Design-Oriented Stability of Outer Voltage Loop in Capacitor Current Controlled Buck Converters

Due to the inherent feedforward of load current, capacitor current (CC) control shows a fast transient response that makes it suitable for the power supplies used in various portable electronic devices. However, considering the effect of the outer voltage loop, the stable range of the duty-cycle is significantly diminished in CC controlled buck converters. To investigate the stability effect of the outer voltage loop on buck converters, a CC controlled buck converter with a proportion-integral (PI) compensator is taken as an example, and its second-order discrete-time model is established. Based on this model, the instability caused by the duty-cycle is discussed with consideration of the outer voltage loop. Then the dynamical effects of the feedback gain of the PI compensator and the equivalent series resistance (ESR) of the output capacitor on the CC controlled buck converter with a PI compensator are studied. Furthermore, the design-oriented closed-loop stability criterion is derived. Finally, PSIM simulations and experimental results are supplied to verify the theoretical analyses.

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Cite this article

[IEEE Style]

X. Zhang, Z. Zhang, B. Bao, H. Bao, Z. Wu, K. Yao, J. Wu, "Design-Oriented Stability of Outer Voltage Loop in Capacitor Current Controlled Buck Converters," Journal of Power Electronics, vol. 19, no. 4, pp. 869-880, 2019. DOI: 10.6113/JPE.2019.19.4.869.

[ACM Style]

Xi Zhang, Zhongwei Zhang, Bocheng Bao, Han Bao, Zhimin Wu, Kaiwen Yao, and Jing Wu. 2019. Design-Oriented Stability of Outer Voltage Loop in Capacitor Current Controlled Buck Converters. Journal of Power Electronics, 19, 4, (2019), 869-880. DOI: 10.6113/JPE.2019.19.4.869.