安森美半导体 Magnetics in Switched-Mode Power Supplies 开关电源中的磁性元件Outline 纲要Block Diagram of a Typical AC-DC Power Supply 一个典型的交流－直流电源的框图 Specification of the Power Supply 电源的技术规格 Key Magnetic Elements in a Power Supply 电源中的关键磁性元件 Review of Magnetic Concepts 磁概念的回顾 Magnetic Materials 磁性材料 Inductors and Transformers 电感和变压器 References 参考文献Block Diagram of an AC-DC Power Supply 交流－直流电源框图Input Filter 输入滤波器 Rectifier 整流器 PFC 功率因数AC Input 交流 输入Power Stage 原边电源TransFormer 变压器Output Circuits 输出电路DC Outputs (to loads) 直流输出 （至负载）Specifications (Abbreviated) 技术规格（精简版）100-Watt Three-Output Power Supply 100瓦3输出电源Input Voltage: 输入电压： Input Current: 输入电流： Input Harmonics: 输入谐波： Hold-up Time: 保持时间： Inrush Current: 浪涌电流： Outputs: 输出：OUTPUT VOLTAGE (V) 输出电压(v) 5 3.3 1290 – 264 Vac, 47-63 Hz 90－264V交流，47－63Hz 2 A maximum. 最大2A。
Meets IEC1000-3-2 A14 for all load conditions. 在所有负载条件下均符合IEC1000-3-2 A14。
20 ms minimum. 最少20ms。
40 A peak at 264 V (cold start) 在264V时40A峰值（冷启动）OUTPUT CURRENT (A) 输出电流(v) MIN.最小值 MAX.最大值 1.5 10 0.3 5 0.3 3 TOTAL REGULATION 总调整率 2.0% 2.0% 2.0%RIPPLE (mV pp) 纹波(mV pp) 50 50 100Specifications (cont’d.) 技术规格（接上）Efficiency: 效率： Temperature: 温度： 75% minimum at full load, 120 Vac input 120V交流输入，满载时最小75％ Operating: See derating curve below 工作温度：见下面的降额曲线– Storage储存100 W-40 oC to +85 oC -40 oC 至 +85 oC200 LFM FORCED AIR COOLING80 W200LFM强制风冷NATURAL CONVECTION COOLING 自然对流冷却50 W 40 W0 oC10 oC20 oC30 oC40 oC50 oC60 oC70 oCTemperature Derating 温度降额Functional Block Diagram 功能框图输入滤波器L 火线 G 大地 N 中线 Power Stage PFC PFC Contro PFC控制l Control Input Filter Rectifier整流器PFC+ Bus Bus ++母线+ Bus Return + Bus + 母线返回 Return原边电源变压器Xfmr输出电路Output Circuits + 12 V, 3 A -+ Bus + 母线+ 5 V, 10 A PWM Control PWMControl PWM控制+ Bus Return + Bus BUS返回 Return+ 3.3 V, 5 A Mag Mag Amp Amp Reset 磁放大器复位 ResetTransformer 变压器Xfmr变压器CR2 CR3 C5L3a + 12 V, 3 A L3b + C6 5 V, 10 A -+ Bus + 母线CR4 CR5Q2+ Bus Return + 母线返回In forward converters, as in most topologies, the transformer simply transmits energy from primary to secondary, with no intent of energy storage. 在正激变换器中，如同在大多数拓扑结构中一样，变压器只是简单的将 能量从初级传递到次级而不储存能量。
Core area must support the flux, and window area must accommodate the current. => Area product. 磁心截面积必须满足磁通量，窗口面积必须与电流相适应。
=>AP值。
Output Circuits 输出电路Popular configuration for these voltages---two secondaries, with a lower voltage output derived from the 5 V output using a mag amp postregulator. 输出电压的典型配置——两个次 级，带有一个由5V输出进行磁放 大器后调整导出的较低的电压输 出。
