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1、开关电源原理与设计 整流输出推挽式变压器开关电源 1 开关电源原理与设计 整流输出推挽式变压器开关电源 整流输出推挽式变压器开关电源，由于两个开关管轮流交替工作，相当于两个开关电源同时输出功率，其输出功率约等于单一开关电源输出功率的两倍。因此，推挽式变压器开关电源输出功率很大，工作效率很高，经桥式整流或全波整流后，仅需要很小的滤波电感和电容，其输出电压纹波就可以达到非常小。图 1-30 是桥式整流输出推挽式变压器开关电源工作原理图，除了整流滤波电路以外，其余部分电路的工作原理基本与图1-27 相同。桥式整流电路由 D1、D2、D3、D4 组成，C 为储能滤波电容，R 为负载电阻，Uo 为直流输
2、出电压，Io 为流过负载电阻的电流。图 1-31 是全波整流输出的推挽式变压器开关电源工作原理图，同样，除了整流滤波电路以外，其余部分电路的工作原理基本与图1-27 和图 1-30 相同。但开关变压器的次级需要多一个绕组，两个绕组N31、N32 轮流输出电压;全波整流电路由D1、D2 组成，C 为储能滤波电容，R 为负载电阻，Uo 为直流输出电压，Io 为流过负载电阻的电流。图 1-30 与图 1-31 比较，桥式整流输出的推挽式变压器开关电源比全波整流输出的推挽式变压器开关电源多用两个整流二极管，但全波整流输出的开关变压器又比桥式整流输出的开关变压器多一组次级线圈。因此，图 1-30 桥式整
3、流输出推挽式变压器开关电源比较适用于输出电流相对较小的情况;而图 1-31 全波整流输出推挽式变压器开关电源比较适用于输出电流相对较大的情况。因为，大电流整流二极管成本高，而且损耗功率也比较大。下面我们来详细分析图 1-30 桥式整流输出推挽式变压器开关电源和图 1-31 全波整流输出推挽式变压器开关电源的工作原理。layout development cities in developed countries show that developing rail transit Guide and an important means of achieving sustainable urba
4、n development.More than the bulk of the urban rail transit vehicles,rail traffic in the urban space layout and guide the evacuation,optimizing the structure and other aspects also play an important role in its role as the scale becomes more important.Rail transit on land development and stimulation
5、is achieved through its good accessibility,under the dual role of mechanisms in land and planning,transport accessibility high land along the rail transit development and high strength,promotion of urban morphology and land use patterns to adjust accordingly.1,and Copenhagen 1947,Copenhagen refers t
6、o shaped planning introduced,requirements land development along narrow of finger corridor concentrated,refers to shaped planning guide big Copenhagen area along track traffic line clear defined of corridor for Metro development,through track traffic and city development of integration,will along de
7、velopment concentrated in track station around a km around,around track site land implementation integrated intensive development,and provides good of non-mobile of way received connection facilities,Ensure that a larger proportion of the regions residents commute using mass transit.Figure 5.1-3 Cop
8、enhagen Metro City Development 2,Tokyo 5.1-4 Tokyo Metro to guide regional development(left:1950,right:2000)formation is the mass transit system of the city of Tokyo,which have been developed under the guidance of.Eastern suburbs.Established to track traffic based on the network-city,using rail-orie
9、nted intensive development mode has been recognized in many cities.Created the urban structure of the node,forming the urban rail transit-dependent and lifestyle,as well as mass transit systems provide adequate passenger protection.5.1.3 to guide the healthy development of 由于图 1-30 桥式整流输出推挽式变压器开关电源或
10、图 1-31 全波整流输出推挽式变压器开关电源的电压输出电路中都接有储能滤波电容，储能滤波电容会对输入脉动电压起到平滑的作用，因此，图 1-30 和图 1-31 中输出电压 Uo 都不会出现很高幅度的电压反冲，其输出电压的峰值 Up 基本上就可以认为是半波平均值 Upa。其值略大于正激输出 nUi，即:桥式整流输出推挽式变压器开关电源或全波整流输出推挽式变压器开关电源，整流滤波输出电压 Uo 的值略大于正激输出 nUi，n 为变压器次级线圈 N3 绕组与初级线圈 N1 绕组或 N2 绕组的匝数比。因此，推挽式变压器开关电源的输出电压 uo，主要还是由(1-131)式来决定。即:推挽式变压器开关
