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Message |
| michael nikolaou... |
 Posted: Tue Oct 20, 2009 4:30 am |
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Guest
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Hi to newsgroup
I'm making a mcu based device which i want to be very small and low cost
The design consumes 100..120 ma at (no spam) 3.3V
The problem is the installation that requires 12 or 24 volts to operate.
I don't want to use a switching regulator to make the voltage drop since its
to much
circuit involved and also not a zener since its to much heat involved .
The mcu has A/D and PWM controller .Is it possible to use a simple mosfet
switch with
a capacitor to make a dropdown to half voltage if the mcu detects 24 volts
input ?.
Is there an easier way ?.
Any help would be appreciated .
MK |
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| Charlie E.... |
| Posted: Tue Oct 20, 2009 8:27 am |
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Guest
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On Tue, 20 Oct 2009 13:30:39 +0300, "michael nikolaou"
<michaelnikolaou_remove_me_ at (no spam) yahoo.com> wrote:
[quote]Hi to newsgroup
I'm making a mcu based device which i want to be very small and low cost
The design consumes 100..120 ma at (no spam) 3.3V
The problem is the installation that requires 12 or 24 volts to operate.
I don't want to use a switching regulator to make the voltage drop since its
to much
circuit involved and also not a zener since its to much heat involved .
The mcu has A/D and PWM controller .Is it possible to use a simple mosfet
switch with
a capacitor to make a dropdown to half voltage if the mcu detects 24 volts
input ?.
Is there an easier way ?.
Any help would be appreciated .
MK
[/quote]
Michael,
Probably not a good idea. You MCU will take a little while to come up
to speed before it can monitor those voltages, and take action. At
24VDC, you chip is already fried by that time. That is a lot of
voltage to drop with just a linear regulator, esp. if that 24VDC is
not well regulated. It is possible, but it isn't simple...
Charlie |
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| michael nikolaou... |
| Posted: Tue Oct 20, 2009 10:48 am |
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Guest
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Hi charlie
Thanks fot the reply
If i halve the duty cycle is should get from 6 to 12 volts input .
This can be regulated to 3.3V with no problem .
Is there no simple circuit, switched capacitor possibly ,
to make this voltage halving ????
"Charlie E." <edmondson at (no spam) ieee.org> wrote in message
news:b0ird55sv4h65492pasfj3o4inu6dlsv4r at (no spam) 4ax.com...
[quote]On Tue, 20 Oct 2009 13:30:39 +0300, "michael nikolaou"
michaelnikolaou_remove_me_ at (no spam) yahoo.com> wrote:
Hi to newsgroup
I'm making a mcu based device which i want to be very small and low cost
The design consumes 100..120 ma at (no spam) 3.3V
The problem is the installation that requires 12 or 24 volts to operate.
I don't want to use a switching regulator to make the voltage drop since
its
to much
circuit involved and also not a zener since its to much heat involved .
The mcu has A/D and PWM controller .Is it possible to use a simple mosfet
switch with
a capacitor to make a dropdown to half voltage if the mcu detects 24 volts
input ?.
Is there an easier way ?.
Any help would be appreciated .
MK
Michael,
Probably not a good idea. You MCU will take a little while to come up
to speed before it can monitor those voltages, and take action. At
24VDC, you chip is already fried by that time. That is a lot of
voltage to drop with just a linear regulator, esp. if that 24VDC is
not well regulated. It is possible, but it isn't simple...
Charlie[/quote] |
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| Tim Wescott... |
| Posted: Tue Oct 20, 2009 10:54 am |
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Guest
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On Tue, 20 Oct 2009 13:30:39 +0300, michael nikolaou wrote:
[quote]Hi to newsgroup
I'm making a mcu based device which i want to be very small and low cost
The design consumes 100..120 ma at (no spam) 3.3V The problem is the installation
that requires 12 or 24 volts to operate. I don't want to use a switching
regulator to make the voltage drop since its to much
circuit involved and also not a zener since its to much heat involved .
The mcu has A/D and PWM controller .Is it possible to use a simple
mosfet switch with
a capacitor to make a dropdown to half voltage if the mcu detects 24
volts input ?.
Is there an easier way ?.
Any help would be appreciated .
[/quote]
Switched-capacitor voltage doublers work pretty well, but I doubt that a
switched-capacitor voltage halver would be less complex than a switching
regulator.
