> Bypass caps are good, like wearing garlic to keep vampires away. They
> both work.
What if I put a bypass cap on the clove of garlic before wearing? Will
that keep twice as many vampires away? (Or a clove of garlic across the
bypass cap in a circuit. Hmm.)
>> If that is true, I would sort of think that the base of Q1 would be
>> towards the R4/R5 junction, the emitter would be grounded, and the
>> collector would go to the R1/R2 junction.
>
> Ideally yes, but the feedback polarity would be wrong.
If it was hooked up like I said, as the base goes more and more
negative, the transistor conducts less and less, and steals less current
from C1? That isn't what you want, yeah.
> When the output finally gets close to -12, the emitter of Q1 hits
> about -0.6, and Q1 starts to conduct.
> It's a common-base, non-inverting amplifier.
Aha. That, and the fact that negative voltages are involved, makes it
make sense to me.
I am used to seeing either common-emitter or common-collector circuits
with a single supply, where the signal into the base tells the
transistor what to do. From that perspective, having a grounded base
seemed weird at first - "it's never gonna do anything". The fact
that it isn't one of those topologies, plus the fact that there is a
negative supply, means the emitter can get down to a voltage where the
transistor will start turning on.
I have seen common-base circuits before, but drawn with the whole
transistor symbol rotated 90 degrees counterclockwise, mostly to
emphasise that something different is happening.
> As the emitter goes negative, Q1 collector current flows, pulling C1
> down, reducing the oscillator duty cycle.
The current "stolen" from C1 via Q1 ends up in the -12 V out, right?
Along with the < 1 mA from the +5 V reference that comes through R4 and
R5?
> It's not super accurate, but I'm just using it to power opamps.
If you needed more accuracy, and as long as the opamps need between a
few and few dozen mA or less, maybe you could follow your circuit with
a 79L12 and be happy. On the other hand, if the opamps only need a
couple of mA total, the current that the 79L12 needs to run becomes a
big part of the load. If you're running on a watch battery or
something, you're counting every mA.
> Certain Engineers Who Must Not Be Named think I should use Cuk
> converters or something complicated like that instead.
PIC, AVR or equal with a software PID loop. :)
Matt Roberds
Reply by John Larkin●July 27, 20132013-07-27
On Sat, 27 Jul 2013 04:13:51 +0000 (UTC), mroberds@att.net wrote:
>John Larkin <jlarkin@highlandtechnology.com> wrote:
>> Here's a schmitt-based voltage flipper. It's actually used on a couple
>> of products.
>>
>> https://dl.dropboxusercontent.com/u/53724080/Circuits/Power/DC_DC2.jpg
>
>Maybe I am extremely confused, but I don't understand why Q1 is
>connected the way it is.
>
>I think R1/R2/C1/U1 makes an oscillator when you turn on the juice.
>That turns Q2 on and off through R3. OK.
Right. The duty cycle, ignoring Q1, is about right to ramp up the load.
>
>When Q2 is on, a magnetic field builds up in L1. When Q2 turns off, the
>field collapses, inducing a voltage in L1. This is rectified by D1 and
>filtered by the capacitor that must not be named to become the -12 V
> out. OK.
VOLDECAP!
>
>C2 is a power supply bypass capacitor, probably to deal with the
>current peaks when Q2 is on. OK.
Bypass caps are good, like wearing garlic to keep vampires away. They both work.
>
>R4/R5/Q1 seem to be part of the feedback. I think the idea is that when
>the -12 V goes too far away from ground, you want the oscillator to have
>Q2 turned on for shorter amounts of time. I further think that the idea
>is to "steal" some of the current that would normally charge C1 and dump
>that current to ground instead, which changes how fast C1 charges.
OK.
>
>If that is true, I would sort of think that the base of Q1 would be
>towards the R4/R5 junction, the emitter would be grounded, and the
>collector would go to the R1/R2 junction.
Ideally yes, but the feedback polarity would be wrong.
>
>I'm not saying it doesn't work (it *is* in production); I am just
>trying to understand how it works.
When the output voltage is too low (that is, not negative enough, like -6 maybe)
the voltage divider R4-R5 will keep the emitter of Q1 positive, which keeps Q1
off. The RC Schmitt oscillator runs at the "powerup" duty cycle and pumps a
bunch of current into Voldecap. When the output finally gets close to -12, the
emitter of Q1 hits about -0.6, and Q1 starts to conduct. It's a common-base,
non-inverting amplifier. As the emitter goes negative, Q1 collector current
flows, pulling C1 down, reducing the oscillator duty cycle. It stabilizes with
the output voltage around -12.
It's not super accurate, but I'm just using it to power opamps.
Certain Engineers Who Must Not Be Named think I should use Cuk converters or
something complicated like that instead.
