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/30/1117605734.gif');}" onmousewheel="return imgzoom(this);">用494的过压保护电路的奇怪问题!!!
我最近用494做一个过压保护电路,见图,空载时4脚有2-3V电压,其并不关断,加上中载时,4脚电压降为1V左右,此时出现"吱吱"的叫声,再加到满载,此时保护电路动作,请问大虾,是哪里的问题啊???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/30/1117605734.gif');}" onmousewheel="return imgzoom(this);">
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/30/1117605734.gif');}" onmousewheel="return imgzoom(this);">