Power solutions for 9V battery

[Douglas Beeson]

Hi all,

I need to generate +15 V and -15 V (just a few mA), as well as standard 5V (about 50 mA), from a 9V battery. I am bewildered by the range of solutions available. I have used LDOs many times, but am discouraged by their low efficiency for this battery-powered project.

I have looked at the LT1054 capacitor-based voltage regulator, and like its simplicity and ability to generate both + and - 15V from the same circuit, but the diode losses and internal losses mean that as the 9V discharges my output will fall to only 11 V or so, which is insufficient.

I can't seem to find an easy way to get -15V from +9V without a gazillion external parts.

What do you all suggest?

thanks,
doug

 

[Jim Thompson]

On Mon, 21 Jul 2014 09:42:10 -0400, Douglas Beeson
<c.difficile@gmail.com> wrote:

Hi all,

I need to generate +15 V and -15 V (just a few mA), as well as standard 5V (about 50 mA), from a 9V battery. I am bewildered by the range of solutions available. I have used LDOs many times, but am discouraged by their low efficiency for this battery-powered project.

I have looked at the LT1054 capacitor-based voltage regulator, and like its simplicity and ability to generate both + and - 15V from the same circuit, but the diode losses and internal losses mean that as the 9V discharges my output will fall to only 11 V or so, which is insufficient.

I can't seem to find an easy way to get -15V from +9V without a gazillion external parts.

What do you all suggest?

thanks,
doug

See...

OldStyleBuckSwitcherWithAddedNegativeOutput.pdf

on the S.E.D/Schematics page of my website for a starting point.

I first used that scheme in the early '80's. I'd probably clock it
now for better control and stability.

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: skypeanalog | |
| Voice480)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.

 

[amdx]

On 7/21/2014 8:42 AM, Douglas Beeson wrote:

Hi all,

I need to generate +15 V and -15 V (just a few mA), as well as standard 5V (about 50 mA), from a 9V battery. I am bewildered by the range of solutions available. I have used LDOs many times, but am discouraged by their low efficiency for this battery-powered project.

I have looked at the LT1054 capacitor-based voltage regulator, and like its simplicity and ability to generate both + and - 15V from the same circuit, but the diode losses and internal losses mean that as the 9V discharges my output will fall to only 11 V or so, which is insufficient.

I can't seem to find an easy way to get -15V from +9V without a gazillion external parts.

What do you all suggest?

thanks,
doug

I hope your app is very intermittent use.
I doubt you will get 4 hrs at 50 ma.
Mikek



---
This email is free from viruses and malware because avast! Antivirus protection is active.
http://www.avast.com

 

[Tim Wescott]

On Mon, 21 Jul 2014 09:42:10 -0400, Douglas Beeson wrote:

Hi all,

I need to generate +15 V and -15 V (just a few mA), as well as standard
5V (about 50 mA), from a 9V battery. I am bewildered by the range of
solutions available. I have used LDOs many times, but am discouraged by
their low efficiency for this battery-powered project.

I have looked at the LT1054 capacitor-based voltage regulator, and like
its simplicity and ability to generate both + and - 15V from the same
circuit, but the diode losses and internal losses mean that as the 9V
discharges my output will fall to only 11 V or so, which is
insufficient.

I can't seem to find an easy way to get -15V from +9V without a
gazillion external parts.

What do you all suggest?

The first thing that I suggest is that you not use a 9V battery. I don't
have my reference materials here to quote exact figures, but there's
significantly more useful energy in a pair of AA cells than in a 9V
battery, for not much weight or space. I'd find the most efficient
switcher chip that I can find that'll boost 3.5 to 1.8V up to 5V, and
then use either switchers or switched-capacitor chips to go from +5V to
+/- 15V.


--
Tim Wescott
Control system and signal processing consulting
www.wescottdesign.com

 

[Tim Wescott]

On Mon, 21 Jul 2014 11:16:32 -0500, Tim Wescott wrote:

On Mon, 21 Jul 2014 09:42:10 -0400, Douglas Beeson wrote:

Hi all,

I need to generate +15 V and -15 V (just a few mA), as well as standard
5V (about 50 mA), from a 9V battery. I am bewildered by the range of
solutions available. I have used LDOs many times, but am discouraged by
their low efficiency for this battery-powered project.