CR2 From 12 V secondary 来自12V次级 From 5 V secondary 来自15V次级 SR1 CR8 CR7 Mag Mag Amp Amp Reset 磁放大器复位 Reset CR3 CR4 CR5 CR6L3a + C5 L3b + C6 L4 + C7 3.3 V, 5 A 5 V, 10 A 12 V, 3 A -Feedback to primary PWM is usually from the 5 V output, leaving the +12 V output quasi-regulated. 至初级PWM的反馈通常来自5V输出，而＋12V输出为准稳压输出。
Leakage Current is Affected by the Transformer 泄漏电流受变压器的影响Without insulation in the appliance, the user provides a path for the electrical current to return to ground! Even with insulation, some small leakage current flows. 如果电器没有绝缘，则用户便为电流提供了一个流回地面的路径！即使绝缘 ，也会有少量的泄漏电流。
The dotted line shows the “third wire” ground, not present in 2-wire (“Class 2”) appliances. 虚线表示“第三线”接地，在2线（“第2类”）电器中是没有的。
Leakage current specifications influence the design of the input filter, as the bypass (“Y”) capacitors conduct current from the line to ground. 泄漏电流的规格会影响输入滤波器的设计，因为旁路（“Y”）电容将电流由火 线导入大地。
Nurse(CPR Trained) 护士（受过CPR培训的）Victim 用户Power Box (circuit breakers) 电源箱（断路器）Power From Utility 来自公共电网的电源120 VacGround 大地Note the polarity dots. 注意带点的极性。
– Outputs conduct while Q2 is on. 当Q2导通时输出导通。
Xfmr CR2 L3a + – Secondary Vpeaks = +Bus • Ns/Np 12 V, 3 A C5 次级Vpeaks = +Bus • Ns/Np CR3 CR4 L3b Note the coupled output choke, L3. + Bus + 注意输出耦合扼流圈，L3。
5 V, 10 A C6 CR5 Q2 – Windings must have same turns ratios as transformer, which is the same as + Bus output voltages plus diode drops of Return CR3 and CR5. – 绕组的匝数比必须与变压器相同，即为 输出电压加上CR3和CR5的二极管压降 。
With output chokes in continuous conduction, each output voltage is the average of its secondary voltage (neglecting diode drops). 输出扼流圈在连续导电的情况下，每个输出电压等于次级电压的平均值（忽略二极管 压降）。
Therefore, each output voltage is its secondary peak voltage times the duty ratio of the primary bus voltage, +Bus, (neglecting diode drops and Q2’s ON voltage). 因此，每个输出电压等于它的次级峰值电压乘以初级母线电压的负荷比，＋Bus（忽 略二极管压降和Q2的导通电压）。
Transformer (cont’d) 变压器（接上）Review of Some Magnetic Concepts 磁概念的回顾Units used in the design of magnetic components 磁性元件设计中用到的单位 Current and magnetic flux 电流和磁通量 Characteristics of magnetic materials 磁性材料的特点 Faraday’s Law (the “transformer equation”) 法拉第定律（“变压器方程”）Units and Their Symbols 单位及其符号Symbol符号 H B µ F φ R P I L N Description说明 field strength 磁场强度 flux density 磁通密度 Permeability 磁导率 magnetomotive force 磁通势 Flux 磁通量 Reluctance 磁阻 Permeance 磁导 Current 电流 Inductance 电感 winding turns 绕组匝数 SI Units SI单位 A-t/m tesla 特斯拉(T) T-m/A-t2 A-t weber/t 韦伯/t (Wb/t) A-t2/Wb henry/t2 享利/t2 ampere 安培(A) henry 享利(H) turn 匝数(t)Note: Units named for famous people are not capitalized (ampere, henry, volt), but their symbols are (A, H, V). 注意：以人名命名的单位不用大写（安培 ampere，亨利henry，伏特 volt ），但其符号必须大写（ A，H，V ）。