建议LZ先了解下安规电容。4 e( U- W* p7 O( M2 d3 z4 R# N
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安规电容是指用于这样的场合，即电容器失效后，不会导致电击，不危及人身安全。安規電容通常只用于抗干擾電路中的濾波作用。
]; p2 ~% ]8 r J# r( j6 P3 k安规电容的放电和普通电容不一样，普通电容在外部电源断开后电荷会保留很长时间，如果用手触摸就会被电到，而安规电容则没这个问题。处于安全考虑和EMC考虑，一般在电源入口建议加上安规电容。9 L6 @& Q( B, A( l x8 ]& Q" x
在交流电源输入端,一般需要增加3个安全电容来抑制EMI传导干扰。它们用在电源滤波器里，起到电源滤波作用，分别对共模，差模工扰起滤波作用。4 w$ h6 E B- s+ k- ?! {7 z
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关于X电容：/ [5 J Y1 C$ U S8 I- b+ n! _
在火线和零线抑制之间并联的电容,一般称之为X电容。由于这个电容连接的位置也比较关键,同样需要符合相关安全标准。X电容同样也属于安全电容之一。根据实际需要,X电容的容值大,但此时必须在X电容的两端并联一个安全电阻,用于防止电源线拔插时,由于该电容的充放电过程而致电源线插头长时间带电。
2 o( b: b3 E4 e8 T4 |$ @+ wIEC 60335-1 clause 22.5 关于此项测试要求：# \8 S0 T1 w1 Y8 U- P) i# o
( x4 s$ X( e5 O+ H' e22.5 Appliances intended to be connected to the supply mains by means of a plug shall be constructed so that in normal use there is no risk of electric shock from charged capacitors having a rated capacitance exceeding 0,1 µF, when the pins of the plug are touched. . X4 \6 {) M9 @* s" c5 z- ]0 P
" f; o! s1 `2 o% h5 D* gCompliance is checked by the following test. The appliance is supplied at rated voltage. Any switch is then placed in the off position and the appliance is disconnected from the supply mains at the instant of voltage peak. One second after disconnection, the voltage between the pins of the plug is measured with an instrument that does not appreciably affect the value to be measured. 3 k# c: s( y' E- |. Y% ]. y
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The voltage shall not exceed 34 V. |
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发表于 2010-6-11 20:16
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