If your production volumes aren't too terribly high there are some nice
switching regulator modules out there. TI makes a wide variety with a
good size/power ratio, that'll take 12-24V easily. I'm sure that TI
isn't the only one.
--
www.wescottdesign.com |
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| Hammy... |
| Posted: Tue Oct 20, 2009 12:03 pm |
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Guest
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On Tue, 20 Oct 2009 11:54:39 -0500, Tim Wescott <tim at (no spam) seemywebsite.com>
wrote:
[quote]If your production volumes aren't too terribly high there are some nice
switching regulator modules out there. TI makes a wide variety with a
good size/power ratio, that'll take 12-24V easily. I'm sure that TI
isn't the only one.
[/quote]
For that matter a switcher with an integrated switch and a fixed
output of 3.3V could be had. This would require less real-estate then
either a TO-220 with a heatsink or your switched capacitor circuit.
Search Digikey and you'll find some 3.3V switchers in a dpak only
requiring a few external components and pretty well idiot proof. A
small SOD Schottkey and a tiny smd cap and inductor would be the only
external components you need.
You could build it on a separate PCB and mount it vertically to your
main PCB. I've done that a few times. For 120 mA output you should be
able to get it down around 1/2" x ˝".
Mount the DPAK on the ground side put your 3 or 4 other components on
the other side. |
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| Joerg... |
| Posted: Tue Oct 20, 2009 12:27 pm |
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Guest
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Charlie E. wrote:
[quote]On Tue, 20 Oct 2009 13:30:39 +0300, "michael nikolaou"
michaelnikolaou_remove_me_ at (no spam) yahoo.com> wrote:
Hi to newsgroup
I'm making a mcu based device which i want to be very small and low cost
The design consumes 100..120 ma at (no spam) 3.3V
The problem is the installation that requires 12 or 24 volts to operate.
I don't want to use a switching regulator to make the voltage drop since its
to much
circuit involved and also not a zener since its to much heat involved .
The mcu has A/D and PWM controller .Is it possible to use a simple mosfet
switch with
a capacitor to make a dropdown to half voltage if the mcu detects 24 volts
input ?.
Is there an easier way ?.
Any help would be appreciated .
MK
Michael,
Probably not a good idea. You MCU will take a little while to come up
to speed before it can monitor those voltages, and take action. At
24VDC, you chip is already fried by that time. That is a lot of
voltage to drop with just a linear regulator, esp. if that 24VDC is
not well regulated. It is possible, but it isn't simple...
[/quote]
You could do it, this way:
Resistor and zener to CPU but much higher zener voltage than the CPU
uses in normal operation, meaning the MCU should have lots of headroom.
Start MCU with bare minimum in code, basically doing nothing other than
the switcher. Now fire up a buck or whatever switcher from 12-24VDC, MCU
controlled hysteretic for example. When that gets into the green zone
let the MCU commence its normal job because now that the switcher has
started it can use all the power it wants.
If you can't spread zener voltage and normal operating voltage that far,
add an extra transistor that turns off the zener after the switcher
start process has run its course. This will cost another port pin.
--
Regards, Joerg
http://www.analogconsultants.com/
"gmail" domain blocked because of excessive spam.
Use another domain or send PM. |
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| Nico Coesel... |
| Posted: Tue Oct 20, 2009 12:35 pm |
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Guest
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"michael nikolaou" <michaelnikolaou_remove_me_ at (no spam) yahoo.com> wrote:
[quote]Hi to newsgroup
I'm making a mcu based device which i want to be very small and low cost
The design consumes 100..120 ma at (no spam) 3.3V
The problem is the installation that requires 12 or 24 volts to operate.
I don't want to use a switching regulator to make the voltage drop since its
to much
circuit involved and also not a zener since its to much heat involved .
[/quote]
Too much circuitry? Look at devices from TI like the TPS5410. Very
small and it will run at a wide variety of input voltages.
--
Failure does not prove something is impossible, failure simply
indicates you are not using the right tools...
"If it doesn't fit, use a bigger hammer!"
-------------------------------------------------------------- |
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| langwadt at (no spam) fonz.dk... |
| Posted: Tue Oct 20, 2009 12:48 pm |
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Guest
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On 20 Okt., 16:27, Charlie E. <edmond... at (no spam) ieee.org> wrote:
[quote]On Tue, 20 Oct 2009 13:30:39 +0300, "michael nikolaou"
michaelnikolaou_remove_... at (no spam) yahoo.com> wrote:
Hi to newsgroup
I'm making a mcu based device which i want to be very small and low cost
The design consumes 100..120 ma at (no spam) 3.3V
The problem is the installation that requires 12 or 24 volts to operate.
