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中英文翻译-使用同步整流器的高效率开关电源单元,中英文,翻译,使用,同步,整流器,高效率,开关电源,单元

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使用同步整流器的高效率开关电源单元1.绪论这份报告描述了一种为主机电脑提供的绝缘开关电源单元(DC/DC转换器),这种单元是利用新开发的用来次级调整的同步调整电路组成的.与传统的开关电源相比，它提高了6%的处理效率和现在已经提高到了1.75倍的每单位量的功率输出。因此这种电源单位具有高效率、低电压和高功率输出的特点。表格1显示其规格的概要。图1就是这个电源单位的外形。整流方式肖特基势垒二极管(SBD)同步整流器输入电压 (V dc)200-373240-400输出电压（V dc）3.62.5/3.3可转换输出电流（A）300360输出功率（W）10801188效率（%）7581功率损耗（W）360278大小 W/H/D（mm）120/381/2009.1（公升）60/381/2505.7（公升）每单位量功率输出（瓦/公升）119208重量（kg）8.55.3气流（m3/min）2.41.5工作温度（）0-450-45表格 1 说明书图1 以前的（左）和新单元（右）2.背景近年来，在规模集成电路技术作用下，已经有了从晶体管-晶体管逻辑电路（TTL）和发射器连接逻辑电路（ECL）的利用到利用高综合的互补金属氧化物半导体（CMOS）的方法。与此同时中央处理器、存储器和类似物的逻辑部分以相当快的速度正逐步走向小型化。尽管如此，把电源部分合成整体是有困难的，刚开始它占用了主机里面的大部分空间。直到现在，水冷却法已经被用来冷却逻辑部分。因为水冷却法是高效率的，它曾经也用来冷却电源。然而使用CMOS会减少逻辑部分使用的电量，这将制造水冷却单元（一种昂贵的组成部分）使多余的电源组成部分小型化。因此，只对电源组成部分用水冷却单元已经变得更加禁止的昂贵。通过减少电源的内在损耗和提高单位的处理效率使电源单位小型化已经变得有必要。此外，电源电压超过时间时从5.0V减少到3.3V，然后到2.5V。再着，由肖特基势垒二极管SBD组成的次级整流部分的损耗已变得相当重要。因此我们作出结论认定减少次级整流部分的损失将在小型化过程中是最重要的因素，并且要而发展使用同步整流电路开关电源单元。3.常规的电路和损耗分析图2是一种开关电源的外形，和图3显示的是损失分析的结果。图上表明次级整流部分损失占有超过40%整体损失。 根据理论分析的观点，这分析的结果建议使用同步整流电路将改善处理效率，如图4显示。图2 常规电路图3 功率损耗比较图4 效率比较4.当前状况的同步整流器同步整流的基本概念已长期存在。 然而，其当作一种产品实际的应用只是最近才开始。 在移动设备中的同步整流器开始于手携式电脑，是一种重要的技术有利于延长这样电源设备的电池使用寿命。自从由于同步整流的作用，当非绝缘模式被使用控制电路就相对容易。 因此促进开关对ICs 的用途, 在CPUs中同步整流为多数DC/DC 交换器而使用 。但是当绝缘模式（需要变压器）被使用时，由于同步整流的作用使得控制电路有困难。因此，下面的问题将会遇到。因而绝缘模式只能用在具体的产品。 5.使用同步整流遇到的问题图5 显示了同步整流电路的正常使用。有很多的问题与这个电路相关。而且, 处理效率不是象我们期望一样好。此外, 其他严重的问题包括并行操作会遇到。图5 早先同步整流电路1)低边开关的推动不足正如图6 说明, 当主要开关(Q01,2 在图5) 被关闭, 变压器被重新设置, 造成引起的电压的消失。然后, 低边开关Q2 被关闭,电流流入BD2（Q2 的部分二极管） , 导致在损失的增量。因此需要加肖特基势垒二极管D2与Q2 平行以增加物理量。当电源的输入电压的范围是宽广的并且其输入电压是高的, 重新设置时间被变短和在当电流流入D2期间总的时间是延长的。因为其处理效率达到的几乎与使用SBD整流电路是一样的, 所以使用同步整流电路的正面作用不是非常重大的。图6 早先电路波形2)在并行操作电流线路图7 显示没有使用阻拦的二极管的单位并行操作。当一个单位的主要开关Q01,2 被关闭, 另一单位输出提供电压给Q2 门。结果, 一个单位(Q2) 打开。然后高电流流经扼流圈而流失。这导致Q2 被损坏和输出电压减小。并且, 当在各个单位的poweron 和poweroff 信号的发生不一至的时候, 将产生同样的问题, 造成对单位的损伤。图7 并行操作3)关断时间的延迟在大多数当前被发展的MOS-FET, 其Vgs的门限电压Vth 从4 V减少到2 V 。正如图8 所示, 当由OV 门电压(斜率A)关断Q1 和Q2, 瞬时斜率的缓和区显示其极限。损失因由变压器产生的电流而增加，原因是关断时间的延迟。图8 门限的两种波形4)浪涌电压因为同步整流电路的操作是双向的, 扼流圈L1 的电流将是连续的。当负载电流小的时候, L1 电流以反向流动。甚至在高边开关Q1最轻微的延迟导致L1 电流通路被切断, 则浪涌电压产生, 正如图9 所示。结果, Q1 和Q2 受到损伤。5)在并行操作过程中的循环电流当有同步整流电路的各个单元是并行操作的， 如果甚至有最轻微输出电压的差别，则大电流会较高的输出电压单元流到较低的输出电压单元。 (这在图10 说明.)通过U2 逆变器电流反馈到主要边， 在此之后，它再一次被U1 逆变器返回次级边。 结果，大的循环电流在U1 和U2之间流动。 因此，即使有轻负载电流，在单位里产生的损失也像用重负载发生一样的大。6.解决问题和新的电路如下内容描述一个解决用第5 部分描述的问题的方法。 图11显示新同步整流电路。 图13是一张说明在并行操作的构造的图表。 图9 产生浪涌电压的装置图10 循环电流的根源图11 新电路1)低边开关的推动不足图11显示Q2和它的操作开关Q3。正如图12说明的，当Q01,2断开这样就产生变压器重新调节电压，使得Q3断开然后正电压通过D3加到Q2门两端。当电压重新调节完成电压被除去时，D3断开，Q2 门不导通。 在这点上，Q2保持在Ciss中的门和源电路上的充电电荷并且终止。结果，并联在Q2上的肖特基势垒二极管显得没有必要。同步整流电路能够最小化它自身的损耗。2）在并行操作中的电流环路图11显示的Q1和Q2通过隔离绕组（N2和N3）来驱动，使得于其他单元的潜在电流可以避免，并且他们可以并行操作。图12 新电路波形3)关闭时间延迟如图11所示，变压器绕组Q1是直接和门和源电路连接。当Q1关闭，一个负电压加在门电路上。当Q01，2打开，在变压器Q2上，正电压产生。因此，门电荷通过Q3放电。然后，相反的电压加在Q2的门电路并且Q1关闭。（图8中的斜线B）4）涌浪电压当一个等同于L1上的电流大小的电流被检测到时（在图11中变压器的电流被检测到），Q4在L1的电流或者相等的电流变成反向前关闭。通过关闭Q4，反向电压加到Q2的门电路并且Q2关闭。然后BD2代替Q2进行整流。在感应电流在反方向流动时关闭Q2，能够截止掉L1上的反向电流并且避免了涌浪电压。同时，整流器前面的下降从0.2v增加到1v。然而，因为负载电流很小，没有热量失灵发生。5）平行操做中的循环电流循环电流通过利用对门电路驱动和停止在截止盘绕的关闭区域的分离来消除掉。7特性图14说明了新单元的效率和内部损耗的标准结果。象在图4上所期望的结果，损耗被降低23%，效率提高6%。图13 并联工作图14 新电源单元的效率8结论我们发展了一种新的同步矫正电路来克服和传统的同步整流电路关联的缺点。我们同时也在着手一种冷的绝缘开关电源提供单元的商业产品，同时它提供高效率，低电压和高输出电流。然而，因为CPUs 这种逻辑部件继续以一种很快的速度进行小型化发展，开关电源单元的小型化外围设备的比以往需求更强烈。因此，我们将需要在允许我们实现更高的效率水平的发展技术上工作。