battery chargers, again
in [Design]
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From: John Larkin on 2 Oct 2009 11:44 On Fri, 02 Oct 2009 07:41:51 -0700, Joerg <invalid(a)invalid.invalid> wrote: >John Larkin wrote: >> On Thu, 01 Oct 2009 14:09:56 -0700, Joerg <invalid(a)invalid.invalid> >> wrote: >> >>> John Larkin wrote: >>>> On Thu, 01 Oct 2009 13:48:49 -0700, Joerg <invalid(a)invalid.invalid> >>>> wrote: >>>> >>>>> John Larkin wrote: >>>>>> On Thu, 01 Oct 2009 13:10:44 -0700, Joerg <invalid(a)invalid.invalid> >>>>>> wrote: >>>>>> >>>>>>> John Larkin wrote: >>>>>>>> On Wed, 30 Sep 2009 14:40:06 -0700, Joerg <invalid(a)invalid.invalid> >>>>>>>> wrote: >>>>>>>> >>>>>>>>> John Larkin wrote: >>>>>>>>>> On Wed, 30 Sep 2009 16:04:00 -0500, Vladimir Vassilevsky >>>>>>>>>> <nospam(a)nowhere.com> wrote: >>>>>>>>>> >>>>>>>>>>> John Larkin wrote: >>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>>> I'm working on a smallish board that has four switchers in one corner >>>>>>>>>>>> and an ADC that's looking for a 1 nV spectral line in the other, >>>>>>>>>>> The 1nV over the background of how many nV/root(Hz) ? >>>>>>>>>> About 1. That's our target noise floor. The existing system is >>>>>>>>>> ballpark 100 nv/rtHz with huge birdies all over the place. >>>>>>>>>> >>>>>>>>>> Never let scientists design electronics. >>>>>>>>>> >>>>>>>>>>>> range >>>>>>>>>>>> of interest straddling all the switcher frequencies. >>>>>>>>>>> Synchronize the switchers away from the particular frequency of interest? >>>>>>>>>> The signals can be all over the place. >>>>>>>>>> >>>>>>>>>>>> I'm planning on >>>>>>>>>>>> spread-spectrum wobulating all the switchers, just in case. >>>>>>>>>>> So the dirt will be in band for sure? >>>>>>>>>> Yup. Operating range is audio to many MHz, all at once. We digitize at >>>>>>>>>> 64 Ms/s and FFT and see what's there. >>>>>>>>>> >>>>>>>>> How many MHz is "many"? And how much power does the biggest of the >>>>>>>>> switchers have to deliver? >>>>>>>> 20-ish. And just a couple of watts. I need 5, 3.3, 2.5, 1.8, 1.2, and >>>>>>>> -5. All from +12. >>>>>>>> >>>>>>> Theoretically you could run it at 27.12MHz but that's nasty. If you >>>>>>> can't stomach the dissipation of linears then you may be stuck with some >>>>>>> spectral dodging scheme like the one I described. We do that in >>>>>>> ultrasound sometimes but there I could always get a few clock control >>>>>>> lines from some a DSP or FPGA. If I bought the digital and SW guys some >>>>>>> beers that night ... >>>>>> I've got a couple of switcher eval boards around. Maybe I should fire >>>>>> some up and experiment with FMing the switcher freqs and see what that >>>>>> does to the spectrum and to the output voltage. >>>>>> >>>>> But first check the limit values. Or at least try them out with a >>>>> potmeter for the frequency set resistor. Easiest would be to have PWM >>>>> chips with a sync input. >>>> One of my guys wants to have the FPGA synthesize a bunch of FMd clocks >>>> and dump that into the reg sync inputs. I was planning to make an >>>> analog triangle and squirt a little of it into the pins where the freq >>>> set resistors connect. >>>> >>> For a test your method would be faster. For production, not so much, >>> because you'd have to have a servo'ed dual MOSFET in that path. Rohm >>> makes them, cheap, if that's the plan at the end. >> >> >> I don't follow that. If I make a simple triangle wave, maybe 0.5 volts >> p-p, a few KHz maybe, and run it through a big resistor into the >> regulator pin that the timing resistor connects to, it should FM the >> switcher's frequency. I'll check all the regs to make sure, but the >> Fset pins