音频LC滤波

vangao

音频中常用到LC滤波，如图。
想请教LC数值是如何计算出来的。

zdbz

<DIV class=quote><B>以下是引用<I>pranoken</I>在2008-1-30 15:58:43的发言：</B>
一般在实际电路中往往是经典电路再微调</DIV>


关键是，这样微调，如何判定微调的方向和效果
判断微调的方向，显然要求懂得这个电路的原理
判断微调后的效果，估计要测试仪器来判断吧
但是，当一个电路的可变参数有好几项时，如何动手微调？LC电路调电感还是调电容？
原理啊原理，在实际电路里，当元器件混杂了寄生参数时，感觉很难把握方向。需要多尝试尝试

vangao

[QUOTE][/QUOTE]

[upload=jpg]UploadFile/2007-12/071221@52RD_未命名.jpg[/upload]

vangao

[QUOTE][/QUOTE][upload=jpg]UploadFile/2007-12/071221@52RD_未命名.jpg[/upload]

vangao

L＝120nH
接地C＝56pF
两路之间的C＝39pF

xioaliagn

低通滤波器 截止频率  搜索这两个关键字相关的看看应该就明白的差不多了. ~

zdbz

<DIV class=quote><B>以下是引用<I>xioaliagn</I>在2007-12-22 14:51:12的发言：</B>
低通滤波器 截止频率  搜索这两个关键字相关的看看应该就明白的差不多了. ~</DIV>


没有那么简单吧
音频上的LC往往是做EMI用的，而这些信号往往是高频信号，所以此时的电感和电容的
寄生效应明显，无法简单的以纯粹的LC电路处理，你去看看L或者C的真正等效电路，在高频时，几乎无法以理论计算得到滤波器的截止频率

zdbz

顶一下
哪位牛人来讲解一下啊

zdbz

再顶一下

xioaliagn

我们用的  接地的两个电容一般是33pF  两路中间的电容是100nF

一直都没有搞清楚这几个电容的值是计算出来的,还是经过无数先辈的测试经验流传下来的.

对于两路中间的电容的作用 我的理解是  为了使部分频率的信号可以互通使得左右两路的部分

信号同步.  还有有的时候左右耳机不同步的现象(就那种有立体声环绕的感觉)是不是也是由于

两路中间的这个电容的原因. (下一步自己准备把两路中间的电容去掉,做下测试...)

明白原理的大虾出来吼一下吧  小弟们就不用揣测,彷徨了[em14]

xioaliagn

Filters are used to eliminate conducted interference on ca-
bles and wires,and can be installed at either the souce or
the victim。 Figure 19 shows an AC power-line filter，The values
of the components are not critical；as a guide ，the capacitors
can be between 0.01uF and 0.001uF，and the inductors are nominally
6.3uH。Capacitor C1 is designed to shunt any high_frequency
differential-mode currents before they
can enter the equipment to be protected,Capacitors C2 and
C3 are included to shunt any common-mode currents to ground.
The inductors ,L1 and L2， are called common-mode chokes，and are placed in
the circuit to impede any common-mode currents。[/COLOR][upload=jpg]UploadFile/2008-1/08111@52RD_fittler.JPG[/upload]

xioaliagn

刚从一个关于EMI的文章里面看到这部分..发现惊人的相似

有没有哪位大虾吧蓝色的部分用行话给翻译一下呀...   看英文看的还是不太明白诶..

riniya

顶一下,我也想知道

zdbz

<DIV class=quote><B>以下是引用<I>xioaliagn</I>在2008-1-11 19:29:44的发言：</B>
Filters are used to eliminate conducted interference on ca-
bles and wires,and can be installed at either the souce or
the victim。 Figure 19 shows an AC power-line filter，The values
of the components are not critical；as a guide ，the capacitors
can be between 0.01uF and 0.001uF，and the inductors are nominally
6.3uH。Capacitor C1 is designed to shunt any high_frequency
differential-mode currents before they
can enter the equipment to be protected,Capacitors C2 and
C3 are included to shunt any common-mode currents to ground.
The inductors ,L1 and L2， are called common-mode chokes，and are placed in
the circuit to impede any common-mode currents。[/COLOR][upload=jpg]UploadFile/2008-1/08111@52RD_fittler.JPG[/upload]</DIV>


这段话的意思是：c1是用来规避差分噪声的，C2，C3还有L1，L2是用来规避和阻碍共模噪声的。关于这两个噪声的定义，建议上网去搜索一下吧

chenhj

<DIV class=quote><B>以下是引用<I>xioaliagn</I>在2008-1-11 19:29:44的发言：</B>
Filters are used to eliminate conducted interference on ca-
bles and wires,and can be installed at either the souce or
the victim。 Figure 19 shows an AC power-line filter，The values
of the components are not critical；as a guide ，the capacitors
can be between 0.01uF and 0.001uF，and the inductors are nominally
6.3uH。Capacitor C1 is designed to shunt any high_frequency
differential-mode currents before they
can enter the equipment to be protected,Capacitors C2 and
C3 are included to shunt any common-mode currents to ground.
The inductors ,L1 and L2， are called common-mode chokes，and are placed in
the circuit to impede any common-mode currents。[/COLOR][upload=jpg]UploadFile/2008-1/08111@52RD_fittler.JPG[/upload]</DIV>


能共享下你的资料吗？

fffsdfsdsdff

2楼正解 电波速度一定，根据接收发射时间差来计算距离, 13楼翻译的意思基本没错 ，但是具体实现机理，比如C1抑制高频可以理解，但是为什么是差分噪声呢  我初学

pranoken

一般在实际电路中往往是经典电路再微调

yangsheng032

建议先看一些EMC的书籍再说，先了解一下什么是差分干扰，什么是共模干扰以及产生的机理，再从电容的特性和电感的特性就知道其原理了。