--
John Larkin Highland Technology Inc
www.highlandtechnology.com jlarkin at highlandtechnology dot com
Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom timing and laser controllers
Photonics and fiberoptic TTL data links
VME analog, thermocouple, LVDT, synchro, tachometer
Multichannel arbitrary waveform generators
Reply by ●July 27, 20132013-07-27
John Larkin <jlarkin@highlandtechnology.com> wrote:
Maybe I am extremely confused, but I don't understand why Q1 is
connected the way it is.
I think R1/R2/C1/U1 makes an oscillator when you turn on the juice.
That turns Q2 on and off through R3. OK.
When Q2 is on, a magnetic field builds up in L1. When Q2 turns off, the
field collapses, inducing a voltage in L1. This is rectified by D1 and
filtered by the capacitor that must not be named to become the -12 V
out. OK.
C2 is a power supply bypass capacitor, probably to deal with the
current peaks when Q2 is on. OK.
R4/R5/Q1 seem to be part of the feedback. I think the idea is that when
the -12 V goes too far away from ground, you want the oscillator to have
Q2 turned on for shorter amounts of time. I further think that the idea
is to "steal" some of the current that would normally charge C1 and dump
that current to ground instead, which changes how fast C1 charges.
If that is true, I would sort of think that the base of Q1 would be
towards the R4/R5 junction, the emitter would be grounded, and the
collector would go to the R1/R2 junction.
I'm not saying it doesn't work (it *is* in production); I am just
trying to understand how it works.
Matt Roberds
Reply by Bill Sloman●July 24, 20132013-07-24
On Wednesday, 24 July 2013 12:31:55 UTC+10, John Larkin wrote:
> On Tue, 23 Jul 2013 18:44:29 -0700, Jim Thompson
> <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote:
> >On Tue, 23 Jul 2013 17:36:05 -0700, John Larkin
> ><jlarkin@highlandtechnology.com> wrote=20
> >=20
> >>On Tue, 23 Jul 2013 16:27:02 -0700 (PDT), Klaus Kragelund
> >><klauskvik@hotmail.com> wrote:=20
> >>>On Wednesday, July 24, 2013 12:28:46 AM UTC+2, John Larkin wrote:=20
> >>>> On Tue, 23 Jul 2013 14:24:47 -0700, "Harry Dellamano"=20
> >>>> <harryd@tdsystems.org> wrote:
> >>>> >"John Larkin" <jlarkin@highlandtechnology.com> wrote in message =20
> >>>> >news:miqtu8logu045op9fds57o7v8o2a26gh6l@4ax.com...
> >>>> >> On Tue, 23 Jul 2013 12:49:12 -0700, "Harry Dellamano"
> >>>> >> <harryd@tdsystems.org> wrote:=20
<snip>
> >>>> >> The thing I posted was just a concept, a starting point for playi=
ng=20
> >>>> >> with. Like I said, I had to run to Safeway.
> >>>> >>
> >>>> >> I did a production board of something similar, a schmitt ac-coupl=
ed=20
> >>>> >> boost converter. It uses a comparator for the source current sens=
ing =20
> >>>> >> and it does have an RC in that path. The breadboard works fine an=
d I=20
> >>>> >> haven't blown up a single IC so far. The first PCB will be here o=
n
> >>>> >> Friday.=20
> >>>> >> =20
> >>>> >> This circuit doesn't mind a shorted load, because the mosfet peak
> >>>> >> current thing always works.=20
> >>>> >>
> >>>> >> Here's a schmitt-based voltage flipper. It's actually used on a c=
> >>>> >>> LTSpice.=20
> >>>> >>=20
> >>>> >> There *is* a schmitt trigger model too!=20
> >>>> > =20
> >>>> > Your sketch is a good case on point. If you replace the LM5112 wit=
h a=20
> >>>> >LTC3801 (6 pins) with your feedback scheme, you now have a solid P=
SU =20
> >>>> >and not a kludge.
> >>>>=20
> >>>> Why would you call a perfectly fine, works-as-designed,=20
> >>>> cute-as-a-button production circuit a kluge? Because it doesn't cost
> >>>> $3 and isn't blessed by some reference design?>=20
> >>>> =20
> >>>> Besides, the LTC3801 isn't good to 12 volts. Would it even work as a=
n=20
> >>>> inverter?=20
> >>>>=20
> >>>> I have used that topology often, with an "off the shelf" =20
> >>>> >coupled shielded inductor, to get tracking +/-V outputs.
> >>>> =20
> >>>> > Safeway?? Have you ever eaten at "Brown Sugar" in Oakland. We shou=
ld=20
> >>>> > meet there some time an have grits an eggs=20
> >>>> =20
> >>>> The food in San Francisco is fabulous, except for two glaring=20
> >>>> exceptions: no decent Cajun/Creole, and no good BBQ. Oakland has bot=
h.=20
> >>>> =20
> >>>> Sure, any time. I love grits. Or come to SF and I'll give you the=20
> >>>> plant tour and take you to Zuni. They have grits, except that they =
=20
> >>>> call it polenta and charge 4 times as much.=20
> >>>> Zuni is where I discovered cranberry beans.
