[电脑基础知识]7 - LLC - Design Considerations for a Half-Bridge LLC Resona.ppt

半桥LLC谐振转换器的设计考虑 Design Considerations for a Half-Bridge LLC Resonant Converter 2 议程Agenda 为何采用HB LLC 变换器Why an HB LLC converter HB LLC变换器和谐振回路的构形Configurations of the HB LLC converter and a resonant tank HB LLC的工作状态 Operating states of the HB LLC HB LLC变换器建模和增益特性HB LLC converter modeling and gain characteristics 原边电流和谐振电容的参数确定Primary currents and resonant cap dimensioning 副边整流设计和输出电容参数的确定Secondary rectification design and output cap dimensioning 谐振电感的平衡性Resonant inductance balance 变压器绕组参数的确定和变压器的制作Transformer winding dimensioning and transformer construction 3 LCD和等离子体TV市场逐年增长。这些市场和其他市场都需要一种 具有如下功能特色的SMPS产品： The LCD and PLASMA TV market is growing each year. These and also other markets call for an SMPS unit that can provide these features: -输出功率范围：150 W600 W Output power from 150 W up to 600 W -宽范围交流输入Universal mains -有源和无源PFC（由所需的功率所决定） Active or passive PFC (given by needed power) -宽度和空间有限，无风扇：通风条件有限Limited width and space, no fan: limited air flow -低待机能耗Low standby power consumption -消费类电子市场：残酷的竞争Consumer Electronics market: fierce competition 上述要求能够通过一个SMPS来实现，该电路可以提供： The above requirements can be fulfilled with an SMPS that provides: 高功率密度High power density 平滑的EMI特征Smooth EMI signature 元件数量少、成本经济性好的解决方案Cost effective solution with minimum component count 为何采用LLC串连谐振变换器？ Why an LLC Series Resonant Converter ? 4 LLC串连谐振变换器的优点 Benefits of an LLC Series Resonant Converter 串连谐振式变换器的类型。与其他谐振结构相比，该谐振器可以在 相对较宽的电压和输出负载范围内工作 Type of serial resonant converter that allows operation in relatively wide input voltage and output load range when compared to the other resonant topologies 元件数量有限：谐振回路元件可以集成到单个变压器（唯一需要的 磁元件）中Limited number of components: resonant tank elements can be integrated to a single transformer only one magnetic component needed 在所有通常负载条件下，原边开关都工作在零电压开关（ZVS）条 件下 Zero Voltage Switching (ZVS) condition for the primary switches under all normal load conditions 副边二极管工作在零电流开关条件下，无反向恢复损耗 Zero Current Switching (ZCS) for secondary diodes, no reverse recovery losses 用于中、高输出电压变换器的高成本效益、高效率和EMI友好的解 决方案 Cost effective, highly efficient and EMI friendly solution for high and medium output voltage converters 5 议程Agenda 为何采用HB LLC 变换器Why an HB LLC converter HB LLC变换器和谐振回路的构形Configurations of the HB LLC converter and a resonant tank HB LLC的工作状态 Operating states of the HB LLC HB LLC变换器建模和增益特性HB LLC converter modeling and gain characteristics 原边电流和谐振电容的参数确定Primary currents and resonant cap dimensioning 副边整流设计和输出电容参数的确定Secondary rectification design and output cap dimensioning 谐振电感的平衡性Resonant inductance balance 变压器绕组参数的确定和变压器的制作Transformer winding dimensioning and transformer construction 6 一种HB LLC的构形单个谐振电容 Configurations of an HB LLC Single Res. Cap -更高的输入电流纹波和RMS值Higher input current ripple and RMS value -流过谐振电容的RMS电流更大Higher RMS current through the resonant capacitor -需要耐高压（600-1500 V）的谐振电容High voltage (600 1500 V) resonant capacitor needed -低成本Low cost -小尺寸/布局简单Small size / easy layout 7 与单电容解决方案相比，这种分体连接具备如下特点Compared to the single capacitor solution this connection offers: -更低的输入电流纹波和RMS值(1/2) Lower input current ripple and RMS value (1/2) -谐振电容承受一半的RMS电流Resonant capacitors handle half RMS current -所用电容的量值为单个谐振电容的一半 Capacitors with half capacitance are used -当可以利用钳位二极管实现低成本、方便的保护时，电路可采用低额定电压（450 V）的谐 振电容Low voltage ratings (450 V) for the resonant capacitors when clamping diodes D3, D4 perform an easy and