are usually at DC, and the Fset resistor usually sets a DC >> current that the chip uses to make frequency. >> > >On most newer ones it does (simulating one right now). But there are >some that do it "NE555-style". Even then you can sometimes get away with >current injection but it needs to be vetted for each chip type you are >using. > > >> If I have, say, a 1 MHz switcher and push it +-1%, that's 20 KHz p-p, >> so I should reduce the amplitude of a 1 MHz birdie by about 20,000:1 >> in a 1 Hz BW situation. Not that much in real life, but even 100:1 is >> a good number. >> > >Why not go all out and do +/-10% or more? The issue would be whether FMing the switch frequency would result in ripple on the output rail. First-order, it shouldn't. I'll have to try it. I've been doing too much business crud and need some hardware time anyhow. Maybe I'll include an FM deviation trimpot on the board. Or make the amplitude and frequency programmable from the FPGA. Or go with Rob's idea and synthesize the switch frequencies and sync all the regulators. John
From: Joerg on 2 Oct 2009 11:59 John Larkin wrote: > On Fri, 02 Oct 2009 07:41:51 -0700, Joerg <invalid(a)invalid.invalid> > wrote: > >> John Larkin wrote: >>> On Thu, 01 Oct 2009 14:09:56 -0700, Joerg <invalid(a)invalid.invalid> >>> wrote: >>> >>>> John Larkin wrote: >>>>> On Thu, 01 Oct 2009 13:48:49 -0700, Joerg <invalid(a)invalid.invalid> >>>>> wrote: >>>>> >>>>>> John Larkin wrote: >>>>>>> On Thu, 01 Oct 2009 13:10:44 -0700, Joerg <invalid(a)invalid.invalid> >>>>>>> wrote: >>>>>>> >>>>>>>> John Larkin wrote: >>>>>>>>> On Wed, 30 Sep 2009 14:40:06 -0700, Joerg <invalid(a)invalid.invalid> >>>>>>>>> wrote: >>>>>>>>> >>>>>>>>>> John Larkin wrote: >>>>>>>>>>> On Wed, 30 Sep 2009 16:04:00 -0500, Vladimir Vassilevsky >>>>>>>>>>> <nospam(a)nowhere.com> wrote: >>>>>>>>>>> >>>>>>>>>>>> John Larkin wrote: >>>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>>> I'm working on a smallish board that has four switchers in one corner >>>>>>>>>>>>> and an ADC that's looking for a 1 nV spectral line in the other, >>>>>>>>>>>> The 1nV over the background of how many nV/root(Hz) ? >>>>>>>>>>> About 1. That's our target noise floor. The existing system is >>>>>>>>>>> ballpark 100 nv/rtHz with huge birdies all over the place. >>>>>>>>>>> >>>>>>>>>>> Never let scientists design electronics. >>>>>>>>>>> >>>>>>>>>>>>> range >>>>>>>>>>>>> of interest straddling all the switcher frequencies. >>>>>>>>>>>> Synchronize the switchers away from the particular frequency of interest? >>>>>>>>>>> The signals can be all over the place. >>>>>>>>>>> >>>>>>>>>>>>> I'm planning on >>>>>>>>>>>>> spread-spectrum wobulating all the switchers, just in case. >>>>>>>>>>>> So the dirt will be in band for sure? >>>>>>>>>>> Yup. Operating range is audio to many MHz, all at once. We digitize at >>>>>>>>>>> 64 Ms/s and FFT and see what's there. >>>>>>>>>>> >>>>>>>>>> How many MHz is "many"? And how much power does the biggest of the >>>>>>>>>> switchers have to deliver? >>>>>>>>> 20-ish. And just a couple of watts. I need 5, 3.3, 2.5, 1.8, 1.2, and >>>>>>>>> -5. All from +12. >>>>>>>>> >>>>>>>> Theoretically you could run it at 27.12MHz but that's nasty. If you >>>>>>>> can't stomach the dissipation of linears then you may be stuck with some >>>>>>>> spectral dodging scheme like the one I described. We do that in >>>>>>>> ultrasound sometimes but there I could always get a few clock control >>>>>>>> lines from some a DSP or FPGA. If I bought the digital and SW guys some >>>>>>>> beers that night ... >>>>>>> I've got a couple of switcher eval boards around. Maybe I should fire >>>>>>> some up and experiment with