I don't want to use a switching regulator to make the voltage drop since its
to much
circuit involved and also not a zener since its to much heat involved .
The mcu has A/D and PWM controller .Is it possible to use a simple mosfet
switch with
a capacitor to make a dropdown to half voltage if the mcu detects 24 volts
input ?.
Is there an easier way ?.
Any help would be appreciated .
MK
Michael,
Probably not a good idea. You MCU will take a little while to come up
to speed before it can monitor those voltages, and take action. At
24VDC, you chip is already fried by that time. That is a lot of
voltage to drop with just a linear regulator, esp. if that 24VDC is
not well regulated. It is possible, but it isn't simple...
Charlie
[/quote]
I think it is doable, switch, L and C before a linear regulator.
out of reset have the switch on let the linear regulator regulate from
the
full 24V (or see if you can drop some over the switch)
when the MCU is up and running, use PWM, the switch, L and C as a
buck
dropping the voltage before the linear regulator to 3.3 + dropout
-Lasse |
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| Joerg... |
| Posted: Tue Oct 20, 2009 12:54 pm |
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Guest
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Nico Coesel wrote:
[quote]"michael nikolaou" <michaelnikolaou_remove_me_ at (no spam) yahoo.com> wrote:
Hi to newsgroup
I'm making a mcu based device which i want to be very small and low cost
The design consumes 100..120 ma at (no spam) 3.3V
The problem is the installation that requires 12 or 24 volts to operate.
I don't want to use a switching regulator to make the voltage drop since its
to much
circuit involved and also not a zener since its to much heat involved .
Too much circuitry? Look at devices from TI like the TPS5410. Very
small and it will run at a wide variety of input voltages.
[/quote]
But mucho Dolares. I'd try using the MCU if possible if this is a high
volume product. But it'll require lots of nifty engineering. For low
volume, yeah, don't bother and use a chip. Then I'd use the MC34063
which costs under 20 cents. None of those high-faluting newfangled ritzy
ones ;-)
--
Regards, Joerg
http://www.analogconsultants.com/
"gmail" domain blocked because of excessive spam.
Use another domain or send PM. |
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| ... |
| Posted: Tue Oct 20, 2009 1:12 pm |
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Guest
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On Oct 20, 2:14 pm, "michael nikolaou"
<michaelnikolaou_rem_o... at (no spam) yahoo.com> wrote:
[quote]Guys
Thanks for all your replies
My small research has found that switcher solutions are.
1. simple and small sized switcher solutions are expensive.
2. Mc33063 are ok in terms of price but the inductor plus the capacitors are
too much board estate
3. Small size means high frequency and so you start with selective
components etc.
I NEED ONLY 120 ma is there nothing low cost and simple ?.
One switcher i located used 10 uH inductor , 47 uF output capacitor at (no spam) 6.3V
and 2.2uF input capacitor
but total cost was 1.8 euros. I's using one ARM7 mcu that costs 3 euro and
i don't want to spend as much for the PSU.
Some lower consumption devices at (no spam) 50 mA were using uA78M33 regulator with a
zener if 24 volts was used.
Joerg do you have schematic to study about the idea you are proposing ?
Any other simple ideas ???
"Joerg" <inva... at (no spam) invalid.invalid> wrote in message
news:7k6faoF389blhU1 at (no spam) mid.individual.net...
Nico Coesel wrote:
"michael nikolaou" <michaelnikolaou_remove_... at (no spam) yahoo.com> wrote:
Hi to newsgroup
I'm making a mcu based device which i want to be very small and low cost
The design consumes 100..120 ma at (no spam) 3.3V
The problem is the installation that requires 12 or 24 volts to operate.
I don't want to use a switching regulator to make the voltage drop since
its to much
circuit involved and also not a zener since its to much heat involved .
Too much circuitry? Look at devices from TI like the TPS5410. Very
small and it will run at a wide variety of input voltages.
But mucho Dolares. I'd try using the MCU if possible if this is a high
volume product. But it'll require lots of nifty engineering. For low
volume, yeah, don't bother and use a chip. Then I'd use the MC34063 which
costs under 20 cents. None of those high-faluting newfangled ritzy ones
;-)
--
Regards, Joerg
http://www.analogconsultants.com/
"gmail" domain blocked because of excessive spam.
