Large Power Ripple at no load conditions
Using PI Expert I designed a SMPS supply with the TOPSWITCH TOP270KG.
Output Voltage: 36V
Output Current 1.5A
Everything is working well and the device performs very good except for the fact that when no or very little load is supplied the output voltage ripple exceeds 400mV at more or less 50Hz. Under load conditions the output ripple is from 20mV to 80mv from 0.1A to 1.5A. The reason for choosing the TOP270KG is because we have very little area for heatsinking. Only D8 and D9 ES3D output diode's is placed and for the snubber circuit only R6, R20, R25 and C4 is placed.
Please see attached schematic diagram for the design.