battery chargers, again
in [Design]
|
From: John Larkin on 29 Sep 2009 23:21 On Tue, 29 Sep 2009 15:56:14 -0700, Joerg <invalid(a)invalid.invalid> wrote: >John Larkin wrote: >> On Tue, 29 Sep 2009 13:29:09 -0700, Joerg <invalid(a)invalid.invalid> >> wrote: >> >>> John Larkin wrote: >>>> On Mon, 28 Sep 2009 19:28:39 -0500, krw <krw(a)att.bizzzzzzzzzzz> wrote: >>>> >>>>> On Mon, 28 Sep 2009 09:06:34 -0700, John Larkin >>>>> <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >>>>> >>>>>> On Mon, 28 Sep 2009 09:04:17 -0500, Tim Wescott <tim(a)seemywebsite.com> >>>>>> wrote: >>>>>> >>>>>>> On Sun, 27 Sep 2009 21:16:46 -0700, John Larkin wrote: >>>>>>> >>>>>>>> Last time a car went dead in the garage, my wife's Fit, I hacked up a >>>>>>>> charger from an old DSL wall-wart and a sabre saw as a series current >>>>>>>> limiter. The garage geometry makes it essentially impossible for us to >>>>>>>> push a car uphill to the street to jump it. Now The Brat left her Echo >>>>>>>> in the garege for a month or so and it went dead, too. So I figure it's >>>>>>>> time to buy a real charger. Went to Kragen Auto Parts and bought two >>>>>>>> (one for here, one for Truckee) chargers. They are all "smart chargers", >>>>>>>> namely switchers with electronics, these days. >>>>>>>> >>>>>>>> The battery is really dead, 1.8 volts. The first charger hums and >>>>>>>> outputs nothing. Tried the next one: it hummed for maybe 3 seconds then >>>>>>>> sparked and smoked inside. >>>>>>>> >>>>>>>> Went back to Kragen and traded up, two better chargers. Neither >>>>>>>> charges... no current, battery steady at 1.8 volts. Both have their >>>>>>>> "charging" LEDs off and "charge complete" LEDs lit. >>>>>>>> >>>>>>>> Back to Kragen, 3rd time, got all my money back. Passed by Bob Pease's >>>>>>>> place all three trips, same collection of rusty VWs everywhere. >>>>>>>> >>>>>>>> A charger that puts zero amps into a dead battery does that by design, >>>>>>>> and there's only one reason to do that: to convince people they need a >>>>>>>> new battery. Kragen's sales pitch was exactly along those lines; "Tt >>>>>>>> won't charge, so all the cells are shorted." >>>>>>>> >>>>>>>> So I went to work and nabbed a cute little Lascar bench power supply. It >>>>>>>> current limits at 1.2 amps, so I just cranked it up. The battery went >>>>>>>> instantly to 16.5 volts, then settled down to 12 or so in a few minutes, >>>>>>>> and is creeping back up. >>>>>>>> >>>>>>>> Interesting. >>>>>>>> >>>>>>>> So I guess I'll buy a couple of 3 amp or so lab supplies, with nice volt >>>>>>>> and amp meters, instead of battery chargers. They're handier to have >>>>>>>> around anyhow, cost about the same as a "good" charger, and aren't booby >>>>>>>> trapped. >>>>>>>> >>>>>>>> What Kragen is doing is fraud. >>>>>>>> >>>>>>>> John >>>>>>> I've never had a battery come back from being that dead, and I've had >>>>>>> numerous chances to try it (I'm stubborn that way). You'll be lucky to >>>>>>> see 12V out of it with the charger disconnected, and I doubt that you'll >>>>>>> see that after the first time you touch the key. If you _do_ get the car >>>>>>> started it'll just be an opportunity for you daughter to get stranded >>>>>>> some place. >>>>>> It started OK after about 6 hours at 1.2 amps, started vigorously >>>>>> after charging all night. My wife's car was zero-volts dead a couple >>>>>> months ago, got rebooted from the DSL wall-wart, and it's fine. >>>>>> Lead-acids will sulphate and lose capacity if they sit dead for a long >>>>>> time. >>>>>> >>>>>>> One new battery is cheaper than one tow truck ride. Do the math. >>>>>> Our insurance covers the truck ride. >>>>> It's the brat's vehicle, IIRC. I wouldn't beg *any* trouble for a >>>>> woman's vehicle. ...for more reasons that I can count. The brat's, >>>>> never. >>>> She left the Echo - her high school car - in our garage because all >>>> she wants to drive now is her Jeep Rubicon. Gotta get her to sell the >>>> Echo so we can have our garage back. >>>> >>> Why is everyone spoiling their kids so much? Same with the daughters of >>> a business friend, they got cars courtesy of daddy. Plus tuition, room >>> and board at rather ritzy colleges. I had to work for my first car. Dad >>> wanted to chip in to get me a somewhat decent looking used car upon >>> nailing my masters but I said I should really try to pay my own way. And >>> did. Couldn't possibly show up for interviews in my old Citroen but the >>> TUEV had just blown it out of the water anyhow, declared it >>> unroadworthy. You could