11、电源的输出电压 uo(K1 或 K2 接通期间)，约等于开关变压器次级线圈 N3 绕组产生的正激式输出电压 Up 或 Up-的半波平均值 Upa 或 Upa-:uo=Upa=nUi K1 接通期间(1-134)或 uo=Upa-=,nUi K2 接通期间(1-135)上式中，uo 为推挽式变压器开关电源的输出电压，n 为变压器次级线圈 N3 绕组与初级线圈 N1 绕组或 N2 绕组的匝数比，Ui 为开关变压器初级线圈 N1 绕组或 N2绕组的输入电压。图 1-32 是桥式整流输出或全波整流输出推挽式变压器开关电源，在两个控制开关 K1 和 K2 交替接通和断开，且占空比 D 均等于 0.5 时
12、，各主要工作点的电压、电流波形。图 1-32-a)和图 1-32-b)分别表示控制开关 K1 接通时，开关变压器初级线圈 N1绕组两端的电压 u1 的波形，以及流过变压器初级线圈 N1 绕组两端的电流 i1 波形;图 1-32-c)和图 1-32-d)分别表示控制开关 K2 接通时，开关变压器初级线圈 N2 绕组两端的电压 u2 的波形，以及流过开关变压器初级线圈 N2 绕组两端的电流 i2 的波形;图 1-32-e)和图 1-32-f)分别表示控制开关 K1 和 K2 轮流接通时，开关变压器次级线圈 N3 绕组两端输出电压 uo 的波形，以及流过开关变压器次级线圈 N3 绕组两端的电流波形。
13、图 1-32-f)中，虚线箭头表示反激式输出电流是由最大值开始，然后逐渐减小到最小值;而实线箭头表示正激式输出电流则是由最小值开始，然后逐渐增加到最大值;因此，两者同时作用的结果，正好输出一个矩形波。layout development cities in developed countries show that developing rail transit Guide and an important means of achieving sustainable urban development.More than the bulk of the urban rail transit
14、vehicles,rail traffic in the urban space layout and guide the evacuation,optimizing the structure and other aspects also play an important role in its role as the scale becomes more important.Rail transit on land development and stimulation is achieved through its good accessibility,under the dual r
15、ole of mechanisms in land and planning,transport accessibility high land along the rail transit development and high strength,promotion of urban morphology and land use patterns to adjust accordingly.1,and Copenhagen 1947,Copenhagen refers to shaped planning introduced,requirements land development
16、along narrow of finger corridor concentrated,refers to shaped planning guide big Copenhagen area along track traffic line clear defined of corridor for Metro development,through track traffic and city development of integration,will along development concentrated in track station around a km around,
17、around track site land implementation integrated intensive development,and provides good of non-mobile of way received connection facilities,Ensure that a larger proportion of the regions residents commute using mass transit.Figure 5.1-3 Copenhagen Metro City Development 2,Tokyo 5.1-4 Tokyo Metro to
18、 guide regional development(left:1950,right:2000)formation is the mass transit system of the city of Tokyo,which have been developed under the guidance of.Eastern suburbs.Established to track traffic based on the network-city,using rail-oriented intensive development mode has been recognized in many
19、 cities.Created the urban structure of the node,forming the urban rail transit-dependent and lifestyle,as well as mass transit systems provide adequate passenger protection.5.1.3 to guide the healthy development of 从图 1-32-e)可以看出，输出电压 uo 虽然还是由两个部分组成，一部分为输入电压 Ui 通过变压器初级线圈 N1 绕组或 N2 感应到次级线圈 N3 绕组的正激式输
20、出电压(uo);另一部分为励磁电流通过变压器初级线圈 N1 绕组或 N2 绕组存储的能量产生的反激式输出电压uo;这里反激式输出电压uo不会再使波形产生反冲，是因为储能滤波电容会把反冲电压吸收掉，使其成为充电流。由于推挽式变压器开关电源输出电压的半波平均值 Upa 幅值基本上是稳定的，它不会像反激式输出开关电源那样，输出电压的幅值随着控制开关占空比的改变而改变。因此，如果需要调整推挽式变压器开关电源输出电压，只能通过改变两个控制开关的占空比，来改变输出电压的平均值。因此，在输出电压可调的推挽式变压器开关电源电路中，必须要在整流输出电路后面加接一个 LC 储能滤波电路，才能从整流输出的脉动直流电