I have looked at the LT1054 capacitor-based voltage regulator, and like
its simplicity and ability to generate both + and - 15V from the same
circuit, but the diode losses and internal losses mean that as the 9V
discharges my output will fall to only 11 V or so, which is
insufficient.

I can't seem to find an easy way to get -15V from +9V without a
gazillion external parts.

What do you all suggest?

The first thing that I suggest is that you not use a 9V battery. I
don't have my reference materials here to quote exact figures, but
there's significantly more useful energy in a pair of AA cells than in a
9V battery, for not much weight or space. I'd find the most efficient
switcher chip that I can find that'll boost 3.5 to 1.8V up to 5V, and
then use either switchers or switched-capacitor chips to go from +5V to
+/- 15V.

From my Radio Shack battery guide, it looks like an apples-to-apples
comparison of 9V batteries with a pair of AA batteries gets you about ten
times more life out of the AA batteries. Even a pair of AAA batteries
looks like it'll get you four times the life.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

 

[Douglas Beeson]

On Mon, 21 Jul 2014 13:11:53 -0500
Tim Wescott <tim@seemywebsite.really> wrote:

On Mon, 21 Jul 2014 11:16:32 -0500, Tim Wescott wrote:

On Mon, 21 Jul 2014 09:42:10 -0400, Douglas Beeson wrote:

Hi all,

I need to generate +15 V and -15 V (just a few mA), as well as standard
5V (about 50 mA), from a 9V battery. I am bewildered by the range of
solutions available. I have used LDOs many times, but am discouraged by
their low efficiency for this battery-powered project.

I have looked at the LT1054 capacitor-based voltage regulator, and like
its simplicity and ability to generate both + and - 15V from the same
circuit, but the diode losses and internal losses mean that as the 9V
discharges my output will fall to only 11 V or so, which is
insufficient.

I can't seem to find an easy way to get -15V from +9V without a
gazillion external parts.

What do you all suggest?

The first thing that I suggest is that you not use a 9V battery. I
don't have my reference materials here to quote exact figures, but
there's significantly more useful energy in a pair of AA cells than in a
9V battery, for not much weight or space. I'd find the most efficient
switcher chip that I can find that'll boost 3.5 to 1.8V up to 5V, and
then use either switchers or switched-capacitor chips to go from +5V to
+/- 15V.

From my Radio Shack battery guide, it looks like an apples-to-apples
comparison of 9V batteries with a pair of AA batteries gets you about ten
times more life out of the AA batteries. Even a pair of AAA batteries
looks like it'll get you four times the life.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

I see your point. I just assumed that it was easier to step down to 5 and up to 15 from somewhere in between, but looking at the chips available I see that most solutions address lower-voltage cells. So I will look at AAs. Thanks, Tim.

doug


--
Douglas Beeson <c.difficile@gmail.com>

 

[Douglas Beeson]

On Mon, 21 Jul 2014 07:37:19 -0700
Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote:

On Mon, 21 Jul 2014 09:42:10 -0400, Douglas Beeson
c.difficile@gmail.com> wrote:

Hi all,

I need to generate +15 V and -15 V (just a few mA), as well as standard 5V (about 50 mA), from a 9V battery. I am bewildered by the range of solutions available. I have used LDOs many times, but am discouraged by their low efficiency for this battery-powered project.

I have looked at the LT1054 capacitor-based voltage regulator, and like its simplicity and ability to generate both + and - 15V from the same circuit, but the diode losses and internal losses mean that as the 9V discharges my output will fall to only 11 V or so, which is insufficient.

I can't seem to find an easy way to get -15V from +9V without a gazillion external parts.

What do you all suggest?

thanks,
doug

See...

OldStyleBuckSwitcherWithAddedNegativeOutput.pdf

on the S.E.D/Schematics page of my website for a starting point.

I first used that scheme in the early '80's. I'd probably clock it
now for better control and stability.

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: skypeanalog | |
| Voice480)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.

Thank, Jim. Did you use a microcontroller or something else for gate control?

doug

--
Douglas Beeson <c.difficile@gmail.com>

 

I would just use a high frequency totam pole feeding two voltage triplers with caps chosen to have some impedance at the operating frequency and just regulatew it by lowering the fequency. It might be bettewr uisually to use higher value caps and put some inductance in there to keep the switching quiet, but this thing is so small you might want to just save the money. If you'r eworried about EMI at al just use the inductance at a level you can control, and raise the frequency to recuce the output.

