We have a power supply (+3.3V+/-4%, 0.6A) based on LNK603 - schematic is attached. I works pretty well at temperatures appr. from -10 to 85degC. Now we faced with necessity to extend the operation temperatures to full industrial range (-40...85degC).
I tried to increase the values of the resistors in the feedback net (in order to shift the level of CV to CC mode switching a bit higher) and the values of the input and output capacitors (just thought that the caps could loose their capacity).
All this did not help much. At temperatures below -12...-15degC the power supply will not start with full load - its output voltage is reduced and ripples increased dramatically. Using a scope one can see two different frequency components in the output voltage ripples - LNK603 switching frequency and an additional frequency of 2...3kHz.
Is there a chance to modify the design to get it working? What modifications are necessary for this?