Analysis and Comparison of Two- and Four-State Operation Modes of Parallel-Hybrid Multi-Path Buck DC-DC Converter

This paper presents a generalized parallel-hybrid multi-path buck converter. The proposed converter can operate in two- or four-state modes to achieve the voltage conversion ratio of
$D/(1+N\cdot D)$
by employing
$N$
stages and a
$D$
duty cycle. Thanks to the charge redistribution in the capacitor-parallel state, both modes can automatically regulate the flying capacitor voltages to the output voltage, requiring no extra inner loops. Despite both modes having the same inductor current reduction and similar transfer functions, the two-state operation mode achieves a lower output impedance and smaller average flying capacitor discharging current. In contrast, the four-state operation mode owns the higher complex pole pair frequencies. Finally, the simulation results show that the proposed converter with two stages in either mode achieves a < 2 V output voltage at an input voltage of 12 V. The two-state operation mode improves the peak and full-load efficiency by 0.6% and 3%, respectively.