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Boost Converter Tutorial?

Started by Jim Thompson February 11, 2012
On Sat, 11 Feb 2012 18:20:30 -0500, Spehro Pefhany
<speffSNIP@interlogDOTyou.knowwhat> wrote:

>On Sat, 11 Feb 2012 11:26:18 -0700, the renowned Jim Thompson ><To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote: > >>On Sat, 11 Feb 2012 13:25:00 -0500, Phil Hobbs >><pcdhSpamMeSenseless@electrooptical.net> wrote: >> >>>Jim Thompson wrote: >>>> >>>> In the past I have designed boost converters in burst mode, with peak >>>> current control, but never with a PWM-controlled loop. >>>> >>>> Outputs: +5 @ 25mA, -5V @ 20mA >>>> >>>> Can someone point me to a tutorial? >>>> >>>> Thanks! >>>> >>>> [Don't point me to an off-the-shelf part. This has to go into a >>>> _custom_ chip... just a little thing... 1mm x 25mm :-] >>> >>>Hmm, an inch long and a millimeter wide--it's for a robotic cockroach, >>>right? >>> >>>Cheers >>> >>>Phil Hobbs >> >>Nope. It goes in something that virtually every person owns :-) >> >> ...Jim Thompson > >Display driver. > > >Best regards, >Spehro Pefhany
Of course ;-) ...Jim Thompson -- | James E.Thompson, CTO | 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.
On Sat, 11 Feb 2012 19:21:29 -0600, Tim Wescott <tim@seemywebsite.com>
wrote:

>On Sat, 11 Feb 2012 13:18:28 -0700, Jim Thompson wrote: > >> On Sat, 11 Feb 2012 13:59:29 -0600, Tim Wescott >> <tim@seemywebsite.please> wrote: >> >>>On Sat, 11 Feb 2012 11:22:38 -0700, Jim Thompson wrote: >>> >>>> In the past I have designed boost converters in burst mode, with peak >>>> current control, but never with a PWM-controlled loop. >>>> >>>> Outputs: +5 @ 25mA, -5V @ 20mA >>>> >>>> Can someone point me to a tutorial? >>>> >>>> Thanks! >>>> >>>> [Don't point me to an off-the-shelf part. This has to go into a >>>> _custom_ chip... just a little thing... 1mm x 25mm :-] >>> >>>Actually, I'd go looking at off-the-shelf parts to snag ideas from. >>> >>>Efficiency? >> >> As high as practical. >> >>>Regulation bounds? >> >> Loose. Lots of compensating innards for power supply variation. >> >>> % of total product cost that'll be taken >>>up by the converter? >> >> They've already committed to external switch(es) >> >> >>>Unless the above answers are "low, loose, and low", I think your biggest >>>challenge won't be the silicon, it'll be finding small, economical & >>>high performance inductors, designing the thing to take advantage of >>>them, and dancing around the inevitable unstable zero in the boost >>>converter. >> >> The inductor _is_ a problem. They're already at their height limit and >> their present implementation (at lower current) is just pushing into >> saturation :-( >> >> >>>Are you planning on paying for the 0.3V drop of a Schottkey on each >>>supply, or the time & trouble to drive the extra two switches & make it >>>synchronous? >> >> That's up for debate. >> >> But this client is no onesy-twosy outfit... they just shipped their >> BILLIONETH chip! > >Oh joy -- so, do you have the frequency headroom to use a lower >inductance coil with the same core, to get the saturation current up?
That's where my thoughts are progressing... ...Jim Thompson -- | James E.Thompson, CTO | 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.
On 2/11/2012 8:21 PM, Tim Wescott wrote:
> On Sat, 11 Feb 2012 13:18:28 -0700, Jim Thompson wrote: > >> On Sat, 11 Feb 2012 13:59:29 -0600, Tim Wescott >> <tim@seemywebsite.please> wrote: >> >>> On Sat, 11 Feb 2012 11:22:38 -0700, Jim Thompson wrote: >>> >>>> In the past I have designed boost converters in burst mode, with peak >>>> current control, but never with a PWM-controlled loop. >>>> >>>> Outputs: +5 @ 25mA, -5V @ 20mA >>>> >>>> Can someone point me to a tutorial? >>>> >>>> Thanks! >>>> >>>> [Don't point me to an off-the-shelf part. This has to go into a >>>> _custom_ chip... just a little thing... 1mm x 25mm :-] >>> >>> Actually, I'd go looking at off-the-shelf parts to snag ideas from. >>> >>> Efficiency? >> >> As high as practical. >> >>> Regulation bounds? >> >> Loose. Lots of compensating innards for power supply variation. >> >>> % of total product cost that'll be taken >>> up by the converter? >> >> They've already committed to external switch(es) >> >> >>> Unless the above answers are "low, loose, and low", I think your biggest >>> challenge won't be the silicon, it'll be finding small, economical& >>> high performance inductors, designing the thing to take advantage of >>> them, and dancing around the inevitable unstable zero in the boost >>> converter. >> >> The inductor _is_ a problem. They're already at their height limit and >> their present implementation (at lower current) is just pushing into >> saturation :-( >> >> >>> Are you planning on paying for the 0.3V drop of a Schottkey on each >>> supply, or the time& trouble to drive the extra two switches& make it >>> synchronous? >> >> That's up for debate. >> >> But this client is no onesy-twosy outfit... they just shipped their >> BILLIONETH chip! > > Oh joy -- so, do you have the frequency headroom to use a lower > inductance coil with the same core, to get the saturation current up? >
Just how big does this inductor have to be? Looking here: http://www.panasonic.com/industrial/components/pdf/AGA0000CE34.pdf A 100 uH 150 mA inductor looks like it could be a chip inductor a few mm high.
Jim Thompson wrote:
> > No. Think teenagers... what are they never seen without ?:-)
A stupid look on their face as they ignore you? ;-) -- You can't have a sense of humor, if you have no sense.
On Sat, 11 Feb 2012 12:53:50 -0700, Jim Thompson wrote:

> No. Think teenagers... what are they never seen without ?:-)
Zits? -- "For a successful technology, reality must take precedence over public relations, for nature cannot be fooled." (Richard Feynman)
On Sat, 11 Feb 2012 13:34:08 -0500, Phil Hobbs wrote:

> Jim Thompson wrote: >> >> On Sat, 11 Feb 2012 13:25:00 -0500, Phil Hobbs >> <pcdhSpamMeSenseless@electrooptical.net> wrote: >> >> >Jim Thompson wrote: >> >> >> >> In the past I have designed boost converters in burst mode, with >> >> peak current control, but never with a PWM-controlled loop. >> >> >> >> Outputs: +5 @ 25mA, -5V @ 20mA >> >> >> >> Can someone point me to a tutorial? >> >> >> >> Thanks! >> >> >> >> [Don't point me to an off-the-shelf part. This has to go into a >> >> _custom_ chip... just a little thing... 1mm x 25mm :-] >> > >> >Hmm, an inch long and a millimeter wide--it's for a robotic cockroach, >> >right? >> > >> >Cheers >> > >> >Phil Hobbs >> >> Nope. It goes in something that virtually every person owns :-) >> >> ...Jim Thompson > > So you decided to take someone's advice about what to do with your > design? > > Cheers > > Phil Hobbs
nnnnkkkkkk-splutter.. :D
On Feb 11, 8:49=A0pm, bitrex <bit...@de.lete.earthlink.net> wrote:
> On 2/11/2012 8:21 PM, Tim Wescott wrote: > > > > > On Sat, 11 Feb 2012 13:18:28 -0700, Jim Thompson wrote: > > >> On Sat, 11 Feb 2012 13:59:29 -0600, Tim Wescott > >> <t...@seemywebsite.please> =A0wrote: > > >>> On Sat, 11 Feb 2012 11:22:38 -0700, Jim Thompson wrote: > > >>>> In the past I have designed boost converters in burst mode, with pea=
k
> >>>> current control, but never with a PWM-controlled loop. > > >>>> Outputs: +5 @ 25mA, -5V @ 20mA > > >>>> Can someone point me to a tutorial? > > >>>> Thanks! > > >>>> [Don't point me to an off-the-shelf part. =A0This has to go into a > >>>> _custom_ chip... just a little thing... 1mm x 25mm :-] > > >>> Actually, I'd go looking at off-the-shelf parts to snag ideas from. > > >>> Efficiency? > > >> As high as practical. > > >>> Regulation bounds? > > >> Loose. =A0Lots of compensating innards for power supply variation. > > >>> =A0 % of total product cost that'll be taken > >>> up by the converter? > > >> They've already committed to external switch(es) > > >>> Unless the above answers are "low, loose, and low", I think your bigg=
est
> >>> challenge won't be the silicon, it'll be finding small, economical& > >>> high performance inductors, designing the thing to take advantage of > >>> them, and dancing around the inevitable unstable zero in the boost > >>> converter. > > >> The inductor _is_ a problem. =A0They're already at their height limit =
and
> >> their present implementation (at lower current) is just pushing into > >> saturation :-( > > >>> Are you planning on paying for the 0.3V drop of a Schottkey on each > >>> supply, or the time& =A0trouble to drive the extra two switches& =A0m=
ake it
> >>> synchronous? > > >> That's up for debate. > > >> But this client is no onesy-twosy outfit... they just shipped their > >> BILLIONETH chip! > > > Oh joy -- so, do you have the frequency headroom to use a lower > > inductance coil with the same core, to get the saturation current up? > > Just how big does this inductor have to be? Looking here:http://www.panas=
onic.com/industrial/components/pdf/AGA0000CE34.pdf
> > A 100 uH 150 mA inductor looks like it could be a chip inductor a few mm > high.
But 4 ohms d.c.r. means it'll drop 600mV @ 150mA. Increasing f by a factor of 3 reduces i^2*r loss by that same factor. Or, keep the loss and trade for a smaller L and C. Switching inductors without magnetic shields make RFI, magnetic nasties, etc. Shielded are better. -- Cheers, James Arthur
On Sat, 11 Feb 2012 20:21:29 -0000, "Ian Field"
<gangprobing.alien@ntlworld.com> wrote:

> >"Jim Thompson" <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote in >message news:i5fdj71se8ju71to9r931quld5qlig3rrd@4ax.com... >> On Sat, 11 Feb 2012 13:34:08 -0500, Phil Hobbs >> <pcdhSpamMeSenseless@electrooptical.net> wrote: >> >>>Jim Thompson wrote: >>>> >>>> On Sat, 11 Feb 2012 13:25:00 -0500, Phil Hobbs >>>> <pcdhSpamMeSenseless@electrooptical.net> wrote: >>>> >>>> >Jim Thompson wrote: >>>> >> >>>> >> In the past I have designed boost converters in burst mode, with peak >>>> >> current control, but never with a PWM-controlled loop. >>>> >> >>>> >> Outputs: +5 @ 25mA, -5V @ 20mA >>>> >> >>>> >> Can someone point me to a tutorial? >>>> >> >>>> >> Thanks! >>>> >> >>>> >> [Don't point me to an off-the-shelf part. This has to go into a >>>> >> _custom_ chip... just a little thing... 1mm x 25mm :-] >>>> > >>>> >Hmm, an inch long and a millimeter wide--it's for a robotic cockroach, >>>> >right? >>>> > >>>> >Cheers >>>> > >>>> >Phil Hobbs >>>> >>>> Nope. It goes in something that virtually every person owns :-) >>>> >>>> ...Jim Thompson >>> >>>So you decided to take someone's advice about what to do with your >>>design? >>> >>>Cheers >>> >>>Phil Hobbs >> >> This is but a small portion of the whole chip. As I said, I have no >> experience (*) with PWM'd boost converters, though lots of those with >> low output current, running burst mode (they have little or no >> stability issues). >> >> As Larkin would snark, If you've got something technical to say, then >> say it, otherwise STFU :-{) >> >> (*) Unlike some posters lurking here, I readily admit areas of which I >> have little or no expertise. Then I listen, learn and ultimately >> become the expert ;-) > > >Yeahbut you tried to cram a burst mode at one of my questions and I hadn't >even asked for a design.
--- Your "questions" are little more than trolls designed to attract and focus attention on you and, since you asked for "help" and it was offered and you rejected it, out of hand, you're an ingrate with an agenda disparate from ours, which is to help. ---
>It wasn't because burst mode was best for my app, it was because you didn't >know PWM - not exactly honest was it.
--- If he didn't know PWM and offered you burst mode instead, why was that dishonest at the time? After all, he did the best he could, with what he had at hand, which was better than anything you could come up with, since you were the one asking for help. -- JF
"John Fields" <jfields@austininstruments.com> wrote in message 
news:pbgjj75oo0aj4iue41q7r459okcavt1kg7@4ax.com...