see the road surface fly by when looking down. >>> >>> >>>> http://www.rubicon-trail.com/ >>>> >>>> But if her car battery did go dead, she wouldn't have any trouble >>>> getting a jump start. >>>> >>> Like Keith, I'd be concerned about what happens afterwards ... >> >> >> Please select one of the following options: >> >> _ >> / / Drive kid to/from school, to/from softball practice, to/from >> friends houses, to/from weekend activities, to/from mall >> >> or >> >> _ >> / / Buy kid a cheap Toyota. >> > >Option three, in Europe in the 70's: > >Tell kid to work and use proceeds to buy a bicycle, which can then >almost indefinitely fulfill all the tasks from option one :-) Except that this town was built on a mountain range. > >Why didn't she just keep the Echo? It's a nice car for college and >university, very economical. Probably sips half the fuel of a Wrangler. >Of course the coolness factor is only 10% or so. Yup. Right after she landed her first real job, she got the Rubicon. I gave her a raise, and she moved into a fancy apartment a couple blocks from PacBell Park. "Sacrifice" ain't what it used to be. > >BTW, my first car _after_ receiving my masters degree was a used >Chrysler Horizon. Before that the predominant mode of transportation was >a 10-speed. I got a yellow Austin-Healey Sprite, new, for about $1900. Freshman at Tulane, two jobs on the side. I had a lot of energy in those days. John
From: Les Cargill on 29 Sep 2009 23:36 Jon Kirwan wrote: > On Mon, 28 Sep 2009 10:45:51 -0500, Tim Wescott <tim(a)seemywebsite.com> > wrote: > >> On Mon, 28 Sep 2009 10:08:54 -0400, Phil Hobbs wrote: >> >>> Spehro Pefhany wrote: >>>> On Mon, 28 Sep 2009 09:53:48 -0400, Phil Hobbs >>>> <pcdhSpamMeSenseless(a)electrooptical.net> wrote: >>>> >>>>> John Larkin wrote: >>>>>> Last time a car went dead in the garage, my wife's Fit, I hacked up a >>>>>> charger from an old DSL wall-wart and a sabre saw as a series current >>>>>> limiter. The garage geometry makes it essentially impossible for us >>>>>> to push a car uphill to the street to jump it. Now The Brat left her >>>>>> Echo in the garege for a month or so and it went dead, too. So I >>>>>> figure it's time to buy a real charger. Went to Kragen Auto Parts and >>>>>> bought two (one for here, one for Truckee) chargers. They are all >>>>>> "smart chargers", namely switchers with electronics, these days. >>>>>> >>>>>> The battery is really dead, 1.8 volts. The first charger hums and >>>>>> outputs nothing. Tried the next one: it hummed for maybe 3 seconds >>>>>> then sparked and smoked inside. >>>>>> >>>>>> Went back to Kragen and traded up, two better chargers. Neither >>>>>> charges... no current, battery steady at 1.8 volts. Both have their >>>>>> "charging" LEDs off and "charge complete" LEDs lit. >>>>>> >>>>>> Back to Kragen, 3rd time, got all my money back. Passed by Bob >>>>>> Pease's place all three trips, same collection of rusty VWs >>>>>> everywhere. >>>>>> >>>>>> A charger that puts zero amps into a dead battery does that by >>>>>> design, and there's only one reason to do that: to convince people >>>>>> they need a new battery. Kragen's sales pitch was exactly along those >>>>>> lines; "Tt won't charge, so all the cells are shorted." >>>>>> >>>>>> So I went to work and nabbed a cute little Lascar bench power supply. >>>>>> It current limits at 1.2 amps, so I just cranked it up. The battery >>>>>> went instantly to 16.5 volts, then settled down to 12 or so in a few >>>>>> minutes, and is creeping back up. >>>>>> >>>>>> Interesting. >>>>>> >>>>>> So I guess I'll buy a couple of 3 amp or so lab supplies, with nice >>>>>> volt and amp meters, instead of battery chargers. They're handier to >>>>>> have around anyhow, cost about the same as a "good" charger, and >>>>>> aren't booby trapped. >>>>>> >>>>>> What Kragen is doing is fraud. >>>>>> >>>>>> John >>>>>> >>>>> Or just get a nasty big iron Craftsman charger off eBay. Two >>>>> transformer taps, rectifier, thermal cutout. >>>>> >>>>> Cheers >>>>> >>>>> Phil Hobbs >>>> Many of the the newer battery chargers seem to do this.. they refuse to >>>> charge if the battery is very dead. It's in the preferred algorithm >>>> description for NiMH batteries too-- I just had to modify a charging >>>> algorithm because people make mistakes and occasionally kill batteries >>>> below the minimum charge voltage per cell and you need to be able to >>>> override the (usually microcontroller-based) smart charger. And had the >>>> same problem recently with a commercial charger for a stacker (sort