21、压中提取平均值输出。图 1-33 是输出电压可调的推挽式变压器开关电源电路。实际上图 1-33 就是在图 1-31 全波整流输出推挽式变压器开关电源电路的基础上，在整流输出电路后面加接了一个 LC 储能滤波电路。LC 储能滤波电路的工作原理与图 1-2 串联式开关电源中的储能滤波电路工作原理基本相同。不过，在全波整流输出的 LC 储能滤波电路中可以省去一个续流二极管，因为用于全波整流的两个二极管可以轮流充当续流二极管的作用。关于 LC 储能滤波电路的详细工作原理，请参考1-2-2(串联式开关电源输出电压滤波电路章节。由于图 1-33 中两个控制开关占空比 D 的可调范围很小(小于 0.5)，并
22、且在一个周期内两个控制开关均需要接通和关断一次，因此，输出电压的可调范围相对来说要比单激式开关电源输出电压的可调范围小很多;但双激式开关电源比单激式开关电源，具有输出功率大、电压纹波小、电压输出特性好等优点。layout development cities in developed countries show that developing rail transit Guide and an important means of achieving sustainable urban development.More than the bulk of the urban rail tran
23、sit vehicles,rail traffic in the urban space layout and guide the evacuation,optimizing the structure and other aspects also play an important role in its role as the scale becomes more important.Rail transit on land development and stimulation is achieved through its good accessibility,under the du
24、al role of mechanisms in land and planning,transport accessibility high land along the rail transit development and high strength,promotion of urban morphology and land use patterns to adjust accordingly.1,and Copenhagen 1947,Copenhagen refers to shaped planning introduced,requirements land developm
25、ent along narrow of finger corridor concentrated,refers to shaped planning guide big Copenhagen area along track traffic line clear defined of corridor for Metro development,through track traffic and city development of integration,will along development concentrated in track station around a km aro
26、und,around track site land implementation integrated intensive development,and provides good of non-mobile of way received connection facilities,Ensure that a larger proportion of the regions residents commute using mass transit.Figure 5.1-3 Copenhagen Metro City Development 2,Tokyo 5.1-4 Tokyo Metr
27、o to guide regional development(left:1950,right:2000)formation is the mass transit system of the city of Tokyo,which have been developed under the guidance of.Eastern suburbs.Established to track traffic based on the network-city,using rail-oriented intensive development mode has been recognized in
28、many cities.Created the urban structure of the node,forming the urban rail transit-dependent and lifestyle,as well as mass transit systems provide adequate passenger protection.5.1.3 to guide the healthy development of 图 1-34 是输出电压可调的推挽式变压器开关电源各主要工作点的电压、电流波形。图 1-34-a)表示控制开关 K1 接通时，开关变压器初级线圈 N1 绕组两端的
29、电压波形;图 1-34-b)表示控制开关 K2 接通时，开关变压器初级线圈 N2 绕组两端的电压波形;图 1-34-c)表示控制开关 K1 和 K2 轮流接通时，开关变压器次级线圈 N3 绕组两端输出电压 uo 的波形。图 1-34-d)表示开关变压器次级线圈 N3 绕组两端输出电压经全波整流后的电压波形。图 1-34-c)中，Up、Up-分别表示开关变压器次级线圈 N3 绕组两端输出电压 uo的正最大值(半波平均值)和负最大值(半波平均值)，Up、Up-分别表示开关变压器次级线圈 N3 绕组两端反激输出电压的正最大值(半波平均值)和负最大值(半波平均值)。这里还需再次说明，实际上反激输出电压
30、Up和Up-的脉冲幅度都很高，只不过它的能量很小，即宽度很窄，layout development cities in developed countries show that developing rail transit Guide and an important means of achieving sustainable urban development.More than the bulk of the urban rail transit vehicles,rail traffic in the urban space layout and guide the evacuat
