The active clamp flyback (ACF) converter utilising gallium nitride (GaN) devices with high-switching frequency and high efficiency is impressive in system miniaturisation for AC–DC adapters. Owing to poor reverse conduction of GaN devices, the improper dead time between two switches can cause large power consumption in high frequency. This study proposes a dynamic dead time optimisation technique for GaNs ideal zero-voltage switching (ZVS) to address the issue. It adjusts the clamp switch on time to avoid large reverse conduction voltage stress on the main switch in different loads conditions. In addition, a new control scheme for clamp switch is introduced for enhancing efficiency in light to medium load. These techniques are experimentally verified on a 45 W (20 V/2.25 A) prototype of an ACF converter with a field-programmable gate array. The controller enables the system to operate at 1 MHz and dynamically modulates the dead-time under universal input and full load. With the light load ZVS control scheme, the system can achieve a maximum efficiency of 94.12 and 80.23% in the worst case. The prototyped converter can achieve power density (exclude case and controller) of 18 W/in ³ .

中文翻译：

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数控基于GaN的MHz有源钳位反激式转换器，具有针对AC-DC适配器的动态死区时间优化

有源钳位反激（ACF）转换器利用具有高开关频率和高效率的氮化镓（GaN）器件，在AC-DC适配器的系统小型化方面令人印象深刻。由于GaN器件的反向导通性差，两个开关之间的死区时间不当会导致高频功耗大。这项研究针对GaN理想的零电压开关（ZVS）提出了一种动态空载时间优化技术，以解决该问题。它调整钳位开关的导通时间，以避免在不同负载条件下主开关上产生较大的反向传导电压应力。此外，还引入了一种用于钳位开关的新控制方案，以提高轻至中等负载的效率。这些技术已在具有现场可编程门阵列的ACF转换器的45 W（20 V / 2.25 A）原型上进行了实验验证。该控制器使系统能够以1 MHz的频率运行，并动态调制通用输入和满载情况下的死区时间。使用轻载ZVS控制方案，该系统在最坏的情况下可以实现94.12和80.23％的最大效率。原型转换器可实现18 W / in的功率密度（不包括外壳和控制器） ³ 。