Use another domain or send PM.
[/quote]
This isn't going to help you because your request is unreasonable, but
it's about as few parts as you can get:
(view in fixed font)
+12-24V
-+-
| o D1
+------+----------------. .--|>|--+-----> +3.3v
| | ) ( |
R1 | L1 ) ( L2 |
| |/ Q1 ) ( |
+----| | '--. |
| |>. | o | |
| | ||--' === |
.---' +----. ||<-. GND |
Z1 ^ | | ||--+ Q2 |
4V | C1 --- | .---' | |
| --- | | | |
=== | | | === |
GND | | | GND |
=== '---)-------------------'
GND |
|
PWM from ARM7 >-------'
Q1 is a linear supply that runs the thing until the ARM gets going.
When the ARM switches Q2, the voltage rises on Q1's emitter and it
quits conducting.
I used a transformer. An inductor would be cheaper of course, but
then I'd have to draw yet another high-side MOSFET gate driver, and
that's boring.
You're really probably better off buying a switcher. If you _really_
need a tiny inductor, especially at 100mA, you're going to need
something fast. That won't be free.
--
Cheers,
James Arthur |
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| michael nikolaou... |
| Posted: Tue Oct 20, 2009 1:14 pm |
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Guest
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Guys
Thanks for all your replies
My small research has found that switcher solutions are.
1. simple and small sized switcher solutions are expensive.
2. Mc33063 are ok in terms of price but the inductor plus the capacitors are
too much board estate
3. Small size means high frequency and so you start with selective
components etc.
I NEED ONLY 120 ma is there nothing low cost and simple ?.
One switcher i located used 10 uH inductor , 47 uF output capacitor at (no spam) 6.3V
and 2.2uF input capacitor
but total cost was 1.8 euros. I's using one ARM7 mcu that costs 3 euro and
i don't want to spend as much for the PSU.
Some lower consumption devices at (no spam) 50 mA were using uA78M33 regulator with a
zener if 24 volts was used.
Joerg do you have schematic to study about the idea you are proposing ?
Any other simple ideas ???
"Joerg" <invalid at (no spam) invalid.invalid> wrote in message
news:7k6faoF389blhU1 at (no spam) mid.individual.net...
[quote]Nico Coesel wrote:
"michael nikolaou" <michaelnikolaou_remove_me_ at (no spam) yahoo.com> wrote:
Hi to newsgroup
I'm making a mcu based device which i want to be very small and low cost
The design consumes 100..120 ma at (no spam) 3.3V
The problem is the installation that requires 12 or 24 volts to operate.
I don't want to use a switching regulator to make the voltage drop since
its to much
circuit involved and also not a zener since its to much heat involved .
Too much circuitry? Look at devices from TI like the TPS5410. Very
small and it will run at a wide variety of input voltages.
But mucho Dolares. I'd try using the MCU if possible if this is a high
volume product. But it'll require lots of nifty engineering. For low
volume, yeah, don't bother and use a chip. Then I'd use the MC34063 which
costs under 20 cents. None of those high-faluting newfangled ritzy ones
;-)
--
Regards, Joerg
http://www.analogconsultants.com/
"gmail" domain blocked because of excessive spam.
Use another domain or send PM.[/quote] |
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| Joerg... |
| Posted: Tue Oct 20, 2009 1:52 pm |
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Guest
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michael nikolaou wrote:
[quote]Guys
Thanks for all your replies
My small research has found that switcher solutions are.
1. simple and small sized switcher solutions are expensive.
2. Mc33063 are ok in terms of price but the inductor plus the capacitors are
too much board estate
3. Small size means high frequency and so you start with selective
components etc.
[/quote]
Not really, the passive parts are easy. But the challenge will be to
find a mainstream (meaning inexpensive) small switcher chip. The cheap
ones are all old and slow, 300kHz or less. This will take some time
because you must always check pricing. You could start by looking at
chips for the Power over Ethernet (PoE) market.
[quote]I NEED ONLY 120 ma is there nothing low cost and simple ?.
One switcher i located used 10 uH inductor , 47 uF output capacitor at (no spam) 6.3V
and 2.2uF input capacitor
but total cost was 1.8 euros. I's using one ARM7 mcu that costs 3 euro and
i don't want to spend as much for the PSU.