9参考文献1 Hirohiko Kizu, Hiroyuki Satoh, Shigeharu Yamashita,Kazutoshi Fuchigami, WaterCooled Switching Power Supply INTELEC 892 Teruhiko Kohama, Tamotsu Ninomiya, Masahito Shoyama, Abnormal Phenomena Caused by Synchronous Rectifiers in Parallel-Module DC-DC Converter System TECHNICAL REPORT OF IEICE. EE97-53, CMP97-158(1998-01)High-Efficiency Switching Power Supply Unit with Synchronous Rectifier Rectification method Input voltage (V dc) Output voltage (V dc) Output current (A) Output power (W) Efficiencv (%) Y. Nakayash i k i , H. Sh imamor i , T. Satoh. T. Ohno Fujitsu Limited 4-1-1 Kami kodanaka, Nakahara-ku Kawasak i -c i ty, 21 1-8588, Japan Schottky Synchronous (SBD) (Sync Rect) 3.6 2.5 / 3.3 switchable 300 360 1080 1188 75 81 barrier diode rectifier 200-373 240-400 1. Introduction Power loss (W) Size W / H I D (mm) Power output per unit volume (W I Liter) Air flow (msl min) Weight (kg) Operating temperature This report describes an insulation type switching power supply unit (DC/DC converter) for mainframe computers that uses a newly developed synchronous rectifying circuit for the secondary rectification component. Compared with conventional switching power supply units, this unit offers 6% higher processing efficiency, and power output per unit volume that has been boosted by 1.75 times. As a result, this unit provides high efficiency, low voltage, and high power output. Table 1 shows the summary of specifications. The unit is illustrated in Figure 1. 360 278 9.1 (Liter) 5.7 (Liter) 120 1381 1200 60 I381 1250 119 208 8.5 5.3 2.4 1.5 0 - 45 0 - 45 Table 1 Specifications 2. Background In recent years, in LSI technology, there has been a shift from the use of transistortransistor logic (TTL) and emittercoupled logic (ECL) to the use of highly integrated complementary metal-oxide semiconductors S. Yamash ita, K. Fuoh i gam i , T. Yamamoto. Fujitsu Denso Limited 1-1 7-3 Sakado, Takatsu-ku. Kawasak i-c i ty, 21 3-8586, Japan (CMOS). At the same time, the logic component of CPUs, memories, and the like have been undergoing miniaturization at a relatively rapid pace. However, since it the power supply component is difficult to integrate, it is beginning to occupy most of the space inside the mainframe. Until now, the water cooling method has been used to cool the logic component. Because the water cooling method is highly effective, it has been used in power supply unit too. However, using CMOS reduces the total amount of electric power used by the logic component, making the water cooling unit (an expensive component) miniaturizing the power supply component unnecessary. Therefore, it has become all the more prohibitively expensive to use a water cooling unit just for the power supply component alone. It has become necessary to miniaturize the power supply unit by reducing the internal loss of the power supply and Figure 1 Previous (left) and new unit (right) 0-7803-5069-3 198/$10.00 01998 IEEE 398 improving the processing efficiency of the unit. In addition, the powersupply voltage has been decreasing over time, from +5.0V to +3.3V, and then to +2.5V. Moreover, the loss of the secondary rectification component made up of the Schottky barrier diode(SBD) has come to be relatively important. We therefore concluded that reducing the loss of the secondary rectification component would be the most important factor in the miniaturization process, and developed a switching power supply unit that uses the synchronous rectifying circuit. 