Help!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! (I am sorry to keep

S

Scott Wiper

Guest
Bad link bellow... Repost

I am stumped here.

I have bought some books on switcher supplys. I am beginning to understand
the three types

A: flyback type switchers.
B: Step up buck switchers.
C: Stepdown buck switchers.

I am trying to do this with transistors for this project.
http://www.travel-net.com/~swiper/switch.gif
I am trying to understand the function of the stepdown buck switcher. I am
useing a ne555 and a 4013 as the timing or switch. The primary DC is comming
a 100W 24VAC stepdown transeformer. I have done it like this. Vout~vz+Vce.

My first question is the output inductor.

Is this inductor used to store energy into the output capasitor?

Is the way I have this setup (Link above)... Will this make the caps burst?

Will this also make the 2N6284 Darlingtons heat up to a point that you can
boil water on them?

I am sorry to keep hounding on this issue but I have built it. I am affraid
what will happen on pwer up.


My last question is I have a LM2574HVT buck switcher that can be adjusted. I
want to use a 12.6V/1.5AH battery to power my portable CD player. For
stupidly long periods of time through the small power socket on the back.

Will there be noise in the audio even if I use the 330uH indctor and the
330uF cap as stated in the aplication notes on the data sheet?

--
My cat Tigger says every morning...
"Before my morning coffee... I might as well be a dog!"
To contact follow the link below.
http://www.travel-net.com/~swiper/email.htm



--
My cat Tigger says every morning...
"Before my morning coffee... I might as well be a dog!"
To contact follow the link below.
http://www.travel-net.com/~swiper/email.htm
 
Scott Wiper wrote:
Bad link bellow... Repost

I am stumped here.

I have bought some books on switcher supplys. I am beginning to understand
the three types

A: flyback type switchers.
B: Step up buck switchers.
Click to expand...
Not familiar with this one. 'Buck' usually refers to lowering voltage
(bucking or holding voltage back).

C: Stepdown buck switchers.

I am trying to do this with transistors for this project.
http://www.travel-net.com/~swiper/switch.gif
I am trying to understand the function of the stepdown buck switcher. I am
useing a ne555 and a 4013 as the timing or switch. The primary DC is comming
a 100W 24VAC stepdown transeformer. I have done it like this. Vout~vz+Vce.

My first question is the output inductor.

Is this inductor used to store energy into the output capasitor?
Click to expand...
There is energy put into an inductor any time its current increases,
and energy comes out any time the current decreases. The inductor in
a buck regulator acts like a current fly wheel, slowing the rise of
current when the switch is on, and keeping the current to the output
going (while ramping down a bit) during the switch off time. It
passes this off switch current through the diode to the other side of
the output (D10 in your 5 volt supply).

Is the way I have this setup (Link above)... Will this make the caps burst?
Click to expand...
The inductor controls the rate of rise of current into the output cap
when the switch is on, so it greatly reduces the ripple current to the
output capacitor. The capacitor that feeds voltage into the switch
still sees either the output current or zero current depending whether
the switch is on of off, so it needs considerable ripple current
capability.

Will this also make the 2N6284 Darlingtons heat up to a point that you can
boil water on them?
Click to expand...
They heat up because you are not driving them correctly. NPN
darlington in this configuration has no voltage gain (it outputs from
the emitter), so it needs a base voltage swing at least as large as
the expected output swing. You are limiting the base swing to much
less than the full input voltage ot the switch, so it never switches
all the way on. Either you need to come up with a way to drive the
base all the way from zero to +12 volts or you need a PNP switch so
that it has voltage gain and you just have to pull current out of the
base to turn it on.

I am sorry to keep hounding on this issue but I have built it. I am affraid
what will happen on pwer up.
Click to expand...
I am afraid for you, after seeing your schematic. You have the
inductor and diode right, but your switch still needs work.

My last question is I have a LM2574HVT buck switcher that can be adjusted. I
want to use a 12.6V/1.5AH battery to power my portable CD player. For
stupidly long periods of time through the small power socket on the back.

Will there be noise in the audio even if I use the 330uH indctor and the
330uF cap as stated in the aplication notes on the data sheet?
Click to expand...
If the switcher pulses at a frequency higher than you can hear, the
ripple voltage from the supply will be inaudible. Does the data sheet
say how many pulses per second this regulator produces?