of >>>> a little fork lift). The deep discharge Marine duty battery was too >>>> dead for the dumbf*ck little LM339 circuit to turn the SCR on. At first >>>> we thought it had failed.. >>> One of the problems with our software-intensive era is that the >>> behaviour of ordinary objects has become arbitrary, like software, >>> instead of merely ornery, like physics. >>> >>> It's nice to warn people, but building something that refuses to do the >>> job it's built for is poor engineering. (Of course our current plague >>> of tort lawyers is partly responsible, but only partly.) >>> >>> Cheers >>> >>> Phil Hobbs >> OTOH, physics combined with real parts can get pretty ornery by itself; >> there are decision trees that would take a square foot of board to do >> with diodes and op-amps that can be done with an 8-pin PIC and a less >> than 256 words of program memory. > > I think Phil's point (or the way I personally took it, anyway, as I > really shouldn't attempt to speak for him) is that software allows > behaviors that aren't at all similar to how nature itself operates. > Nature is very, very consistent and once one learns it well, those > lessons can be applied in new situations. When software is inserted > into the mix, that can be quite a different story where no possible > prior experience elsewhere may act to inform expectations. > > Prior digital states matter in bizarre ways, sometimes. > > Despite some possible advantages, I'll take an analog, physical > connection between my steering column and the wheels over a digital, > software controlled one almost every time. At least I know how to > interpret some of the feedback I get that way based on other > experiences in life. > > What would be nice is if software people would know enough physics and > mathematics to carefully design and thoroughly test algorithms that > will behave more closely to their physical analogs found in nature -- > or else develop new models that are "readily learnable" from natural > experiences elsewhere, so that whatever the behavior happens to be it > is close enough to what one might find at our macro scale of life to > be considered congruent to natural laws. But that requires a solid > knowledge of those laws in order to know which end is up. > >> I can't agree with you more that building something that can't do it's >> job is poor engineering. I think much of the reason that software >> becomes a problem is when people with only software expertise are called >> on to write software to embody things like charge algorithms. > > Software people involved in embedded work that interacts with nature > (as opposed to embedded work, for example, that is about iPods or cell > phones, where the nature-part of the system may be limited to knowing > the human eye and hand well), should know some electronics, physics, > numerical methods, signal processing, and mathematics. In the end, it > is the embedded software developer who is bringing everything together > into a successful system (or one that isn't.) They must be able to > interpret the work of physicists, electronics designers, and so on and > be involved early so that issues related to software that others may > not be as well informed about can be brought forward earlier and > considered. This can include a wide spate, from numerical issuess few > physicists may be aware of when they write things down to issues that > others should have been aware of, but missed, such as z-space vs > s-space. It's always good to have someone else similarly informed > looking over the work to help catch things before they are baked into > the system. > > Of course, if it is a hand-held iPod, you might want someone versed in > various media formats and play methods. > > It boils down to having an embedded software engineer familiar with > the application space, I suppose. And not merely "a programmer." > This sounds more like a requirements problem to me. If your programmers are making up requirements... you have a much more inetresting problem. >> Consequently one ends up with a whole bunch of guesses embodied in the >> software, rather than a bunch of (or a few) correct conclusions. > > Indeed. When ignorant, a software programmer may not even realize > they are making flawed assumptions on their own or implementing the > flawed assumptions of others (such as a physicist's natural assumption > that operations and constants are infinitely precise.) > > Jon Everybody's ignorant about something. -- Les Cargill
