Single-Sensor Sampling Current Control Strategy of Multiphase Interleaved DC-DC Converters

For multiphase interleaved DC-DC converters, current sharing among inductors is an important issue, so this paper proposes a single-sensor sampling current algorithm with current dynamic sharing capability. Firstly, a detailed mathematical model is presented according to the converter operation mode. The factors affecting current imbalance among phases are analyzed, and the analytical expressions of the phase current, parasitic resistance, load current and duty cycle are derived. Secondly, considering the non-ideal characteristics of the switches, all the parasitic resistances are estimated with constant duty-cycle test method by turning-on each phase. Taking the output of voltage loop controller as the reference value, the duty cycle compensation factors are introduced to obtain balanced inductor current. Besides, the control loop based on small-signal modeling is analyzed using the frequency-response method, and supported with the Matlab/SISO design tool, the zero position and loop gain of the controller are optimized. Stability against the load variations is investigated by means of the root locus analysis. Meanwhile, to further improve the dynamic performance, the feedforward control is implemented and the output impedance can be reduced dramatically. Finally, the experimental setup based on a three-phase interleaved Buck converter is constructed, and the steady-state and dymamic experimental results verify the correctness of the proposed control strategy. © 2022, Electrical Technology Press Co. Ltd. All right reserved.