The step by step design procedure for AN4143

[Richard]

http://www.fairchildsemi.com/an/AN/AN-4134.pdf

http://www.fairchildsemi.com/collateral/AN-4134.xls

The xls file is to be used with the design steps in the pdf file.

In the pdf file, I'm getting stuck at : Step (3) (b) RCD reset

In Excel: You need to choose the Excel sheet "Forward with RCD reset": I
have a probblem with cell C30. I don't know how to get a value to put into
cell C30, nor do I know what the parameter is. Cell F30 surely is the
nominal snubber capacitor voltage, that is, the voltage across the snubber
capacitor. So, what is the parameter that goes in cell C30? TIA.

 

[John Popelish]

Richard wrote:

http://www.fairchildsemi.com/an/AN/AN-4134.pdf

http://www.fairchildsemi.com/collateral/AN-4134.xls

The xls file is to be used with the design steps in the pdf file.

In the pdf file, I'm getting stuck at : Step (3) (b) RCD reset

In Excel: You need to choose the Excel sheet "Forward with RCD reset": I
have a probblem with cell C30. I don't know how to get a value to put into
cell C30, nor do I know what the parameter is.

C30 is the turns ratio between the primary and the reset winding.
This choice affects both the maximum duty cycle (what fraction of the
time the primary switch can be on) and the peak switch voltage as a
multiple of the input bus voltage. 1:1 is pretty normal value. As
long as you are not trying to squeeze the transformer down to the
absolute minimum size, this is not terribly critical.

Cell F30 surely is the
nominal snubber capacitor voltage, that is, the voltage across the snubber
capacitor. So, what is the parameter that goes in cell C30? TIA.

I don't see any F30 value. There is an E30 that runs over the F30
cell, but that is the just the minimum limit for the value you can
type into C30.

--
John Popelish

 

[Richard]

"John Popelish" <jpopelish@rica.net> wrote in message
news:40E17932.FEEB2E0D@rica.net...

Richard wrote:

http://www.fairchildsemi.com/an/AN/AN-4134.pdf

http://www.fairchildsemi.com/collateral/AN-4134.xls

The xls file is to be used with the design steps in the pdf file.

In the pdf file, I'm getting stuck at : Step (3) (b) RCD reset

In Excel: You need to choose the Excel sheet "Forward with RCD reset": I
have a probblem with cell C30. I don't know how to get a value to put
into
cell C30, nor do I know what the parameter is.

C30 is the turns ratio between the primary and the reset winding.
This choice affects both the maximum duty cycle (what fraction of the
time the primary switch can be on) and the peak switch voltage as a
multiple of the input bus voltage. 1:1 is pretty normal value. As
long as you are not trying to squeeze the transformer down to the
absolute minimum size, this is not terribly critical.

Cell F30 surely is the
nominal snubber capacitor voltage, that is, the voltage across the
snubber
capacitor. So, what is the parameter that goes in cell C30? TIA.

I don't see any F30 value. There is an E30 that runs over the F30
cell, but that is the just the minimum limit for the value you can
type into C30.

--
John Popelish

John

You are looking at the wrong sheet. You are looking at the "Forward with
reset winding sheet" whereas the sheet I'm looking at is the "Forward with
RCD reset" sheet.

These Excel sheets are protected, yet I did crack the protection. I don't
think you need to password though. But if you do I can email it.

If you reply again, please go over to the other thread that has not got an
error in the subject line, ie, the thread "The step by step design procedure
for AN4134" Thanks.

 

[John Popelish]

Richard wrote:

You are looking at the wrong sheet. You are looking at the "Forward with
reset winding sheet" whereas the sheet I'm looking at is the "Forward with
RCD reset" sheet.

Sorry about that. and I thought I had checked your post to get the
right one.

These Excel sheets are protected, yet I did crack the protection. I don't
think you need to password though. But if you do I can email it.

If you reply again, please go over to the other thread that has not got an
error in the subject line, ie, the thread "The step by step design procedure
for AN4134" Thanks.

Will do.

--
John Popelish