That method also allows you to buy cheaper caps, because when you intend to really use their Xc, it costs money. Four one dollar inductors from Digikey might just save you that much in caps and make for better reliability. Plus if you use a chip to drive the totem pole, alot of them are set up for above resonance so it will be easier to us something off the shelf.

The ONLY reason capacitive with lowering frequency to lower output is a lower component count. You can probably do it because the current is so low. But the inductors would be better. You lower all peak currents, that ight save you money on EVERYTHING.

It really seems to me that there is an off the shelf solution for this, but I figure you are asking because you want to built it INTO something.

 

[Tim Wescott]

On Mon, 21 Jul 2014 15:27:15 -0400, Douglas Beeson wrote:

On Mon, 21 Jul 2014 13:11:53 -0500 Tim Wescott <tim@seemywebsite.really
wrote:

On Mon, 21 Jul 2014 11:16:32 -0500, Tim Wescott wrote:

On Mon, 21 Jul 2014 09:42:10 -0400, Douglas Beeson wrote:

Hi all,

I need to generate +15 V and -15 V (just a few mA), as well as
standard 5V (about 50 mA), from a 9V battery. I am bewildered by the
range of solutions available. I have used LDOs many times, but am
discouraged by their low efficiency for this battery-powered
project.

I have looked at the LT1054 capacitor-based voltage regulator, and
like its simplicity and ability to generate both + and - 15V from
the same circuit, but the diode losses and internal losses mean that
as the 9V discharges my output will fall to only 11 V or so, which
is insufficient.

I can't seem to find an easy way to get -15V from +9V without a
gazillion external parts.

What do you all suggest?

The first thing that I suggest is that you not use a 9V battery. I
don't have my reference materials here to quote exact figures, but
there's significantly more useful energy in a pair of AA cells than
in a 9V battery, for not much weight or space. I'd find the most
efficient switcher chip that I can find that'll boost 3.5 to 1.8V up
to 5V, and then use either switchers or switched-capacitor chips to
go from +5V to +/- 15V.

From my Radio Shack battery guide, it looks like an apples-to-apples
comparison of 9V batteries with a pair of AA batteries gets you about
ten times more life out of the AA batteries. Even a pair of AAA
batteries looks like it'll get you four times the life.

--

Tim Wescott Wescott Design Services http://www.wescottdesign.com



I see your point. I just assumed that it was easier to step down to 5
and up to 15 from somewhere in between, but looking at the chips
available I see that most solutions address lower-voltage cells. So I
will look at AAs. Thanks, Tim.

I do think the best way to get to 15V is from the 5V rail -- but each
individual circuit always ends up with its own quirks.

I'm going to take the opportunity to voice a pet peeve here:

<rant=on>
If you do use just two cells, make damned sure that you use a regulator
that's good down to 1.8V, or 2V at worst. NiMH and dry cells both are
good all the way down to 0.9V/cell: not working down that far is just
throwing away useful energy that could go to make your customer happy.
</rant>

Have fun.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

 

[Jim Thompson]

On Mon, 21 Jul 2014 15:29:38 -0400, Douglas Beeson
<c.difficile@gmail.com> wrote:

On Mon, 21 Jul 2014 07:37:19 -0700
Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote:

On Mon, 21 Jul 2014 09:42:10 -0400, Douglas Beeson
c.difficile@gmail.com> wrote:

Hi all,

I need to generate +15 V and -15 V (just a few mA), as well as standard 5V (about 50 mA), from a 9V battery. I am bewildered by the range of solutions available. I have used LDOs many times, but am discouraged by their low efficiency for this battery-powered project.

I have looked at the LT1054 capacitor-based voltage regulator, and like its simplicity and ability to generate both + and - 15V from the same circuit, but the diode losses and internal losses mean that as the 9V discharges my output will fall to only 11 V or so, which is insufficient.

I can't seem to find an easy way to get -15V from +9V without a gazillion external parts.

What do you all suggest?

thanks,
doug

See...

OldStyleBuckSwitcherWithAddedNegativeOutput.pdf

on the S.E.D/Schematics page of my website for a starting point.

I first used that scheme in the early '80's. I'd probably clock it
now for better control and stability.

