Modeling and Design of Load Current Based Adaptive Voltage Positioning (AVP) Control for Multiphase Buck Converter Using Digital Current Estimation Algorithm

This article proposes a load current-based adaptive voltage positioning (AVP) control scheme, which applies the load current as the current injection information directly instead of the inductor current feedback of the existing research, the proposed architecture does not need the inner current loop and the entire loop bandwidth only depends on the voltage loop, so the control bandwidth is increased and the transient speed is enhanced. The small signal model is proposed, including the modelling of the closed-loop output impedance and the design process of the loop compensators. Besides, since the load current is hard to sample in the high-power system, the digital load current estimation algorithm is proposed, to calculate the load current by digital controllers and used in the proposed AVP control. The proposed algorithm is constructed in field-programmable gate array (FPGA) and is applied on the 4-phase buck system, the maximum load step of 100 A is tested with the current slew rate of 370 A\μs, the voltage tolerance window is 40 mV (R_LL = 0.4 mΩ) and the system recovery time is only 3 and 7 μs under the load step-up and step-down respectively. The proposed algorithm is compared with the commonly used active droop AVP control and AVP in constant on-time control, to prove its fast transient response.