31、ion,optimizing the structure and other aspects also play an important role in its role as the scale becomes more important.Rail transit on land development and stimulation is achieved through its good accessibility,under the dual role of mechanisms in land and planning,transport accessibility high l
32、and along the rail transit development and high strength,promotion of urban morphology and land use patterns to adjust accordingly.1,and Copenhagen 1947,Copenhagen refers to shaped planning introduced,requirements land development along narrow of finger corridor concentrated,refers to shaped plannin
33、g guide big Copenhagen area along track traffic line clear defined of corridor for Metro development,through track traffic and city development of integration,will along development concentrated in track station around a km around,around track site land implementation integrated intensive developmen
34、t,and provides good of non-mobile of way received connection facilities,Ensure that a larger proportion of the regions residents commute using mass transit.Figure 5.1-3 Copenhagen Metro City Development 2,Tokyo 5.1-4 Tokyo Metro to guide regional development(left:1950,right:2000)formation is the mas
35、s transit system of the city of Tokyo,which have been developed under the guidance of.Eastern suburbs.Established to track traffic based on the network-city,using rail-oriented intensive development mode has been recognized in many cities.Created the urban structure of the node,forming the urban rai
36、l transit-dependent and lifestyle,as well as mass transit systems provide adequate passenger protection.5.1.3 to guide the healthy development of 其幅度被限幅和平均以后就变得很低了。在整流输出电路中，反激输出电压Up、Up-的幅度一般都不会高于 Up、Up-的幅度，其幅度高于 Up、Up-将要被滤波电容两端的电压限幅，或通过变压器两个初级线圈的互感作用被输入电源电压限幅。图 1-34-d)中，实线波形对应控制开关 K1 接通时，开关变压器次级线圈 N
37、3 绕组两端输出电压经桥式或全波整流后的波形;虚线波形对应控制开关 K2 接通时，开关变压器次级线圈 N3 绕组两端输出电压经桥式或全波整流后的波形。Ua 表示整流输出电压的平均值。从图 1-34-d)可以看出，仅用储能电容对整流输出电压进行滤波，是很难从脉动直流中取出输出电压的平均值的，必须同时使用储能滤波电感才能取出输出电压的平均值。图 1-33 中，储能滤波电感和储能滤波电容参数的计算，与图 1-2 的串联式开关电源中储能滤波电感和储能滤波电容参数的计算方法很相似。根据图 1-33 和图1-34，我们把整流输出电压 uo 和 LC 滤波电路的电压 uc、电流 iL 画出如图 1-35，以
38、便用来计算推挽式变压器开关电源储能滤波电感、电容的参数。图 1-35-a)是整流输出电压 uo 的波形图。实线表示控制开关 K1 接通时，推挽式变压器开关电源开关变压器次级线圈 N3 绕组输出电压经整流后的波形;虚线表示控制开关 K2 接通时，推挽式变压器开关电源开关变压器次级线圈 N3 绕组输出电压经整流后的波形。Up 表示整流输出峰值电压(正激输出电压)，Up-表示整流输出最低电压(反激输出电压)，Ua 表示整流输出电压的平均值。图 1-35-b)是滤波电容器两端电压的波形图，或滤波电路输出电压的波形图。Uo 表示输出电压，或滤波电容器两端电压的平均值;Uc 表示电容充电电压增量，2Uc
39、等于输出电压纹波。1-8-1-3-1(推挽式变压器开关电源储能滤波电感参数的计算 在图 1-33 中，当控制开关 K1 接通时，输入电压 Ui 通过控制开关 K1 加到开关变压器线圈 N1 绕组的两端，在控制开关 K1 接通 Ton 期间，开关变压器线圈 N3 绕组输出一个幅度为 Up(半波平均值)的正激电压 uo，然后加到储能滤波电感 L 和储能滤波电容 C 组成的滤波电路上，在此期间储能滤波电感 L 两端的电压 eL 为:eL=Ldi/dt=Up Uo K1 接通期间(1-136)式中:Ui 为输入电压，Uo 为直流输出电压，即:Uo 为滤波电容两端电压 uc 的平均值。在此顺便说明:由于
40、电容两端的电压变化增量 U 相对于输出电压 Uo 来说非常小，为了简单，我们这里把 Uo 当成常量来处理。对(1-136)式进行积分得:layout development cities in developed countries show that developing rail transit Guide and an important means of achieving sustainable urban development.More than the bulk of the urban rail transit vehicles,rail traffic in the urb
