| Author |
Message |
Guest
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 Posted:
Sat Feb 12, 2005 6:10 am Post subject:
5V regulator for batteries cheap efficient? |
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I know I can't have everything, but I'm going to ask for it anyway.
The circuit is 8 or so opamps, comparators, and logic circuits driven
by +/-5 V. It will run on batteries. Is there a comparatively cheap
(double the price? maybe triple) but more efficient regulator than the
7805/7905 for this application? i don't want the batteries throwing
all their energy into heatsinks and running out in 5 minutes. if
switching, it's got to have decent noisefreeness. noise above the
audio band is fine.
Any suggestions? the lm2940 looks promising, but you folks probably
know better...
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Ken Smith
Guest
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| Posted:
Sat Feb 12, 2005 5:08 pm Post subject:
Re: 5V regulator for batteries cheap efficient? |
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In article <1108185958.959874.84180@l41g2000cwc.googlegroups.com>,
<u035m4i02@sneakemail.com> wrote:
| Quote: | I know I can't have everything, but I'm going to ask for it anyway.
The circuit is 8 or so opamps, comparators, and logic circuits driven
by +/-5 V. It will run on batteries. Is there a comparatively cheap
(double the price? maybe triple) but more efficient regulator than the
7805/7905 for this application? i don't want the batteries throwing
all their energy into heatsinks and running out in 5 minutes. if
switching, it's got to have decent noisefreeness. noise above the
audio band is fine.
Any suggestions? the lm2940 looks promising, but you folks probably
know better...
|
If the input voltage is over 10V and the current is low enough, a switched
capacitor converter may the way to go.
--
--
kensmith@rahul.net forging knowledge |
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Mike Harrison
Guest
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| Posted:
Sat Feb 12, 2005 5:35 pm Post subject:
Re: 5V regulator for batteries cheap efficient? |
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On 11 Feb 2005 21:25:58 -0800, u035m4i02@sneakemail.com wrote:
| Quote: | I know I can't have everything, but I'm going to ask for it anyway.
The circuit is 8 or so opamps, comparators, and logic circuits driven
by +/-5 V. It will run on batteries. Is there a comparatively cheap
(double the price? maybe triple) but more efficient regulator than the
7805/7905 for this application? i don't want the batteries throwing
all their energy into heatsinks and running out in 5 minutes. if
switching, it's got to have decent noisefreeness. noise above the
audio band is fine.
Any suggestions? the lm2940 looks promising, but you folks probably
know better...
|
How much does your product draw..? If more than a few tens of mA then only a switcher will give you
significantly better efficiency. If a few mA, then look at the Holtek HT7150 - quiescent a couple
of microamps, and takes input up to 24V. About US$0.30 from memory.
Also look at OnSemi 78LC/FC series - similar efficiency but lower input range
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richard mullens
Guest
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| Posted:
Sat Feb 12, 2005 8:21 pm Post subject:
Re: 5V regulator for batteries cheap efficient? |
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Mike Harrison wrote:
| Quote: | On 11 Feb 2005 21:25:58 -0800, u035m4i02@sneakemail.com wrote:
I know I can't have everything, but I'm going to ask for it anyway.
The circuit is 8 or so opamps, comparators, and logic circuits driven
by +/-5 V. It will run on batteries. Is there a comparatively cheap
(double the price? maybe triple) but more efficient regulator than the
7805/7905 for this application? i don't want the batteries throwing
all their energy into heatsinks and running out in 5 minutes. if
switching, it's got to have decent noisefreeness. noise above the
audio band is fine.
Any suggestions? the lm2940 looks promising, but you folks probably
know better...
How much does your product draw..? If more than a few tens of mA then only a switcher will give you
significantly better efficiency. If a few mA, then look at the Holtek HT7150 - quiescent a couple
of microamps, and takes input up to 24V. About US$0.30 from memory.
Also look at OnSemi 78LC/FC series - similar efficiency but lower input range
Replaced by HT7150-1 |
3 microamp typical quiescent. 6 max.
