Hi, I'm working on a 40W flyback SMPS controlled by LM5023. I got good thermal and regulation results at full load. However, I have some questions regarding LM5023 funcionality.
1) When the supply is working at very low or zero load, an acoustic noise appears. When the load is put above 200mA the supply works quiet, but around 1A the noise comes back and then disappear as the load gets higher than 1.2A. My question: could this be a compensation loop problem? If so, how can I improve loop response? Is there a way to get rid of audible noise at low load since LM5023 has a pulse skip function?
2) A was looking as TI's documentation around LM5023.
This document is about the evaluation board: http://www.ti.com/lit/an/snva686/snva686.pdf
In this image compensation network parts are spotted in red and the SS circuit in blue.
So I found this other document about a reference design: www.ti.com/.../tidrhr2.pdf
I marked in this schematic too compensation network in red and SS circuit in blue.
a) what are the behaviour differences between this two kinds of compensation network?
b) what is the role of the resistor in parallel at the SS pin?