--
John Popelish
 
"Scott Wiper" <nobody@devnull.spamcop.met> wrote in message
news:2cuzc.5462$vO1.45643@nnrp1.uunet.ca...
Bad link bellow... Repost

I am stumped here.

I have bought some books on switcher supplys. I am beginning to understand
the three types

A: flyback type switchers.
B: Step up buck switchers.
C: Stepdown buck switchers.

I am trying to do this with transistors for this project.
http://www.travel-net.com/~swiper/switch.gif
I am trying to understand the function of the stepdown buck switcher. I am
useing a ne555 and a 4013 as the timing or switch. The primary DC is
comming
a 100W 24VAC stepdown transeformer. I have done it like this. Vout~vz+Vce.

My first question is the output inductor.

Is this inductor used to store energy into the output capasitor?

Is the way I have this setup (Link above)... Will this make the caps
burst?

Will this also make the 2N6284 Darlingtons heat up to a point that you can
boil water on them?

I am sorry to keep hounding on this issue but I have built it. I am
affraid
what will happen on pwer up.


My last question is I have a LM2574HVT buck switcher that can be adjusted.
I
want to use a 12.6V/1.5AH battery to power my portable CD player. For
stupidly long periods of time through the small power socket on the back.

Will there be noise in the audio even if I use the 330uH indctor and the
330uF cap as stated in the aplication notes on the data sheet?

--
My cat Tigger says every morning...
"Before my morning coffee... I might as well be a dog!"
To contact follow the link below.
http://www.travel-net.com/~swiper/email.htm



--
My cat Tigger says every morning...
"Before my morning coffee... I might as well be a dog!"
To contact follow the link below.
http://www.travel-net.com/~swiper/email.htm


Scott,
Click to expand...

You might want to spend some time at the TI and National web sites. They
have good ap notes on switchers, with more useful information than books.
Forget about using Darlington transistors, and NE555 type things. Switchers
can be non trivial even when you use the right stuff.

Tam
 
"John Popelish" <jpopelish@rica.net> wrote in message
news:40CE754D.657C381A@rica.net...
Scott Wiper wrote:


If the switcher pulses at a frequency higher than you can hear, the
ripple voltage from the supply will be inaudible. Does the data sheet
say how many pulses per second this regulator produces?
Click to expand...
It says 52KHZ is the switch frequency.

--
John Popelish
 
"Tam/WB2TT" <t-tammaru@c0mca$t.net> wrote in message
news:GbKdnYUoztXu6FPd4p2dnA@comcast.com...

"Scott Wiper" <nobody@devnull.spamcop.met> wrote in message
news:2cuzc.5462$vO1.45643@nnrp1.uunet.ca...

Scott,

You might want to spend some time at the TI and National web sites. They
have good ap notes on switchers, with more useful information than books.
Forget about using Darlington transistors, and NE555 type things. Switchers
can be non trivial even when you use the right stuff.

Tam
Click to expand...
I will check this out because of these books on switchers... My brain has
gone completely into fart mode.

I a powered it up. No bursting but the first darlington gets slightly warm
(2.0A including battery float current) and the second not even with a 2.5A
load
 
"Scott Wiper" <nobody@devnull.spamcop.met> wrote in message
news:2cuzc.5462$vO1.45643@nnrp1.uunet.ca...
Is this inductor used to store energy into the output capasitor?
Click to expand...
Combined with the following capacitor, it integrates the incoming current.
Hence given a load, a constant, rather than pulsating, voltage is produced
across it. In essense it averages the PWM output of the switching device.

And yeah, your switch sucks. :p You need a PNP, and I don't like that
1N5402 there. Needs to be UF5402 if you're going to run it anywhere near
50kHz.

Tim

--
"I've got more trophies than Wayne Gretsky and the Pope combined!"
- Homer Simpson
Website @ http://webpages.charter.net/dawill/tmoranwms
 
"Tim Williams" <tmoranwms@charter.net> wrote in message
news:10ct0vhh5p8nb1c@corp.supernews.com...
"Scott Wiper" <nobody@devnull.spamcop.met> wrote in message
news:2cuzc.5462$vO1.45643@nnrp1.uunet.ca...
Is this inductor used to store energy into the output capasitor?

Combined with the following capacitor, it integrates the incoming current.
Hence given a load, a constant, rather than pulsating, voltage is produced
across it. In essense it averages the PWM output of the switching device.

