1394C-AM04,1394C-AM04
1394C-AM04
開關(guān)損耗也是一定的,
而且開關(guān)頻率越高,開關(guān)損耗越大,同
時在開關(guān)過程中還會激起電路分布電感和寄生 電容的振蕩,帶來附加損耗,因此,硬開關(guān)DC/DC轉(zhuǎn)換器的開關(guān)頻率不能太高。軟開關(guān)DC/DC轉(zhuǎn)換器的開關(guān)管,在開通或關(guān)斷過程中,或是加于 其上的電壓為零,即零電壓開關(guān)(Zero-Voltage-Switching,ZVS),或是通過開關(guān)管的電流為零
,即零電流開關(guān)(Zero-Current·Switching,ZCS)。這種軟開關(guān)方式可以顯著地減小開關(guān)損耗,以及開關(guān)過程中激起的振蕩,
使開關(guān)頻率可以大幅度提高,為轉(zhuǎn)換器的小型化和模塊化創(chuàng)造 了條件。功率場效應(yīng)管(MOSFET)是應(yīng)用較多的開關(guān)器件,
它有較高的開關(guān)速度,但同時也有較大的寄生電容。它關(guān)斷時,在外電壓的作用下, 其寄生電容充滿電
,如果在其開通前不將這一部分電荷放掉,則將消耗于器件內(nèi)部,這就是容性開通損耗。為了減小或消除這種損耗,功率場 效應(yīng)管宜采用零電壓開通方式(ZVS)。絕緣柵雙極性晶體管(Insu1ated Gate Bipo1ar tansistor,IGBT)
是一種復(fù)合開關(guān)器件,關(guān)斷時的電流拖 尾會導(dǎo)致較大的關(guān)斷損耗,如果在關(guān)斷前使流過它的電流降到零,
則可以顯著地降低開關(guān)損耗,因此IGBT宜采用零電流(ZCS)關(guān)斷方式。IGBT在 零電壓條件下關(guān)斷,同樣也能減小關(guān)斷損耗,但是MOSFET在零電流條件下開通時,并不能減小容性開通損耗。諧振轉(zhuǎn)換器(ResonantConverter ,RC)、準(zhǔn)諧振轉(zhuǎn)換器(Qunsi-Tesonant Converter,QRC)、多諧振轉(zhuǎn)換器(Mu1ti-ResonantConverter,MRC)、零電壓開關(guān)PWM轉(zhuǎn)換器(ZVS PWM Converter)、零電流開關(guān)PWM轉(zhuǎn)換器(ZCS PWM Converter)、零電壓轉(zhuǎn)換(Zero-Vo1tage-Transition,ZVT)PWM轉(zhuǎn)換器和零電流轉(zhuǎn)換(Zero- Vo1tage-Transition,ZVT)PWM轉(zhuǎn)換器等,均屬于軟開關(guān)直流轉(zhuǎn)換器。
電力電子開關(guān)器件和零開關(guān)轉(zhuǎn)換器技術(shù)的發(fā)展,促使了高頻開關(guān)電源的發(fā)展
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