FMing the switcher freqs and see what that >>>>>>> does to the spectrum and to the output voltage. >>>>>>> >>>>>> But first check the limit values. Or at least try them out with a >>>>>> potmeter for the frequency set resistor. Easiest would be to have PWM >>>>>> chips with a sync input. >>>>> One of my guys wants to have the FPGA synthesize a bunch of FMd clocks >>>>> and dump that into the reg sync inputs. I was planning to make an >>>>> analog triangle and squirt a little of it into the pins where the freq >>>>> set resistors connect. >>>>> >>>> For a test your method would be faster. For production, not so much, >>>> because you'd have to have a servo'ed dual MOSFET in that path. Rohm >>>> makes them, cheap, if that's the plan at the end. >>> >>> I don't follow that. If I make a simple triangle wave, maybe 0.5 volts >>> p-p, a few KHz maybe, and run it through a big resistor into the >>> regulator pin that the timing resistor connects to, it should FM the >>> switcher's frequency. I'll check all the regs to make sure, but the >>> Fset pins are usually at DC, and the Fset resistor usually sets a DC >>> current that the chip uses to make frequency. >>> >> On most newer ones it does (simulating one right now). But there are >> some that do it "NE555-style". Even then you can sometimes get away with >> current injection but it needs to be vetted for each chip type you are >> using. >> >> >>> If I have, say, a 1 MHz switcher and push it +-1%, that's 20 KHz p-p, >>> so I should reduce the amplitude of a 1 MHz birdie by about 20,000:1 >>> in a 1 Hz BW situation. Not that much in real life, but even 100:1 is >>> a good number. >>> >> Why not go all out and do +/-10% or more? > > The issue would be whether FMing the switch frequency would result in > ripple on the output rail. First-order, it shouldn't. I'll have to try > it. I've been doing too much business crud and need some hardware time > anyhow. > I don't think 10% will cause much in additional ripple. Certainly not if it's current-controlled siwtchers. > Maybe I'll include an FM deviation trimpot on the board. ... Trimpot? Euww ... > ... Or make the amplitude and frequency programmable from the FPGA. ... With a new "Larkin Switcher Agility" taskbar on the GUI :-) Seems nowadays every li'l program wants its own taskbar until the browser screen arrives at the size of a stamp. > ... Or go with Rob's > idea and synthesize the switch frequencies and sync all the > regulators. > I'd scatter them and not let them run in unison. Makes for a finer mush, or in chef-speak "puree'd". -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
From: John Larkin on 2 Oct 2009 12:34 On Fri, 02 Oct 2009 08:59:14 -0700, Joerg <invalid(a)invalid.invalid> wrote: >John Larkin wrote: >> On Fri, 02 Oct 2009 07:41:51 -0700, Joerg <invalid(a)invalid.invalid> >> wrote: >> >>> John Larkin wrote: >>>> On Thu, 01 Oct 2009 14:09:56 -0700, Joerg <invalid(a)invalid.invalid> >>>> wrote: >>>> >>>>> John Larkin wrote: >>>>>> On Thu, 01 Oct 2009 13:48:49 -0700, Joerg <invalid(a)invalid.invalid> >>>>>> wrote: >>>>>> >>>>>>> John Larkin wrote: >>>>>>>> On Thu, 01 Oct 2009 13:10:44 -0700, Joerg <invalid(a)invalid.invalid> >>>>>>>> wrote: >>>>>>>> >>>>>>>>> John Larkin wrote: >>>>>>>>>> On Wed, 30 Sep 2009 14:40:06 -0700, Joerg <invalid(a)invalid.invalid> >>>>>>>>>> wrote: >>>>>>>>>> >>>>>>>>>>> John Larkin wrote: >>>>>>>>>>>> On Wed, 30 Sep 2009 16:04:00 -0500, Vladimir Vassilevsky >>>>>>>>>>>> <nospam(a)nowhere.com> wrote: >>>>>>>>>>>> >>>>>>>>>>>>> John Larkin wrote: >>>>>>>>>>>>> >>>>>>>>>>>>> >>>>>>>>>>>>>> I'm working on a smallish board that has four switchers in one corner >>>>>>>>>>>>>> and an