A starting point for Switching Mode Power Supply Design

[Myauk]

Hello

I am studying Power Supply Cook Book, MARTY BROWN, 2nd Edition, Newnes
Copyright 2001.

I have constructed linear power supplies, I know every details about
one zener, one resistor regulation, one zener, one transistor
regulation and I know the basis and constructed regulators with three
terminal regulators as well as floating regulators.

I have tested and understand characteristics bipolar, some types of
MOSFETs and PWM ICs.

I understand how SMPS works in general as well as some specifications.
I know very well that to be able to design SMPS well, I need to
construct Swith Mode Power Supplies practically. Studying without
practical experiments is not good.

The problem here is I do not know where to start with SMPS designs
because I am not familiar especially with the ferrite core transformers
( I have designed Iron Core, 50 Hz, Auto Transformers for Voltage
Regulators).

And I am worried the first SMPS I construct would not work well.

I am afraid High Voltage Spikes because I just could not figure out
what would happen if I do things wrong (especially with turn ratios)

More over I do not have an oscilloscope yet.

My friend told me to try with a relay, a 2M resistor, 1N4007 Diode and
a filter capacitor.

Do you have any suggestion?

I am doing all this because I would like to be a real electrical
engineer who could design power supplies for any devices. ( I found
that almost all of power supplies of consumer and industrial electronic
systems use SMPS )

Regards

 

[Tam/WB2TT]

Hello

I am studying Power Supply Cook Book, MARTY BROWN, 2nd Edition, Newnes
Copyright 2001.

I have constructed linear power supplies, I know every details about
one zener, one resistor regulation, one zener, one transistor
regulation and I know the basis and constructed regulators with three
terminal regulators as well as floating regulators.

I have tested and understand characteristics bipolar, some types of
MOSFETs and PWM ICs.

I understand how SMPS works in general as well as some specifications.
I know very well that to be able to design SMPS well, I need to
construct Swith Mode Power Supplies practically. Studying without
practical experiments is not good.

The problem here is I do not know where to start with SMPS designs
because I am not familiar especially with the ferrite core transformers
( I have designed Iron Core, 50 Hz, Auto Transformers for Voltage
Regulators).

And I am worried the first SMPS I construct would not work well.

I am afraid High Voltage Spikes because I just could not figure out
what would happen if I do things wrong (especially with turn ratios)

More over I do not have an oscilloscope yet.

My friend told me to try with a relay, a 2M resistor, 1N4007 Diode and
a filter capacitor.

Do you have any suggestion?

I am doing all this because I would like to be a real electrical
engineer who could design power supplies for any devices. ( I found
that almost all of power supplies of consumer and industrial electronic
systems use SMPS )

Regards

When trying to learn about SMPS, start out simple. Buck, and buck boost
supplies only need an inductor, not a transformer. National Semiconductor,
and TI web sites are a good source for all kinds of application notes. Also,
some of the National literature gives manufacturer's part numbers for
inductors, and possibly transformers.

You really don't want to start from scratch, there are many ICs available
for various configurations.

Tam

 

[David L. Jones]

Hello

I am studying Power Supply Cook Book, MARTY BROWN, 2nd Edition, Newnes
Copyright 2001.

I have constructed linear power supplies, I know every details about
one zener, one resistor regulation, one zener, one transistor
regulation and I know the basis and constructed regulators with three
terminal regulators as well as floating regulators.

I have tested and understand characteristics bipolar, some types of
MOSFETs and PWM ICs.

I understand how SMPS works in general as well as some specifications.
I know very well that to be able to design SMPS well, I need to
construct Swith Mode Power Supplies practically. Studying without
practical experiments is not good.

The problem here is I do not know where to start with SMPS designs
because I am not familiar especially with the ferrite core transformers
( I have designed Iron Core, 50 Hz, Auto Transformers for Voltage
Regulators).

And I am worried the first SMPS I construct would not work well.

I am afraid High Voltage Spikes because I just could not figure out
what would happen if I do things wrong (especially with turn ratios)

More over I do not have an oscilloscope yet.

My friend told me to try with a relay, a 2M resistor, 1N4007 Diode and
a filter capacitor.

Do you have any suggestion?

