CN112994462A - Llc电路 - Google Patents

Llc电路 Download PDF

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CN112994462A
CN112994462A CN201911288938.7A CN201911288938A CN112994462A CN 112994462 A CN112994462 A CN 112994462A CN 201911288938 A CN201911288938 A CN 201911288938A CN 112994462 A CN112994462 A CN 112994462A
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杨华
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
    • H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
    • H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
    • H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
    • H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/33569—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements
    • H02M3/33576—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements having at least one active switching element at the secondary side of an isolation transformer
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/14—Arrangements for reducing ripples from dc input or output
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
    • H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
    • H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
    • H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
    • H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/33507—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of the output voltage or current, e.g. flyback converters
    • H02M3/33515—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of the output voltage or current, e.g. flyback converters with digital control
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/02—Conversion of ac power input into dc power output without possibility of reversal
    • H02M7/04—Conversion of ac power input into dc power output without possibility of reversal by static converters
    • H02M7/12—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/21—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M7/217—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M7/219—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only in a bridge configuration

Abstract

本发明涉及LLC电路，包括依次连接的逆变电路、谐振电路、变压器和整流电路，所述变压器副边绕组的两端连接整流电路形成第一电压输出，所述变压器副边绕组的两端之间设有一个分接头，该分接头与所述变压器副边绕的两端中的其中一端连接整流电路形成第二电压输出；由于变压器采取了分段式设计，电源的输出电压可分成高压段和低压段，通过变换匝比，LLC电路分别在两个较小电压范围内工作，电源的工作频率f可以在各自的谐振频率点fr、fr2附近的较小范围内变化，且不会偏离其较多，故损耗可以大幅降低，同时LLC电路很容易进入连续模式，大幅减小其输出纹波。