From: John Devereux on 30 Sep 2009 00:30 John Larkin <jjlarkin(a)highNOTlandTHIStechnologyPART.com> writes: > On Tue, 29 Sep 2009 17:58:04 +0100, John Devereux > <john(a)devereux.me.uk> wrote: > >>John Larkin <jjlarkin(a)highNOTlandTHIStechnologyPART.com> writes: >> >>> On Tue, 29 Sep 2009 16:35:25 +0100, John Devereux >>> <john(a)devereux.me.uk> wrote: >> >>[...] >> >> >>>>Don't lead acid batteries charge at "constant voltage"? >>> >>> You could, but it's more common to connect them to a power supply that >>> has current and voltage limiting. The old dumb chargers were just a >>> high leakage inductance transformer and a rectifier, very sloppy >>> voltage and current limiting, and they worked fine. It was prudent to >>> remove them once the battery was charged, so's not to boil out all the >>> water in the battery. >>> >>>> >>>>That is, it is traditionally safe to apply a constant e.g. 14V to a good >>>>"12V" battery, and the charging will be self-limiting. When it's full, >>>>the current drops to a safe minimal value. >>>> >>>>But if you had a battery where 5 out of 6 cells are shorted out, then >>>>you are relying on that one good cell to terminate the charge >>>>safely. >>> >>> The cells weren't "shorted out", they were discharged. The fix is to >>> charge them. I have no idea of how you define "terminate the charge >>> safely." Personally, I'd terminate the charge when the battery is >>> charged. >> >>*Your* battery was (let us assume), but - playing devils advocate - it >> might be that this is in general a sign of a failed battery, not simply >> a discharged one. > > There's an easy way to find out: recharge it and see what happens. > >> >>> But it never will, your constant-current charger will keep on >>>>pushing maximum current through it, electrolysing the fluid. >>> >>> Please explain the chemistry of that. It sounds like no batteries can >>> be charged, ever. >> >>No idea really... I seem to recall something about overcharging >>liberating hydrogen and oxygen? The excess energy has to go somewhere, >>right? >> >>Wikipedia agrees with me, so there! >> >>"overcharging with high charging voltages will generate oxygen and >>hydrogen gas by electrolysis of water, forming an explosive mix." >> >><http://en.wikipedia.org/wiki/Lead-acid_battery> > > > 1.2 amps from a Lascar bench supply, overnight, is hardly > overcharging. Contrary to stated theory, the car works fine now. I thought we were discussing why the *battery chargers you bought* might refuse to charge? How many amps were those supposed to be? > I guess several of the posters here, if they left their lights on and > killed their battery, will always have their car towed and the battery > replaced. They have no need for jumper cables, and are happy buying > chargers that only charge batteries that don't need to be charged. Not me, I would have (and have done) exactly what you did. I have a nice 5A current limited bench supply that works great for that. <http://www.tti-test.com/go/er/elr-index.htm> But then *I'm* not going to sue TTi if my battery starts bubbling hydrogen :) -- John Devereux
From: Jon Kirwan on 30 Sep 2009 02:09 On Tue, 29 Sep 2009 23:36:30 -0400, Les Cargill <lcargill99(a)comcast.net> wrote: >Jon Kirwan wrote: >> On Mon, 28 Sep 2009 10:45:51 -0500, Tim Wescott <tim(a)seemywebsite.com> >> wrote: >> >>> On Mon, 28 Sep 2009 10:08:54 -0400, Phil Hobbs wrote: >>> >>>> Spehro Pefhany wrote: >>>>> On Mon, 28 Sep 2009 09:53:48 -0400, Phil Hobbs >>>>> <pcdhSpamMeSenseless(a)electrooptical.net> wrote: >>>>> >>>>>> John Larkin wrote: >>>>>>> Last time a car went dead in the garage, my wife's Fit, I hacked up a >>>>>>> charger from an old DSL wall-wart and a sabre saw as a series current >>>>>>> limiter. The garage geometry makes it essentially impossible for us >>>>>>> to push a car uphill to the street to jump it. Now The Brat left her >>>>>>> Echo in the garege for a month or so and it went dead, too. So I >>>>>>> figure it's time to buy a real charger. Went to Kragen Auto Parts and >>>>>>> bought two (one for here, one for Truckee) chargers. They are all >>>>>>> "smart chargers", namely switchers with electronics, these days. >>>>>>> >>>>>>> The battery is really dead, 1.8 volts. The first charger hums and >>>>>>> outputs nothing. Tried the next one: it hummed for maybe 3 seconds >>>>>>> then sparked and smoked inside. >>>>>>> >>>>>>> Went back to Kragen and traded up, two better chargers. Neither >>>>>>> charges... no current, battery steady at 1.8 volts. Both have their >>>>>>> "charging" LEDs off and "charge complete" LEDs lit. >>>>>>> >>>>>>> Back to Kragen, 