Some lower consumption devices at (no spam) 50 mA were using uA78M33 regulator with a
zener if 24 volts was used.
Joerg do you have schematic to study about the idea you are proposing ?
[/quote]
No, that would be a little R&D project. Requires tight reigns on the
firmware because the switcher must never skip a beat. But if you have a
free timer in your ARM MCU it can be done.
[quote]Any other simple ideas ???
[/quote]
Another option would be to use a CD40106 or something similar as a
Schmitt oscillator, with its VCC capped/zenered around 6-8V. This can
drive a little FET, a simple logic level device like a 2N7002 as long as
doesn't cost much. Pipe Vref out of your MCU (hoping it has that ...)
and use a cheap opamp to pull the Schmitt oscillator input "to the side"
when the target voltage is reached. That reduces the duty cycle as much
as needed to maintain regulation, pretty much like the throttle on a
gasoline-powered generator. If the target voltage doesn't have to be
very precise you could also use a NPN plus zener for that, without a
reference source. Probably a TL431-type device would work as well and
those are quite cheap, in the penny range.
--
Regards, Joerg
http://www.analogconsultants.com/
"gmail" domain blocked because of excessive spam.
Use another domain or send PM. |
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| Jon Kirwan... |
| Posted: Tue Oct 20, 2009 2:31 pm |
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Guest
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On Tue, 20 Oct 2009 12:52:04 -0700, Joerg <invalid at (no spam) invalid.invalid>
wrote:
[quote]michael nikolaou wrote:
Guys
Thanks for all your replies
My small research has found that switcher solutions are.
1. simple and small sized switcher solutions are expensive.
2. Mc33063 are ok in terms of price but the inductor plus the capacitors are
too much board estate
3. Small size means high frequency and so you start with selective
components etc.
Not really, the passive parts are easy. But the challenge will be to
find a mainstream (meaning inexpensive) small switcher chip. The cheap
ones are all old and slow, 300kHz or less. This will take some time
because you must always check pricing. You could start by looking at
chips for the Power over Ethernet (PoE) market.
I NEED ONLY 120 ma is there nothing low cost and simple ?.
One switcher i located used 10 uH inductor , 47 uF output capacitor at (no spam) 6.3V
and 2.2uF input capacitor
but total cost was 1.8 euros. I's using one ARM7 mcu that costs 3 euro and
i don't want to spend as much for the PSU.
Some lower consumption devices at (no spam) 50 mA were using uA78M33 regulator with a
zener if 24 volts was used.
Joerg do you have schematic to study about the idea you are proposing ?
No, that would be a little R&D project. Requires tight reigns on the
firmware because the switcher must never skip a beat. But if you have a
free timer in your ARM MCU it can be done.
Any other simple ideas ???
Another option would be to use a CD40106 or something similar as a
Schmitt oscillator, with its VCC capped/zenered around 6-8V. This can
drive a little FET, a simple logic level device like a 2N7002 as long as
doesn't cost much. Pipe Vref out of your MCU (hoping it has that ...)
and use a cheap opamp to pull the Schmitt oscillator input "to the side"
when the target voltage is reached. That reduces the duty cycle as much
as needed to maintain regulation, pretty much like the throttle on a
gasoline-powered generator. If the target voltage doesn't have to be
very precise you could also use a NPN plus zener for that, without a
reference source. Probably a TL431-type device would work as well and
those are quite cheap, in the penny range.
[/quote]
This has been an interesting discussion. What is bothering me a lot,
in reading it, is the "ONLY 120mA" thing! 120mA? Only? Cripes. If
I were imagining being as space-constrained as the OP suggests, I'd IN
THE FIRST PLACE start asking myself why I actually need 120mA! Is it
the processor, itself? If so, look to get rid of it and find
something else. Doing so may put constraints on the application
itself (doing logarithms on a PIC16 is quite different in speed than
doing them on an ARM9, for example), but it may greatly relax the
power supply design issues. Everything is trade-off. But I'm
bothered by the casual acceptance of a 120mA spec as gospel when there
is a serious space and cost issue here.
What is sucking that power? Can it be changed? If not, why not?
Jon |
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| don... |
| Posted: Tue Oct 20, 2009 4:47 pm |
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Guest
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michael nikolaou wrote:
[quote]Guys
Thanks for all your replies
My small research has found that switcher solutions are.
1. simple and small sized switcher solutions are expensive.
