Simple boost converter with 555

[Zed]

Hi there!

I need a simple circuit that increases its 12 - 14 V input with 3 -
5 V on its output. I would like to make it with NE555. Please send me
a link where I can find a really simple circuit.

 

[Fred Bloggs]

Hi there!

I need a simple circuit that increases its 12 - 14 V input with 3 -
5 V on its output. I would like to make it with NE555. Please send me
a link where I can find a really simple circuit.

Ummmm, 12-14V on the input converted to 3-5V on its output is not a
boost, it is a buck. And if you think 3-5V is an "increase" of 12-14V,
then you have other issues that must be addressed prior to working with
electronics.

 

[MooseFET]

Ummmm, 12-14V on the input converted to 3-5V on its output is not a
boost, it is a buck. And if you think 3-5V is an "increase" of 12-14V,
then you have other issues that must be addressed prior to working with
electronics.

He may mean that the 3-5V is the amount of increase from the 12-14V.
Hopefully the OP will respond and let us know if this is the case.

He also didn't tell us how much current he needs to make.

I think we should put a zener diode on pin 5 of the LM555 so that we
can make it only cycle if the output voltage is below the requirement.

 

[Zed]

Ummmm, 12-14V on the input converted to 3-5V on its output is not a
boost, it is a buck. And if you think 3-5V is an "increase" of 12-14V,
then you have other issues that must be addressed prior to working with
electronics.

Well, my english is far from being perfect, but I wrote:
' ... that increases its 12 - 14 V input WITH 3 -5 V on its output...'
So I need 12 - 14 V to boost up to 15 - 19 V.

 

[Zed]

He may mean that the 3-5V is the amount of increase from the 12-14V.
Hopefully the OP will respond and let us know if this is the case.

He also didn't tell us how much current he needs to make.

I think we should put a zener diode on pin 5 of the LM555 so that we
can make it only cycle if the output voltage is below the requirement.

I have to supply one or two OPAs. So it takes approximately 100mA.
Maximum.

 

[[email protected]]

Well, my english is far from being perfect, but I wrote:
' ... that increases its 12 - 14 V input WITH 3 -5 V on its output...'
So I need 12 - 14 V to boost up to 15 - 19 V.

Seems to me a simple circuit you could roll together yourself is a
charge pump doubler. However, this is not what your spec requires. I
think it would be far simpler just to buy a chip that does the job
rather than roll your own.

 

[[email protected]]

Well, my english is far from being perfect, but I wrote:
' ... that increases its 12 - 14 V input WITH 3 -5 V on its output...'
So I need 12 - 14 V to boost up to 15 - 19 V.

Ah, you meant to say, "that increases its 12 - 14 V input ***BY*** 3
-5 V on its output...".

For a second there, thought you wanted to increase 3-5VDC to 12-14V.
(As an aside, the 555 requires at least 4.5VDC, preferably 5V, to
operate properly.)

M

 

[default]

Hi there!

I need a simple circuit that increases its 12 - 14 V input with 3 -
5 V on its output. I would like to make it with NE555. Please send me
a link where I can find a really simple circuit.

Check out
http://www.linux-cae.net/Projects/PowerSupply/voltdoubler.gif

This circuit uses a 555 to take the incoming voltage and add it to
itself; input 12, get out 24 . . . then add a 15-18 volt three
terminal regulator or use a zener in series to subtract the excess
voltage from the output.

A little more effort and there may be a way to use the XS voltage -
zener and transistor to switch off the 555 so it would be turning on
and off a pulse train. Turn on an NPN transistor to ground and use
the reset pin of the 555 to pull low when the output exceeded whatever
voltage you want .
--

 

[default]

Hi there!

I need a simple circuit that increases its 12 - 14 V input with 3 -
5 V on its output. I would like to make it with NE555. Please send me
a link where I can find a really simple circuit.

http://www.aaroncake.net/circuits/6-12conv.asp?showcomments=all

4 transistor circuit for 800 ma - change one diode to change output
voltage

--

 

[Stranger]

"Zed" <[email protected]> a écrit dans le message de

He may mean that the 3-5V is the amount of increase from the 12-14V.
Hopefully the OP will respond and let us know if this is the case.

He also didn't tell us how much current he needs to make.

I think we should put a zener diode on pin 5 of the LM555 so that we
can make it only cycle if the output voltage is below the requirement.

I have to supply one or two OPAs. So it takes approximately 100mA.
Maximum.

