A Zero-Voltage Switching Buck Converter With Enhanced Efficiency Over a Wide Load Range

This article presents a wide-input-range buck converter featuring a conduction-loss-minimized zero-voltage switching (ZVS) technique. The proposed ZVS topology enables accurate ZVS operation across a wide range of input voltage ( $V_{\mathrm {IN}}$ ) and load current ( $I_{\mathrm {O}}$ ). By keeping the auxiliary inductor current pulse in the ZVS branch separate from the main current paths, conduction loss is minimized, thereby enhancing efficiency across the entire load range. Furthermore, by reducing the voltage across the auxiliary inductor using an auxiliary capacitor, a small inductor is sufficient for ZVS. Furthermore, by implementing the ZVS control circuit directly in the high-voltage (HV) domain, propagation delays between HV and low-voltage (LV) domains are avoided, and thus, accurate ZVS operation is achieved. The converter was fabricated in a 0.18- $\mu $ m BCD process with all power switches integrated on chip. Measurement results show that the converter achieves peak efficiencies of 91.7% and 92.5% at 42-to-5-V and 24-to-3.3-V conversion, respectively. Efficiency improvement is achieved across the entire 4-A load current range with just a 30-nH auxiliary inductor.