Abstract A digital control scheme is proposed to improve the light-load efficiency for Buck converters with synchronous rectification. The method adopts a fixed switching frequency at heavy load, and smoothly switches to constant on-time control mode at light load for the purpose of reducing the switching losses. In addition, different from traditional control methods, the proposed approach dynamically estimates the inductor current zero crossing point accurately based on on-time of the drive signal and inductor volt-second balance to force converters work in discontinuous conduction mode, which significantly reduces conduction losses at light loads. These features ensure the converters own higher efficiency over a wide load range. Theoretical analysis and experimental results are provided to verify the proposed scheme.
Xu Yang. The Analysis of Digital Control Approach to Improve Light-Load Efficiency for Buck Converters with Synchronous Rectification[J]. Electrical Engineering, 2017, 18(2): 14-19.
[1] Zhang M T, Jovanovic M M, Lee F C. Design consign considerations for low-voltage on-board DC/DC modules for next generations of data processing circuits[J]. IEEE Trans. Power Electron., 1996, 11: 328-337. [2] Li J, Lee F C. Modeling of V2 current-mode control[J]. IEEE Trans. Circuits and Systems I: Regular Papers, 2010, 57: 2552-2563. [3] Jian Sun. Characterization and performance com- parison of ripple-based control for voltage regulator modules[J]. IEEE Transactions on Power Electronics, 2006, 21: 346-353. [4] Zhou X, Zhang X, Liu J, et al. Investigation of candidate VRM topologies for future micro- processors[C]//in Proc. IEEE APEC Conf. Rec., 1998: 145-150. [5] Redl R, Sun J. Ripple-based control of switching regulators—an overview[J]. IEEE Transactions on Power Electronics, 2009, 24: 2669-2680. [6] Chen C J, Chen D, Tseng C W, et al. A novel ripple-based constant on-time control with virtual inductor current ripple for Buck converter with ceramic output capacitors[C]//Applied Power Electronics Conference and Exposition, 2011: 1488- 1493. [7] B Arbetter R E, Maksimovic D. DC-DC converter design for battery-operated systems[Z]. 1995: 103-109. [8] Cheng K Y, Yu F, Mattavelli P, et al. Characterization and performance comparison of digital V2-type constant on-time control for buck converters[Z]. 2010: 1-6. [9] Wei I C, Chen D, Lin Y C, et al. The stability modeling of ripple-based constant on-time control schemes used in the converters operating in DCM[C]//International Conference on Renewable Energy Research and Applications, 2012: 1-8. [10] Cheng K Y, Tian S, Yu F, et al. Digital hybrid ripple-based constant on-time control for voltage regulator modules[J]. Power Electronics IEEE Transactions on, 2011, 29(6): 3132-3144. [11] Zhou X, Donati M, Amoroso L, et al. Improved light-load efficiency for synchronous rectifier voltage regulator module[J]. IEEE Transactions on Power Electronics, 2000, 15(5): 826-834. [12] 王程左. 采用新型无损电流采样的同步整流BUCK DC-DC控制器研究[D]. 成都: 电子科技大学, 2015. [13] Qian T. Subharmonic analysis for buck converters with constant on-time control and ramp compensation[J]. Industrial Electronics IEEE Transactions on, 2013, 60(5): 1780-1786. [14] Robert W E, Dragan maksimovic. fundamentals of power electronics[M]. 2-nd Ed., Kluwer, Berlin, 2002. [15] 叶俊, 张峰. Buck同步整流电路MOSFET损耗的计算[J]. 电力电子技术, 2007, 41(12): 109-111. [16] Klien J. AN-6005-Synchronous Buck MOSFET Loss Calculations [EB/OL]. [201603]. https://www.fair- childsemi.com/application-notes/an/an-6005.pdf [17] Com T. cn/cn/lit/ds/sprs698e/sprs698e[EB/OL] [2016-08-15]. http://www.ti.com.cn/cn/lit/ug/spruh18e/ spruh18e.pdf.
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