Problem solved, i added 1N4007 and 47ohm 2W resistor between VCC of the power supply and VCC of the PWM controller. Power supply is now fully functional. R12 is increased to 3.9k, short circuit current is about 4.6amps, before it was 0.28 amps. Max power i manage to get out is 87 watts, for this shunt configuration, i can increase R12 to about 4.6k, above that, power supply decrease voltage under load to 19V, and start to make continous sound, very quietly. Below that, there is no sound at all, across whole output current range, and voltage is steady, at 3A (rated current) i have about 35-40 mV of voltage drop. That is very good stabilized.