2. Mc33063 are ok in terms of price but the inductor plus the capacitors are
too much board estate
3. Small size means high frequency and so you start with selective
components etc.
I NEED ONLY 120 ma is there nothing low cost and simple ?.
One switcher i located used 10 uH inductor , 47 uF output capacitor at (no spam) 6.3V
and 2.2uF input capacitor
but total cost was 1.8 euros. I's using one ARM7 mcu that costs 3 euro and
i don't want to spend as much for the PSU.
Some lower consumption devices at (no spam) 50 mA were using uA78M33 regulator with a
zener if 24 volts was used.
Joerg do you have schematic to study about the idea you are proposing ?
Any other simple ideas ???
It would appear that you are new to this engineering thing.[/quote]
Microcontrollers are so cheap because the manufactures figured you would
spend the money to make it work.
Power devices cost more then CPU silicon, always have.
Welcome to the real world.
Morpheus
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| Joerg... |
| Posted: Tue Oct 20, 2009 4:49 pm |
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Guest
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Jon Kirwan wrote:
[quote]On Tue, 20 Oct 2009 12:52:04 -0700, Joerg <invalid at (no spam) invalid.invalid
wrote:
michael nikolaou wrote:
Guys
Thanks for all your replies
My small research has found that switcher solutions are.
1. simple and small sized switcher solutions are expensive.
2. Mc33063 are ok in terms of price but the inductor plus the capacitors are
too much board estate
3. Small size means high frequency and so you start with selective
components etc.
Not really, the passive parts are easy. But the challenge will be to
find a mainstream (meaning inexpensive) small switcher chip. The cheap
ones are all old and slow, 300kHz or less. This will take some time
because you must always check pricing. You could start by looking at
chips for the Power over Ethernet (PoE) market.
I NEED ONLY 120 ma is there nothing low cost and simple ?.
One switcher i located used 10 uH inductor , 47 uF output capacitor at (no spam) 6.3V
and 2.2uF input capacitor
but total cost was 1.8 euros. I's using one ARM7 mcu that costs 3 euro and
i don't want to spend as much for the PSU.
Some lower consumption devices at (no spam) 50 mA were using uA78M33 regulator with a
zener if 24 volts was used.
Joerg do you have schematic to study about the idea you are proposing ?
No, that would be a little R&D project. Requires tight reigns on the
firmware because the switcher must never skip a beat. But if you have a
free timer in your ARM MCU it can be done.
Any other simple ideas ???
Another option would be to use a CD40106 or something similar as a
Schmitt oscillator, with its VCC capped/zenered around 6-8V. This can
drive a little FET, a simple logic level device like a 2N7002 as long as
doesn't cost much. Pipe Vref out of your MCU (hoping it has that ...)
and use a cheap opamp to pull the Schmitt oscillator input "to the side"
when the target voltage is reached. That reduces the duty cycle as much
as needed to maintain regulation, pretty much like the throttle on a
gasoline-powered generator. If the target voltage doesn't have to be
very precise you could also use a NPN plus zener for that, without a
reference source. Probably a TL431-type device would work as well and
those are quite cheap, in the penny range.
This has been an interesting discussion. What is bothering me a lot,
in reading it, is the "ONLY 120mA" thing! 120mA? Only? Cripes. If
I were imagining being as space-constrained as the OP suggests, I'd IN
THE FIRST PLACE start asking myself why I actually need 120mA! Is it
the processor, itself? If so, look to get rid of it and find
something else. Doing so may put constraints on the application
itself (doing logarithms on a PIC16 is quite different in speed than
doing them on an ARM9, for example), but it may greatly relax the
power supply design issues. Everything is trade-off. But I'm
bothered by the casual acceptance of a 120mA spec as gospel when there
is a serious space and cost issue here.
What is sucking that power? Can it be changed? If not, why not?
[/quote]
I sure hope it's not the MCU alone because that would spell trouble.
Often there are other things like ADCs, analog stuff etc. 120mA is
really a piece of cake from a power converter point of view. After all,
that's only 600mW if his VCC is 5V. Low enough for an energy star :-)
Michael may have to go with a SEPIC if he wants the FET to switch to GND
but that's not a big deal either, just two parts more. Since the advent
of PoE he's got plenty of options.
--
Regards, Joerg
http://www.analogconsultants.com/
"gmail" domain blocked because of excessive spam.
Use another domain or send PM. |
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