cheap overload protection 一种HB LLC的构形谐振电容采用分体结构 Configurations of an HB LLC Split Res. Cap 8 谐振回路构形分立元件解决方案 Resonant Tank Configurations Discrete Solution 谐振电感放置在变压器之外 Resonant inductance is located outside of the transformer 优点Advantages: -更高的设计灵活形（设计者可以选择任意满足需要的Ls 和 Lm组合Greater design flexibility (designer can setup any Ls and Lm value) ） -更低的EMI辐射Lower radiated EMI emission 这种解决方案的缺点在于Disadvantages of this solution are: -原边和副边绕组之间的绝缘变得复杂 Complicated insulation between primary and secondary windings -绕组的冷却条件较差Worse cooling conditions for the windings -需要对更多的元件进行安装 More components to be assembled 9 变压器的漏电感被用作一个谐振电感 Leakage inductance of the transformer is used as a resonant inductance 优点Advantages: -低成本，只需一个磁性元件Low cost, only one magnetic component is needed - SMPS的尺寸往往更小Usually smaller size of the SMPS -变压器绕组的冷却条件更好Better cooling conditions for transformer windings -原边和副边之间可以方便地实现绝缘 Insulation between primary and secondary side is easily achieved 缺点Disadvantages: - 灵活性较差（可用的LS电感范围有限） Less flexibility (achievable Ls inductance range is limited) - EMI辐射更强Higher radiated EMI emission - 采用集成化谐振回路的LLC的工作方式与采用分立的Ls解决方案之间存在轻微的差别 LLC with integrated resonant tank operates in a slightly different way than the solution with discrete Ls - 原边和副边之间存在更强的邻近效应 Strong proximity effect in the primary and secondary windings 谐振回路构形集成化的解决方案 Resonant Tank Configurations Integrated Solution 10 议程Agenda 为何采用HB LLC 变换器Why an HB LLC converter HB LLC变换器和谐振回路的构形Configurations of the HB LLC converter and a resonant tank HB LLC的工作状态 Operating states of the HB LLC HB LLC变换器建模和增益特性HB LLC converter modeling and gain characteristics 原边电流和谐振电容的参数确定Primary currents and resonant cap dimensioning 副边整流设计和输出电容参数的确定Secondary rectification design and output cap dimensioning 谐振电感的平衡性Resonant inductance balance 变压器绕组参数的确定和变压器的制作Transformer winding dimensioning and transformer construction 11 LCC变换器的工作状态： LLC converter can operate: a) Fmin Fs之间 between Fmin and Fs， c)高于Fs above Fs b)直接谐振在Fs 上direct in Fs d) Fmin和Fs 之间过载 between Fmin and Fs overload e) Fmin以下below Fmin 。 LLCLLC变换器的工作状态变换器的工作状态 Operating States of the LLC ConverterOperating States of the LLC Converter 可以确定两个谐振频率Two resonant frequencies can be defined: 分立谐振回路解决方案Discrete resonant tank solution 12 c) Fop Fs 时，基于分立谐振回路的解决方案的工作波形 Operating waveforms for Fop Fs Discrete resonant tank solution CBADEF LLCLLC变换器的工作状态变换器的工作状态 Operating States of the LLC ConverterOperating States of the LLC Converter 13 -集成化的谐振回路的行为特性不同于分立式的谐振回路 Integrated resonant tank behaves differently than the discrete resonant tank -漏电感来自于变压器绕组的耦合 leakage inductance is given by the transformer coupling -只有在原边和副边之间存在能量的传递时， Llk才起作用 Llk participates only if there is a energy transfer between primary and secondary -一旦副边的二极管在ZCS条件下闭合时Llk没有能量 Once the secondary diodes are closed under ZCS, Llk has no energy 在HB LLC中，副边的二极管在ZCS条件下始终处于关断状态。谐振电感和磁化电感永远 不会象在基于分立谐振元件的解决方案中那样共同参与谐振。 Secondary diodes are always turned OFF under ZCS condition in HB LLC. The resonant inductance Ls and magnetizing inductance Lm never participate in the resonance together as with discrete resonant tank solution! LLCLLC变换器的工作状态变换器的工作状态 Operating States of the LLC ConverterOperating States of the LLC Converter 集成化的谐振回路解决方案Integrated resonant tank solution 14 LLC变换器再次可以工作在： LLC converter can again operate: a) Fmin Fs之间 between Fmin and Fsc)高于Fs above Fs b)直接谐振在Fs 上direct in Fsd) Fmin和Fs 之间过载 between Fmin and Fs overload e)低于Fmin