Recently I designed a power supply based on TNY264 datasheet schematic and tested it.
It works perfectly but at small loads the TNY generates a loud hissing sound.
Only after load of about 100-120mA does the hiss fall to an acceptable level.
It becomes audible propably, when the power-supply stops an restarts several times per second because the load is too light to have it run continuously.
Please tell me what can I change to need a smaller load works correctly without hissing.