> On Sat, 11 Feb 2012 20:21:29 -0000, "Ian Field" > <gangprobing.alien@ntlworld.com> wrote: > >> >>"Jim Thompson" <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote >>in >>message news:i5fdj71se8ju71to9r931quld5qlig3rrd@4ax.com... >>> On Sat, 11 Feb 2012 13:34:08 -0500, Phil Hobbs >>> <pcdhSpamMeSenseless@electrooptical.net> wrote: >>> >>>>Jim Thompson wrote: >>>>> >>>>> On Sat, 11 Feb 2012 13:25:00 -0500, Phil Hobbs >>>>> <pcdhSpamMeSenseless@electrooptical.net> wrote: >>>>> >>>>> >Jim Thompson wrote: >>>>> >> >>>>> >> In the past I have designed boost converters in burst mode, with >>>>> >> peak >>>>> >> current control, but never with a PWM-controlled loop. >>>>> >> >>>>> >> Outputs: +5 @ 25mA, -5V @ 20mA >>>>> >> >>>>> >> Can someone point me to a tutorial? >>>>> >> >>>>> >> Thanks! >>>>> >> >>>>> >> [Don't point me to an off-the-shelf part. This has to go into a >>>>> >> _custom_ chip... just a little thing... 1mm x 25mm :-] >>>>> > >>>>> >Hmm, an inch long and a millimeter wide--it's for a robotic >>>>> >cockroach, >>>>> >right? >>>>> > >>>>> >Cheers >>>>> > >>>>> >Phil Hobbs >>>>> >>>>> Nope. It goes in something that virtually every person owns :-) >>>>> >>>>> ...Jim Thompson >>>> >>>>So you decided to take someone's advice about what to do with your >>>>design? >>>> >>>>Cheers >>>> >>>>Phil Hobbs >>> >>> This is but a small portion of the whole chip. As I said, I have no >>> experience (*) with PWM'd boost converters, though lots of those with >>> low output current, running burst mode (they have little or no >>> stability issues). >>> >>> As Larkin would snark, If you've got something technical to say, then >>> say it, otherwise STFU :-{) >>> >>> (*) Unlike some posters lurking here, I readily admit areas of which I >>> have little or no expertise. Then I listen, learn and ultimately >>> become the expert ;-) >> >> >>Yeahbut you tried to cram a burst mode at one of my questions and I hadn't >>even asked for a design. > > --- > Your "questions" are little more than trolls designed to attract and > focus attention on you and, since you asked for "help" and it was > offered and you rejected it, out of hand, you're an ingrate with an > agenda disparate from ours, which is to help. > --- > >>It wasn't because burst mode was best for my app, it was because you >>didn't >>know PWM - not exactly honest was it. > > --- > If he didn't know PWM and offered you burst mode instead, why was that > dishonest at the time? > > After all, he did the best he could, with what he had at hand, which > was better than anything you could come up with, since you were the > one asking for help.
Do try to pay attention sometimes! All I asked for was load curves for bicycle dynamos. I didn't ask anyone to design it for me - I already have that well in hand. I didn't reject the few (unsolicited) solutions from the minority of smart-asses pretending to know more than they did - I just ignored them.
On Tue, 14 Feb 2012 13:14:29 -0000, "Ian Field"
<gangprobing.alien@ntlworld.com> wrote:


>I didn't reject the few (unsolicited) solutions from the minority of >smart-asses pretending to know more than they did - I just ignored them.
--- Well, since ignorance seems to be your strong suit, that was probably a good move on your part. -- JF