...Jim Thompson
[snip]


Thank, Jim. Did you use a microcontroller or something else for gate control?

doug

Me? The Analog dance master >:-} Simple-minded hysteretic control,
switch on at 4.99V, off at 5.01V, so the switching rate wanders with
load... that's why I added the "...probably clock it now..." comment.

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: skypeanalog | |
| Voice480)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.

 

[Maynard A. Philbrook Jr.]

In article <7NudnY7T8YolBlDOnZ2dnUVZ5tSdnZ2d@giganews.com>,
tim@seemywebsite.really says...

will look at AAs. Thanks, Tim.

I do think the best way to get to 15V is from the 5V rail -- but each
individual circuit always ends up with its own quirks.

I'm going to take the opportunity to voice a pet peeve here:

rant=on
If you do use just two cells, make damned sure that you use a regulator
that's good down to 1.8V, or 2V at worst. NiMH and dry cells both are
good all the way down to 0.9V/cell: not working down that far is just
throwing away useful energy that could go to make your customer happy.
/rant

Have fun.

I have a Fluke process DMM, that uses a 9V battery. from the day I
got to the day I laid it to rest, when ever I used the current mode
in it (24V out), I'd get ~ 10 mins of use and the DMM was dead.

That's a nice design Fluke came out with, as useless as tits on a bull.

Reminds me something SLOW_MAN would design, if he knew how.

Jamie

 

[Douglas Beeson]

On Mon, 21 Jul 2014 19:07:08 -0700 (PDT)
jurb6006@gmail.com wrote:

I would just use a high frequency totam pole feeding two voltage triplers with caps chosen to have some impedance at the operating frequency and just regulatew it by lowering the fequency. It might be bettewr uisually to use higher value caps and put some inductance in there to keep the switching quiet, but this thing is so small you might want to just save the money. If you'r eworried about EMI at al just use the inductance at a level you can control, and raise the frequency to recuce the output.

That method also allows you to buy cheaper caps, because when you intend to really use their Xc, it costs money. Four one dollar inductors from Digikey might just save you that much in caps and make for better reliability. Plus if you use a chip to drive the totem pole, alot of them are set up for above resonance so it will be easier to us something off the shelf.

The ONLY reason capacitive with lowering frequency to lower output is a lower component count. You can probably do it because the current is so low. But the inductors would be better. You lower all peak currents, that ight save you money on EVERYTHING.

It really seems to me that there is an off the shelf solution for this, but I figure you are asking because you want to built it INTO something.

Thanks for the feedback. I'm afraid I'm a little too novice to take your suggestion and turn it into a circuit straight away. I am looking to buy most of the power solution -- money really isn't an object because I'm only building about 10 of them, not for profit -- and I'd really like to avoid soldering 25 parts just to get +/- 15 V and 5V.

In the past, I built a boost SMPS using a Maxim part that required an inductor, a Schottky, and a couple of caps and that's about how much effort I want to put into this. It just seems like there are SO many IC options to choose from that's it hard to see the forest, so to speak.

doug



--
Douglas Beeson <c.difficile@gmail.com>

 

[Douglas Beeson]

On Mon, 21 Jul 2014 18:01:12 -0500
Tim Wescott <tim@seemywebsite.really> wrote:

On Mon, 21 Jul 2014 15:27:15 -0400, Douglas Beeson wrote:

On Mon, 21 Jul 2014 13:11:53 -0500 Tim Wescott <tim@seemywebsite.really
wrote:

On Mon, 21 Jul 2014 11:16:32 -0500, Tim Wescott wrote:

On Mon, 21 Jul 2014 09:42:10 -0400, Douglas Beeson wrote:

Hi all,

I need to generate +15 V and -15 V (just a few mA), as well as
standard 5V (about 50 mA), from a 9V battery. I am bewildered by the
range of solutions available. I have used LDOs many times, but am
discouraged by their low efficiency for this battery-powered
project.

I have looked at the LT1054 capacitor-based voltage regulator, and
like its simplicity and ability to generate both + and - 15V from
the same circuit, but the diode losses and internal losses mean that
as the 9V discharges my output will fall to only 11 V or so, which
is insufficient.

I can't seem to find an easy way to get -15V from +9V without a
gazillion external parts.

What do you all suggest?

The first thing that I suggest is that you not use a 9V battery. I
don't have my reference materials here to quote exact figures, but
there's significantly more useful energy in a pair of AA cells than
in a 9V battery, for not much weight or space. I'd find the most
efficient switcher chip that I can find that'll boost 3.5 to 1.8V up
to 5V, and then use either switchers or switched-capacitor chips to
go from +5V to +/- 15V.

