開關(guān)電源中的磁性元件

1、安森美半導(dǎo)體 Magnetics in Switched-Mode Power Supplies開關(guān)電源中的磁性元件Outline 綱要 Block Diagram of a Typical AC-DC Power Supply 一個(gè)典型的交流直流電源的框圖 Specification of the Power Supply電源的技術(shù)規(guī)格 Key Magnetic Elements in a Power Supply電源中的關(guān)鍵磁性元件 Review of Magnetic Concepts磁概念的回顧 Magnetic Materials 磁性材料 Inductors and Transfo

2、rmers電感和變壓器References參考文獻(xiàn)Block Diagram of an AC-DC Power Supply 交流直流電源框圖 Input Filter 輸入濾波器 Rectifier 整流器 PFC 功率因數(shù) AC Input 交流 輸入 Power Stage原邊電源 TransFormer 變壓器 Output Circuits 輸出電路 DC Outputs (to loads 直流輸出 （至負(fù)載）Specifications (Abbreviated 技術(shù)規(guī)格（精簡版） 100-Watt Three-Output Power Supply 100 瓦 3 輸出電源

3、Input Voltage: 輸入電壓： Input Current: 輸入電流： Input Harmonics: 輸入諧波： Hold-up Time: 保持時(shí)間： Inrush Current: 浪涌電流：Outputs: 輸出： OUTPUT VOLTAGE (V 輸出電壓 (v 5 3.3 12 90 264 Vac, 47-63 Hz 90264V 交流， 47 63Hz 2 A maximum. 最大 2A 。 Meets IEC1000-3-2 A14 for all load conditions. 在所有負(fù)載條件下均符合 IEC1000-3-2 A14。 20 ms min

4、imum. 最少20ms。 40 A peak at 264 V (cold start 在 264V 時(shí) 40A 峰值（冷啟動） OUTPUT CURRENT (A 輸出電流 (v MIN. 最小值 MAX. 最大值 1.5 10 0.3 5 0.3 3 TOTAL REGULATION 總調(diào)整率 2.0% 2.0% 2.0% RIPPLE (mV pp 紋波 (mV pp 50 50 100Specifications (cont技術(shù)規(guī)d格.（接上）Efficiency: 效率： Temperature: 溫度： 75% minimum at full load, 120 Vac inpu

5、t 120V 交流輸入，滿載時(shí)最小 75 Operating: See derating curve below工作溫度：見下面的降額曲線 Storage儲存 100 W -40 oC to +85 oC -40 oC 至 +85 oC 200 LFM FORCED AIR COOLING 80 W 200LFM 強(qiáng)制風(fēng)冷 NATURAL CONVECTION COOLING 自然對流冷卻 50 W 40 W 0 oC 10 oC 20 oC 30 oC 40 oC 50 oC 60 oC 70 oC Temperature Derating溫度降額Review of Some Magneti

6、c Concepts磁概念的回顧Units used in the design of magnetic components磁性元件設(shè)計(jì)中用到的單位 Current and magnetic flux電流和磁通量Characteristics of magnetic materials磁性材料的特點(diǎn)Faraday s Law (the“ transformer equation法拉第定律（” “變壓器方程 ”）Flux Direction as a Result of Current FlowRight-Hand Rule右手法則電流流動引起的磁通方向磁通方向右手法則Wrap one s r

7、ight hand around a conductor with thumb pointing in the direction of current flow. Fingers point in the direction of flux lines. 右手握住導(dǎo)體，拇指指向電流流動的方向。四指代表磁力線的方向。Wound Coil Characteristics 線圈特性 flux turns in weber turns = volt secondsSlope = L = inductance (henries磁通匝數(shù)以韋伯匝數(shù)為單位 =伏特 秒 斜率 L電感（亨利） I curren