below Fmin 可以定义两种谐振频率Two resonant frequencies can be defined: 集成化的谐振回路解决方案Integrated resonant tank solution LLCLLC变换器的工作状态变换器的工作状态 Operating States of the LLC ConverterOperating States of the LLC Converter 15 议程Agenda 为何采用HB LLC 变换器Why an HB LLC converter HB LLC变换器和谐振回路的构形Configurations of the HB LLC converter and a resonant tank HB LLC的工作状态 Operating states of the HB LLC HB LLC变换器建模和增益特性HB LLC converter modeling and gain characteristics 原边电流和谐振电容的参数确定Primary currents and resonant cap dimensioning 副边整流设计和输出电容参数的确定Secondary rectification design and output cap dimensioning 谐振电感的平衡性Resonant inductance balance 变压器绕组参数的确定和变压器的制作Transformer winding dimensioning and transformer construction 16 LLCLLC变换器建模变换器建模等效电路等效电路 LLC Converter Modeling Equivalent CircuitLLC Converter Modeling Equivalent Circuit 等效电路的传递函数Transfer function of equivalent circuit: Z1, Z2 与频率有关= LLC变换器的行为特性类似于一个与频率有关的分压器。负载越高， Lm所受到的、由 Rac所产生的嵌位作用就越大。于是，LLC谐振回路的谐振频率在Fs 和 Fmin之间变化。 Z1, Z2 are frequency dependent = LLC converter behaves like frequency dependent divider. The higher load, the Lm gets to be more clamped by Rac. Resonant frequency of LLC resonant tank thus changes between Fs and Fmin. LLC变换器可以通过一阶基波近似来描述。仅仅是近似精度极为有限！在 Fs处达到最高精度 LLC converter can be described using firs fundamental approximation. Only approximation accuracy is limited! Best accuracy is reached around Fs. 17 在使用基频近似时，实际的负载电阻必须被修改，因为实际的谐振回路是由电压方 波驱动的 Real load resistance has to be modified when using fundamental approximation because the real resonant tank is driven by square wave voltage. 考虑方波的基频分量，在 RMS电压是： Considering the fundamental component of the square wave, the RMS voltage is: 在全波桥电路中，RMS电流为： In a full-wave bridge circuit the RMS current is: AC电阻Rac 可以表示为：The AC resistance Rac can be expressed as: LLCLLC变换器建模变换器建模等效电路等效电路 LLC Converter Modeling Equivalent CircuitLLC Converter Modeling Equivalent Circuit 18 谐振回路方程谐振回路方程 Resonant Tank Equations Resonant Tank Equations 品质因数Quality factor: 特性阻抗Characteristic impedance: Lm/Ls 比： Lm/Ls ratio: 最小谐振频率：Minimum resonant frequency:串连谐振频率：Series resonant frequency: 与负载有关Load dependent ! ！ 变换器的增益：Gain of the converter: 19 归一化的增益特性归一化的增益特性Normalized Gain CharacteristicNormalized Gain Characteristic 区域1：ZCS区 Region 3: ZCS region 区域1和区域2:ZVS工作区 Region 1 and 2: ZVS operating regions Q=0.05 Heavy load ZCS ZVS Q=200 Light load 20 增益特性讨论增益特性讨论Gain Characteristic DiscussionGain Characteristic Discussion -所需要的工作区是在增益特性曲线的右侧 （负斜率意味着原边MOSFET工作在ZVS模式下） The desired operating region is on the right side of the gain characteristic (negative slope means ZVS mode for primary MOSFETs). -LLC变换器工作在fs1的状态下，其增益为1（对于分立谐振回路元件解决方案） 由变压器的匝数比来决定。从效率和EMI的角度来看，该工作点 是最有吸引力的 正弦原边电流、MOSFET和副边二极管得到了最优化的利用。该工作点只能在特定 的工作电压和负载条件下达到（往往是指满负载和名义值Vbulk ）。 Gain of the LLC converter, which operates in the fs is 1 (for discrete resonant tank solution) - i.e. is given by the transformer turns ratio. This operating point is the most attractive from the efficiency and EMI point of view sinusoidal primary current, MOSFETs and secondary diodes optimally used. This operating point can be reached only for specific input voltage and load (usually full load and nominal Vbulk). 增益特性曲线的形状以及所需要的工作频率范围将由如下参数给出： Gain characteristics shape and also needed operating frequency range is given by these parameters: - Lm/Ls比 Lm/Ls ratio -谐振回路的特征阻抗Characteristic impedance of the resonant tank -负载值Load value -变压器匝数比Transformer turns ratio 21 如何获取增益特性？如何获取增益特性？