> >>>>=20
> >>>> https://dl.dropboxusercontent.com/u/53724080/Food/Cranberry1.jpg=20
> >>>>=20
> >>>We should all meet at some time. I actually have met Joerg, great guy =
with > >>>his heart the right place (give my regards to your wife, if you r=
ead this)=20
> >>>=20
> >>>But, we would need bouncers, to keep JT and JL apart, although it seem=
s to > >>>be better the last couple of days ;-)
> >>>
> >>I've met Joerg too, took him to Zeitgeist for beers and burgers.
> >>=20
> >>Let's leave JT out. I shipped him a six-pack of our house beer, and he
> >>thanked me by saying truly vile things about my wife. Not that he's
> >>ever met her... just to be nasty.=20
> >
> >There you go again, tipping over the edge of your manic-depressive
> >self... what a sick puppy :-(
>=20
> There's nothing manic-depressive about calling you the coarse asshole tha=
t you
> are. And nothing wrong with defending my wife; she's worth a hundred of y=
ou.
A curiously quantitative assessment from somebody who can write dozens of l=
ines on electronics without getting closer to numbers than saying that some=
thing didn't include a $3 part.
Also a bit silly. Jim Thompson's net social worth may well be negative - an=
ybody who publicly speculates about shooting his neighbours after the count=
ry falls apart can't be considered as an asset to his neighbourhood - and i=
f John Larkin's wife worth was a 100 times more negative than Jim Thompson'=
s it would be a very negative assessment.
--=20
Bill Sloman, Sydney
Reply by John Larkin●July 23, 20132013-07-23
On Tue, 23 Jul 2013 18:44:29 -0700, Jim Thompson
<To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote:
>On Tue, 23 Jul 2013 17:36:05 -0700, John Larkin
><jlarkin@highlandtechnology.com> wrote:
>
>>On Tue, 23 Jul 2013 16:27:02 -0700 (PDT), Klaus Kragelund
>><klauskvik@hotmail.com> wrote:
>>
>>>On Wednesday, July 24, 2013 12:28:46 AM UTC+2, John Larkin wrote:
>>>> On Tue, 23 Jul 2013 14:24:47 -0700, "Harry Dellamano"
>>>>
>>>> <harryd@tdsystems.org> wrote:
>>>>
>>>>
>>>>
>>>> >
>>>>
>>>> >"John Larkin" <jlarkin@highlandtechnology.com> wrote in message
>>>>
>>>> >news:miqtu8logu045op9fds57o7v8o2a26gh6l@4ax.com...
>>>>
>>>> >> On Tue, 23 Jul 2013 12:49:12 -0700, "Harry Dellamano"
>>>>
>>>> >> <harryd@tdsystems.org> wrote:
>>>>
>>>> >>
>>>>
>>>> >>>
>>>>
>>>> >>> You folks are correct, it is not the cost of the parts but design time,
>>>>
>>>> >>>risk, heat and EMI just to name a few. I believe that you are taking a
>>>>
>>>> >>>risk
>>>>
>>>> >>>in your design without protection features that are normally needed. Such
>>>>
>>>> >>>as
>>>>
>>>> >>>under voltage shutdown and poor short circuit protection. If the 16V
>>>>
>>>> >>>supply
>>>>
>>>> >>>come up low or if the output is shorted you have a good chance of letting
>>>>
>>>> >>>the smoke out. In normal operation your design has a large charge dumping
>>>>
>>>> >>>spike at R1 at turn on. This screams for a 1nF cap at Q1-B to ground to
>>>>
>>>> >>>mitigate the spike but will greatly effect short circuit protection.
>>>>
>>>> >>>Needs
>>>>
>>>> >>>lots of tweaking.
>>>>
>>>> >>
>>>>
>>>> >> The thing I posted was just a concept, a starting point for playing
>>>>
>>>> >> with. Like I said, I had to run to Safeway.
>>>>
>>>> >>
>>>>
>>>> >> I did a production board of something similar, a schmitt ac-coupled
>>>>
>>>> >> boost converter. It uses a comparator for the source current sensing
>>>>
>>>> >> and it does have an RC in that path. The breadboard works fine and I
>>>>
>>>> >> haven't blown up a single IC so far. The first PCB will be here on
>>>>
>>>> >> Friday.
>>>>
>>>> >>
>>>>
>>>> >> This circuit doesn't mind a shorted load, because the mosfet peak
>>>>
>>>> >> current thing always works.
>>>>
>>>> >>
>>>>
>>>> >> Here's a schmitt-based voltage flipper. It's actually used on a couple
>>>>
>>>> >> of products.
