A Novel Current-Mode COT-Controlled Buck Converter for Phase-Interleaved Parallel Applications

In this paper, a parallel current-mode COT-mode BUCK converter circuit is proposed for the problems of uneven load current distribution and large output ripple that may occur in the parallel connection of buck DC-DCs. The converter employs a programmable phase-shifting circuit based on the COT mode, which allows multiple phase differences to be set for the switching cycles of each parallel branch, enabling the inductor current currents of each parallel converter to achieve a balanced interleaving capability from 2-phase to 12-phase, which minimizes the output voltage ripple and improves the load response speed. The designed converter has been circuit and layout designed based on the Hitek <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$0.18\mu \mathrm{m}30\mathrm{V}$</tex> BCD process. Simulation results show that the input voltage is 4V to 20V, the single-phase output current is 5A, the dual-phase parallel output current is 10A, the operating frequency range is 800kHz to 2MHz, and the dual-phase parallel connection can reduce the output voltage ripple from 5.016 m V to 1. 737m V compared with single-phase. The converter has a high conversion efficiency under light load conditions and up to 91<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">%</sup>under heavy load conditions (VouT=3.3V, ILoAD=5A). The simulation results verify the effectiveness of the proposed phase shift circuit.