I am doing all this because I would like to be a real electrical
engineer who could design power supplies for any devices. ( I found
that almost all of power supplies of consumer and industrial electronic
systems use SMPS )

Regards

Have a look at the HP Power Supply Cookbook:
http://www.slack.com/pdf/HP-AN90B.pdf

Also, application notes from the manufacturers of SMPS control chips
(like Micrel for example) are an excellent source of design info.

Try here for starters:
http://www.micrel.com/page.do?page=product-info/switch_mode_volt_regs.shtml

You don't need transformers for some types of SMPS's, DC-DC buck
converters for example. Start with them and build your confidence in
the design and measurement techniques used.
Don't play around with mains powered SMPS's until you have the skills.

Go to eBay and get yourself an oscilloscope!!

Dave

 

[linnix]

...

You don't need transformers for some types of SMPS's,

You certainly want (not need) a transformer for the first stage (AC
voltage reduction). It would be much easier to work with a 30V to 60V
second stage. Of course, you can switch directly from 300V DC (200V
AC), but not really necessary.

DC-DC buck converters for example. Start with them and build your confidence in
the design and measurement techniques used.

Don't play around with mains powered SMPS's until you have the skills.

Same goes for linear supplies.

 

[[email protected]]

An excellent learning tool is available for free. It is
LTSpice/Switcher CADIII and it is a PSpice tool for SMPS and general
circuit simulation. There are lots of example SMPS circuits included.
You can see the waveforms by probing around the circuit with your
mouse.

Download @ http://www.linear.com/company/software.jsp

Good luck - Roger

 

[John Popelish]

Myauk wrote:
(snip)

The problem here is I do not know where to start with SMPS designs
because I am not familiar especially with the ferrite core transformers
( I have designed Iron Core, 50 Hz, Auto Transformers for Voltage
Regulators).

Start collecting ferrite cores, bobbins and magnet wire any where you
can scrounge them. Study design guides from the core manufacturers
and others:
http://www-s.ti.com/sc/techlit/slup123.pdf
http://www-s.ti.com/sc/techlit/slup127.pdf
http://www-s.ti.com/sc/techlit/slup128.pdf
http://www-s.ti.com/sc/techlit/slup171.pdf
http://www.ee.surrey.ac.uk/Workshop/advice/coils/index.html
http://www.mag-inc.com/
(design guide at end of)
http://www.fair-rite.com/newfair/pdf/15th_Edition_Fair-Rite_Catalog.pdf#page=1

And I am worried the first SMPS I construct would not work well.

Quite likely, the second, third and fourth also. There is a lot to
learn between basic concepts and practical details.

I am afraid High Voltage Spikes because I just could not figure out
what would happen if I do things wrong (especially with turn ratios)

More over I do not have an oscilloscope yet.

Sorry, I can't imagine developing a good SMPS design without both a
good simulator and a good oscilloscope.

My friend told me to try with a relay, a 2M resistor, 1N4007 Diode and
a filter capacitor.

You lost me.

Do you have any suggestion?

Until you get an oscilloscope, you can study, simulate and blow stuff
up. And you might even make some supplies that function.

I am doing all this because I would like to be a real electrical
engineer who could design power supplies for any devices. ( I found
that almost all of power supplies of consumer and industrial electronic
systems use SMPS )

Download a free copy of LTspice, the best switch mode simulator available:
http://www.linear.com/designtools/softwareRegistration.jsp

Study:
http://www.national.com/appinfo/power/files/f5.pdf
http://www.smpstech.com/
http://schmidt-walter.fbe.fh-darmstadt.de/smps_e/smps_e.html

 

[Tam/WB2TT]

....................................
Don't play around with mains powered SMPS's until you have the skills.
.................................
Dave

Good point. a +12 to +5 V converter might be a good place to start.

Tam

 

[Rene Tschaggelar]

Hello

More over I do not have an oscilloscope yet.

Yes, get one. Perhaps from ebay.

Rene

 

[Myauk]

Thank you very much for the resources and suggestions.

I have a good reference book but application notes are essential!

More over I am going to test simulation software.

SMPS with 12 V output should be my starting point.

I will start buying things now. (going to ebay)

I will try to come up with more detailed questions practically and
theoractically in six months

Regards