【正文】
開關(guān)的能量轉(zhuǎn)化成了損耗或無(wú)損耗電流或開關(guān)的過 0 電流或過 0 電壓,第一個(gè)被稱為緩沖,最后一個(gè)被成為過 0 電流或過 0電壓的開關(guān)。 The switching losses can be usually minimized in two ways。當(dāng)開關(guān)電流等于Is時(shí),二極管關(guān)斷并且開關(guān)兩端電壓線性下降至 0。當(dāng)開關(guān) 電流等于Is時(shí),二極管關(guān)斷并且開關(guān)兩端電壓線性下降至 0。流過開關(guān)的電流線性下降到零。當(dāng)開關(guān)打開后,開關(guān)兩端電壓開始上升到 Uo,此時(shí)二極管一直關(guān)斷。假使開關(guān)初始狀態(tài)為閉合,則通過開關(guān)的電流為 Is。當(dāng) f 取最大時(shí) Psw=1/2UsIo。此時(shí)余留的電流正轉(zhuǎn)向二極管V1, V1導(dǎo)通。此時(shí)二極管仍截止,二極管截止,流過開關(guān)的電流相當(dāng)于流過電感的電流,維持在恒定的 Io。二極管壓降為 0,此時(shí)開關(guān)兩端電壓維持在 +Us 當(dāng)電流建立完成后,二極管 V1 截止,開關(guān)兩端電壓線性下降為 0。電感電流為 +Io 慣性流過二極管 V1。我們測(cè)試開關(guān)損耗時(shí)分兩種情況:感性負(fù)載和容性負(fù)載。 TransitionState Losses 轉(zhuǎn)換損耗 : The practical switching devices have limited capabilities of rate of voltage transition and the rate of current nonabrupt transition rates give rise to power losses in the switching will examine these switching losses in two cases separately:the inductive and capacitive loads. 在實(shí)際的開關(guān)裝置限制了電壓變換率和電流變化率。斷態(tài)損耗的公式為 Poh=Uoff ir. The Usoff and Ir are respectively the reverse bias voltage in the offstate and the reverse current through the example,the typical power diodes and the power transistors have high reverse voltages in hundreds to thousands of volts and microamps to milliamps through them in the off state. 其中 Uoff 在斷態(tài)時(shí)的反向偏置電壓, ir 是流過開關(guān)的反向漏電流。這個(gè)通態(tài)損耗非常重要。例如,典型的功率二 極管和功率晶體管有近似 ~1 伏的通態(tài)壓降。 OnState Losses 通態(tài)損耗 : The electrical sw