3rd time, got all my money back. Passed by Bob >>>>>>> Pease's place all three trips, same collection of rusty VWs >>>>>>> everywhere. >>>>>>> >>>>>>> A charger that puts zero amps into a dead battery does that by >>>>>>> design, and there's only one reason to do that: to convince people >>>>>>> they need a new battery. Kragen's sales pitch was exactly along those >>>>>>> lines; "Tt won't charge, so all the cells are shorted." >>>>>>> >>>>>>> So I went to work and nabbed a cute little Lascar bench power supply. >>>>>>> It current limits at 1.2 amps, so I just cranked it up. The battery >>>>>>> went instantly to 16.5 volts, then settled down to 12 or so in a few >>>>>>> minutes, and is creeping back up. >>>>>>> >>>>>>> Interesting. >>>>>>> >>>>>>> So I guess I'll buy a couple of 3 amp or so lab supplies, with nice >>>>>>> volt and amp meters, instead of battery chargers. They're handier to >>>>>>> have around anyhow, cost about the same as a "good" charger, and >>>>>>> aren't booby trapped. >>>>>>> >>>>>>> What Kragen is doing is fraud. >>>>>>> >>>>>>> John >>>>>>> >>>>>> Or just get a nasty big iron Craftsman charger off eBay. Two >>>>>> transformer taps, rectifier, thermal cutout. >>>>>> >>>>>> Cheers >>>>>> >>>>>> Phil Hobbs >>>>> Many of the the newer battery chargers seem to do this.. they refuse to >>>>> charge if the battery is very dead. It's in the preferred algorithm >>>>> description for NiMH batteries too-- I just had to modify a charging >>>>> algorithm because people make mistakes and occasionally kill batteries >>>>> below the minimum charge voltage per cell and you need to be able to >>>>> override the (usually microcontroller-based) smart charger. And had the >>>>> same problem recently with a commercial charger for a stacker (sort of >>>>> a little fork lift). The deep discharge Marine duty battery was too >>>>> dead for the dumbf*ck little LM339 circuit to turn the SCR on. At first >>>>> we thought it had failed.. >>>> One of the problems with our software-intensive era is that the >>>> behaviour of ordinary objects has become arbitrary, like software, >>>> instead of merely ornery, like physics. >>>> >>>> It's nice to warn people, but building something that refuses to do the >>>> job it's built for is poor engineering. (Of course our current plague >>>> of tort lawyers is partly responsible, but only partly.) >>>> >>>> Cheers >>>> >>>> Phil Hobbs >>> OTOH, physics combined with real parts can get pretty ornery by itself; >>> there are decision trees that would take a square foot of board to do >>> with diodes and op-amps that can be done with an 8-pin PIC and a less >>> than 256 words of program memory. >> >> I think Phil's point (or the way I personally took it, anyway, as I >> really shouldn't attempt to speak for him) is that software allows >> behaviors that aren't at all similar to how nature itself operates. >> Nature is very, very consistent and once one learns it well, those >> lessons can be applied in new situations. When software is inserted >> into the mix, that can be quite a different story where no possible >> prior experience elsewhere may act to inform expectations. >> >> Prior digital states matter in bizarre ways, sometimes. >> >> Despite some possible advantages, I'll take an analog, physical >> connection between my steering column and the wheels over a digital, >> software controlled one almost every time. At least I know how to >> interpret some of the feedback I get that way based on other >> experiences in life. >> >> What would be nice is if software people would know enough physics and >> mathematics to carefully design and thoroughly test algorithms that >> will behave more closely to their physical analogs found in nature -- >> or else develop new models that are "readily learnable" from natural >> experiences elsewhere, so that whatever the behavior happens to be it >> is close enough to what one might find at our macro scale of life to >> be considered congruent to natural laws. But that requires a solid >> knowledge of those laws in order to know which end is up. >> >>> I can't agree with you more that building something that can't do it's >>> job is poor engineering. I think much of the reason that software >>> becomes a problem is when people with only software expertise are called >>> on to write software to embody things like charge algorithms. >> >> Software people involved in embedded work that interacts with nature >> (as opposed to embedded work, for example, that is about iPods or cell >> phones, where the nature-part