干货分享，强大的4开关升降压BOB电源，可升可降、能大能小

[{"insert":"基于电感器的开关架构电源有3中常见的拓扑结构，分别是"},{"attributes":{"bold":true},"insert":"BUCK降压电源"},{"insert":"、"},{"attributes":{"bold":true},"insert":"BOOST升压电源"},{"insert":"以及"},{"attributes":{"bold":true},"insert":"BUCK-BOOST负压电源"},{"insert":"，今天介绍的第4中拓扑——"},{"attributes":{"bold":true},"insert":"4开关BOB电源"},{"insert":"，在手机、汽车、嵌入式等领域都有广泛应用，它的基本工作原理是怎样的呢？有什么优势呢？"},{"attributes":{"align":"justify"},"insert":"\n"},{"attributes":{"bold":true},"insert":"一. 4开关拓扑"},{"attributes":{"align":"center"},"insert":"\n"},{"insert":"4开关BOB电源全称是BUCK or BOOST升降压电源，顾名思义，既可以降压，又可以升压，兼容BUCK和BOOST电源的功能。"},{"attributes":{"align":"justify"},"insert":"\n"},{"insert":"下图是4开关BOB电源的拓扑示意图，4个开关带一个电感，通过控制开关的导通、断开的不同状态来衍生出不同的电源架构。"},{"attributes":{"align":"justify"},"insert":"\n"},{"insert":" "},{"insert":{"image":"https://community-1252773949.cos.ap-guangzhou.myqcloud.com/article/2033/a5f77d2bd2585700.png"}},{"attributes":{"align":"center"},"insert":"\n"},{"insert":" "},{"attributes":{"align":"center"},"insert":"\n"},{"attributes":{"bold":true},"insert":"二. 降压模式"},{"attributes":{"align":"center"},"insert":"\n"},{"insert":"当S4处于常闭、S3处于常开状态时，反复开关的管子是S1和S2，这就构成了BUCK降压结构。下图就是BUCK的结构，有S1、S2两个工作管子，这种BUCK被称为同步BUCK，效率会高一些。有两种工作周期，1：S1闭合、S2断开，对电感L1充电，见下图绿色曲线；2：S1断开、S2闭合，电感对负载放电，见下图蓝色曲线。"},{"attributes":{"align":"justify"},"insert":"\n"},{"insert":" "},{"insert":{"image":"https://community-1252773949.cos.ap-guangzhou.myqcloud.com/article/2033/63f8bc64b51431e4.png"}},{"attributes":{"align":"center"},"insert":"\n"},{"insert":" "},{"attributes":{"align":"justify"},"insert":"\n"},{"insert":"将上图中的S2代替为二极管也可以起到降压作用，然而效率会降低一些，二极管会消耗一部分功率，这种结构被称为非同步BUCK，只有S1一个管子动作。当S1闭合时，对电感L1充电，见下图绿色曲线；当S1断开时，电感L1通过负载——>二极管D2进行放电，见下图蓝色曲线。"},{"attributes":{"align":"justify"},"insert":"\n"},{"insert":" "},{"insert":{"image":"https://community-1252773949.cos.ap-guangzhou.myqcloud.com/article/2033/24beaf8c3d85e098.png"}},{"attributes":{"align":"center"},"insert":"\n"},{"insert":"对于非同步BUCK，如果在上图中SW点开关节点位置测量电压，会发现一个奇怪的"},{"attributes":{"bold":true},"insert":"负电压"},{"insert":"，如下图红色圈圈中那样，这是因为二极管需要有一个导通低电压，一般是0.7V，就刚好出现这个小小的负电压。"},{"attributes":{"align":"justify"},"insert":"\n"},{"insert":"在历史文章中有更详细的介绍："},{"attributes":{"align":"justify"},"insert":"\n"},{"insert":"《为什么BUCK降压电路会出现奇怪的负电压？》："},{"attributes":{"align":"justify"},"insert":"\n"},{"attributes":{"underline":true,"color":"#0000ff","link":"https://www.dianyuan.com/eestar/article-3210.html"},"insert":"https://www.dianyuan.com/eestar/article-3210.html"},{"attributes":{"align":"justify"},"insert":"\n"},{"insert":" "},{"insert":{"image":"https://community-1252773949.cos.ap-guangzhou.myqcloud.com/article/2033/d1eae6e2f3c91fcd.png"}},{"attributes":{"align":"center"},"insert":"\n"},{"insert":"BUCK的电路详细原理以及电感选型的详细内容参考以前的文章："},{"attributes":{"align":"justify"},"insert":"\n"},{"insert":"《DCDC BUCK电路原理详细分析》："},{"attributes":{"align":"justify"},"insert":"\n"},{"insert":"https://www.dianyuan.com/eestar/article-1574.html"},{"attributes":{"align":"justify"},"insert":"\n"},{"insert":"《怎么选择BUCK降压电源的电感？》："},{"attributes":{"align":"justify"},"insert":"\n"},{"insert":"https://www.dianyuan.com/eestar/article-1299.html"},{"attributes":{"align":"justify"},"insert":"\n"},{"insert":{"image":"https://community-1252773949.cos.ap-guangzhou.myqcloud.com/article/2033/e8edb77b7ee78598.png"}},{"insert":" "},{"attributes":{"align":"center"},"insert":"\n"},{"insert":" "},{"attributes":{"align":"center"},"insert":"\n"},{"attributes":{"bold":true},"insert":"三. 