Ricoh has/had some LDO regulators with quiescent current around 1 microamp eg Rx5RL - see
http://www.ricoh.com/LSI/product_power/info/selectionguide.pdf |
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Ken Smith
Guest
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| Posted:
Sat Feb 12, 2005 11:02 pm Post subject:
Re: 5V regulator for batteries cheap efficient? |
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In article <1108227866.479654.115350@c13g2000cwb.googlegroups.com>,
<u035m4i02@sneakemail.com> wrote:
| Quote: | I'd estimate about 65 mA total.
|
65 mA is enough to make a switcher worth the work. If you don't need too
tight of regulation, you can use one chip to make both voltages. This may
save you a bit of power. Something like this:
--!!---------------+--->!---+----- +5V
! ! !
! [L] ---
! ! ---
! ! !
(+)-----[L]----+---+--!!-----+-->!--+--+--------+------ GND
! ! !
Floating / switcher ! ---
Battery ! chip [L] ---
! ! !
(-)------------+-------------+------+------------------ -5V
You may even be able to find the inductors almost all as one part. IIRC.
J.W. Miller has a multiwinding inductor.
The input side inductor could be part of that plus a small independant choke
in series.
--
--
kensmith@rahul.net forging knowledge |
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Guest
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| Posted:
Sat Feb 12, 2005 11:04 pm Post subject:
Re: 5V regulator for batteries cheap efficient? |
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| I'd estimate about 65 mA total. |
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Rich Grise
Guest
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| Posted:
Sun Feb 13, 2005 1:10 pm Post subject:
Re: 5V regulator for batteries cheap efficient? |
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On Fri, 11 Feb 2005 21:25:58 -0800, u035m4i02 wrote:
| Quote: | I know I can't have everything, but I'm going to ask for it anyway.
The circuit is 8 or so opamps, comparators, and logic circuits driven
by +/-5 V. It will run on batteries. Is there a comparatively cheap
(double the price? maybe triple) but more efficient regulator than the
7805/7905 for this application? i don't want the batteries throwing
all their energy into heatsinks and running out in 5 minutes. if
switching, it's got to have decent noisefreeness. noise above the
audio band is fine.
Any suggestions? the lm2940 looks promising, but you folks probably
know better...
|
Use stuff that's not so persnickety about its supply voltage, like CMOS.
I've never heard of an opamp that can run off +-5V that couldn't run off
+-6.
IOW, lose the regulators, and redesign the circuit to work off raw battery
power.
Good Luck!
Rich |
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Brian
Guest
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| Posted:
Mon Feb 14, 2005 1:53 pm Post subject:
Re: 5V regulator for batteries cheap efficient? |
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"Ken Smith" <kensmith@green.rahul.net> wrote in message
news:cum1ua$lhf$7@blue.rahul.net...
| Quote: | In article <1108227866.479654.115350@c13g2000cwb.googlegroups.com>,
u035m4i02@sneakemail.com> wrote:
I'd estimate about 65 mA total.
65 mA is enough to make a switcher worth the work. If you don't need too
tight of regulation, you can use one chip to make both voltages. This may
save you a bit of power. Something like this:
--!!---------------+--->!---+----- +5V
! ! !
! [L] ---
! ! ---
! ! !
(+)-----[L]----+---+--!!-----+-->!--+--+--------+------ GND
! ! !
Floating / switcher ! ---
Battery ! chip [L] ---
! ! !
(-)------------+-------------+------+------------------ -5V
You may even be able to find the inductors almost all as one part. IIRC.
J.W. Miller has a multiwinding inductor.
The input side inductor could be part of that plus a small independant
choke
in series.
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Wouldn't the added efficiency depend on what his input voltage is? If only
6 volts (4AA) a switcher would offer little, no? |
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Guest
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| Posted:
Mon Feb 14, 2005 10:31 pm Post subject:
Re: 5V regulator for batteries cheap efficient? |
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Actually, this is the best idea yet. There is nothing in the circuit
that needs exactly 5 V, except a comparator that I want to replace
anyway. So this will save parts and be the most efficient.
....
Or will it? Will running it off higher battery voltage actually be
less efficient or will the batteries last longer this way? |
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Ken Smith
Guest
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| Posted:
Tue Feb 15, 2005 3:34 am Post subject:
Re: 5V regulator for batteries cheap efficient? |
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In article <B7KdnUEfS6h7xY3fRVn-rA@centurytel.net>,
Brian <brian@w3gate.com> wrote:
[... switcher circuit ..]
| Quote: | Wouldn't the added efficiency depend on what his input voltage is? If only
6 volts (4AA) a switcher would offer little, no?
|
Yes:
If his input is already plus and minus 5V a switcher must be a net loss.
