Abstract：The rapid development of portable electronic devices increases design complexity: more unit modules inside the machine and the power supply voltage levels of different modules are usually different. The single-inductor dual-output (SIDO) Buck-Boost switching converter realizes dual output with one inductor, which has the characteristics of no electromagnetic interference and a simple structure. In addition, the converter has a buck-boost feature, realizing multi-grade voltage output (relative to the input supply voltage). It provides a new solution to the problem of power supply for electronic products that require multiple voltage levels, and has received much attention from scholars at home and abroad. However, this converter is a non-minimum phase system because the voltage of one of the output branches will be negatively regulated when the duty cycle is suddenly changed. The negative regulation phenomenon will lead to a longer transition time, and the converter will form positive feedback and become unstable during the negative regulation time. In addition, the non-minimum phase system cannot use the traditional frequency domain method for controller design, which makes the controller design more complicated. Therefore, it is important to study the non-minimum phase characteristics and control strategy of the SIDO Buck-Boost converter. Firstly, this paper analyzes the working principle of the SIDO Buck-Boost converter and establishes the transient mathematical model of control-output of inductor current continuous conduction mode using the state space averaging method. The analysis of the mathematical model shows that the model of the first conduction branch of the converter contains the right half-plane zero point. In contrast, the model of the back conduction branch does not contain it. By analyzing the negative regulation voltage generation mechanism of the converter, it is found that the negative regulation phenomenon exists in the output voltage of the pilot branch when the sudden change of duty cycle occurs, and does not exist in the output voltage of the back-lead branch. The analysis of the negative regulation voltage mechanism verifies the correctness of the mathematical modeling results. Then, the mathematical model of the internal dynamics of the branch containing the right half-plane zero is established. It is found that when the output voltage of the branch containing the right half-plane zero is selected as the output variable, the system has unstable zero dynamics. When the inductor current is selected as the output variable, the system does not have unstable zero dynamics. Therefore, this paper transforms the control of output voltage into the control of inductor current by introducing inductor current feedback to the branch containing the right half-plane zero, using a two-loop structure, with the inductor current as the controlled quantity in the inner loop and the capacitor voltage as the controlled quantity in the outer loop. As a result, the system is transformed into a minimum-phase system, and the transient response speed of the system is improved. The other branch uses voltage control, simplifying the control structure of the system. Then, the SIDO Buck-Boost converter operating mode and the output ripple voltage are used as constraints to obtain the inductor and capacitor parameters design method. Based on the obtained inductor and capacitor parameters combined with the Routh-Hurwitz stability criterion, the range of control parameters is obtained, and the control parameters are optimized by applying the characteristic root sensitivity theory. Finally, the simulation and experimental platforms are built to test the transient performance of the load and input supply voltage mutations, respectively. The results show that the method of using current control for the branch containing the right half-plane zero point and voltage control for the other branch improves the transient performance of the system compared with the voltage control for both branches, and effectively suppresses the cross-regulation between the output branches, which is of practical engineering application.
李慧慧, 皇金锋. 单电感双输出Buck-Boost变换器的非最小相位特性分析及控制策略[J]. 电工技术学报, 2023, 38(14): 3875-3887.
Li Huihui, Huang Jinfeng. Analysis of Non-Minimum Phase Characteristics and Control Strategies for Single-Inductor Dual-Output Buck-Boost Converters. Transactions of China Electrotechnical Society, 2023, 38(14): 3875-3887.
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2023, Vol. 38 
