Coupled-inductor buck converters are more effective in high step-down applications compared to conventional buck converters given the same circuit complexity. A coupled-inductor buck converter can adopt synchronous conduction mode to fully mitigate turn-on loss and operate at high frequency. However, this typically induces large circulating currents and harms the converter's light-load efficiency. To alleviate these issues, this paper analyzes the mechanisms behind synchronous conduction mode and then proposes a dual-loop control method solution. The variable-frequency outer loop of the proposed control minimizes conduction and deadtime loss, while the voltage-mode-controlled inner loop provides the necessary output voltage regulation. Experiments are conducted with a compact prototype converter using switching frequencies higher than 2 MHz, and the prototype is verified under load transients to validate both control loops. The results show that the light-load efficiency can be boosted by more than 8%.

中文翻译：

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低功耗应用中的双环路控制耦合电感器Buck转换器

考虑到相同的电路复杂度，与传统的降压转换器相比，耦合电感降压转换器在高降压应用中更有效。耦合电感降压转换器可以采用同步传导模式，以充分减轻导通损耗并在高频下工作。但是，这通常会产生较大的循环电流并损害转换器的轻载效率。为了缓解这些问题，本文分析了同步传导模式背后的机理，然后提出了一种双环控制方法解决方案。所提出的控制装置的变频外环使导通和空载时间损失最小，而电压模式控制的内环提供了必要的输出电压调节。使用开关频率高于2 MHz的紧凑型原型转换器进行实验，并在负载瞬变情况下验证了原型，以验证两个控制回路。结果表明，轻载效率可以提高8％以上。