From my Radio Shack battery guide, it looks like an apples-to-apples
comparison of 9V batteries with a pair of AA batteries gets you about
ten times more life out of the AA batteries. Even a pair of AAA
batteries looks like it'll get you four times the life.

--

Tim Wescott Wescott Design Services http://www.wescottdesign.com



I see your point. I just assumed that it was easier to step down to 5
and up to 15 from somewhere in between, but looking at the chips
available I see that most solutions address lower-voltage cells. So I
will look at AAs. Thanks, Tim.

I do think the best way to get to 15V is from the 5V rail -- but each
individual circuit always ends up with its own quirks.

I'm going to take the opportunity to voice a pet peeve here:

rant=on
If you do use just two cells, make damned sure that you use a regulator
that's good down to 1.8V, or 2V at worst. NiMH and dry cells both are
good all the way down to 0.9V/cell: not working down that far is just
throwing away useful energy that could go to make your customer happy.
/rant

Have fun.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

I am having fun already ;-) I realized from another comment that my circuit is probably sucking too much current. Need now to look for a low-power comparator that is fast enough for the zero cross detection that I need. Was looking at the LT1719 but it sucks 9 mA and I need two of them.

Thanks!
doug


--
Douglas Beeson <c.difficile@gmail.com>

 

[Tim Wescott]

On Tue, 22 Jul 2014 10:35:11 -0400, Douglas Beeson wrote:

On Mon, 21 Jul 2014 18:01:12 -0500 Tim Wescott <tim@seemywebsite.really
wrote:

On Mon, 21 Jul 2014 15:27:15 -0400, Douglas Beeson wrote:

On Mon, 21 Jul 2014 13:11:53 -0500 Tim Wescott
tim@seemywebsite.really
wrote:

On Mon, 21 Jul 2014 11:16:32 -0500, Tim Wescott wrote:

On Mon, 21 Jul 2014 09:42:10 -0400, Douglas Beeson wrote:

Hi all,

I need to generate +15 V and -15 V (just a few mA), as well as
standard 5V (about 50 mA), from a 9V battery. I am bewildered by
the range of solutions available. I have used LDOs many times,
but am discouraged by their low efficiency for this
battery-powered project.

I have looked at the LT1054 capacitor-based voltage regulator,
and like its simplicity and ability to generate both + and - 15V
from the same circuit, but the diode losses and internal losses
mean that as the 9V discharges my output will fall to only 11 V
or so, which is insufficient.

I can't seem to find an easy way to get -15V from +9V without a
gazillion external parts.

What do you all suggest?

The first thing that I suggest is that you not use a 9V battery.
I don't have my reference materials here to quote exact figures,
but there's significantly more useful energy in a pair of AA cells
than in a 9V battery, for not much weight or space. I'd find the
most efficient switcher chip that I can find that'll boost 3.5 to
1.8V up to 5V, and then use either switchers or switched-capacitor
chips to go from +5V to +/- 15V.

From my Radio Shack battery guide, it looks like an apples-to-apples
comparison of 9V batteries with a pair of AA batteries gets you
about ten times more life out of the AA batteries. Even a pair of
AAA batteries looks like it'll get you four times the life.

--

Tim Wescott Wescott Design Services http://www.wescottdesign.com



I see your point. I just assumed that it was easier to step down to 5
and up to 15 from somewhere in between, but looking at the chips
available I see that most solutions address lower-voltage cells. So I
will look at AAs. Thanks, Tim.

I do think the best way to get to 15V is from the 5V rail -- but each
individual circuit always ends up with its own quirks.

I'm going to take the opportunity to voice a pet peeve here:

rant=on
If you do use just two cells, make damned sure that you use a regulator
that's good down to 1.8V, or 2V at worst. NiMH and dry cells both are
good all the way down to 0.9V/cell: not working down that far is just
throwing away useful energy that could go to make your customer happy.
/rant

Have fun.

--

Tim Wescott Wescott Design Services http://www.wescottdesign.com



I am having fun already ;-) I realized from another comment that my
circuit is probably sucking too much current. Need now to look for a
low-power comparator that is fast enough for the zero cross detection
that I need. Was looking at the LT1719 but it sucks 9 mA and I need two
of them.