100mA is quite a load for a charge pump. Usually a charge can give 10mA or
so without to much problem.
Better go with a switching step-up regulator, that is, a small coil is
needed for an efficiency conversion.

Stranger

 

[Zed]

Check outhttp://www.linux-cae.net/Projects/PowerSupply/voltdoubler.gif

This circuit uses a 555 to take the incoming voltage and add it to
itself;  input 12, get out 24 . . . then add a 15-18 volt three
terminal regulator or use a zener in series to subtract the excess
voltage from the output.

A little more effort and there may be a way to use the XS voltage -
zener and transistor to switch off the 555 so it would be turning on
and off a pulse train.  Turn on an NPN transistor to ground and use
the reset pin of the 555 to pull low when the output exceeded whatever
voltage you want .
--

That's what I need. But I can't see the maximum output current of
this circuit. How can I calculate it?

 

[Paul Burke]

I have to supply one or two OPAs. So it takes approximately 100mA.
Maximum.

12-14V seems plenty to run a few op amps. What output swing do you need?
And 100mA could run a steel furnace (almost) let alone a few opamps.

 

[[email protected]]

That's what I need. But I can't see the maximum output current of
this circuit. How can I calculate it?

I already told you how to do this in my other post. But why roll your
own? Would it kill you to buy a 7662? Forget the zener. Follow the
doubler with a LDO.

Regarding current, recall that current is a flow of charge versus
time.Charge is voltage times capacitance. If you think of the charged
cap as a packet of charge that is delivered to the load in a finite
time period, you can estimate the current. It is a matter of sizing
the capacitors relative to the frequency of the oscillator.

 

[Zed]

12-14V seems plenty to run a few op amps. What output swing do you need?
And 100mA could run a steel furnace (almost) let alone a few opamps.

I would like to build an adjustable power supply. I have a 12V/3000mA
transformer.
I want to adjust the output 0 - 12 V. I would like to use a simple
transistor
regulation ( H1061 ). The regulation will be solved by OPAs. As I will
need
the transistor use as a Darlington, I need to boost up the 12V power
for the OPAs to let them drive the transistor to 12V.
( Sorry, my english is not too good. ;-) I hope you can understand
me. )

 

[Zed]

I already told you how to do this in my other post. But why roll your
own? Would it kill you to buy a 7662? Forget the zener. Follow the
doubler with a LDO.

Of course it wouldn't. But I don't have any 7662 on my shelf. Unlike
555. I am a hobbist. So it is a great opportunity to try 555. ( I
never
used 555 before. )

Regarding current, recall that current is a flow of charge versus
time.Charge is voltage times capacitance. If you think of the charged
cap as a packet of charge that is delivered to the load in a finite
time period, you can estimate the current. It is a matter of sizing
the capacitors relative to the frequency of the oscillator.

OK, I will make my calculations.

 

[default]

That's what I need. But I can't see the maximum output current of
this circuit. How can I calculate it?

The maximum output current without external pass transistors will be
whatever the 555 can deliver. My 1970's copy of the Linear Databook
gives it at 200 milliamps source or sink, with a 600 milliwatt maximum
power dissipation.


--

 

[MooseFET]

I have to supply one or two OPAs. So it takes approximately 100mA.
Maximum.

That is about at the limit for a LM555 based design.

 

[MooseFET]

I would like to build an adjustable power supply. I have a 12V/3000mA
transformer.
I want to adjust the output 0 - 12 V. I would like to use a simple
transistor
regulation ( H1061 ). The regulation will be solved by OPAs. As I will
need
the transistor use as a Darlington, I need to boost up the 12V power
for the OPAs to let them drive the transistor to 12V.
( Sorry, my english is not too good. ;-) I hope you can understand
me. )

Run a voltage doubler on the output of the transformers to make
roughly twice the voltage. It just needs a couple of diodes like
1N400X and a capacitor to do.

 

[[email protected]]

Of course it wouldn't. But I don't have any 7662 on my shelf. Unlike
555. I am a hobbist. So it is a great opportunity to try 555. ( I
never
used 555 before. )

Oh, and you have all the fets handy to make the cap fly? And the level
shifters to drive the fets. You can probably find some circuits that
use diodes where possible to save some circuitry. Granted at less
efficiency.

 

[gearhead]

http://www.aaroncake.net/circuits/6-12conv.asp?showcomments=all

4 transistor circuit for 800 ma - change one diode to change output
voltage

--

0.1 uF cap across the C-B of Q4 in that circuit, maybe.