500) {this.resized=true; this.width=500; this.alt='这是一张缩略图，点击可放大。\n按住CTRL，滚动鼠标滚轮可自由缩放';this.style.cursor='hand'}" onclick="if(!this.resized) {return true;} else {window.open('http://u.dianyuan.com/bbs/u/58/1104501191728242.jpg?x-oss-process=image/watermark,g_center,image_YXJ0aWNsZS9wdWJsaWMvd2F0ZXJtYXJrLnBuZz94LW9zcy1wcm9jZXNzPWltYWdlL3Jlc2l6ZSxQXzQwCg,t_20');}" onmousewheel="return imgzoom(this);">为什么恒流源经常热保护?请PI工程师帮忙分析
我用TNY268P设计出一块贴片恒流器,输入220VAC,输入是39V0.3A,而实际使用时电流只用到0.14A/33V,变压器是EPD15贴片EE16,安装于密封的塑料壳内,老化两天后,因其内部发热大,无法散热而出现热保护,但是露天老化没问题,请PI工程师指出电路是否设计错误或元选择出错!
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