>>>>
>>>> >>
>>>>
>>>> >> https://dl.dropboxusercontent.com/u/53724080/Circuits/Power/DC_DC2.jpg
>>>>
>>>> >>
>>>>
>>>> >>
>>>>
>>>> >>> I used the LT1242 only because it was the only model available in
>>>>
>>>> >>> LTSpice.
>>>>
>>>> >>
>>>>
>>>> >> There *is* a schmitt trigger model too!
>>>>
>>>> >>
>>>>
>>>> >>
>>>>
>>>> >> --
>>>>
>>>> >>
>>>>
>>>> >> John Larkin Highland Technology, Inc
>>>>
>>>> >>
>>>>
>>>> >
>>>>
>>>> > Your sketch is a good case on point. If you replace the LM5112 with a
>>>>
>>>> >LTC3801 (6 pins) with your feedback scheme, you now have a solid PSU and
>>>>
>>>> >not a kludge.
>>>>
>>>>
>>>>
>>>> Why would you call a perfectly fine, works-as-designed,
>>>>
>>>> cute-as-a-button production circuit a kluge? Because it doesn't cost
>>>>
>>>> $3 and isn't blessed by some reference design?
>>>>
>>>>
>>>>
>>>> Besides, the LTC3801 isn't good to 12 volts. Would it even work as an
>>>>
>>>> inverter?
>>>>
>>>>
>>>>
>>>> I have used that topology often, with an "off the shelf"
>>>>
>>>> >coupled shielded inductor, to get tracking +/-V outputs.
>>>>
>>>> > Safeway?? Have you ever eaten at "Brown Sugar" in Oakland. We should meet
>>>>
>>>> >there some time an have grits an eggs.
>>>>
>>>>
>>>>
>>>> The food in San Francisco is fabulous, except for two glaring
>>>>
>>>> exceptions: no decent Cajun/Creole, and no good BBQ. Oakland has both.
>>>>
>>>>
>>>>
>>>> Sure, any time. I love grits. Or come to SF and I'll give you the
>>>>
>>>> plant tour and take you to Zuni. They have grits, except that they
>>>>
>>>> call it polenta and charge 4 times as much.
>>>>
>>>>
>>>>
>>>> Zuni is where I discovered cranberry beans.
>>>>
>>>>
>>>>
>>>> https://dl.dropboxusercontent.com/u/53724080/Food/Cranberry1.jpg
>>>>
>>>>
>>>
>>>We should all meet at some time. I actually have met Joerg, great guy with his heart the right place (give my regards to your wife, if you read this)
>>>
>>>But, we would need bouncers, to keep JT and JL apart, although it seems to be better the last couple of days ;-)
>>>
>>>Cheers
>>>
>>>Klaus
>>
>>I've met Joerg too, took him to Zeitgeist for beers and burgers.
>>
>>Let's leave JT out. I shipped him a six-pack of our house beer, and he
>>thanked me by saying truly vile things about my wife. Not that he's
>>ever met her... just to be nasty.
>
>There you go again, tipping over the edge of your manic-depressive
>self... what a sick puppy :-(
>
> ...Jim Thompson
There's nothing manic-depressive about calling you the coarse asshole that you
are. And nothing wrong with defending my wife; she's worth a hundred of you.
--
John Larkin Highland Technology Inc
www.highlandtechnology.com jlarkin at highlandtechnology dot com
Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom timing and laser controllers
Photonics and fiberoptic TTL data links
VME analog, thermocouple, LVDT, synchro, tachometer
Multichannel arbitrary waveform generators
Reply by Jim Thompson●July 23, 20132013-07-23
On Tue, 23 Jul 2013 17:36:05 -0700, John Larkin
<jlarkin@highlandtechnology.com> wrote:
>On Tue, 23 Jul 2013 16:27:02 -0700 (PDT), Klaus Kragelund
><klauskvik@hotmail.com> wrote:
>
>>On Wednesday, July 24, 2013 12:28:46 AM UTC+2, John Larkin wrote:
>>> On Tue, 23 Jul 2013 14:24:47 -0700, "Harry Dellamano"
>>>
>>> <harryd@tdsystems.org> wrote:
>>>
>>>
>>>
>>> >
>>>
>>> >"John Larkin" <jlarkin@highlandtechnology.com> wrote in message
>>>
>>> >news:miqtu8logu045op9fds57o7v8o2a26gh6l@4ax.com...
