怎么将直流5伏改成3伏？怎样把直流5V电压变3v电压？

　　怎么将直流5伏改成3伏？

　　你可以串连三支硅整流二极管，压降在两伏左右，输出电压就会达到你的要求了，不过充电器的电压波纹比较大，不适合用于对直流电要求较高的电路。

　　怎样把直流5V电压变3v电压？

　　首先把两个【电阻串联】。

　　电阻【串联中心点】引出一条线。

　　【2K电阻】一端接电源的【正极】，【3K电阻】一端接电源的【负极】。

　　通电后电阻【串联中心点对地电压】为【3V】。

　　总结：1.首先把两个【电阻串联】。

　　2、电阻【串联中心点】引出一条线。

　　3、【2K电阻】一端接电源【正极】，【3K电阻】一端接电源【负极】。

　　4、通电后电阻【串联中心点对地电压】为【3V】。

　　怎样把直流5V电压变3V电压？

　　1??根据你的描写，把5V的直流变成3V我就猜到你的5V直流是个旧手机充电器，你想把这输出5V变成3V的目的是当两节1．5V的电池使用.。这个办法好，我都用这个办法做了好多电源，你可以用如下方法获得：

　　＊打开充电器盒，找到输出端有个0、5X0、3Cm大的黑长方形零件叫光耦，只要你在输出端的两脚上找个有焊接线的地方并联一只几十欧的电阻，立马变成从5V输出为3V，太简单了、

　　＊为了调准为3V，你可以用电位器并联，调节旋扭正好为3V时，再量一下电阻，换一只固定电阻就好了。

　　＊你大胆的尝试，光耦输出的十一两脚如短路了，输出就为零伏了，我在多次试验中没有发生故障，而且我改制为1．5V～12V来微调选电压！

　　＊因为你要的是电池的输出电流，所以这个充电器降为3V时，电流不低于3V电池的工作电流。

　　2??你如果没有以上的动手能力，那还有简单的就是找三只二极管串联在正线上，那就可得到2．9V电压，你再并一只电解电容，又能得到3V直流。

　　3??如果你有动手能力，又是小变压箬，你可以将次级线圈减去输出的粗线匝数，停下来插上220V测量，当低压输出交流为2．8V时就好，然后用桥式整流再滤波，这样会得到3．2V直流，多0．2V作为电压降消耗，正好为3V直流。

　　4??如果变压器的电压在6～12V，你无法减少线圈数，也可整流滤波后，找个可装散热片的三极管，进行降压成3V。它的缺点电压高，降压低时，电流超载就发热，要装散热片！

　　【图1为手机充电器原理图】、【图2为光耦图，R是你要并的电阻】、【图3是变压器输出降为3．2V】、【图4电板上黑箭头处为光耦】、【图5为我用手机充电器改装的调压电源】、【图6为我组装的旧锂电照明灯，就用这个调压电源充的电，一直很正常】

　　谢谢你的阅读??！

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　　最简单的办法就是使用LM1117 3.3V稳压模块，输入5V输出3.3V

　　最简单的是在5V输出端串联3个1N4007二极管，但是效率较低！若想效率高，必须用5V转3V的DC-DC转换器！！