8、t in amperes電流以安培為單位 Using volt-seconds and amperes, the wound component can be analyzed easily by circuit engineers using time-domainanalysis. 使用伏特 秒和安培，電路工程師可以方便地使用時(shí)域分析法來分析磁性元件。The “ Transformer Equation 變壓”器方“程 ” E = 4 B? Ae ? f N (Faraday s Law （法拉第定律） B in tesla, Ae in m2, f in Hz B 的單位是特斯拉， Ae

9、 的單位是 m2 ，f 的單位是 Hz Modern SI units 通用 SI 單位 The saturation flux density, Bmax, determines the maximum volts per turn that can be applied to a given transformer or inductor winding at a given frequency. 飽和磁通密度，即 Bmax，決定了特定變壓器或電感繞 組在特定頻率下每一匝可以施加的最大電壓。Transformer Equation from Faraday從法sLaw拉第定律得出的變壓器方

10、程Watch closely, now: 現(xiàn)在，請仔細(xì)觀察： ? E=N ?t = ?B Ae B ?B ? = B? ? Ae = 2 B ? Ae 1 1 1 ?t = T = ? 2 2 f E ? 1 = = ?2 BAe ? 1 = 4 B ? Ae ? f N ?t 2f Note: This applies to square waves (where ?t = half of the period注.意：該方程適用于方波（ ?t = 半個(gè)周期）。An Extremely Important Fact 一個(gè)非常重要的定律E ? = = 4 B? Ae ? f N ?tUnless

11、 the flux is changing, there will be no voltage.只有磁通變化才會有感應(yīng)電壓。 If the flux swings back and forth, so will the voltage. 如果磁通往返擺動，電壓也會擺動。 In order for there to be a net dc voltage, the flux must be continually increasing為.了得到一個(gè)純直流電壓，磁通必須不斷增大。 Therefore, our chances of inventing amagnetic rectifier are

12、 ZERO. 因此，我們發(fā)明磁整流器的可能性為零。 The average voltage (dc across a winding (neglecting winding resistance is ALWAYS ZERO. This is one of the most useful facts in our bag of tools一.個(gè)繞組（忽略繞線電阻）兩端的平均電壓（直流）總是零。這是最有用的 定律之一。Popular Materials 常用材料 Material 材料 Permeability (relative 磁導(dǎo)率（相對） Bsat Loss 0.1 T, 100 kHz

13、 (tesla損耗 0.1 T, 100 Bsat kHz （特斯 拉） (mW/cm30.5 80 Usage用途 Pow er Transform ers Filter Inductors (gapped PFC Inductors (gapped 電源變壓器 濾波 電感（有空隙） PFC 電感（有空隙） EMI Filters (com m on-mode only EMI 濾波器（僅限常用模式） Ferrite 鐵氧體 (Mag. Inc. P Ferrite 鐵氧體 (Mag. Inc. W Molypermalloy 鉬坡莫合金 (Mag. Inc. MPP Sendust鋁硅鐵

14、(Mag. Inc. Kool-Mu Powdered iron 鐵粉 (Micrometals 52 80% Cobalt tape 80%鈷帶 (Honeywell 2714A 2500 10,000 0.42 250 60 0.75 340 Filter Inductors PFC Inductors濾波電感 PFC 電感 60 1 850 Filter Inductors PFC Inductors濾波電感 PFC 電感 75 1.4 3200 Filter Inductors PFC Inductors 濾波電感 PFC 電感 100,000 0.55 90 Mag. Am ps磁放

15、大器 Note the wide range of permeability and power loss.注意寬范圍的磁導(dǎo)率和功耗。Inductors and Transformers電感和變壓器 Inductor operation (example: buck regulator 電感工作原理（例如：降壓調(diào)整器） Conduction modes 導(dǎo)電模式 Continuous mode 連續(xù)模式 Critical conduction mode 臨界導(dǎo)電模式 Discontinuousmode 不連續(xù)模式 The boost regulator升壓調(diào)整器 Transformer ope