And yeah, your switch sucks. :p You need a PNP, and I don't like that
1N5402 there. Needs to be UF5402 if you're going to run it anywhere near
50kHz.

Tim
Click to expand...
It's working but I have none into total brainicus farticus (Brain fart). One
good thing no boiling water and no poped caps and the voltage is steady
A.13.96VDC and B.5.43VDC both are now warm but Q2 is warm now (49C).
--
"I've got more trophies than Wayne Gretsky and the Pope combined!"
- Homer Simpson
Website @ http://webpages.charter.net/dawill/tmoranwms
 
"Tam/WB2TT" <t-tammaru@c0mca$t.net> wrote in message
news:GbKdnYUoztXu6FPd4p2dnA@comcast.com...
"Scott Wiper" <nobody@devnull.spamcop.met> wrote in message
news:2cuzc.5462$vO1.45643@nnrp1.uunet.ca...
Bad link bellow... Repost

I am stumped here.

I have bought some books on switcher supplys. I am beginning to
understand
the three types

A: flyback type switchers.
B: Step up buck switchers.
C: Stepdown buck switchers.

I am trying to do this with transistors for this project.
http://www.travel-net.com/~swiper/switch.gif
I am trying to understand the function of the stepdown buck switcher. I
am
useing a ne555 and a 4013 as the timing or switch. The primary DC is
comming
a 100W 24VAC stepdown transeformer. I have done it like this.
Vout~vz+Vce.

My first question is the output inductor.

Is this inductor used to store energy into the output capasitor?

Is the way I have this setup (Link above)... Will this make the caps
burst?

Will this also make the 2N6284 Darlingtons heat up to a point that you
can
boil water on them?

I am sorry to keep hounding on this issue but I have built it. I am
affraid
what will happen on pwer up.


My last question is I have a LM2574HVT buck switcher that can be
adjusted.
I
want to use a 12.6V/1.5AH battery to power my portable CD player. For
stupidly long periods of time through the small power socket on the
back.

Will there be noise in the audio even if I use the 330uH indctor and the
330uF cap as stated in the aplication notes on the data sheet?

Scott,

You might want to spend some time at the TI and National web sites. They
have good ap notes on switchers, with more useful information than books.
Forget about using Darlington transistors, and NE555 type things.
Switchers
can be non trivial even when you use the right stuff.

Tam
Click to expand...
Hi Scott,

there are a couple of problems. If you have the parts, its OK to use 555
timers and the like to build a DIY switcher - its just silly to build a
product that way. Darlington transistors are terribly slow, and 1N54xx
diodes are TERRIBLE - they have a reverse-recovery time measured in tens of
microseconds, so will get HOT (I once repaired 50 videogame smps that had
been "fixed" by a tech that used 1N5407 instead of fast Trr (use < 300ns,
70ns is great) diodes. They all worked, for a few days....I charged $35
each, and it took me half a day to fix them all - so very profitable :). A
suitable part would be (say) UF5404 - similar ratings but a high-speed
diode.

you could replace the darlington with a PNP (like say MJE2955), and use the
same TIP41 (slow as all hell) to drive it - pull the pnp base down via a
resistor using the TIP41 collector. The faster your smps runs, the harder
the base drive job becomes, BUT the output inductance & capacitance
required gets smaller. 144Hz is astonishingly low, and likely due to the
terribly slow transistors

cheers
Terry
 
Scott Wiper wrote:
"John Popelish" <jpopelish@rica.net> wrote in message
news:40CE754D.657C381A@rica.net...
Scott Wiper wrote:

If the switcher pulses at a frequency higher than you can hear, the
ripple voltage from the supply will be inaudible. Does the data sheet
say how many pulses per second this regulator produces?

It says 52KHZ is the switch frequency.
Click to expand...
I'm not sure what planet you're from, but I can't hear that. ;-)

--
John Popelish
 
"Scott Wiper" <nobody@devnull.spamcop.met> wrote in message
news:X7vzc.5476$vO1.45403@nnrp1.uunet.ca...

Scott,

One of the better papers I have on switching power supplies is
"Understanding Buck Power Stages in Switchmode Power Supplies" that I had
downloaded from the TI web site. The product ID is SLVA057.

If you are messing around with things other than switch mode controller ICs,
you should be aware that at load currents below a critical value, the output
voltage no longer is determined solely by the duty cycle of the switch.
Controller ICs know how to handle that.

