I am trying to desing a power supply, including a 12v flyback regulator
(it's for my incar mp3 player).

The regulator I have is a national LM2587, there are designs in the app
notes but all include a transformer. As I think I'll need more than one
regulator (for more current) I'd prefer not to. Is it possible to built
one with an inductor?



--
Anthony Toft <toftat@...>

--- In Electronics_101@..., Anthony Toft <toftat@c...> wrote:

I am trying to desing a power supply, including a 12v flyback regulator
(it's for my incar mp3 player).

The regulator I have is a national LM2587, there are designs in the app
notes but all include a transformer. As I think I'll need more than one
regulator (for more current) I'd prefer not to. Is it possible to built
one with an inductor?



--
Anthony Toft <toftat@c...>

I don't know about the LM2587 and would need more details of what you
are trying to do. If you are connecting to mains voltage then you
need a transformer for safety/isolation. If you are converting from a
car battery or something like that then you can just use an inductor -
a transofrmer is not necessary. I do not know if the LM2587 is
suitable for that configuration as I have never used it, but certainly
other switching regulator chips are.

Keith.

I don't know about the LM2587 and would need more details of what you
are trying to do. If you are connecting to mains voltage then you

No, no mains at all, it is for in car use only.

need a transformer for safety/isolation. If you are converting from a
car battery or something like that then you can just use an inductor -
a transofrmer is not necessary. I do not know if the LM2587 is

Yes, it will be in car, the data sheet says that for the input voltage I
am looking at (10-15v) I have to use it in flyback mode, all the example
circuits have a transformer in them.

suitable for that configuration as I have never used it, but certainly
other switching regulator chips are.

How can you measure the inductance? Incase I choose to make my own
tranformer? The problem is I will need 2 (for current requirements) and
after the regulators the magnetics are the most expensive part of the
circuit by half.

--
Anthony Toft <toftat@...>

How can you measure the inductance? Incase I choose to make my own
tranformer? The problem is I will need 2 (for current requirements) and
after the regulators the magnetics are the most expensive part of the
circuit by half.

You can get meters, looking like digital multimeters, that can measure this.
they are in about the same price range as digital multimeters.
the professional version is a "resistance, inductance, capacitance measuring bridge"
but a simple component meter is ok.
You can even get multimeters with inductance measuring range.

Another approach is with a scope and a ac signal.


But you can buy ready-made inductors for which the value is known.


What do you need the 12V for?
You should be able to use 5V components, or use a regulator only limiting, no stepup,
for motors (fans, maybe harddisk).


If you take apart a old PC power supply you will find a inductor which carries one winding
for 5V and one for 12V, maybe even one for 3,3V.
you can use it , using the 5V winding for primary and the 12V winding for secondary.


ST

Probably. Give me a link to the data sheet and I will look it up
for you. Transformers are usually for isolation, if you are willing
to give up isolation you are probably all right.

As for inductors / transformers on these application notes - DON'T
try to do it yourself! The characteristics are usually so
intertwined that the manufacturer recommends vendor and part
number. Substitute and the circuit won't work. They usually sell
evaluation boards with the necessary parts - a very annoying, but
necessary investment for the hobbyist, because your chances of
getting samples of the oddball inductors, special capacitors,
schottky diodes, wierd transistors are almost zero - much less
making a PC board layout without parasitics that will ruin your
design.

--- In Electronics_101@..., "Bruce Carter" <brucec@m...>
wrote:

Probably. Give me a link to the data sheet and I will look it up
for you. Transformers are usually for isolation, if you are willing
to give up isolation you are probably all right.

As for inductors / transformers on these application notes - DON'T
try to do it yourself! The characteristics are usually so
intertwined that the manufacturer recommends vendor and part
number. Substitute and the circuit won't work. They usually sell
evaluation boards with the necessary parts - a very annoying, but
necessary investment for the hobbyist, because your chances of
getting samples of the oddball inductors, special capacitors,
schottky diodes, wierd transistors are almost zero - much less
making a PC board layout without parasitics that will ruin your
design.

I disagree. I often wind my own inductors because what I want usually
doesn't exist. For power inductors I quite like the Micrometals E
cores becuase they have high energy storage without having to mess
about with gapping and are cheap. If you want gapped ferrites then
MMG Neosid do a good range.

To answer the issue of measuring the inductance, it is easy to do. I
often use resonance - put a known capacitor across it, a series
resistor and hook it up to a scope and signal generator. However, you
shouldn't need to measure it. Design it, wind it, use it.

I am not quite sure of what you want to get out of the regulator. If
it is for car use and it runs off 12V, why regulate? Does the
equipment you want to use require a very precise voltage?

Keith.

As for inductors / transformers on these application notes - DON'T
try to do it yourself!