16、ration 變壓器工作原理 Flyback converter 反激變換器 Forward converter 正激變換器Inductor Operation 電感工作 v 0 time v Current (i 電流 時(shí)間 i 0 Voltage and current are related by: V = L di/dt. 電壓和電流的關(guān)系為： V = L di/dt 。 Slope of current = V / L. 電流的斜率 = V / L 。 Positive voltage: Current ramps up.正電壓：電流斜升。 Negative voltage: Cur

17、rent ramps down.負(fù)電壓：電流斜降。(Continuous Conduction 降壓調(diào)整器（連續(xù)導(dǎo)電） Inductor current is continuous. 電感電流連續(xù)。 Vout is the average of the voltage at its input (V1. Vin = Vout 是其輸入電壓（ V1）的平均值。 15 V Output voltage is the input voltage times the duty ratio (D of the switch. 輸出電壓為輸入電壓乘以開關(guān)的占空比（ D）。 When switch in o

18、n, inductor current flows from the battery. 接通時(shí)，電感電流從電池流出。When switch is off, it flows through the diode. 斷開時(shí)，電流流過二極管。 Neglecting losses in the switches and inductor, D is independent of load current忽.略開關(guān)和電感中的損耗， D 與負(fù)載電流無關(guān)。 A characteristic of buck regulators and its derivatives: 降壓調(diào)整器的特征曲線及其導(dǎo)數(shù)： Inp

19、ut current is discontinuous (chopped, and output current is continuous (smooth輸.入電流不連續(xù)（斬波），輸出電流連續(xù) （平滑）。 i1 v1 i2 i3 Vout = 5 V Load (R Buck Regulator 負(fù)載（ R） v1 0i1 0 i2 0 i3 0 time 時(shí)間(Critical Conduction 降壓調(diào)整器（臨界導(dǎo)電）Inductor current is still continuous,but just“ touches ” zero as the switch turns on電

20、感again電流.仍然是連續(xù)的，但在開關(guān)再次接通時(shí)電流 “達(dá) 到”零點(diǎn)。 This is called“critical conduction這被.稱為 “”臨界導(dǎo)電 ”。 Output voltage is still equal to the input voltage times D. 輸出電壓仍等于輸入電壓乘 以 D。 i1 v1 Vin = 15 V i2 i3 Vout = 5 V Load (R 負(fù)載（ R） Buck Regulator v1 0 i1 i2 i3 0 time 時(shí)間(Discontinuous Conduction 降壓調(diào)整器（不連續(xù)導(dǎo)電） In this c

21、ase, the current in the inductor is zero during part of each period.在這種情況下，電感中的電流在每個(gè)周期的一段時(shí)間中為零。 Output voltage is still (as always the average of v1輸.出電壓仍然（始終）是 v1 的平均值。 Output voltage is NOT the input voltage times the duty ratio (D of the switch. 輸出電壓不是輸入電壓乘以開關(guān)的占 空比（ D）。 While the load current is

22、below the critical value, D varies with load current (while Vout remains constant.當(dāng)負(fù)載電流低于臨界值時(shí)， D 隨著負(fù)載 電流而變化（而 Vout 保持不變）。 i1 i1 Vin = 15 V i2 v1 i3 i2 Vout = 5 V Load (R 負(fù)載（ R） Buck Regulator v1 0 i1 i2 i3 time 時(shí)間Boost Regulator 升壓調(diào)整器 Output voltage is always greater than (or equal to the input volt

23、age. 輸出電壓始終大于（或等于）輸入電壓。 Input current is continuous, and output current is discontinuous (the opposite of a buck regulator輸.入電流連續(xù)，輸出電流不連續(xù)（與降壓調(diào) 整器相反）。 Relationship of the output voltage to the duty ratio, D, is not as simple as in the buck regulator. In the continuousconduction case, it is:輸出電壓與負(fù)荷比（

