A Two-Phase Buck Converter With Ramped-Interleaved Digital Current Mode Constant On-Time Control

This paper proposes a digital ramp interleaved current-mode constant-on-time (COT) control methodology that eliminates the need for a pulse distributor by utilizing the amplitude of the ramp to convey phase information. This approach realizes the natural transition from independent triggering during the load-shedding process to interleaved triggering in the steady-state process. In a multiphase buck topology, the relationship between the total inductor current ripple, duty cycle, and number of phases is established. Under specific conditions regarding duty cycle and phase count, it is possible to encounter zero duty cycle. In such scenarios, if the total inductor current is utilized as the input for the current loop, it may result in system instability. In this paper, the input of the current loop is modified to utilize the phase-wise branch inductance current in order to mitigate ripple cancellation effects. This approach results in a greater ripple compared to the total inductance current, which enhances the accuracy of digital sampling. Ultimately, the formulas for the current-sharing ring and phase deviation were derived and phase deviation were derived, and a methodology for regulating equal current by adjusting the Ton duration was investigated. The simulation results indicate that the conventional phase-based COT exhibits a switching time of 1.6μs for heavy load cutting and 4 μs for light load cutting, whereas the digital slope-interleaved current-mode COT control demonstrates a reduced switching time of 1 μs for heavy loads and 3.3 μs for light loads.