>>>
>>> >> On Tue, 23 Jul 2013 12:49:12 -0700, "Harry Dellamano"
>>>
>>> >> <harryd@tdsystems.org> wrote:
>>>
>>> >>
>>>
>>> >>>
>>>
>>> >>> You folks are correct, it is not the cost of the parts but design time,
>>>
>>> >>>risk, heat and EMI just to name a few. I believe that you are taking a
>>>
>>> >>>risk
>>>
>>> >>>in your design without protection features that are normally needed. Such
>>>
>>> >>>as
>>>
>>> >>>under voltage shutdown and poor short circuit protection. If the 16V
>>>
>>> >>>supply
>>>
>>> >>>come up low or if the output is shorted you have a good chance of letting
>>>
>>> >>>the smoke out. In normal operation your design has a large charge dumping
>>>
>>> >>>spike at R1 at turn on. This screams for a 1nF cap at Q1-B to ground to
>>>
>>> >>>mitigate the spike but will greatly effect short circuit protection.
>>>
>>> >>>Needs
>>>
>>> >>>lots of tweaking.
>>>
>>> >>
>>>
>>> >> The thing I posted was just a concept, a starting point for playing
>>>
>>> >> with. Like I said, I had to run to Safeway.
>>>
>>> >>
>>>
>>> >> I did a production board of something similar, a schmitt ac-coupled
>>>
>>> >> boost converter. It uses a comparator for the source current sensing
>>>
>>> >> and it does have an RC in that path. The breadboard works fine and I
>>>
>>> >> haven't blown up a single IC so far. The first PCB will be here on
>>>
>>> >> Friday.
>>>
>>> >>
>>>
>>> >> This circuit doesn't mind a shorted load, because the mosfet peak
>>>
>>> >> current thing always works.
>>>
>>> >>
>>>
>>> >> Here's a schmitt-based voltage flipper. It's actually used on a couple
>>>
>>> >> of products.
>>>
>>> >>
>>>
>>> >> https://dl.dropboxusercontent.com/u/53724080/Circuits/Power/DC_DC2.jpg
>>>
>>> >>
>>>
>>> >>
>>>
>>> >>> I used the LT1242 only because it was the only model available in
>>>
>>> >>> LTSpice.
>>>
>>> >>
>>>
>>> >> There *is* a schmitt trigger model too!
>>>
>>> >>
>>>
>>> >>
>>>
>>> >> --
>>>
>>> >>
>>>
>>> >> John Larkin Highland Technology, Inc
>>>
>>> >>
>>>
>>> >
>>>
>>> > Your sketch is a good case on point. If you replace the LM5112 with a
>>>
>>> >LTC3801 (6 pins) with your feedback scheme, you now have a solid PSU and
>>>
>>> >not a kludge.
>>>
>>>
>>>
>>> Why would you call a perfectly fine, works-as-designed,
>>>
>>> cute-as-a-button production circuit a kluge? Because it doesn't cost
>>>
>>> $3 and isn't blessed by some reference design?
>>>
>>>
>>>
>>> Besides, the LTC3801 isn't good to 12 volts. Would it even work as an
>>>
>>> inverter?
>>>
>>>
>>>
>>> I have used that topology often, with an "off the shelf"
>>>
>>> >coupled shielded inductor, to get tracking +/-V outputs.
>>>
>>> > Safeway?? Have you ever eaten at "Brown Sugar" in Oakland. We should meet
>>>
>>> >there some time an have grits an eggs.
>>>
>>>
>>>
>>> The food in San Francisco is fabulous, except for two glaring
>>>
>>> exceptions: no decent Cajun/Creole, and no good BBQ. Oakland has both.
>>>
>>>
>>>
>>> Sure, any time. I love grits. Or come to SF and I'll give you the
>>>
>>> plant tour and take you to Zuni. They have grits, except that they
>>>
>>> call it polenta and charge 4 times as much.
>>>
>>>
>>>
>>> Zuni is where I discovered cranberry beans.
>>>
>>>
>>>
>>> https://dl.dropboxusercontent.com/u/53724080/Food/Cranberry1.jpg
>>>
>>>
>>
>>We should all meet at some time. I actually have met Joerg, great guy with his heart the right place (give my regards to your wife, if you read this)
>>
>>But, we would need bouncers, to keep JT and JL apart, although it seems to be better the last couple of days ;-)
>>
>>Cheers
>>
>>Klaus
>
>I've met Joerg too, took him to Zeitgeist for beers and burgers.
>
>Let's leave JT out. I shipped him a six-pack of our house beer, and he
>thanked me by saying truly vile things about my wife. Not that he's
>ever met her... just to be nasty.
There you go again, tipping over the edge of your manic-depressive
self... what a sick puppy :-(
...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 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.
Reply by John Larkin●July 23, 20132013-07-23
On Tue, 23 Jul 2013 16:27:02 -0700 (PDT), Klaus Kragelund
<klauskvik@hotmail.com> wrote:
>On Wednesday, July 24, 2013 12:28:46 AM UTC+2, John Larkin wrote:
>> On Tue, 23 Jul 2013 14:24:47 -0700, "Harry Dellamano"
>>
>> <harryd@tdsystems.org> wrote:
>>
>>
>>
>> >
>>
>> >"John Larkin" <jlarkin@highlandtechnology.com> wrote in message
>>
>> >news:miqtu8logu045op9fds57o7v8o2a26gh6l@4ax.com...
