A 12V-Input 1V-1.8V-Output 94.7%-Peak-Efficiency 685A/cm³-Current-Density Hybrid DC-DC Converter with a Charge Converging Phase

Large voltage-conversion-ratio (VCR) DC-DC converters (e.g. 12V to 1-to-1.8V) with high efficiency and high current density are essential for industrial and automotive applications. Conventional buck converters have to use high-voltage transistors that incur large power loss and bulky inductors that occupy significant board area, leading to compromised efficiency and current density. Recent advancements in hybrid converters [1] –[6] provide promising solutions for such applications. These converters introduce flying capacitors to lower the voltage stress of the power transistors or to reduce the inductor current (LL). For instance, double step-down (DSD) related converters [1], [2] and a switched-capacitor buck converter [3] are proposed to lower the voltage stress of the power transistors to up to VI / 4, allowing the use of low-voltage transistors for improved efficiency. However, the inductors still have to handle the entire output current (I₀) as that in a conventional buck converter, requiring bulky inductors with low DCR and thereby limiting current density. Dual-path hybrid converters are proposed in [4] –[6] to reduce I <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</inf> by leveraging the flying capacitors to provide additional current paths. However, the reduction in I <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</inf> is relatively modest, only 20% in [4], [5] for a 12V-to-1.2V conversion scenario. Although [6] achieves a significant reduction of 40%, it requires a complex switched-capacitor network with 12 switches. In this paper, we propose a dual-path hybrid buck converter featuring a charge converging phase (CCP-HB) that consistently reduces IL to less than 0.5 I₀.