41、an space layout and guide the evacuation,optimizing the structure and other aspects also play an important role in its role as the scale becomes more important.Rail transit on land development and stimulation is achieved through its good accessibility,under the dual role of mechanisms in land and pl
42、anning,transport accessibility high land along the rail transit development and high strength,promotion of urban morphology and land use patterns to adjust accordingly.1,and Copenhagen 1947,Copenhagen refers to shaped planning introduced,requirements land development along narrow of finger corridor
43、concentrated,refers to shaped planning guide big Copenhagen area along track traffic line clear defined of corridor for Metro development,through track traffic and city development of integration,will along development concentrated in track station around a km around,around track site land implement
44、ation integrated intensive development,and provides good of non-mobile of way received connection facilities,Ensure that a larger proportion of the regions residents commute using mass transit.Figure 5.1-3 Copenhagen Metro City Development 2,Tokyo 5.1-4 Tokyo Metro to guide regional development(left
45、:1950,right:2000)formation is the mass transit system of the city of Tokyo,which have been developed under the guidance of.Eastern suburbs.Established to track traffic based on the network-city,using rail-oriented intensive development mode has been recognized in many cities.Created the urban struct
46、ure of the node,forming the urban rail transit-dependent and lifestyle,as well as mass transit systems provide adequate passenger protection.5.1.3 to guide the healthy development of 式中 i(0)为初始电流(t=0 时刻流过电感 L 的电流)，即:控制开关 K1 刚接通瞬间，流过电感 L 的电流，或称流过电感 L 的初始电流。从图 1-35 中可以看出i(0)=Ix。当控制开关 K 由接通期间 Ton 突然转换到
47、关断期间 Toff 的瞬间，流过电感 L的电流 iL 达到最大值:(1-139)和(1-140)式就是计算推挽式变压器开关电源输出电压的表达式。式中，Uo 为推挽式变压器开关电源输出电压，Ui 为推挽式变压器开关电源输入电压，Up 为推挽式变压器开关电源开关变压器次级线圈 N3 绕组的正激输出电压，Up-为推挽式变压器开关电源开关变压器次级线圈 N3 绕组的反激输出电压，n 为开关电源次级线圈 N3 绕组与初级线圈 N1 绕组或 N2 绕组的匝数比。根据上面分析结果，(1-138)式可以写为:由(1-75)式可知，当控制开关 K1、K2 的占空比均为 0.5 时，Upa 与 Upa-基本相等，
48、由此我们也可以认为 Up 与 Up-基本相等。由于，当控制开关 K1、K2 的占空比均为 0.5 时，(1-141)式和(1-142)式的计算结果为 0。因此，当控制开关 K1、K2 的占空比均为 0.5 时，推挽式变压器开关电源经整流后输出的电压波形基本上是纯直流，没有交流成分，输出电压 Uo 等于最大值 Up，因此，可以不需要储能电感滤波。但是，如果要求输出电压可调，推挽式变压器开关电源的两个控制开关 K1、K2的占空比必须要小于 0.5;因为推挽式变压器开关电源正反激两种状态都有电压输出，所以在同样输出电压(平均值)的情况下，两个控制开关 K1、K2 的占空比相当于要小一倍。由此可知，当
49、要求输出电压可调范围为最大时，占空比最好取值为0.25。当两个控制开关 K1、K2 的占空比取值均为 0.25 时，Upa=3Upa-，由此我们也可以认为 Up 等于 3Up-。把上面已知条件代入(1-142)式，可求得:layout development cities in developed countries show that developing rail transit Guide and an important means of achieving sustainable urban development.More than the bulk of the urban ra
50、il transit vehicles,rail traffic in the urban space layout and guide the evacuation,optimizing the structure and other aspects also play an important role in its role as the scale becomes more important.Rail transit on land development and stimulation is achieved through its good accessibility,under