Step Down Bypass

[BGT]

Hopefully my little diagram will make sense as to what I would like to do. My question is: would this be a safe way to switch between 12v & 9v (DC) or would this somehow damage the step down converter ?

the convertor is:
XL4015 Constant current/Constant voltage, Adjustable 5A Step Down Buck

 

[danadak]

Short answer is no. This would potentially dump current into the output of the
converter. No predicting what it would do.

A Schottky diode in output of converter then tie that to bypass switch output
and load should work. Note consult datasheet for converter, if it needs a minimum
load to stay in regulation. Note diode will drop the converter output when in use by its
forward V drop, so converter should be slightly adjusted, its output V, to
minimize diode V loss.

Note also the Schottky Vf versus T is ~ -1 to -2 mV / C, depending on Schottky
type.....


Regards, Dana.

 

[BGT]

What sort of size spec of diode should I be looking for ?

Bearing in mind I have access to a large amount of electrical bits and pieces, what am I looking for ?

 

[bertus]

Hello,

Try this, as @danadak suggested:


The SR diode will drop about 0.5 Volts at 5A.

Bertus

 

[Delta Prime]

Careful now... Zeners and Schottky
Schematic symbols could be rather confusing.

 

[Delta Prime]

Even worse! As far as confusing. This is on a data sheet
Explicitly for a Schottky Diode.
Look at the schematic symbol they have chosen.

 

[Bluejets]

or this............

 

[Delta Prime]

or this............

Courtesy of Berkeman, mentor
Physics Forums.com

DesignFast Component Selection Made Simple - DesignFast

DesignFast™ allows you to search and find products from trusted distributors containing millions of parts from thousands of manufacturers.

www.datasheetpro.com