3. Conventional circuit and loss analysis Figure 2 shows an outline of the switching supply circuit, and Figure 3 shows the result of the loss analysis. These figures indicate that the loss of the secondary rectification component occupies more than 40% of the total loss. From the point of view of academic analysis, the results of this analysis suggested that using the synchronous rectifying circuit would lead to the improved processing efficiency shown in Figure 4. (7-F SBD Figure 2 Circuit of conventional unit 90 I I Q 80 W ic ! . i . .y . . i . . . i . . i . . . j 0 , : :a . r)v 0 1 2 3 45 6 Output voltage (VI Synchronous rectifier (Sync Rect) - SBD rectifier - Figure 4 Efficiency comparisons 4. Current circumstances of Sync Rect The fundamental concept of synchronous rectification has long existed. However, its practical application as a product has taken place only recently. Synchronous rectification in mobile equipment, beginning with laptop computers, is an important technology useful in extending the service life of the batteries that power such devices. Since it is relatively easy to control the circuit for the synchronous rectification operation when the non- insulation mode is used, thereby facilitating the switch to the use of ICs, synchronous rectification is used for the majority of DC/DC converters in CPUs. However, it is difficult to control the circuit for the synchronous rectification operation when the insulation method (required for the transformer) is used. Consequently, the problems given below were encountered. Accordingly, the insulation method is only used with specific products. 5. Problems encountered with Sync Rect Figure 5 shows the synchronous rectifying circuit generally used. There are a number of problems associated with this circuit. Moreover, the processing efficiency was not as good as we had anticipated. Furthermore, another serious problem involving parallel operation was encountered. Figure 3 Power loss comparisons 399 INPUT - OUTPUT Figure 5 Circuit of previous synchronous rectifier 1) Insufficient driving of low side switch As Figure 6 illustrates, when the main switches(Q01,2 in Figure 5) are turned off, the transformer is reset, resulting in the elimination of the generated voltage. Then, the low side switch Q2 is turned off, the current flows into the BD2 (which is a body diode of Q2), leading to an increase in the loss. The Schottky barrier diode D2 therefore needs to be mounted parallel with Q2 to increase the physical quantity. shortened and the amount of time during which the current flows into the D2 is extended. Since the processing efficiency achieved is almost the. same as that obtained with the SBD rectifying circuit, the positive effects of using the synchronous rectifying circuit are not very significant. 2) Current detour at-parallel operation Figure 7 shows the units operating in parallel without using the blocking diode. When the main switches Q01,2 of one unit are turned off, the other unit outputs and applies the voltage to the Q2 gate. As a result, one unit (Q2) is turned on. Then high current flows through the choke coil into the drain. This results in the Q2 being damaged and the output voltage being reduced. Also, when the time of the generation of the poweron and poweroff signal differ between the units, it causes the same symptom to be generated, resulting in damage to the unit. Power supply f Other unit outputs I A 4 I Y output I :- I I: D2 -f on Figure 7 Parallel operation F - 7 - : I I Vt 0 plb-r . L. v g s q Low I + magnifL vgs ov : Power dissipation Figure 6 Waveforms of previous circuit When the range of the input voltage of the power supply TofF-B Toff-A is broad and such input voltage is high, the reset time is Figure 8 2-types of gate waveforms 400 3) Delay of turning off time In most of the currently developed MOS-FET, the threshold voltage Vth of Vgs is reduced from 4 V to 2 V. As Figure 8 illustrates, when turning off Q1 and Q2 by OV gate voltage (slope A), the moderate part of the slope of the transient phenomena indicates the threshold. The loss is increased by the pass current that flows from the transformers due to the delay in the turning off time. 4) Surge