Tam
 
Hi,

i would suggest that your circuit is not working at all how you think, the
555 and 4013 are probably performing no function at all whatsoever, the
switches used at 144khz need a considerable time to switch off and this is
dependant on the negative drive current available, wich seems to be
insignificant in your circuit, although as they are not saturated less will
be needed, i doubt that they will actualy turn off at all given that the off
period is only 3us, in fact whats worse is that they wil probably switch off
enuf for the output voltage to fall so the lower diode conducts but still
continue to draw almost the same current, thus wasting a very considerable
amount of power indeed.

also under reasonable load current the output voltage would be 50% of the
output voltage from the switch wich in this case is detemined by the zener
diodes in their drive circuit. under no load condition tho voltage would
rise towards 100% of this value, wich is what seems to be the case.

if u find the heat disapation is not to much of a problem then maybe u cld
just try using linear regulators, i would gues that linear regulators would
actualy run cooler less power !!

sorry to dampen your enthusiasm like this ...

Colin =^.^=



"Scott Wiper" <nobody@devnull.spamcop.met> wrote in message
news:jIvzc.5480$vO1.45753@nnrp1.uunet.ca...
"Tim Williams" <tmoranwms@charter.net> wrote in message
news:10ct0vhh5p8nb1c@corp.supernews.com...
"Scott Wiper" <nobody@devnull.spamcop.met> wrote in message
news:2cuzc.5462$vO1.45643@nnrp1.uunet.ca...
Is this inductor used to store energy into the output capasitor?

Combined with the following capacitor, it integrates the incoming
current.
Hence given a load, a constant, rather than pulsating, voltage is
produced
across it. In essense it averages the PWM output of the switching
device.

And yeah, your switch sucks. :p You need a PNP, and I don't like that
1N5402 there. Needs to be UF5402 if you're going to run it anywhere near
50kHz.

Tim

It's working but I have none into total brainicus farticus (Brain fart).
One
good thing no boiling water and no poped caps and the voltage is steady
A.13.96VDC and B.5.43VDC both are now warm but Q2 is warm now (49C).
--
"I've got more trophies than Wayne Gretsky and the Pope combined!"
- Homer Simpson
Website @ http://webpages.charter.net/dawill/tmoranwms
Click to expand...
 
--
"The difference between fiction and reality
is that fiction must make sense."
--Tom Clancey
__________________________________

"Scott Wiper" <nobody@devnull.spamcop.met> wrote in message
news:2cuzc.5462$vO1.45643@nnrp1.uunet.ca...
Bad link bellow... Repost

I am stumped here.

I have bought some books on switcher supplys. I am beginning to
understand
the three types

A: flyback type switchers.
B: Step up buck switchers.
C: Stepdown buck switchers.

I am trying to do this with transistors for this project.
http://www.travel-net.com/~swiper/switch.gif
Click to expand...
..........

It's inefficient because the output emitter of the 2N6284 can only
rise to about 19 volts when turned full on.
(36.5-15.1-.0.5-0.7-0.7) The zener is the major culprit.
The voltage drop times current is dissipated in the 2N6284 during
it's on period.
Similar story for Q5.
Best to use a switcher chip designed to do what you want.
GC
 
"Scott Wiper" <nobody@devnull.spamcop.met> wrote in message
news:2cuzc.5462$vO1.45643@nnrp1.uunet.ca...
Bad link bellow... Repost

I am stumped here.

I have bought some books on switcher supplys. I am beginning to
understand
the three types

A: flyback type switchers.
B: Step up buck switchers.
C: Stepdown buck switchers.

I am trying to do this with transistors for this project.
http://www.travel-net.com/~swiper/switch.gif
Click to expand...
It's inefficient because the output emitter of the 2N6284 can only
rise to about 19 volts when turned full on.
(35.6-15.1-.0.5-0.7-0.7) The zener is the major culprit.
The voltage drop times current is dissipated in the 2N6284 during
it's on period.
Similar story for Q5.
Best to use a switcher chip designed to do what you want.
GC
 
"Tam/WB2TT" <t-tammaru@c0mca$t.net> wrote in message
news:pJudnVqrILVimFLdRVn-sA@comcast.com...
If you are messing around with things other than switch mode controller
ICs,
you should be aware that at load currents below a critical value, the
output
voltage no longer is determined solely by the duty cycle of the switch.
Controller ICs know how to handle that.

Tam
Click to expand...

Discontinuous mode...
 
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