ADC that's looking for a 1 nV spectral line in the other, >>>>>>>>>>>>> The 1nV over the background of how many nV/root(Hz) ? >>>>>>>>>>>> About 1. That's our target noise floor. The existing system is >>>>>>>>>>>> ballpark 100 nv/rtHz with huge birdies all over the place. >>>>>>>>>>>> >>>>>>>>>>>> Never let scientists design electronics. >>>>>>>>>>>> >>>>>>>>>>>>>> range >>>>>>>>>>>>>> of interest straddling all the switcher frequencies. >>>>>>>>>>>>> Synchronize the switchers away from the particular frequency of interest? >>>>>>>>>>>> The signals can be all over the place. >>>>>>>>>>>> >>>>>>>>>>>>>> I'm planning on >>>>>>>>>>>>>> spread-spectrum wobulating all the switchers, just in case. >>>>>>>>>>>>> So the dirt will be in band for sure? >>>>>>>>>>>> Yup. Operating range is audio to many MHz, all at once. We digitize at >>>>>>>>>>>> 64 Ms/s and FFT and see what's there. >>>>>>>>>>>> >>>>>>>>>>> How many MHz is "many"? And how much power does the biggest of the >>>>>>>>>>> switchers have to deliver? >>>>>>>>>> 20-ish. And just a couple of watts. I need 5, 3.3, 2.5, 1.8, 1.2, and >>>>>>>>>> -5. All from +12. >>>>>>>>>> >>>>>>>>> Theoretically you could run it at 27.12MHz but that's nasty. If you >>>>>>>>> can't stomach the dissipation of linears then you may be stuck with some >>>>>>>>> spectral dodging scheme like the one I described. We do that in >>>>>>>>> ultrasound sometimes but there I could always get a few clock control >>>>>>>>> lines from some a DSP or FPGA. If I bought the digital and SW guys some >>>>>>>>> beers that night ... >>>>>>>> I've got a couple of switcher eval boards around. Maybe I should fire >>>>>>>> some up and experiment with FMing the switcher freqs and see what that >>>>>>>> does to the spectrum and to the output voltage. >>>>>>>> >>>>>>> But first check the limit values. Or at least try them out with a >>>>>>> potmeter for the frequency set resistor. Easiest would be to have PWM >>>>>>> chips with a sync input. >>>>>> One of my guys wants to have the FPGA synthesize a bunch of FMd clocks >>>>>> and dump that into the reg sync inputs. I was planning to make an >>>>>> analog triangle and squirt a little of it into the pins where the freq >>>>>> set resistors connect. >>>>>> >>>>> For a test your method would be faster. For production, not so much, >>>>> because you'd have to have a servo'ed dual MOSFET in that path. Rohm >>>>> makes them, cheap, if that's the plan at the end. >>>> >>>> I don't follow that. If I make a simple triangle wave, maybe 0.5 volts >>>> p-p, a few KHz maybe, and run it through a big resistor into the >>>> regulator pin that the timing resistor connects to, it should FM the >>>> switcher's frequency. I'll check all the regs to make sure, but the >>>> Fset pins are usually at DC, and the Fset resistor usually sets a DC >>>> current that the chip uses to make frequency. >>>> >>> On most newer ones it does (simulating one right now). But there are >>> some that do it "NE555-style". Even then you can sometimes get away with >>> current injection but it needs to be vetted for each chip type you are >>> using. >>> >>> >>>> If I have, say, a 1 MHz switcher and push it +-1%, that's 20 KHz p-p, >>>> so I should reduce the amplitude of a 1 MHz birdie by about 20,000:1 >>>> in a 1 Hz BW situation. Not that much in real life, but even 100:1 is >>>> a good number. >>>> >>> Why not go all out and do +/-10% or more? >> >> The issue would be whether FMing the switch frequency would result in >> ripple on the output rail. First-order, it shouldn't. I'll have to try >> it. I've been doing too much business crud and need some hardware time >> anyhow. >> > >I don't think 