>>
>> >> On Tue, 23 Jul 2013 12:49:12 -0700, "Harry Dellamano"
>>
>> >> <harryd@tdsystems.org> wrote:
>>
>> >>
>>
>> >>>
>>
>> >>> You folks are correct, it is not the cost of the parts but design time,
>>
>> >>>risk, heat and EMI just to name a few. I believe that you are taking a
>>
>> >>>risk
>>
>> >>>in your design without protection features that are normally needed. Such
>>
>> >>>as
>>
>> >>>under voltage shutdown and poor short circuit protection. If the 16V
>>
>> >>>supply
>>
>> >>>come up low or if the output is shorted you have a good chance of letting
>>
>> >>>the smoke out. In normal operation your design has a large charge dumping
>>
>> >>>spike at R1 at turn on. This screams for a 1nF cap at Q1-B to ground to
>>
>> >>>mitigate the spike but will greatly effect short circuit protection.
>>
>> >>>Needs
>>
>> >>>lots of tweaking.
>>
>> >>
>>
>> >> The thing I posted was just a concept, a starting point for playing
>>
>> >> with. Like I said, I had to run to Safeway.
>>
>> >>
>>
>> >> I did a production board of something similar, a schmitt ac-coupled
>>
>> >> boost converter. It uses a comparator for the source current sensing
>>
>> >> and it does have an RC in that path. The breadboard works fine and I
>>
>> >> haven't blown up a single IC so far. The first PCB will be here on
>>
>> >> Friday.
>>
>> >>
>>
>> >> This circuit doesn't mind a shorted load, because the mosfet peak
>>
>> >> current thing always works.
>>
>> >>
>>
>> >> Here's a schmitt-based voltage flipper. It's actually used on a couple
>>
>> >> of products.
>>
>> >>
>>
>> >> https://dl.dropboxusercontent.com/u/53724080/Circuits/Power/DC_DC2.jpg
>>
>> >>
>>
>> >>
>>
>> >>> I used the LT1242 only because it was the only model available in
>>
>> >>> LTSpice.
>>
>> >>
>>
>> >> There *is* a schmitt trigger model too!
>>
>> >>
>>
>> >>
>>
>> >> --
>>
>> >>
>>
>> >> John Larkin Highland Technology, Inc
>>
>> >>
>>
>> >
>>
>> > Your sketch is a good case on point. If you replace the LM5112 with a
>>
>> >LTC3801 (6 pins) with your feedback scheme, you now have a solid PSU and
>>
>> >not a kludge.
>>
>>
>>
>> Why would you call a perfectly fine, works-as-designed,
>>
>> cute-as-a-button production circuit a kluge? Because it doesn't cost
>>
>> $3 and isn't blessed by some reference design?
>>
>>
>>
>> Besides, the LTC3801 isn't good to 12 volts. Would it even work as an
>>
>> inverter?
>>
>>
>>
>> I have used that topology often, with an "off the shelf"
>>
>> >coupled shielded inductor, to get tracking +/-V outputs.
>>
>> > Safeway?? Have you ever eaten at "Brown Sugar" in Oakland. We should meet
>>
>> >there some time an have grits an eggs.
>>
>>
>>
>> The food in San Francisco is fabulous, except for two glaring
>>
>> exceptions: no decent Cajun/Creole, and no good BBQ. Oakland has both.
>>
>>
>>
>> Sure, any time. I love grits. Or come to SF and I'll give you the
>>
>> plant tour and take you to Zuni. They have grits, except that they
>>
>> call it polenta and charge 4 times as much.
>>
>>
>>
>> Zuni is where I discovered cranberry beans.
>>
>>
>>
>> https://dl.dropboxusercontent.com/u/53724080/Food/Cranberry1.jpg
>>
>>
>
>We should all meet at some time. I actually have met Joerg, great guy with his heart the right place (give my regards to your wife, if you read this)
>
>But, we would need bouncers, to keep JT and JL apart, although it seems to be better the last couple of days ;-)
>
>Cheers
>
>Klaus
I've met Joerg too, took him to Zeitgeist for beers and burgers.
Let's leave JT out. I shipped him a six-pack of our house beer, and he
thanked me by saying truly vile things about my wife. Not that he's
ever met her... just to be nasty.
