SMPS : How to decide minimum AC input voltage to SMPS that gives correct output ?

[htcompany]

Hello,

I have designed an SMPS with dual outputs of 5Vdc and 12Vdc and i have to prepare a datasheet for that SMPS. For that, i need to specify one parameter for minimum and maximum AC input voltage by which SMPS can function and give correct outputs. i have tested maximum input voltage of 440Vac which gives correct outputs of 5Vdc and 12Vdc. but i am unable to decide minimum AC input voltage. i had applied input of 9Vac through stepdown transformer, but there was no output i.e. 0Vdc o/p.

How can i decide minimum AC input that can give correct 5Vdc and 12Vdc outputs ?

 

[FvM]

I had applied input of 9Vac through stepdown transformer, but there was no output i.e. 0Vdc o/p.

Raise input voltage until you get specified output? Repeat with rated load current?

 

[KlausST]

Hi,

you designed it, therefore you should know what happens when input voltage drops.

I assume. Either the power path is not able to control the full output current, or the driver IC goes into undervoltage lockout.

Klaus

 

[schmitt trigger]

Klaus;
Most likely the second cause

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