開關(guān)電源設(shè)計外文翻譯-其他專業(yè)-預(yù)覽頁
【正文】 ed in the leakage inductance during the “on” time is returned to the supply rail Vdc via diodes D5, D6. 譯文： 第三章 半橋和全橋變換器拓?fù)? 概述 半橋和全橋拓?fù)溟_關(guān)管的穩(wěn)態(tài)關(guān)斷電壓等于直流輸入電壓，而不像推挽、單端正激或交錯正激拓?fù)淠菢訛殡妷旱膬杀??！豆β室驍?shù)校正開關(guān)電源的研究與設(shè)計》外文翻譯 Switching Power Supply Design(開關(guān)電源設(shè)計 ) CHAPTER 3 Half and FullBridge Converter Topologies Introduction Halfbridge and fullbridge topologies stress their transistors to a voltage equal to the DC input voltage not to twice this value, as do the pushpull, singleended, and interleaved forward converter to pologies. Thus the bridge topologies are used mainly in offline converters where supply voltage would be more than the switching transistors could safely tolerate. Bridge topologies are almost always used where the normal AC input voltage is 220 V or higher, and frequently even for 120V AC inputs. An additional valuable feature of the bridge topologies is that primary leakage inductance spikes (Figures and ) are easily clamped to the DC supply bus and the energy stored in the leakage inductance is returned to the input instead of having to be dissipated in a resistive snub ber element. HalfBridge Converter Topology Basic Operation Halfbridge converter topology is shown in Figure . Its major advantage is that, like the doubleended forward converter, it subjects the “off” transistor to only V dc and not twice that value. Thus it is widely used in equipment intended for the European market, where the AC input voltage is 220 V. First consider the input rectifier and filter in Figure . It is used universally when the equipment is to work from either120VACAmerican power or 220V AC European power. The circuit always yields roughly 320V rectified DC voltage, whether the input is 120 or FIGURE Halfbridge converter. One end of the power transformer primary is connected to the junction of filter capacitors C1, C2 via a small DC locking capacitor Cb . The other end is connected to the junction of Q1, Q2, which turn “on” and “off” on alternate half cycles. With S1 in the closed position, the circuit is a voltage doubler 。272/2 or 177。為此，輸入網(wǎng)壓為 220V或更高的場合幾乎都使用橋式拓?fù)?。其主要?yōu)點(diǎn)是，開關(guān)管關(guān)斷時承受電壓為 Vdc（與雙端正激變換器相同），而不是像推挽拓?fù)浠蚴菃味苏ぷ儞Q器那樣為 2Vdc。不管輸入網(wǎng)壓是 120V AC還是 220V AC，該電路整流得到的直流電壓均為320V。在輸入電壓的正半周， A點(diǎn)相對于 B點(diǎn)為正，電源通過 D1給 C1充電， C1電壓為上正下負(fù)，峰值約為 =168V；在輸入電壓的負(fù)半周， A點(diǎn)電壓相對于 B點(diǎn)為負(fù)，電源通過 D2給 C2充電， C2電壓為上正下負(fù)，峰值也為 =168V，這樣兩個電容串聯(lián)的輸出為 336V。 假設(shè)整流后輸入的直流電壓為 336V，該電路工作情況如下。圖 Q Q2輪流導(dǎo)通半個周期。當(dāng)開關(guān) S1閉合時，電路為倍壓整流器；而斷開時，電路為全波整流器。應(yīng)選擇合適的次級匝數(shù)使在 導(dǎo)通時間不大于 。該市中的 dB值為峰值磁密期望值（頻率低于 50KHz時選用 1600G，頻率越高該值越?。┑膬杀?。由于每周期有兩個脈寬為 ，電壓為Vdc/2時的輸入功率為 =（ Vdc/2）（ Ipft）（ ），其中， Ipft為初級電流脈沖等效為平頂脈沖后的峰值 Ipft（半橋） = （ ） 初級線徑的選擇 在輸出功率相同的條件下，半橋變換器的初級線徑要比推挽電路有兩個初級且每個初級承受的電壓是半橋電路電壓的兩倍，因此兩種拓?fù)涞睦@組尺寸相差不多。這與全波整流型推挽電路次級的相關(guān)計算完全相同。 在半橋電路中，若 C C2接點(diǎn)處電壓不能精確到電源電壓的一半，則導(dǎo)通時初級承受的電壓將與 Q2導(dǎo)通時的不相等，磁通會沿磁滯回線正向或反向持續(xù)增加直至使磁芯飽和，損壞開關(guān)管。由于該電容占用一本分電壓，使次級電壓降低 ，使獲得同樣輸出電壓所需的導(dǎo)通時間延長。 272/2=177。 Q1導(dǎo)通時，負(fù)載電流和勵磁電流流過 Q變壓器 T1的漏感、 Np并聯(lián)的勵磁電感及按匝數(shù)比平方折算到初級的次級負(fù)載等效阻抗，最后流經(jīng) Cb到達(dá) C C2接點(diǎn)， Np同名端電壓為正； Q1關(guān)斷時，勵磁電感迫使所有繞組電壓極性反向， Np同名端電壓力圖變得很負(fù)，使 Q1承受遠(yuǎn)大于 Vdc的電壓就不會低于負(fù)母線電壓。
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