10% will cause much in additional ripple. Certainly not if >it's current-controlled siwtchers. > > >> Maybe I'll include an FM deviation trimpot on the board. ... > > >Trimpot? Euww ... The point being that, when the actual instrument is up and being driven by chemists, I'd like a quick and easy way to play with the spread-spectrum parameters to see the effects. I can always nail down the values once I know what works best. I often use fixed resistors but also put down pads for a pot so we can tweak the first articles without soldering. > >> ... Or make the amplitude and frequency programmable from the FPGA. ... > > >With a new "Larkin Switcher Agility" taskbar on the GUI :-) Exactly. The trimpot sounds easier. > >Seems nowadays every li'l program wants its own taskbar until the >browser screen arrives at the size of a stamp. > > >> ... Or go with Rob's >> idea and synthesize the switch frequencies and sync all the >> regulators. >> > >I'd scatter them and not let them run in unison. Makes for a finer mush, >or in chef-speak "puree'd". Certainly, if we do the digital sync thing, each reg would have its own synthesizer. If analog, I can just set their cf's here and there and scale the FMs with resistors. John
From: Joerg on 2 Oct 2009 12:49 John Larkin wrote: > On Fri, 02 Oct 2009 08:59:14 -0700, Joerg <invalid(a)invalid.invalid> > wrote: > >> John Larkin wrote: [...] >>> Maybe I'll include an FM deviation trimpot on the board. ... >> >> Trimpot? Euww ... > > The point being that, when the actual instrument is up and being > driven by chemists, I'd like a quick and easy way to play with the > spread-spectrum parameters to see the effects. I can always nail down > the values once I know what works best. I often use fixed resistors > but also put down pads for a pot so we can tweak the first articles > without soldering. > I just had my potmeter comeuppance yesterday. I am very much against those things and it proved the point. Built a tester jig for a client, just for engineering, they didn't want SCADA controls on that (tried to convince them and now wish they had agreed ...). Sure enough the Murata "10-turn" potmeter exhibits a huge dead spot around the point where they said they wanted it. Like a half turn of slack and you can't get the pot inside that area. Hurumph! I believe nowadays they just put cheap regular pots in there and roach a worm gear onto them so they can be called 10-turn. [...] -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
From: John Larkin on 2 Oct 2009 13:32
On Fri, 02 Oct 2009 07:59:11 -0700, Joerg <invalid(a)invalid.invalid> wrote: >John Larkin wrote: >> On Thu, 01 Oct 2009 14:10:05 -0700, Rich Grise <richgrise(a)example.net> >> wrote: >> >>> On Wed, 30 Sep 2009 20:38:29 -0400, Spehro Pefhany wrote: >>>> On Tue, 29 Sep 2009 15:18:12 -0700, the renowned Rich Grise >>>>> On Tue, 29 Sep 2009 10:24:57 -0700, John Larkin wrote: >>>>>> ... >>>>>> 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. >>>>>> >>>>> Ouch! John, I've never heard you scathe before, but geez! This post >>>>> singed my eyebrows! >>>>> >>>>> Keep it up. >:-> It helps dispel that "leprechaun" image. ;-D >>>> Something like this http://www.speff.com/jl.jpg ? >>>> >>> Eek! Heavens, no! John is cute as a button! It's just that he's about >>> 5'6" or so, a bit wiry, and Irish. :-) (I met him face-to-face at a trade >>> show in Long Beach a couple of years ago, and picked up some of his >>> refrigerator magnets.) :-) >>> >> >> That's what we give out these days, instead of pots of gold. >> > >Just got assembled boards back from AA-PCB yesterday. They threw in a >bag of trail mix. I usually get Bible verse flyers. John |