24、D）的關(guān)系不如在降壓 調(diào)整器中那么簡單。在連續(xù)導(dǎo)電的情況下： i1 v1 Vin = 5V i2 i3 Vout = 15 V Load (R 負(fù)載（ R） Vout = 15 V Vin = 5 V v1 0 i1 0 ? 1 ? Vo = Vin ? ? ? 1- D ? In this example, Vin = 5, 在本例中， Vin = 5， Vout = 15, and D = 2/3. Vout = 15， D = 2/3。 i2 0 i3 0 time 時(shí)間Transformer (No Energy Storage變壓器（無能量存儲） 輸入 IN ? OUT輸出 Ampe

25、re-turns of all windings sum to zero. 所有繞組的安匝數(shù)之和為零。 Right-hand rule applies to the applied current and the resulting flux. The opposite occurs on the output winding. 右手法則適用于所施加的電流和它所產(chǎn)生的磁通。輸出繞組上出現(xiàn)相 反的電流。Including Effect of Primary Inductance Transformer Operation 變壓器工作原理 包括初級電感的作用 v 0 time 時(shí)間 i turns

26、 ratio: 1:2 i2 匝數(shù)比 i sec. i1 v sec. Load (R負(fù)載（ R） i 0 v sec. 0 i1 i2 0 0 i sec. 0 Transformer is shown as an ideal transformer, with its primary (magnetizing inductance as an inductor in parallel with the primary.變壓器看作理想的變壓器，它的初級（磁化）電感與初級并聯(lián)。(Really a Multi-Winding Inductor 反激變壓器（實(shí)際是多繞組電感） turns rati

27、o: 匝數(shù)比 i sec. i pri. 1:2 Vin v pri. 0 v pri. v sec. Vout Load (R 負(fù)載（ R） Flyback Transformer v drain 0 Vout v sec. 0 i pri. 0 time 時(shí)間 i sec. 0 Here, the primaryinductance is intentionally low, to determine the peak current and hence the stored energy. When the primary switch is turned off, the energy

28、 is delivered to the secondary反.激的初級電感一般很低，用于確定峰值電流和存儲的能量。當(dāng)初級開關(guān)斷開時(shí)， 能量傳送到次級。Forward Converter Transformer正激變換變壓器i 匝數(shù)比 turns ratio: 1:2 i pri. i1i2 i sec. 3 Vin v pri. 0 Vout v sec. Load (R 負(fù)載（ R） iRESET v drain 0 1 v sec. 0 i pri.0 i1 0 v node 0 Vout iRESET 0 i2 0 time 時(shí)間 i sec. 0 i3 0 Primary induc

29、tance is high, as there is no need for energy storage正.激的初級電感一般很高，因?yàn)闊o需存儲能量，是純粹的變壓器。Magnetizing current (i1 flows in the“magnetizing inductance” andcauses core reset (voltage reversal after primary switch turns off磁.化電流（ i1 ）流入“磁化電感 ”，使磁芯在初級開關(guān)斷開后去磁（電壓反向）。References參考文獻(xiàn) 1. 2. 3. 4. Dixon, Unitrode (Te

30、xas Instruments MagneticsDesign Handbook, MAG 100A Carsten,“ Simplified Calculation of Magnetic andElectrical Losses in Unity Power Factor Boost Preregulators,” published by MicrometalsCarsten,“ High Frequency Conductor Losses in Switchmode Magnetics,” HFPC 1986Proceedings Urling, Niemela, Skutt and

31、 Wilson,“ Characterizing-FrequencyHighEffectsin Transformer Windings-A Guide to Several Significant Articles,” IEEE PESCConference Record, June 1989, pp. 373-385 McLyman, Transformer and Inductor DesignHandbook, Marcel Dekker, Second Edition, 1988 McLyman, Magnetic Core Selection for Transformers and Inductors, Marcel Dekker, 1982 McLyman, Designing Magnetic Components for High Frequency Dc-Dc Converters, KG Magnetics, 1993 Watson, Applications of Magnetism, John Wiley & Sons, 1980 Hayt, Engineering Electromagnetics, Mc