零电压开关降压变换器提供最大功率密度、效率

　　零电压开关降压变换器提供最大功率密度、效率

　　与传统的脉冲宽度调制（PWM）或硬开关结构相比，使用谐振拓扑的降压变换器比基于传统结构的电源提供更高的性能。虽然晚了传统高密度、硬开关稳压器具有演化的改进的半导体集成、低电阻MOSFET，和先进的包装，他们的设计是不足以满足新的电力需求，主要是由于在调节MOSFET的开关损耗，提高开关频率或增加输入电压。

　　此外，传统的降压稳压器表现出更高的栅极驱动损耗，由于米勒电荷消耗在栅极驱动电路。同样，高侧MOSFET的体二极管传导有助于更高的功率损耗，由于反向恢复和长导（图1）。因此，必须克服或大幅降低这些损失，以实现调节器性能的任何显著提高。此外，硬开关拓扑需要一个比较大的输出电感，这增加了调节器的尺寸和成本。

　　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.