts year 'round. I > can't do that. I wear long-sleeved shirts (Oxfords, preferred) even > for mowing the lawn.
I am just the opposite. I wear shorts and T-shirts as long as I can. Only in really cold weather it's lumberjack shirts and jeans. For a winter coat or jacket it almost would have to drop to below 0F. -- Regards, Joerg http://www.analogconsultants.com/
On Mon, 21 Oct 2013 10:31:19 -0700, Phil Hobbs  
<pcdhSpamMeSenseless@electrooptical.net> wrote:

>> ...snip... > > You can see the aforementioned table and bookshelf in my virtual lab > tour, http://electrooptical.net/www/EOILab/EOILab.html . > > It looks pretty much like that, except that I have a bunch more > furniture (two big lab benches and a table in the whiteboard/reception > area, plus some more in the admin/layout space). I also have way more > equipment. I've been meaning to replace the pictures, but the lab > hasn't been that clean since 2011. ;) > > Cheers > > Phil Hobbs >
I have a voltmeter.
RobertMacy wrote:
> On Mon, 21 Oct 2013 10:31:19 -0700, Phil Hobbs > <pcdhSpamMeSenseless@electrooptical.net> wrote: > >>> ...snip... >> >> You can see the aforementioned table and bookshelf in my virtual lab >> tour, http://electrooptical.net/www/EOILab/EOILab.html . >> >> It looks pretty much like that, except that I have a bunch more >> furniture (two big lab benches and a table in the whiteboard/reception >> area, plus some more in the admin/layout space). I also have way more >> equipment. I've been meaning to replace the pictures, but the lab >> hasn't been that clean since 2011. ;) >> >> Cheers >> >> Phil Hobbs >> > > > I have a voltmeter.
I raise you one: I have a megacycle meter 8-) This one: http://www.ohio.edu/people/postr/bapix/Dip_59.htm -- Regards, Joerg http://www.analogconsultants.com/
On 10/21/2013 10:53 AM, RobertMacy wrote:
> On Mon, 21 Oct 2013 08:00:04 -0700, John S <Sophi.2@invalid.org> wrote: > >>> ...snip.... >> >> Hi, Robert - >> >> The thread has grown more to than I can re-read to capture all your >> requirements. However, here are my thoughts... >> >> Max allowed input voltage: 100V >> Input current capability: 50mA >> Output voltage required: 5V >> Output current required: .8A >> ....snip...loss of extra thoughts due to using AIOE that won't let me >> quote more than ?? number of lines... >> -If it can be open or very high, then you need to provide another >> device at the input, perhaps a depletion FET capabale of about 100mA >> at a few hundred volts to stop things when the duty cycle is commanded >> to be at 100% or a bit less. >> >> Just some thoughts. I apologize if I have stepped on any toes. > > You've got the gist of the problem. I made up some of the numbers and > didn't notice they didn't quite correlate. But you see the premise for > the problem. > > To maintain some semblance of efficiency, I can't simply 'shunt' unused > power off.
So, you cannot provide a short circuit for the current source? You are in deep trouble.
On Mon, 21 Oct 2013 11:09:59 -0700, John S <Sophi.2@invalid.org> wrote:

> On 10/21/2013 10:53 AM, RobertMacy wrote: >> ...snip... >> To maintain some semblance of efficiency, I can't simply 'shunt' unused >> power off. > > So, you cannot provide a short circuit for the current source? You are > in deep trouble.
I CAN short circuit the current source, but I CANNOT afford to shunt off POWER. As in, 'unused' power removed to somewhere else.
On 10/21/2013 10:57 AM, George Herold wrote:
> On Monday, October 21, 2013 11:14:10 AM UTC-4, John S wrote: >> On 10/21/2013 9:53 AM, George Herold wrote: >> >>> On Monday, October 21, 2013 8:57:43 AM UTC-4, John S wrote: >> >>>> On 10/20/2013 7:53 PM, George Herold wrote: >> >>>> >> >>>>> On Sunday, October 20, 2013 9:05:15 AM UTC-4, John S wrote: >> >>>> >> >>>>>> On 10/19/2013 4:50 PM, Jasen Betts wrote: >> >>>> >> >>> <snip> >> >>> >> >>>>> I was going to say it looked a bit like what I drew for a >>>>> current boost. But I had the diode and inductor switched >>>>> around. >> >>>> >> >>>>> >> >>>> >> >>>>> +----+--FET--+-LLL--+ >> >>>>> | | | | >> >>>>> ^ C _ R >> >>>>> I C ^ R >> >>>>> | | | | >> >>>>> +----+-------+------+ >> >>>> >> >>>>> >> >>>> >> >>>>> Something like that, >> >>>> >> >>>>> >> >>>> >> >>>>> George H. >> >>>> >> >>>> >> >>>> >> >>>> Thanks, George. It believe this is a standard buck switcher >>>> without the >> >>>> >> >>>> output filter capacitor. >> >>> >> >>> Hi John, Here's the current to current buck that I drew... from >>> upstream >> >>> https://www.dropbox.com/s/h2a8dyz0vzoovev/DSCF0031.JPG >> >>> I guess I could try simulating these, if I ever get 'free' time. >> >>> >> >>> George H. >> >> >> >> Yes, thank you, George. I saw it. But your image and your ASCII >> drawing >> >> above do not agree. Your ASCII drawing is a standard buck without >> an >> >> output filter capacitor. I agree with your ASCII (with, possibly, >> the >> >> requirement for an output filter capacitor) for a scheme which >> could work. > > Grin.. sure... the ascii is a current boost and the first dropbox > scribble is a current buck. I'm not sure what you mean about the > ascii drawing... It's being fed from a current source.. so how can > it be a 'standard buck'. (The output is also a (DC) current.. so I > can't really put a capacitor there.)
I don't really care about the source. It's max voltage is specified at 100V, no? It' max (and constant) current is specified at .05A, no? There is therefore a maximum power output capability of 5W. No? It does not matter what topology you use, you cannot get more out than you put in. Where am I wrong here?
> You should also note that the ascii has a current source feeding > right into a capacitor! (But that really does seem analogous to the > voltage boost where the voltage source feeds an inductor... both > will 'rail out' if not part of the switching scheme.)
Who cares? You cannot amplify power (in this particular scenario). If the output is 5V, what is the current? I think maybe 1A. That's current amplification if you put 100V into a buck switcher at 50mA and regulate the output to 5V. This is not what I am suggesting, so see my other post. (snipped fun times)
John S wrote:
> On 10/21/2013 10:53 AM, RobertMacy wrote: >> On Mon, 21 Oct 2013 08:00:04 -0700, John S <Sophi.2@invalid.org> wrote: >> >>>> ...snip.... >>> >>> Hi, Robert - >>> >>> The thread has grown more to than I can re-read to capture all your >>> requirements. However, here are my thoughts... >>> >>> Max allowed input voltage: 100V >>> Input current capability: 50mA >>> Output voltage required: 5V >>> Output current required: .8A >>> ....snip...loss of extra thoughts due to using AIOE that won't let me >>> quote more than ?? number of lines... >>> -If it can be open or very high, then you need to provide another >>> device at the input, perhaps a depletion FET capabale of about 100mA >>> at a few hundred volts to stop things when the duty cycle is commanded >>> to be at 100% or a bit less. >>> >>> Just some thoughts. I apologize if I have stepped on any toes. >> >> You've got the gist of the problem. I made up some of the numbers and >> didn't notice they didn't quite correlate. But you see the premise for >> the problem. >> >> To maintain some semblance of efficiency, I can't simply 'shunt' unused >> power off. > > So, you cannot provide a short circuit for the current source? You are > in deep trouble.
The current source won't be 100% efficient. What Robert probably wants to avoid is having to shunt some of the current to ground. This will cause loss because another part of that current is used to make a different secondary current. That means there is going to be voltage drop. If you shunt past that -> wasted energy. The ideal situation would be, for example, a flyback that regulates to an output current that has the desired ratio to the input current and at that point sets its input impedance in such a way that it uses up all the current coming in, wasting none. Sounds feasible. Of course, with AC Robert would need a rectifier and, if AC is to be delivered at the output, a FET bridge. -- Regards, Joerg http://www.analogconsultants.com/
On Mon, 21 Oct 2013 10:55:11 -0700, Joerg <invalid@invalid.invalid> wrote:

>> ...snip... > I raise you one: I have a megacycle meter 8-) > > This one: > > http://www.ohio.edu/people/postr/bapix/Dip_59.htm >
That's too bad you won't be able to use it, since it measures megacycles and megacycles no longer exist. Unless you can find some equipment that produces megacycles, like...perhaps I can help, I have an original pair of WWII walkietalkies! You have NO idea how long it took me to stop saying megacycles/kilocycles and start saying megaHertz/kiloHertz.
RobertMacy wrote:
> On Mon, 21 Oct 2013 10:55:11 -0700, Joerg <invalid@invalid.invalid> wrote: > >>> ...snip... >> I raise you one: I have a megacycle meter 8-) >> >> This one: >> >> http://www.ohio.edu/people/postr/bapix/Dip_59.htm >> > > That's too bad you won't be able to use it, since it measures megacycles > and megacycles no longer exist. Unless you can find some equipment that > produces megacycles, like...perhaps I can help, I have an original pair > of WWII walkietalkies! >
I stopped keeping such stuff after moving to California, where houses neither have basements nor attics.
> You have NO idea how long it took me to stop saying > megacycles/kilocycles and start saying megaHertz/kiloHertz.
You can be lucky not to have gone to school in Europe. There, the bureaucrats change units at a whim. First we learned kilopond, then that went out of fashion and Newton was en vogue. Even worse with pressure: Torr, then it was changed to atmospheres, then it was change to bar, then it was changed to Pascal. Crazy. Now that I moved to the US and workd in some fields such as aerospace where metric isn't used I became used to imperial units. Not as easy in the math but the nice thing is that the units never change. -- Regards, Joerg http://www.analogconsultants.com/