TYN280 12W輸出一直無法平穩?會有吱吱聲??

我的規格如下90-264VAC
輸出24V /0.5A
線路圖附上~
但是我效率72%上下~變壓器會有吱吱聲~
尤其在110V時候聲音更大~
220V就變小??


2009.12.7 PAR 30 R set 1K=20/k---20mA LT817B
PI TYN280 + RT8456 V F W PF Out I(A) LED V LED W Power EFF %
T2 AC 110V 60HZ 13.259 0.5944 0.502 19.6 9.8392 74.20770797
T2 AC 220V 60HZ 13.628 0.4813 0.51 19.6 9.996 73.34898738
T2 AC 230V 50HZ 13.674 0.4883 0.508 19.5 9.906 72.44405441
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我變壓器是用EE16....
140:36圈數比
0.24線徑*140圈:0.29線徑*36圈
請高手幫忙~~