零電壓開關(guān)降壓變換器提供最大功率密度、效率

　　零電壓開關(guān)降壓變換器提供最大功率密度、效率

　　與傳統(tǒng)的脈沖寬度調(diào)制（PWM）或硬開關(guān)結(jié)構(gòu)相比，使用諧振拓?fù)涞慕祲鹤儞Q器比基于傳統(tǒng)結(jié)構(gòu)的電源提供更高的性能。雖然晚了傳統(tǒng)高密度、硬開關(guān)穩(wěn)壓器具有演化的改進(jìn)的半導(dǎo)體集成、低電阻MOSFET，和先進(jìn)的包裝，他們的設(shè)計(jì)是不足以滿足新的電力需求，主要是由于在調(diào)節(jié)MOSFET的開關(guān)損耗，提高開關(guān)頻率或增加輸入電壓。

　　此外，傳統(tǒng)的降壓穩(wěn)壓器表現(xiàn)出更高的柵極驅(qū)動(dòng)損耗，由于米勒電荷消耗在柵極驅(qū)動(dòng)電路。同樣，高側(cè)MOSFET的體二極管傳導(dǎo)有助于更高的功率損耗，由于反向恢復(fù)和長(zhǎng)導(dǎo)（圖1）。因此，必須克服或大幅降低這些損失，以實(shí)現(xiàn)調(diào)節(jié)器性能的任何顯著提高。此外，硬開關(guān)拓?fù)湫枰粋€(gè)比較大的輸出電感，這增加了調(diào)節(jié)器的尺寸和成本。

　　Figure 1： In conventional buck regulators， the hard-switching transition and body diode reverse recovery expose the high-side MOSFET Q1 to very high turn-on losses.

　　Benefits of zero-voltage switching

　　Another， better alternative is to use resonant topology like zero-voltage switching （ZVS）， which enables operation at higher frequency and higher voltages without sacrificing efficiency and size. The ZVS-based regulators are also known as soft-switching regulators. Some key benefits of ZVS buck regulator topology include low turn-on losses， negligible body diode conduction time due to ideal rectifier switching， high-frequency operation maintained at high input voltage， simple internal compensation – which allows for high bandwidth， gain， and phase margin – and fast transient response with a small amount of output capacitance. What is more， it offers 20 ns minimum on time to support very high conversion ratios and delivers excellent light-load efficiency due to a high-efficiency biasing system combined with pulse skipping.