LAUSR

The quadrilateral control method for four-switch Buck–Boost converter can enable all of the power switches to achieve zero-voltage-switching (ZVS), thereby achieving high power density. However, the inductor current requires to be sensed and regulated to ensure the realization of ZVS, which will introduce the additional losses and degrade the efficiency. In this article, a high-efficiency control strategy based on lossless current sampling is proposed, which can achieve the minimum height of the inductor current over the whole working conditions. Moreover, to ensure the smooth switching between different modes, a transition mode is inserted when the input voltage is close to the output voltage. Finally, a prototype with input voltage of 40–60V and output parameters of 48V/6A is built to verify the effectiveness of the proposed sampling circuit and control strategy. The peak efficiency is 98.88%, while the full-load efficiency at the nominal input voltage is 98.14%. Meanwhile, a video material is provided to demonstrate the extremely low root mean square (RMS) value of the inductor current and the smooth switching process under different input voltage and load conditions.