--
John Larkin Highland Technology, Inc
jlarkin at highlandtechnology dot com
http://www.highlandtechnology.com
Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom laser drivers and controllers
Photonics and fiberoptic TTL data links
VME thermocouple, LVDT, synchro acquisition and simulation
Reply by Klaus Kragelund●July 23, 20132013-07-23
On Wednesday, July 24, 2013 12:28:46 AM UTC+2, John Larkin wrote:
> On Tue, 23 Jul 2013 14:24:47 -0700, "Harry Dellamano"
>
> <harryd@tdsystems.org> wrote:
>
>
>
> >
>
> >"John Larkin" <jlarkin@highlandtechnology.com> wrote in message
>
> >news:miqtu8logu045op9fds57o7v8o2a26gh6l@4ax.com...
>
> >> On Tue, 23 Jul 2013 12:49:12 -0700, "Harry Dellamano"
>
> >> <harryd@tdsystems.org> wrote:
>
> >>
>
> >>>
>
> >>> You folks are correct, it is not the cost of the parts but design time,
>
> >>>risk, heat and EMI just to name a few. I believe that you are taking a
>
> >>>risk
>
> >>>in your design without protection features that are normally needed. Such
>
> >>>as
>
> >>>under voltage shutdown and poor short circuit protection. If the 16V
>
> >>>supply
>
> >>>come up low or if the output is shorted you have a good chance of letting
>
> >>>the smoke out. In normal operation your design has a large charge dumping
>
> >>>spike at R1 at turn on. This screams for a 1nF cap at Q1-B to ground to
>
> >>>mitigate the spike but will greatly effect short circuit protection.
>
> >>>Needs
>
> >>>lots of tweaking.
>
> >>
>
> >> The thing I posted was just a concept, a starting point for playing
>
> >> with. Like I said, I had to run to Safeway.
>
> >>
>
> >> I did a production board of something similar, a schmitt ac-coupled
>
> >> boost converter. It uses a comparator for the source current sensing
>
> >> and it does have an RC in that path. The breadboard works fine and I
>
> >> haven't blown up a single IC so far. The first PCB will be here on
>
> >> Friday.
>
> >>
>
> >> This circuit doesn't mind a shorted load, because the mosfet peak
>
> >> current thing always works.
>
> >>
>
> >> Here's a schmitt-based voltage flipper. It's actually used on a couple
>
> >> of products.
>
> >>
>
> >> https://dl.dropboxusercontent.com/u/53724080/Circuits/Power/DC_DC2.jpg
>
> >>
>
> >>
>
> >>> I used the LT1242 only because it was the only model available in
>
> >>> LTSpice.
>
> >>
>
> >> There *is* a schmitt trigger model too!
>
> >>
>
> >>
>
> >> --
>
> >>
>
> >> John Larkin Highland Technology, Inc
>
> >>
>
> >
>
> > Your sketch is a good case on point. If you replace the LM5112 with a
>
> >LTC3801 (6 pins) with your feedback scheme, you now have a solid PSU and
>
> >not a kludge.
>
>
>
> Why would you call a perfectly fine, works-as-designed,
>
> cute-as-a-button production circuit a kluge? Because it doesn't cost
>
> $3 and isn't blessed by some reference design?
>
>
>
> Besides, the LTC3801 isn't good to 12 volts. Would it even work as an
>
> inverter?
>
>
>
> I have used that topology often, with an "off the shelf"
>
> >coupled shielded inductor, to get tracking +/-V outputs.
>
> > Safeway?? Have you ever eaten at "Brown Sugar" in Oakland. We should meet
>
> >there some time an have grits an eggs.
>
>
>
> The food in San Francisco is fabulous, except for two glaring
>
> exceptions: no decent Cajun/Creole, and no good BBQ. Oakland has both.
>
>
>
> Sure, any time. I love grits. Or come to SF and I'll give you the
>
> plant tour and take you to Zuni. They have grits, except that they
>
> call it polenta and charge 4 times as much.
>
>
>
> Zuni is where I discovered cranberry beans.
>
>
>
> https://dl.dropboxusercontent.com/u/53724080/Food/Cranberry1.jpg
>
>
We should all meet at some time. I actually have met Joerg, great guy with his heart the right place (give my regards to your wife, if you read this)
But, we would need bouncers, to keep JT and JL apart, although it seems to be better the last couple of days ;-)
Cheers
Klaus
Reply by John Larkin●July 23, 20132013-07-23
On Tue, 23 Jul 2013 14:24:47 -0700, "Harry Dellamano"
<harryd@tdsystems.org> wrote:
>
>"John Larkin" <jlarkin@highlandtechnology.com> wrote in message
>news:miqtu8logu045op9fds57o7v8o2a26gh6l@4ax.com...
>> On Tue, 23 Jul 2013 12:49:12 -0700, "Harry Dellamano"
>> <harryd@tdsystems.org> wrote:
>>
>>>
>>> You folks are correct, it is not the cost of the parts but design time,
>>>risk, heat and EMI just to name a few. I believe that you are taking a
>>>risk
>>>in your design without protection features that are normally needed. Such
>>>as
>>>under voltage shutdown and poor short circuit protection. If the 16V
>>>supply
>>>come up low or if the output is shorted you have a good chance of letting
>>>the smoke out. In normal operation your design has a large charge dumping
>>>spike at R1 at turn on. This screams for a 1nF cap at Q1-B to ground to
>>>mitigate the spike but will greatly effect short circuit protection.