I disagree. I often wind my own inductors because what I want usually
doesn't exist. For power inductors I quite like the Micrometals E
cores becuase they have high energy storage without having to mess
about with gapping and are cheap. If you want gapped ferrites then
MMG Neosid do a good range.

i disagree too / agree with keith.
Buying the demo board is no way of learning how to do it.
it is a way of buying a ready-made unit, but then i can just go out and buy
the supply module and that would maybe be even cheaper.

To answer the issue of measuring the inductance, it is easy to do. I
often use resonance - put a known capacitor across it, a series
resistor and hook it up to a scope and signal generator. However, you
shouldn't need to measure it. Design it, wind it, use it.

Best approach if you have a scope and a generator.
You can test it close to the frequency you will use it.

If you use a small component tester you might want to make sure the measuring frequency
isn't so far off that the result is worthless. of course you can calculate the error.

ST

开云体育

On Fri, 23 Apr 2004 18:31:54 -0500, Curtis Sakima <csakima@...> wrote:

I too, go with rollin' your own. One of my biggest gripes about modern
society is the steady loss of so-called "basic knowledge". The sort of
hands-on understanding of how things work. Our society is slowly degrading
to a state of "industry has the concentration of all knowledge" with Joe
Public worshipping it like it's "all magic". Kinda the "Star Trek
away-team landing on a primitive society" type of syndrome. We need to keep
up with the understanding of technology. And rollin' ya own ... is a very
good way.

One of the best test equipment I've found for doing what you're doing ....
is a RF network analyser. Tells you at what frequency the thingy's
capacitive ... inductive ... at resonance .... etc.... etc.

Curtis

agree, this wants to make you buy way too expensive "prebuilt" solutions and
also leads to dramatic loss of interest in the basics which in turn leads
to no people who really know what they do in the future, which in turn leads
to electric toothbrushes requiring a 100Mhz processor to turn the motor on/off which
in turn leads to the toothbrush being too expensive and the toothbrush industry
collapsing ;-).


I find rf network analysers a bit expensive... but they are not bad... not vital but not bad at all..

ST

I too, go with rollin' your own. One of my biggest gripes about modern
society is the steady loss of so-called "basic knowledge". The sort of
hands-on understanding of how things work. Our society is slowly degrading
to a state of "industry has the concentration of all knowledge" with Joe
Public worshipping it like it's "all magic". Kinda the "Star Trek
away-team landing on a primitive society" type of syndrome. We need to keep
up with the understanding of technology. And rollin' ya own ... is a very
good way.

One of the best test equipment I've found for doing what you're doing ....
is a RF network analyser. Tells you at what frequency the thingy's
capacitive ... inductive ... at resonance .... etc.... etc.

Curtis

Dazzle Mom this coming Mother's Day season with flowers!

On Fri, 2004-04-23 at 09:21, Bruce Carter wrote:

Probably. Give me a link to the data sheet and I will look it up
for you. Transformers are usually for isolation, if you are willing
to give up isolation you are probably all right.

The data sheet can be found at...

<>

Thanks for the help, I think I know how theoretically it works (the
whole collapsing field thing) which is why I think the transformer is
needed, but I am struggling up the curve, I am a software guy...

--
Anthony Toft <toftat@...>

--- In Electronics_101@..., "Keith" <keith@k...> wrote:

--- In Electronics_101@..., "Bruce Carter" <brucec@m...>
wrote:

Probably. Give me a link to the data sheet and I will look it up
for you. Transformers are usually for isolation, if you are willing
to give up isolation you are probably all right.

As for inductors / transformers on these application notes - DON'T
try to do it yourself! The characteristics are usually so
intertwined that the manufacturer recommends vendor and part
number. Substitute and the circuit won't work. They usually sell
evaluation boards with the necessary parts - a very annoying, but
necessary investment for the hobbyist, because your chances of
getting samples of the oddball inductors, special capacitors,
schottky diodes, wierd transistors are almost zero - much less
making a PC board layout without parasitics that will ruin your
design.

I disagree. I often wind my own inductors because what I want usually
doesn't exist. For power inductors I quite like the Micrometals E
cores becuase they have high energy storage without having to mess
about with gapping and are cheap. If you want gapped ferrites then
MMG Neosid do a good range.

To answer the issue of measuring the inductance, it is easy to do. I
often use resonance - put a known capacitor across it, a series
resistor and hook it up to a scope and signal generator. However, you
shouldn't need to measure it. Design it, wind it, use it.

I am not quite sure of what you want to get out of the regulator. If
it is for car use and it runs off 12V, why regulate? Does the
equipment you want to use require a very precise voltage?

Keith.

Yeah it's a good practice to breadboard and build your own inductive
elements/transformers. I have used a pulse source and scope to measure
the charcteristics of power inductors by measuring the slope and the
point at which it saturates. The staturation point is as important as
the inductance in most power supply circuits.