Hybrid interleaving with adaptive PLL loop for adaptive on-time controlled switching converters

摘要

Recently, pulse distribution method and Phase Lock Loop (PLL) method have been widely used for adaptive on-time controlled multi-phase DC-DC converters. The former is simple, but suffers duty cycle jittering with ripple cancellation effect of current feedback. Besides, the transient response is impaired by inability to synchronize PWM signals among phases. The latter is less noise-sensitive and allows overlapping of the PWM signals for faster response. However, the stability problem of PLL loop occurs under wide duty cycle range, but there is no model to predict the issue so far. Moreover, the circuit complexity increases with one PLL loop per phase. This paper presents an accurate small-signal model of PLL loop based on describing function to provide feedback design guideline. Next, an adaptive PLL loop is proposed to auto-tune control bandwidth under wide duty cycle range. After that, hybrid interleaving structure is proposed to significantly reduce the circuit complexity of PLL method, while remains comparable transient performance. Finally, the simulation and experimental results confirm the model accuracy and the effectiveness of proposed methods.