If it is plus and minus 30V a switcher is a good answer. Somewhere
between the two, the efficiency of the two methods are equal.
an No:
He needs plus and minus 5V this means two batteries, a false ground, or a
switcher of some type.
--
--
kensmith@rahul.net forging knowledge |
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richard mullens
Guest
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| Posted:
Tue Feb 15, 2005 5:50 am Post subject:
Re: 5V regulator for batteries cheap efficient? |
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u035m4i02@sneakemail.com wrote:
| Quote: | Actually, this is the best idea yet. There is nothing in the circuit
that needs exactly 5 V, except a comparator that I want to replace
anyway. So this will save parts and be the most efficient.
...
Or will it? Will running it off higher battery voltage actually be
less efficient or will the batteries last longer this way?
|
Run it off a higher voltage, and a greater current will be drawn by your devices. But you will have saved the power used by the
regulator. |
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Guest
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| Posted:
Tue Feb 15, 2005 12:29 pm Post subject:
Re: 5V regulator for batteries cheap efficient? |
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| Quote: | Run it off a higher voltage, and a greater current will be drawn by
your devices. But you will have saved the power used by the |
regulator.
But will the battery last longer? I guess since the chips are optimal
at +/-10 V I should just like it the way it is.
| Quote: | If his input is already plus and minus 5V a switcher must be a net
loss. |
If it is plus and minus 30V a switcher is a good answer. Somewhere
between the two, the efficiency of the two methods are equal.
| Quote: | He needs plus and minus 5V this means two batteries, a false ground,
or a |
switcher of some type.
Input is likely two 9V or so. |
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Ken Smith
Guest
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| Posted:
Tue Feb 15, 2005 2:54 pm Post subject:
Re: 5V regulator for batteries cheap efficient? |
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In article <n4-dnSxDCb3rW4zfRVn-qA@centurytel.net>,
Brian <brian@w3gate.com> wrote:
[.. +/- 9V batteries ..]
| Quote: | Then I would lose the regulator and run straight from the batteries.
|
At low currents, straight off the battery makes sense. At higher current,
a switcher would greatly increase the battery life.
| Quote: | In a battery circuit ground usually is false, no?
|
Yes effectively
--
--
kensmith@rahul.net forging knowledge |
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Brian
Guest
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| Posted:
Tue Feb 15, 2005 3:52 pm Post subject:
Re: 5V regulator for batteries cheap efficient? |
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Then I would lose the regulator and run straight from the batteries.
In a battery circuit ground usually is false, no?
<u035m4i02@sneakemail.com> wrote in message
news:1108448978.677051.12810@f14g2000cwb.googlegroups.com...
| Quote: | Run it off a higher voltage, and a greater current will be drawn by
your devices. But you will have saved the power used by the
regulator.
But will the battery last longer? I guess since the chips are optimal
at +/-10 V I should just like it the way it is.
If his input is already plus and minus 5V a switcher must be a net
loss.
If it is plus and minus 30V a switcher is a good answer. Somewhere
between the two, the efficiency of the two methods are equal.
He needs plus and minus 5V this means two batteries, a false ground,
or a
switcher of some type.
Input is likely two 9V or so.
|
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Ken Smith
Guest
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| Posted:
Wed Feb 16, 2005 2:39 pm Post subject:
Re: 5V regulator for batteries cheap efficient? |
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In article <8JmdnaefCoMeu47fRVn-sw@centurytel.net>,
Brian <brian@w3gate.com> wrote:
| Quote: |
[.. +/- 9V batteries ..]
Then I would lose the regulator and run straight from the batteries.
At low currents, straight off the battery makes sense. At higher current,
a switcher would greatly increase the battery life.
[...]
I assume yoy mean boosting the voltage.
|
No, with a 9V battery making 5V with a bucker will extend the battery life
quite a bit when the current requirments are enough that the overhead to
run the chip is not important in the total system power.
Unfortunately, there are no large P-MODFETs that can be certain to be
biased to a low on resistance by 5V. Parts like Supertex's TP0604 would
be a good choice for the pass element of a bucker at modest currents.
You can also "abuse" a booster swither chip to make a minus side bucker.
Since the OP is making +/-5V from a pair of 9V batteries, you could do
this twice and wire the resulting 5V circuits in series. The 9V batteries
would not have any common connection.
--
--
kensmith@rahul.net forging knowledge |
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