>>>Needs
>>>lots of tweaking.
>>
>> The thing I posted was just a concept, a starting point for playing
>> with. Like I said, I had to run to Safeway.
>>
>> I did a production board of something similar, a schmitt ac-coupled
>> boost converter. It uses a comparator for the source current sensing
>> and it does have an RC in that path. The breadboard works fine and I
>> haven't blown up a single IC so far. The first PCB will be here on
>> Friday.
>>
>> This circuit doesn't mind a shorted load, because the mosfet peak
>> current thing always works.
>>
>> Here's a schmitt-based voltage flipper. It's actually used on a couple
>> of products.
>>
>> https://dl.dropboxusercontent.com/u/53724080/Circuits/Power/DC_DC2.jpg
>>
>>
>>> I used the LT1242 only because it was the only model available in
>>> LTSpice.
>>
>> There *is* a schmitt trigger model too!
>>
>>
>> --
>>
>> John Larkin Highland Technology, Inc
>>
>
> Your sketch is a good case on point. If you replace the LM5112 with a
>LTC3801 (6 pins) with your feedback scheme, you now have a solid PSU and
>not a kludge.
Why would you call a perfectly fine, works-as-designed,
cute-as-a-button production circuit a kluge? Because it doesn't cost
$3 and isn't blessed by some reference design?
Besides, the LTC3801 isn't good to 12 volts. Would it even work as an
inverter?
I have used that topology often, with an "off the shelf"
>coupled shielded inductor, to get tracking +/-V outputs.
> Safeway?? Have you ever eaten at "Brown Sugar" in Oakland. We should meet
>there some time an have grits an eggs.
The food in San Francisco is fabulous, except for two glaring
exceptions: no decent Cajun/Creole, and no good BBQ. Oakland has both.
Sure, any time. I love grits. Or come to SF and I'll give you the
plant tour and take you to Zuni. They have grits, except that they
call it polenta and charge 4 times as much.
Zuni is where I discovered cranberry beans.
https://dl.dropboxusercontent.com/u/53724080/Food/Cranberry1.jpg
--
John Larkin Highland Technology, Inc
jlarkin at highlandtechnology dot com
http://www.highlandtechnology.com
Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom laser drivers and controllers
Photonics and fiberoptic TTL data links
VME thermocouple, LVDT, synchro acquisition and simulation
Reply by Harry Dellamano●July 23, 20132013-07-23
"John Larkin" <jlarkin@highlandtechnology.com> wrote in message
news:miqtu8logu045op9fds57o7v8o2a26gh6l@4ax.com...
> On Tue, 23 Jul 2013 12:49:12 -0700, "Harry Dellamano"
> <harryd@tdsystems.org> wrote:
>
>>
>> You folks are correct, it is not the cost of the parts but design time,
>>risk, heat and EMI just to name a few. I believe that you are taking a
>>risk
>>in your design without protection features that are normally needed. Such
>>as
>>under voltage shutdown and poor short circuit protection. If the 16V
>>supply
>>come up low or if the output is shorted you have a good chance of letting
>>the smoke out. In normal operation your design has a large charge dumping
>>spike at R1 at turn on. This screams for a 1nF cap at Q1-B to ground to
>>mitigate the spike but will greatly effect short circuit protection.
>>Needs
>>lots of tweaking.
>
> The thing I posted was just a concept, a starting point for playing
> with. Like I said, I had to run to Safeway.
>
> I did a production board of something similar, a schmitt ac-coupled
> boost converter. It uses a comparator for the source current sensing
> and it does have an RC in that path. The breadboard works fine and I
> haven't blown up a single IC so far. The first PCB will be here on
> Friday.
>
> This circuit doesn't mind a shorted load, because the mosfet peak
> current thing always works.
>
> Here's a schmitt-based voltage flipper. It's actually used on a couple
> of products.
>
> https://dl.dropboxusercontent.com/u/53724080/Circuits/Power/DC_DC2.jpg
>
>
>> I used the LT1242 only because it was the only model available in
>> LTSpice.
>
> There *is* a schmitt trigger model too!
>
>
> --
>
> John Larkin Highland Technology, Inc
>
Your sketch is a good case on point. If you replace the LM5112 with a
LTC3801 (6 pins) with your feedback scheme, you now have a solid PSU and
not a kludge. I have used that topology often, with an "off the shelf"
coupled shielded inductor, to get tracking +/-V outputs.
Safeway?? Have you ever eaten at "Brown Sugar" in Oakland. We should meet
there some time an have grits an eggs.
Cheers, Harry