If you're getting the +/-15V for the comparator -- look at something more
modern. Maybe something that's not old enough to drink yet, or at least
something that's not old enough to be President.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

 

[Douglas Beeson]

On Tue, 22 Jul 2014 17:33:00 -0500
Tim Wescott <tim@seemywebsite.really> wrote:

On Tue, 22 Jul 2014 10:35:11 -0400, Douglas Beeson wrote:

On Mon, 21 Jul 2014 18:01:12 -0500 Tim Wescott <tim@seemywebsite.really
wrote:

On Mon, 21 Jul 2014 15:27:15 -0400, Douglas Beeson wrote:

On Mon, 21 Jul 2014 13:11:53 -0500 Tim Wescott
tim@seemywebsite.really
wrote:

On Mon, 21 Jul 2014 11:16:32 -0500, Tim Wescott wrote:

On Mon, 21 Jul 2014 09:42:10 -0400, Douglas Beeson wrote:

Hi all,

I need to generate +15 V and -15 V (just a few mA), as well as
standard 5V (about 50 mA), from a 9V battery. I am bewildered by
the range of solutions available. I have used LDOs many times,
but am discouraged by their low efficiency for this
battery-powered project.

I have looked at the LT1054 capacitor-based voltage regulator,
and like its simplicity and ability to generate both + and - 15V
from the same circuit, but the diode losses and internal losses
mean that as the 9V discharges my output will fall to only 11 V
or so, which is insufficient.

I can't seem to find an easy way to get -15V from +9V without a
gazillion external parts.

What do you all suggest?

The first thing that I suggest is that you not use a 9V battery.
I don't have my reference materials here to quote exact figures,
but there's significantly more useful energy in a pair of AA cells
than in a 9V battery, for not much weight or space. I'd find the
most efficient switcher chip that I can find that'll boost 3.5 to
1.8V up to 5V, and then use either switchers or switched-capacitor
chips to go from +5V to +/- 15V.

From my Radio Shack battery guide, it looks like an apples-to-apples
comparison of 9V batteries with a pair of AA batteries gets you
about ten times more life out of the AA batteries. Even a pair of
AAA batteries looks like it'll get you four times the life.

--

Tim Wescott Wescott Design Services http://www.wescottdesign.com



I see your point. I just assumed that it was easier to step down to 5
and up to 15 from somewhere in between, but looking at the chips
available I see that most solutions address lower-voltage cells. So I
will look at AAs. Thanks, Tim.

I do think the best way to get to 15V is from the 5V rail -- but each
individual circuit always ends up with its own quirks.

I'm going to take the opportunity to voice a pet peeve here:

rant=on
If you do use just two cells, make damned sure that you use a regulator
that's good down to 1.8V, or 2V at worst. NiMH and dry cells both are
good all the way down to 0.9V/cell: not working down that far is just
throwing away useful energy that could go to make your customer happy.
/rant

Have fun.

--

Tim Wescott Wescott Design Services http://www.wescottdesign.com



I am having fun already ;-) I realized from another comment that my
circuit is probably sucking too much current. Need now to look for a
low-power comparator that is fast enough for the zero cross detection
that I need. Was looking at the LT1719 but it sucks 9 mA and I need two
of them.

If you're getting the +/-15V for the comparator -- look at something more
modern. Maybe something that's not old enough to drink yet, or at least
something that's not old enough to be President.

Ha! I think the LT1719 dates from 1998 so still not old enough to drink. And no, I'm looking at a 5V single-supply solution for the comparator. The 15 V is for FET gate drive and a current sense amp.

thnks,
doug

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

--
Douglas Beeson <c.difficile@gmail.com>

 

[Jasen Betts]

On 2014-07-22, Douglas Beeson <c.difficile@gmail.com> wrote:

On Mon, 21 Jul 2014 19:07:08 -0700 (PDT)
jurb6006@gmail.com wrote:

Thanks for the feedback. I'm afraid I'm a little too novice to take your suggestion and turn it into a circuit straight away. I am looking to buy most of the power solution -- money really isn't an object because I'm only building about 10 of them, not for profit -- and I'd really like to avoid soldering 25 parts just to get +/- 15 V and 5V.

buy some DC-DC converters modules on E-bay.

you may need 3 per unit (one for each output voltage) but it's only three "parts"

--
umop apisdn


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