利盈娱乐(中国)创新平台有限公司

MOS开关电源原理

线(xian)性(xing)电源的(de)(de)动态(tai)响应非常快，稳(wen)压(ya)(ya)性(xing)能好，只可惜其(qi)功率转(zhuan)(zhuan)(zhuan)换(huan)效率太低。要想提高效率，就(jiu)必须使图(tu) 1-2中(zhong)的(de)(de)功率调(diao)整器件（即(ji)调(diao)整管）处于开(kai)(kai)关(guan)上作状(zhuang)态(tai)，再(zai)对(dui)图(tu)1-2所示电路相应地稍加改变(bian)即(ji)成为开(kai)(kai)关(guan)型(xing)稳(wen)压(ya)(ya)电源。转(zhuan)(zhuan)(zhuan)变(bian)后的(de)(de)降压(ya)(ya)型(xing)开(kai)(kai)关(guan)电源原理图(tu)如图(tu)1-8所示。调(diao)整管作为开(kai)(kai)关(guan)而(er)言，导通时（压(ya)(ya)降小）几(ji)乎不(bu)消耗能量，关(guan)断时漏电流很小，也几(ji)乎不(bu)消耗能量，从而(er)大(da)大(da)提高了转(zhuan)(zhuan)(zhuan)换(huan)效率，其(qi)功率转(zhuan)(zhuan)(zhuan)换(huan)效率可达(da)80%以上。

在图1-8中，波动的直流电压U输入高频变换器（即开关管VT和碳化硅二极管VD），经高频变(bian)换(huan)器(qi)(qi)转变(bian)为(wei)高频(≥20kHz)脉(mai)冲方波电(dian)(dian)压(ya)(ya)(ya)，该脉(mai)冲j‘波电(dian)(dian)压(ya)(ya)(ya)通(tong)过(guo)输出(chu)滤波器(qi)(qi)（电(dian)(dian)感L和(he)电(dian)(dian)容c）变(bian)成平滑(hua)的(de)直流电(dian)(dian)压(ya)(ya)(ya)供给(ji)负载。高频变(bian)换(huan)器(qi)(qi)和(he)输出(chu)滤波器(qi)(qi)一起构成主(zhu)回路(lu)，完成能量处理任务。而(er)稳(wen)定输出(chu)电(dian)(dian)压(ya)(ya)(ya)的(de)任务是靠控(kong)制回路(lu)对主(zhu)回路(lu)的(de)控(kong)制作用来实(shi)现的(de)。控(kong)制回路(lu)包括取样(yang)电(dian)(dian)压(ya)(ya)(ya)部(bu)分(fen)、基准(zhun)电(dian)(dian)压(ya)(ya)(ya)部(bu)分(fen)、比较放大(da)(da)器(qi)(qi)（误差放大(da)(da)器(qi)(qi)）、电(dian)(dian)压(ya)(ya)(ya)／脉(mai)冲转换(huan)器(qi)(qi)等(deng)。开关电(dian)(dian)源稳(wen)定输出(chu)电(dian)(dian)压(ya)(ya)(ya)可以直观(guan)理解为(wei)通(tong)过(guo)控(kong)制滤波电(dian)(dian)容的(de)充、放点(dian)时(shi)间来实(shi)现。

具(ju)体的(de)(de)MOS稳压过程为：MOS当(dang)开关电(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)的(de)(de)负载电(dian)(dian)(dian)(dian)(dian)(dian)流增(zeng)大或输入(ru)电(dian)(dian)(dian)(dian)(dian)(dian)压U降(jiang)低(di)时(shi)，输出电(dian)(dian)(dian)(dian)(dian)(dian)压U轻微下(xia)降(jiang)，控(kong)制(zhi)回路(lu)就(jiu)使(shi)(shi)高(gao)(gao)频变(bian)(bian)换器输出的(de)(de)脉冲(chong)方波的(de)(de)宽(kuan)(kuan)度变(bian)(bian)宽(kuan)(kuan)，即(ji)给(ji)电(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)多充(chong)电(dian)(dian)(dian)(dian)(dian)(dian)点(dian)( 充(chong)电(dian)(dian)(dian)(dian)(dian)(dian)时(shi)间(jian)加长），少放点(dian)电(dian)(dian)(dian)(dian)(dian)(dian)（放电(dian)(dian)(dian)(dian)(dian)(dian)时(shi)间(jian)减(jian)短(duan)），从而使(shi)(shi)电(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)C上(shang)的(de)(de)电(dian)(dian)(dian)(dian)(dian)(dian)压（即(ji)输出电(dian)(dian)(dian)(dian)(dian)(dian)压）回升起(qi)到稳定(ding)输出电(dian)(dian)(dian)(dian)(dian)(dian)压的(de)(de)作用(yong)。反之，、当(dang)外界因素引(yin)起(qi)输出电(dian)(dian)(dian)(dian)(dian)(dian)压偏高(gao)(gao)时(shi)，控(kong)制(zhi)电(dian)(dian)(dian)(dian)(dian)(dian)路(lu)使(shi)(shi)高(gao)(gao)频变(bian)(bian)换器输出脉冲(chong)方波的(de)(de)宽(kuan)(kuan)度变(bian)(bian)窄，即(ji)给(ji)电(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)少充(chong)点(dian)电(dian)(dian)(dian)(dian)(dian)(dian)，从而使(shi)(shi)电(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)c上(shang)的(de)(de)电(dian)(dian)(dian)(dian)(dian)(dian)压同落，稳定(ding)输出电(dian)(dian)(dian)(dian)(dian)(dian)压。

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