How to Obtain Gain Characteristics?How to Obtain Gain Characteristics? 使用任何一种仿真软件（如PSpice，Icap4等）中的基频近似和AC仿真 Use fundamental approximation and AC simulation in any simulation software like PSpice, Icap4 etc Rac就是所用的参数 Rac is the parameter ! 1V幅值的AC电源 1 V amplitude AC supply 在给定的Rac参数下，可以直接绘制增益曲线 Direct gain plot for given Rac 22 分立元件解决方案的仿真原理图 Simulation schematic for discrete solution 集成解决方案的仿真原理图Simulation schematic for integrated solution 对于分立和集成谐振回路对于分立和集成谐振回路 Discrete and Integrated Tank Gain DifferencesDiscrete and Integrated Tank Gain Differences 23 满载时的满载时的QQ和和k k因数优化因数优化 Full Load Q and k Factors OptimizationFull Load Q and k Factors Optimization 这两个因数的恰当选择是LLC谐振变换器设计的关键！它们的选择将影响到变换器 的如下特性：Proper selection of these two factors is the key point for the LLC resonant converter design! Their selection will impact these converter characteristics: -输出电压调节所需的工作频率范围 Needed operating frequency range for output voltage regulation -线性和负载调节率范围 Line and load regulation ranges -谐振回路中循环能量的大小 Value of circulating energy in the resonant tank -变换器的效率 Efficiency of the converter 在优化时，效率、线性和负载调节率范围往往是最重要的判据 The efficiency, line and load regulation ranges are usually the most important criteria for optimization. 品质因数Q直接受负载的影响。它由满负载条件下的Ls 和 Cs 元件值决定： Quality factor Q directly depends on the load. It is given by the Ls and Cs components values for full load conditions: 24 -更高的Q值可以实现更大的Fop范围要在给定的负载下获得更高的Q值 ，必须降低特性阻抗， = 更高的Cs Higher Q factor results in larger Fop range Characteristic impedance has to be lower for higher Q and given load = higher Cs -低Q因数会造成调压能力的下降！ Low Q factor can cause the loss of regulation capability! -在Q值很低的情况下，LLC增益特性退化到SRC。 LLC gain characteristics are degraded to the SRC for very low Q values. 0.000 0.050 0.100 0.150 0.200 0.250 1.00E+041.00E+051.00E+06 频率 Hz Gain - Q=2Q=3Q=4 n=8, Ls/Lm=6, Q=parameter, Rload=2.4 Gmin Gmax DfQ=4 DfQ=3 Needed gains band 实现满负载稳压 时所需的增益分 布带for full load regulation 满载时的满载时的QQ和和k k因数优化因数优化 Full Load Q and k Factors OptimizationFull Load Q and k Factors Optimization 25 -k=Lm/Ls比决定了Lm 中存储多少能量。The k=Lm/Ls ratio dictates how much energy is stored in the Lm. -更高的k值将造成磁化电流和变换器增益的降低Higher k will result in the lower magnetizing current and gain of the converter. - K因数更高，则所需的调节频率范围也越大 Needed regulation frequency range is higher for larger k factor. 0.000 0.050 0.100 0.150 0.200 0.250 1.00E+041.00E+051.00E+06 频率 Hz Gain - k=2k=4k=6k=8k=10 Gmax Gmin Needed gains band for full load regulation Dfk=6 Dfk=2 n=8, Cs=33nF, Ls=100uH, Lm=parameter, Rload=2.4 满载时的满载时的QQ和和k k因数优化因数优化 Full Load Q and k Factors OptimizationFull Load Q and k Factors Optimization 26 在实践中， Ls （集成化的变压器解决方案中的漏电感）只能在有限的范围内取值 ，而且由变压器的构造（以满足所需的功率水平）和匝数比所决定。 Practically, the Ls (i.e. leakage inductance of the integrated transformer version) has only limited range of values and is given by the transformer construction (for needed power level) and turns ratio. Q因数的计算由所需要的标称工作频率fs所给出。 The Q factor calculation is then given by the wanted nominal operating frequency fs. K因数也必须计算出来，以确保输出电压调节率（线电压和负载发生变化）所需的 增益。 The k factor has to be then calculated to assure gains needed for the output voltage regulation (with line and load changes). 在设定K因数时，可以让变换器在轻负载时无法继续维持稳压作用可以轻松地 实现忽略模式，以降低无负载条件下的功耗。 The k factor can be set in such a way that converter wont be able to maintain regulation at light loads skip mode can be easily implemented to lower no load consumption. 