of the system may be limited to knowing >> the human eye and hand well), should know some electronics, physics, >> numerical methods, signal processing, and mathematics. In the end, it >> is the embedded software developer who is bringing everything together >> into a successful system (or one that isn't.) They must be able to >> interpret the work of physicists, electronics designers, and so on and >> be involved early so that issues related to software that others may >> not be as well informed about can be brought forward earlier and >> considered. This can include a wide spate, from numerical issuess few >> physicists may be aware of when they write things down to issues that >> others should have been aware of, but missed, such as z-space vs >> s-space. It's always good to have someone else similarly informed >> looking over the work to help catch things before they are baked into >> the system. >> >> Of course, if it is a hand-held iPod, you might want someone versed in >> various media formats and play methods. >> >> It boils down to having an embedded software engineer familiar with >> the application space, I suppose. And not merely "a programmer." >> > >This sounds more like a requirements problem to me. If your programmers >are making up requirements... you have a much more inetresting problem. > >>> Consequently one ends up with a whole bunch of guesses embodied in the >>> software, rather than a bunch of (or a few) correct conclusions. >> >> Indeed. When ignorant, a software programmer may not even realize >> they are making flawed assumptions on their own or implementing the >> flawed assumptions of others (such as a physicist's natural assumption >> that operations and constants are infinitely precise.) >> >> Jon > >Everybody's ignorant about something. Which tells you nothing useful. In sharp contrast to what I wrote. Jon
From: Jan Panteltje on 30 Sep 2009 08:40
On a sunny day (Tue, 29 Sep 2009 16:09:58 -0700) it happened Joerg <invalid(a)invalid.invalid> wrote in <7ifie9F2vl82lU1(a)mid.individual.net>: >> Yea, but for some application this is really nice. >> http://panteltje.com/panteltje/pic/pwr_pic/ >> Well, I very rarely experience bangs, if so it is because of new years fireworks. >> > >That's because your switchers are probably fairly small or you can >afford to oversize your inductors. If your SMPS is >100W, the inductor >must be small and the whole thing has to be very fault tolerant you >either have current mode control or you cannot do it, usually. If you looked at the diagram, and also the picture of the test setup here: http://panteltje.com/panteltje/pic/pwr_pic/ then you would have noticed a current transformer. In the picture you can also clearly see the small ring core current transformer I used. That is why it never goes 'bang' here. There are 2 possibilities with this circuit, when controlled externally via RS232, you can set the reference voltage of the comparator that compares the output peak current to an internal reference, so cycle by cycle current limit. Or you can use a potentiometer, and set that reference voltage by hand, This is why I mentioned lab supply. as this provides the current limit in that application. Because of the cycle by cycle current limit things work safely. In a true 'current mode' supply the reference voltage of the cycle by cycle current comparator is set by comparing the output voltage against a reference voltage, so you in fact set the output voltage by regulating the output current. The advantage is that you only have a single pole in your feedback loop. The PIC example does not do that however, because it is using an on / off stabilisation loop for the voltage regulation, one that does not require a complicated feedback filter either, and is lightning fast (much faster then you can do with a PID in software). So in fact has the advantages of a true current mode, while possibly being faster. I think, but have not tried, if you wanted, you could clamp down the reference of the current comparator with the output of the voltage comparator, making a real current mode, but I see no advantage here at all. Just a difference in wiring. As to how much power, that is an incredible misconception. That only depends on the external circuit, not on the controller. Sure you will need other switching components, with different drivers, but for the control loop it makes no difference if you regulate 1 mW or 1 kW. If you were really fast, like Lucky Luke, who shoots faster then light (his shadow), then you could do it by hand.. |