升压模式"},{"attributes":{"align":"center"},"insert":"\n"},{"insert":"当S1处于常闭、S2处于常开状态时，反复开关的管子是S3和S4，这就构成了boost升压结构。下图就是BOOST的结构，有S3、S4两个工作管子，有两种工作周期，1：S3闭合、S4断开，对电感L1充电，见下图蓝色曲线；2：S3断开、S4闭合，电感对负载放电，见下图绿色曲线。"},{"attributes":{"align":"justify"},"insert":"\n"},{"insert":" "},{"insert":{"image":"https://community-1252773949.cos.ap-guangzhou.myqcloud.com/article/2033/a2d2f4d7dc263faa.png"}},{"attributes":{"align":"center"},"insert":"\n"},{"insert":"同样地，也可以把S4代替为二极管，依然实现升压结构。"},{"attributes":{"align":"justify"},"insert":"\n"},{"insert":" "},{"insert":{"image":"https://community-1252773949.cos.ap-guangzhou.myqcloud.com/article/2033/fb7df7fd6ed28bf4.png"}},{"attributes":{"align":"center"},"insert":"\n"},{"insert":"总而言之，4开关架构电源，通过对开关进行配置，可以自由工作在降压或者是升压的模式。"},{"attributes":{"align":"justify"},"insert":"\n"},{"insert":"BUCK的电路原理以及电感选型的详细内容参考以前的文章："},{"attributes":{"align":"justify"},"insert":"\n"},{"insert":"《BOOST升压电路原理详解》"},{"attributes":{"align":"justify"},"insert":"\n"},{"insert":"https://www.dianyuan.com/eestar/article-1698.html"},{"attributes":{"align":"justify"},"insert":"\n"},{"insert":"《怎么选择boost升压电路的电感？只要三个公式》"},{"attributes":{"align":"justify"},"insert":"\n"},{"attributes":{"underline":true,"color":"#0000ff","link":"https://www.dianyuan.com/eestar/article-2890.html"},"insert":"https://www.dianyuan.com/eestar/article-2890.html"},{"attributes":{"align":"justify"},"insert":"\n"},{"insert":" "},{"insert":{"image":"https://community-1252773949.cos.ap-guangzhou.myqcloud.com/article/2033/e5a3cad99e6f6c9f.png"}},{"attributes":{"align":"center"},"insert":"\n"},{"insert":" "},{"attributes":{"align":"center"},"insert":"\n"},{"attributes":{"bold":true},"insert":"四. 为什么需要BOB？"},{"attributes":{"align":"center"},"insert":"\n"},{"insert":"我们为什么需要BOB电源，这种电源有什么优势？"},{"attributes":{"align":"justify"},"insert":"\n"},{"insert":"有一些对于电源噪声要求比较高的场合，我们倾向于使用低噪声的LDO，LDO的输入一般通过开关电源提供，最典型的架构是BUCK+LDO或者是BOOST+LDO。为了达到对电源的高效利用，电源系统中往往一个开关电源后面会接多路LDO，见下面示意图，比如开关电源的输入是3.0V，需要搭配多种LDO电源。"},{"attributes":{"align":"justify"},"insert":"\n"},{"insert":" "},{"insert":{"image":"https://community-1252773949.cos.ap-guangzhou.myqcloud.com/article/2033/9108f5859b911849.png"}},{"attributes":{"align":"center"},"insert":"\n"},{"insert":"有同学会说，为什么不直接用一个BOOST声压电源来覆盖这么多种电源需求呢？"},{"attributes":{"align":"justify"},"insert":"\n"},{"insert":"如果使用BOOST这种一刀切满足所有LDO要求的方法，假如高电压的负载没有工作时，见下图红色部分，依然使用BOOST的话，绿色LDO会额外增加功耗，因为LDO功耗与输入和输出的压差成正比。对于下图中，BOOST输出是3.5V可以满足所有LDO的需求，但是在3.3/2.9/2.8等LDO关闭时，BOOST继续输出3.5V的话，就会给LDO带来额外功耗，LDO1.0的功耗是(3.5-1.0)*Io（Io是LDO的负载电流），无论怎么降低BOOST的输出电源，它也不会低于3.0V。"},{"attributes":{"align":"justify"},"insert":"\n"},{"insert":" "},{"insert":{"image":"https://community-1252773949.cos.ap-guangzhou.myqcloud.com/article/2033/9d95d02c0450c999.png"}},{"attributes":{"align":"center"},"insert":"\n"},{"insert":"不要小看这些功耗，对于移动嵌入式等产品而言，续航就是生命！"},{"attributes":{"align":"justify"},"insert":"\n"},{"insert":"所以，升降压电源就给我们带来了更好的选择，假如高电压LDO没有工作时，升降压电源可以通过BUCK模式降低自己的输出到1.2V，这样的话LDO的功耗就会大大降低，"},{"attributes":{"align":"justify"},"insert":"\n"},{"insert":"（(1.2-1.0)*Io）/（(3.5-1.0)*Io）=8%，这种架构的功耗只有原来功耗的8%，收益很明显，当然实际的功耗收益和负载的工作状态息息相关。"},{"attributes":{"align":"justify"},"insert":"\n"},{"insert":" "},{"insert":{"image":"https://community-1252773949.cos.ap-guangzhou.myqcloud.com/article/2033/0df576b83003bdff.png"}},{"attributes":{"align":"center"},"insert":"\n"},{"insert":"以上就是4开关电源的工作原理，你学废了吗？"},{"attributes":{"align":"justify"},"insert":"\n"},{"attributes":{"bold":true},"insert":"感谢点赞、分享、在看，让知识变得更简单"},{"attributes":{"align":"right"},"insert":"\n"},{"insert":"\n"}]