Comprehensive Analysis and Design of Current-Balance Loop in Constant On-Time Controlled Multi-Phase Buck Converter

Abstract

Constant on-time (COT) controlled multi-phase buck converter has been widely used in high-current applications such as computing devices to achieve high entire-load-range efficiency. However, the literature lacks comprehensive analysis and design guide of the current-balance loop in COT control, resulting in possible low efficiency, per-phase current protection false-trigger, and stability issue. To solve the aforementioned issues, dc inductor current equations and small-signal models are proposed for COT control with the current-balance loop. Current-balance loop gain design guideline is then proposed to achieve accurate dc current balance and stability. Experiment and simulation results verify the analysis and the accuracy of the proposed models. INDEX TERMS Multi-phase converter, constant on-time (COT) control, current-balance, small-signal model.

The study on the effect of voltage ripple on multiphase buck converters with phase shedding control scheme for SCADA applications

“…The charging and discharging of the equivalent output capacitor constitute the majority of the output voltage ripple amplitude. The ripple's volume is defined by the load current, total output capacitor, switching frequency, and number of phases supplied to the system [2]. In (3) describes the relation between output voltage ripple, output capacitance and switching frequency and how these parameters are utilised to reduce output voltage ripple.…”

“…As the demand for processing from processors increases, the needed output current of converters for computing devices continues to grow as well. The multi-phase interleaved buck converter is widely used to deliver more output current with lower output voltage ripple [2]. For low voltage and high current applications, a multi-phase buck converter is recommended because it minimizes current stress in each phase while also reducing output capacitor size due to ripple cancellation [3].…”

Multiphase digital integration constant on‐time–controlled Buck converter with high‐resolution current balance scheme for ultrafast load transient

“…Also, the control resolution is a critical point of digital COT current balance realization, the system stability is affected if the resolution is bad. However, the COT current balance scheme in Chen et al 19 is analog and does not have a resolution issue. The delayline-based structures proposed in the previous studies [21][22][23][24][25] are widely used in digital control to improve the digital PWM (DPWM) resolution in PWM-controlled converters.…”

“…Also, the number of phases might be limited by hardware for analog implementation. In the aspect of the multiphase current balance, the method in Chen et al 19 and Tsai et al 20 gives the model of the multiphase model of analog COT current balance. However, only a two‐phase current balance model is given in those papers.…”

Analysis of Multi-Phase Trans-Inductor Voltage Regulator with Fast Transient Response for Large Load Current Applications

“…At the same time, their current fluctuates rapidly in their power demand, which requires a fast transient response from the power supply. Multi-phase constant-ontime (COT) voltage regulators are used to supply these CPUs with large current step and a large load current slew rate [1].…”