I’m using the MP175 for my non-isolated 12V rail off of the rectified 120VAC. How can I improve the output regulation at higher load currents?
The MP175 load regulation can be improved by using 2x STTH2R065 in parallel for the free-wheeling diode to reduce its forward drop thereby improving the load regulation.
Also you can find the forward drop of the freewheeling diode from the Vf/If characteristics of the diode from the datasheet and use that forward drop as a DC offset to the feedback resistor divider network and then calculate the resistors needed to get a more accurate regulation point. Bear in mind that the FB pin samples the voltage at the midpoint of the resistor divider network only when the freewheeling diode is conducting.