Description

LLC电路
技术领域
本发明涉及一种高压宽输出分段式LLC电路。
背景技术
LLC即DC转DC，电源主功率拓扑电路的一种，具有较好的软开关特性，为目前大功率电源中最常用的电路拓扑之一。目前，LLC电路拓扑在大功率整流电路中较为常见，其优良的软开关特性可以大幅减小电源的开关损耗，提供能量的传输效率，显著降低电源的噪声和EMI，是目前使用最普遍的大功率拓扑之一。
对于车载电池充电机等大功率充电器，由于电池型号众多，充电机要实现对各种不同型号电池均能充电，其需要有较宽的输出电压范围(输出高压与输出低压比值接近2。)
LLC电路拓扑在这些宽范围输出应用时，由于其输入输出传输特性，决定了其在低压输出时会存在如下问题：1，严重的断续模式，电源的纹波很大，难以达到充电电池的使用要求；2，连续工作时，电源工作频率接近上限值，整机损耗大幅增加，极大地增加了电源的散热要求。
目前常用的LLC高压电路如图1所示。电路的主要部分是：开关电路、变压器、谐振电路和整流滤波电路，开关电路可为半桥电路，也可为全桥电路，谐振电路的输出端与变压器的原边绕组耦合，变压器的副边绕组的输出端连入整流滤波电路，其中全桥开关电路包括四个功率MOSFET(Q1、Q2、Q3、Q4，)谐振电路包括谐振电容Cr、励磁电感Lp和谐振电感Ls，变压器的原、副边的匝数相同，整流电路为双桥臂式整流电路。
LLC电路器件：变压器，电感和谐振电容选定后，其Lp、Ls，Cr值确定，则其它相关参数：变压器匝比n(＝Np/Ns、)LLC的谐振频率
Figure BDA0002315244560000011
最低工作频率fmin、最高工作频率fmax等值均确定，其中，fmin<fr<fmax。
为保证电路在高压满载时能稳定工作，谐振频率fr一般较接近电源的最低工作频率fmin。对于LLC电路拓扑，工作频率f越接近谐振频率fr，电源的工作效率越高。当LLC电路进入降压区时，电源的工作频率f>fr；此时，输出电压越低，电路的工作频率f就越大，其偏离谐振频率fr也越多，由变压器和电感等器件产生的损耗就越大。
对于低压输出时，由于其输入输出传输特性，电源为了维持输出电压恒定，在空载和轻载情况下均处于断续状态。当输出电压接近下限电压时，电源会处于严重的断续状态，此时其输出纹波很大。当给电源加以重载时其才会进入连续模式；而进入连续模式后，电源仍以接近最大频率fmax工作，电源的损耗很大，其散热要求更高。
发明内容
本发明的目的是提供一种LLC电路，以解决现有LLC电路在宽电压输出应用时，低压输出频率远离谐振频率而使整机损耗增大的问题。
为实现上述目的，本发明的LLC电路包括依次连接的逆变电路、谐振电路、变压器和整流电路，所述变压器副边绕组的两端连接整流电路形成第一电压输出，所述变压器副边绕组的两端之间设有一个分接头，该分接头与所述变压器副边绕的两端中的其中一端连接整流电路形成第二电压输出。
所述整流电路为三相全桥整流电路，所述分接头连接整流电路中间相，副边绕组两端分别连接两相的桥臂，副边绕组其中一端通过开关连接，当开关闭合时，电路处于高压段；开关断开时，电路处于低压段。
所述开关为继电器或可控交流开关。
所述整流电路为两相全桥电路，副边绕组其中一端连接到其中一相，另外一相选择连接分接头或副边绕组另外一端，且可通过开关选择连通。
所述开关为继电器或可控交流开关。
本发明的LLC电路，由于变压器采取了分段式设计，电源的输出电压可分成高压段和低压段，它们对应的匝比分别为n1、n2(n1<n2。)通过变换匝比，LLC电路可以分别在两个较小电压范围内工作，在这两个电压范围内，电源的工作频率f可以在各自的谐振频率点fr、fr2(fr2近似于fr)附近的较小范围内变化，且不会偏离其较多，故损耗可以大幅降低，同时LLC电路很容易进入连续模式，可以大幅减小其输出纹波。
附图说明
图1是现有LLC电路的电路图；
图2是LLC电路实施例的开关为继电器的电路图；
图3是LLC电路实施例的开关为交流开关的电路图；
图4是高压段时，电流的流向示意图；
图5是高压段时，原边电流反向时输出电流的流向示意图；
图6是低压段时，电流的流向示意图；
图7是低压段时，原边电流反向时输出电流的流向示意图；
图8是高压段时，LLC电路的saber仿真电路图；
图9是低压段时，LLC电路的saber仿真电路图；
图10是图8、9输出电压对比图；
图11是高压段时，中间桥臂和输出电压的波形图；
图12是LLC电路第二实施例的电路图。
具体实施方式
如图2所示，LLC电路包括依次连接的逆变电路、谐振电路、变压器和整流电路，变压器副边绕组的两端连接整流电路形成第一电压输出，变压器副边绕组的两端之间设有一个分接头，该分接头与变压器副边绕的两端中的其中一端连接整流电路形成第二电压输出。整流电路为三相全桥整流电路，分接头连接整流电路中间相，副边绕组两端分别连接两相的桥臂，副边绕组其中一端通过开关连接；开关为继电器或可控交流开关。
副边绕组其中一端与三相全桥整流滤波电路的输入端之间的连线上设有开关，用于高、低压切换时，副边匝数的切换控制，该开关为继电器，也可以为可控交流开关，当开关闭合时，电路处于高压段；开关断开时，电路处于低压段；如图3所示。
本LLC电路由于变压器采取了分段式设计，电源的输出电压可分成高压段和低压段，它们对应的匝比分别为n1、n2(n1<n2，n1与变压器匝比n相近。)开关闭合时，电路处于高压段，开关断开时，电路处于低压段。通过变换匝比，LLC电路可以分别在两个较小电压范围内工作，在这两个电压范围内，电源的工作频率f可以在各自的谐振频率点fr、fr2(fr2近似于fr)附近的较小范围内变化，且不会偏离其较多，故损耗可以大幅降低，同时LLC电路很容易进入连续模式，可以大幅减小其输出纹波。
如图4所示，为继电(器或交流开关)导通，处于高压段时，电流的流向；图5所示为原边电流反向时，输出电流的流向。
如图6所示，为继电(器或交流开关)断开，处于低压段时，电流的流向；图7所示为原边电流反向时，输出电流的流向。
如图8所示，为继电器(或交流开关)导通，处于高压段时，LLC电路的saber仿真电路；图9所示为低压段时，LLC电路的saber仿真电路；图8、图9所示两电路输出电压仿真对比结果如图10所示。通过观察可以发现，两输出电压风别为322V和228V，与两种情况下变压器的副边的匝数比16:11很接近，即可以通过改变变压器副边的匝数的方式来修改LLC电路的输出电压可行。
继电器(或交流开关)闭合时，处于高压段时，中间桥臂和输出电压的工作波形如图11所示。可以看出，输出电压的电压始终高于中间桥臂的整流波形的峰值，即中间桥臂的整流二极管始终处于反向截止状态。故，前面电路中对于电流走向的分析正确。
如图12所示，整流电路也可以为两相全桥电路，副边绕组其中一端连接到其中一相，另外一相选择连接分接头或副边绕组另外一端，且可通过开关选择连通；开关为继电器或可控交流开关。
LLC电路从低压段向高压段的切换，两种开关各自的优点如下：
继电器：导通损耗小，电源的效率高；
交流开关：可以实现充电机从低压段向高压段的无缝切换，即在充电过程中，充电机可以直接从低压段向高压段切换，而不需要降低或关闭充电机的输出电流；占用空间相对较小。
将LLC电路用于车载充电机之类的大功率充电电源中，电源上有单片机或者DSP之类的数字芯片，用来读取电池的工作状态，控制充电机的充电状态和通讯。通过该数字芯片读取电池的工作状态，可以获知当前电池的电压等信息。当电池的电压达到高压段和低压段的临界点时，数字芯片给出信号，控制继电器(或交流开关)闭合，这样就实现了充电机从低压段向高压段的转变。
当充电机高压输出时，继电器(或交流开关)闭合，电流按图4、图5所示的路径流动。在该范围内，输出电压在相对较小的范围内变化，其最低工作电压较原最低工作电压高很多，有助于减小LLC电路在该低压点时的损耗，且该电路很容易进入连续模式。
当充电机低压输出时，继电器(或交流开关)断开，电流按图6、图7所示的路径流动。由于此时变压器的副边匝数减小，匝比n(等于原边匝数比副边匝数)增加，故此时LLC电路的谐振电压点已由前面的高电压值转变成目前的低电压值(该谐振电压在低压段范围内，)此时的谐振频率为fr2与fr接近，最小工作频率fmin2与fmin接近，最大工作频率fmax2与fmin1接近。此时，LLC输出电压在另一个较小的范围内变化，其工作频率f在谐振频率fr2上下较小的范围内变化，可以提高其效率，并使得LLC在低压段也能得到很好的连续效果，可以大幅减小电源的输出纹波。

