半桥电路上桥臂MOS管发热严重-----弄了很久,恳请大家帮忙分析啊!

最近做了一个半桥结构充电电路,调试了很久上面的MOS管总是发热,进行很多尝试,仍然无法解决,恳请大家帮忙.

参数如图:
380V输入、输出70V*1.5A=105W;
MOS管:IRFBG30;
整流二极管:MUR860;
驱动电路:IR2102;
高频变压器:磁芯EC35,
          原边46匝/0.25mm双线并绕
          副边16匝/0.6mm
工作频率:40KHz;
我把现象说得详细些,大家耐心看,
工作现象:
(一).40KHz工作时,变压器原边未加隔直电容情况下,当直流输出1A时(设计为1.5A)上臂MOS管发热严重,20秒左右就烫手,30秒时手不敢碰

,估计能到100°C,而下桥臂只是温热而已,感觉还以接受.全过程变压器温度正常,也无明显噪音.
   采取措施及现象:
  (1)测量分压电容两侧电压,上桥臂电压比下桥臂电压高20%左右.怀疑是偏压造成单管发热.......采取如下措施.
  (2)开始怀疑是变压器副边绕线不平衡所致,但采用双组线并绕,取一组头尾对接作为抽头方式重新缠绕变压器后,电压不平衡现象仍没有

消除,单管发热依旧.
  (3)考虑到可能是功率管之间的差异造成的电压,分别多次更换了上下臂的管子,一直是上桥臂电容电压高,其发热现象也未消除.
  (4)在变压器原边加3.3uF隔直电容,分压电容的电压平衡了,变压器输出波形正负半周也平衡了,但是上桥臂MOS管依然发热.
  (5)怀疑上桥臂驱动信号驱动不足,使MOS管在一定时间内处于放大状态导致管子发热,对驱动电路部分原件参数进行了经过一些调整,在

空载时驱动波形如图1.1(图片比较模糊,大家原谅啊,不过还是可以看出波形),脉宽4us,电压15V,上升时间不到0.5US.当接上负载时上桥

臂驱动波形如图1.2和图1.3所示(高压,没敢两路波形一起测,下桥臂波形良好不波动,也无毛刺,所以未拍照).图1.3是动态拍照,可以看

出驱动信号来回变化的两个轮廓.不知道是不是这个变化使管子发热.(后面变压器波形也变化,也可能是驱动信号变化引起的,请大家帮忙

分析)
  (6)图2.1.是上臂MOS管漏源极电压Uds,(动态显示).可以看到是有两种来回变化的波形轮廓,组成.对这两种波形捕捉拍照如图2.2、图

2.3所示.
       图2.2中箭头1、2所示为上下管分别导通时上管漏源电压,可以看出导通完全.但是在图图2.1中箭头4所指可以看出什么那?,是不是

可以认为上桥臂MOS管在某一时刻没有完全截止,以至电压没有达到箭头2所指的位置.(不知道我这么分析对不对)
       图3.1~图3.4是下桥臂MOS管漏源电压波形,有重影的是动态显示情况下拍的照.
       图4.1、图4.2是变压器原边电压波形.
       图5.1~图5.3是变压器副边电压波形.
(二)20KHz工作时,变压器有噪音.不知道是不是在两管交替导通时驱动信号毛刺造成了很短时间的直通,使变压器产生噪音.
(三)380V输入电压突然加入时,有时MOS管栅、源极(G、S)烧通.是什么原因那? 是不是电路中MOS管加上双向稳压管就可以避免那?

弄了很久,单管发热问题不能解决,恳请大家帮忙啊!!!
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