lewis.zhang 发表于 2010-11-15 07:55

关于EMC整改

关于产品EMC整改的一些问题请教各位：
我们一款产品EMC测试出现以下问题整改一直不过，

1，产品金属外壳，有一块塑料面板上有一液晶显示屏，显示工作电压之类，静电抗扰度空气放电8KV时显示屏会花。不能自动恢复，只有重新开机才可以恢复。有什么办法？

2，传导整改后曲线很好，很低，但就是在150KHz处有一个尖峰超过限值。请问是什么原因？有什么整改方案？

3，辐射整改不过，没有余量。

谢谢！

kamleung 发表于 2010-11-15 13:08

May I know where the air discharge is applicable when the ED problem occured,
         -near the edge of your plastic cover, or
         - at the centre of your plastic cover?

lewis.zhang 发表于 2010-11-15 14:33

near the edge of the LCD screen.

kamleung 发表于 2010-11-16 13:03

As your product is made with metal case, the electrical charges will jump onto the metal case when the ESD gun is closed to the edge of LCD screeen. Then, the elctrical charges are brought to the system ground through the metal case. That means the pins of LCD display should be shielded by the metal case and therefore the controller IC will not be affected by the ESD charges. Any way, may I know whether your metal case is grounded or not?

lewis.zhang 发表于 2010-11-16 14:13

The metal case is grounded, and the LCD display screwed on the plastic panel.

lewis.zhang 发表于 2010-11-16 14:25

引用第4楼lewis.zhang于2010-11-16 14:13发表的:
The metal case is grounded, and the LCD display screwed on the plastic panel.

kamleung 发表于 2010-11-16 17:00

To make further suggestions, just to confirm the arrangement again with the two pictures. If any of my undertandings are wrong, please feel free to correct me.

bob_dai 发表于 2010-11-16 21:03

楼上的蛮专业

lewis.zhang 发表于 2010-11-16 21:46

The LCD display and the black panel are plastic, no metal used in the two pictures.

kamleung 发表于 2010-11-17 13:30

As the black panel is plastic, it cannot help to protect the LCD display. The electrical charge may creep towards the pins of LCD when the 8kV ESD gun is applied. Two suggestionsare made in the above two pictures. Hopefully, it may help.
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