Claims (5)

1.LLC电路，包括依次连接的逆变电路、谐振电路、变压器和整流电路，所述变压器副边绕组的两端连接整流电路形成第一电压输出，其特征在于：所述变压器副边绕组的两端之间设有一个分接头，该分接头与所述变压器副边绕的两端中的其中一端连接整流电路形成第二电压输出。
2.根据权利要求1所述的LLC电路，其特征在于：所述整流电路为三相全桥整流电路，所述分接头连接整流电路中间相，副边绕组两端分别连接两相的桥臂，副边绕组其中一端通过开关连接，当开关闭合时，电路处于高压段；开关断开时，电路处于低压段。
3.根据权利要求2所述的LLC电路，其特征在于：所述开关为继电器或可控交流开关。
4.根据权利要求1所述的LLC电路，其特征在于：所述整流电路为两相全桥电路，副边绕组其中一端连接到其中一相，另外一相选择连接分接头或副边绕组另外一端，且可通过开关选择连通。
5.根据权利要求4所述的LLC电路，其特征在于：所述开关为继电器或可控交流开关。
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CN114142733A (zh) * 2021-11-15 2022-03-04 矽力杰半导体技术(杭州)有限公司 开关电源电路

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114142733A (zh) * 2021-11-15 2022-03-04 矽力杰半导体技术(杭州)有限公司 开关电源电路
CN114142733B (zh) * 2021-11-15 2023-10-27 矽力杰半导体技术(杭州)有限公司 开关电源电路

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