Understanding TOP258PN current limit design

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I am new to power design, so hope I dont ask stupid questions. I have a chinese engineer team who have done a AC/DC power design for us. It converts 230V AC input down to 12V DC output. It uses a TOP258PN for controling.


As I understand from the datasheet the external 22k resistor R44 (see attached schematic drawing) sets the current limit.


I have measured it to be:


207V AC input -> 12V DC current limit = 0.86A

230V AC input -> 12V DC current limit = 0.88A

253V AC input -> 12V DC current limit = 0.92A


Is there other important parameters like temperature, component tolerances etc, that will have measurable impact on the current limit?


How close to this current limit would be a reasonable considering everything would be ok to say to a cutsomer that the power supply can deliver (meaning 12V DC output current)



Øystein Kristiansen

Hardware Design Engineer

Tlf: +47 93 03 15 09

E-post: oystein.kristiansen@defa.com


Abels gate 5

7030 Trondheim