voltage Since the operation of synchronous rectifying circuit is bi-directional, the current of the choke coil L1 will not be discontinuous. When the load current is small, the L1 current flows in the reverse direction. Even the slightest delay in turning on the high side switch Q1 causes the current route of L1 to be cut, and the surge voltage to be generated, as Figure 9 illustrates. As a result, Q1 and Q2 incur damage. I 3odv diode l - I + T Figure 9 Mechanism of producing a surge voltage 5) Circulating current in parallel operation When the units with the synchronous rectifying circuit are operated in parallel, if there is even the slightest difference in the output voltages, the large current flows from the higher output voltage unit into the lower output voltage unit. (This is illustrated in Figure 10.) The current is fed back to the primary side by the U2 inverter, after which it is once again returned to the secondary side by the U1 inverter. As a result, a large circulating current flows between U1 and U2. Therefore, even with a light-load current, the loss generated in the unit is as extensive as that occurring with heavy loads. I12 Iout I1 , 1 I I IOUt = I2 - I3 Figure 10 Root of circulating current 6. Solving problems and the new circuit The following describes a solution to the problems described in Section 5. Figure 11 shows the new synchronous rectifying circuit. Figure 13 is a diagram illustrating the configuration at parallel operation. 1) Insufficient driving of low side switch Figure 11 shows Q2 and its driving switch Q3. As Figure 12 illustrates, when Q01,2 are turned off and it generates the transformer reset voltage, Q3 is turned off and the positive voltage is applied to the Q2 gate through D3. When the reset is completed and the voltage is removed, D3 is turned off and the Q2 gate is disconnected. At this point, Q2 holds the electric charge in Ciss between th gate and the source and stays on. As a result, the Schottky barrier diode connected to Q2 in parallel becomes unnecessary. The synchronous rectifying circuit is able to minimize the loss on its own. t 2) Current detour at parallel operation Since both Q1 and Q2 use separate windings (N2 and N3) for the drive as shown in Figure 1 1 , a sneak current from other unit can be avoided, and they can operate in parallel. 3) Delay of turning off time As shown in Figure 11, winding of transformer Q1 is directly connected between the gate and the source. When Q1 is turned off, a negative voltage can be applied to the gate. In the transformer of Q2, positive voltage is -. I *Q4 is controlled by the current of L1 Figure 11 New circuit 4) Surge voltage When a current equivalent to the current of L1 is detected (the transformer current is detected in Figure ll), Q4 is turned off before the current of L1 or the equivalent flows in the negative direction. By turning off Q4, the reverse voltage is applied to the Q2 gate and Q2 is turned off. BD2 then operates the rectification instead of Q2. Turning off Q2 before the choke coil current flows in the negative direction can stop the negative current of L1 and avoid the surge voltage. At this time, the forward drop of the rectifier increases from 4 3 on 0.2 V to 1 V. However, because the load current is small, no thermal failure occurs. 0 . . . . . . Vds QO tLLr-Lr 0 Off Off Gs; A 0 vgs2 5) Circulating current in parallel operation The circulating current is eliminated by using the separate winding for the gate driving and stopping the synchronous rectifier in the cut-off area of the choke coil. 7. Characteristics Figure 12 Waveform of new circuit Figure 14 shows the measured results of the internal loss and the eff