CHAPTER 3
Half- and Full-Bridge
Converter Topologies
3.1 Introduction
Half-bridge and full-bridge topologies stress their transistors to a voltage equal to the DC input voltage not to twice this value, as do the push-pull, single-ended, 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 120-V AC inputs.
An additional valuable feature of the bridge topologies is that primary leakage inductance spikes (Figures 2.1 and 2.10) 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.
3.1 概述
半橋和全橋拓?fù)溟_(kāi)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(cuò)正激拓?fù)淠菢訛殡妷旱膬杀?。所以橋式拓?fù)鋸V泛用于直接電網(wǎng)的離線式變換器。而對(duì)推挽等拓?fù)鋪?lái)說(shuō)，兩倍的電網(wǎng)整流電壓將超過(guò)其開(kāi)關(guān)管的安全耐壓容限。為此，輸入網(wǎng)壓為220V或更高的場(chǎng)合幾乎都使用橋式拓?fù)?。?dāng)輸入網(wǎng)壓為120V時(shí)也有使用橋式拓?fù)涞那闆r。
橋式拓?fù)涞牧硪粌?yōu)點(diǎn)是，能將變壓器初級(jí)側(cè)的漏感尖峰電壓（如圖2.1和圖2.10所示）箝位于直流母線電壓，并將漏感儲(chǔ)存的能量歸還到輸入母線，而不是消耗于電阻元件。