耦合电感波形怪异

我正在调试一多路输出双管正激电路,主路和辅路用了耦合电感,但两路均空载时,测得波形异常,且当主路带轻载时,辅路的直流偏压会更高,且慢慢升高.
辅路轻载,主路空载时,辅路波形正常,主路波形会出现直流偏压,如图示:什么原因,还请大侠出手指点一二,不胜感激~~~搞了三天,不得其解

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/74/547821233714179.jpg?x-oss-process=image/watermark,g_center,image_YXJ0aWNsZS9wdWJsaWMvd2F0ZXJtYXJrLnBuZz94LW9zcy1wcm9jZXNzPWltYWdlL3Jlc2l6ZSxQXzQwCg,t_20');}" onmousewheel="return imgzoom(this);">