满载时的满载时的QQ和和k k因数优化因数优化 Full Load Q and k Factors OptimizationFull Load Q and k Factors Optimization 27 议程Agenda 为何采用HB LLC 变换器Why an HB LLC converter HB LLC变换器和谐振回路的构形Configurations of the HB LLC converter and a resonant tank HB LLC的工作状态 Operating states of the HB LLC HB LLC变换器建模和增益特性HB LLC converter modeling and gain characteristics 原边电流和谐振电容的参数确定Primary currents and resonant cap dimensioning 副边整流设计和输出电容参数的确定Secondary rectification design and output cap dimensioning 谐振电感的平衡性Resonant inductance balance 变压器绕组参数的确定和变压器的制作Transformer winding dimensioning and transformer construction 28 Fsw = Fs 原边电流原边电流单谐振电容单谐振电容 Primary Currents Single Resonant CapPrimary Currents Single Resonant Cap IIN, IDM1 ICs VCs IDM2 29 IIN ICs2 VCs2 ICs1 IDM1 IDM2 原边电流原边电流分体谐振电容分体谐振电容 Primary Currents Split Resonant Cap Primary Currents Split Resonant Cap Fsw=Fs 30 单体和分体谐振电容解决方案24 V/10 A应用 Single and split resonant capacitor solutions - 24 V / 10 A application 原边电流的比较 Comparison of Primary Currents 参数 Parameter 单电容 Single Cap 分体电容 Split Caps ICs_Pk2.16 A1.08 A ICs_RMS1.52 A0.76 A IIN_Pk2.16 A1.08 A IIN_RMS1.07 A0.76 A 分体式的解决方案可以让谐振电容的电流降低50，并让输入 rms电流降低30 Split solution offers 50% reduction in resonant capacitor current and 30% reduction in input rms current 根据电流和电压额定值来选择谐振电容Select resonant capacitor(s) for current and voltage ratings 31 - 体二极管仅在死区时间（A）中导通 Body diode is conducting during the dead time only (A) - MOSFET在余下时间中导通（B） MOSFET is conducting for the rest of the period (B) - 导通损耗由Qg所决定（在驱动电路而非MOSFET中消耗） Turn ON losses are given by Qg (burned in the driver not in MOSFET) - MOSFET在非零电流状态下关断关断损耗 MOSFET turns OFF under non-zero current = turn OFF losses 原边开关元件参数的确定原边开关元件参数的确定 Primary Switches DimensioningPrimary Switches Dimensioning A B 32 MOSFET RMS电流值的计算MOSFET RMS current calculation -体二极管导通时间可以忽略The body diode conduction time is negligible -假定MOSFET电流为半正弦波形 Assume that the MOSFET current has half sinusoid waveform 关断电流的计算Turn OFF current calculation -假定磁化电流是线性增长的Assume that the magnetizing current increases linearly -关断损耗（EOFF IOFF) 可以在 MOSFET的数据表中找到 Turn OFF losses (EOFF IOFF) can be find in the MOSFET datasheet 原边开关元件参数的确定原边开关元件参数的确定 Primary Switches DimensioningPrimary Switches Dimensioning 33 议程Agenda 为何采用HB LLC 变换器Why an HB LLC converter HB LLC变换器和谐振回路的构形Configurations of the HB LLC converter and a resonant tank HB LLC的工作状态 Operating states of the HB LLC HB LLC变换器建模和增益特性HB LLC converter modeling and gain characteristics 原边电流和谐振电容的参数确定Primary currents and resonant cap dimensioning 副边整流设计和输出电容参数的确定Secondary rectification design and output cap dimensioning 谐振电感的平衡性Resonant inductance balance 变压器绕组参数的确定和变压器的制作Transformer winding dimensioning and transformer construction 34 副边整流器的设计Secondary Rectifier Design 副边整流器工作在ZCS状态下Secondary rectifiers work in ZCS 可能采用的架构Possible configurations: a) 推挽结构提供低电压/大 电流输出Push-Pull configuration for low voltage / high current output b) 桥式结构提供高压/小电 流输出Bridge configuration for high voltage / low current output c) 桥式结构与2个副边绕组的组 合提供互补的输出电压Bridge configuration with two secondary windings for complementary output voltages 优点Advantages: -与桥式结构相比，二极管压降减少了一半。 Half the diode drops compared to bridge -单体封装，可以使用成对加工的双二极管 Single package, dual diode can be used -空间利用率高Space efficient 缺点：Disadvantages: - 需要附加的线圈Need additional winding - 更高的整流器击穿电压 Higher rectifier breakdown voltage - 线圈之间需要更好的匹配 Need good matching between windings 推挽结构 Push-Pull Configuration 35 计算式Equations 24 V/10 A输出 output RMS二极管电流 RMS diode current 平均二极