摘要:
揭示了脉冲跨周期调制(pulse skipped modulation, PSM)电感电流连续导电模式(continuous conduc-tion mode, CCM)Buck变换器中存在的低频波动现象,分析了PSM调制CCM Buck变换器的能量转换过程,阐述了低频波动的产生机理,给出了低频波动的判断条件。建立了PSM调制CCM Buck变换器的同步开关映射模型,基于该模型给出了电感电流与输出电压随输出电容等效串联电阻(equivalent series resistance, ESR)变化的分岔图,分析了ESR对低频波动的影响。为消除PSM调制CCM Buck中存在的低频波动,提出了电容电流脉冲跨周期调制(capacitor current pulse skipped modulation, CC-PSM )方法。研究结果表明：在ESR较小时, CC-PSM调制CCM Buck变换器消除了PSM调制CCM Buck变换器存在的低频波动。仿真与实验结果验证了理论分析的正确性。
Abstract:
Low-frequency oscillation phenomenon in pulse skipped modulation (PSM) buck converter operating in continuous conduction mode (CCM) is reported in this paper. Energy transfer difference between the PSM-controlled buck converter operating in discontinuous conduction mode (DCM) and that in CCM is studied. The mechanism of low-frequency phenomenon in PSM-controlled CCM buck converter is revealed, and a discrete-time model of PSM-controlled buck converter operating in CCM is established. Based on this model, the border collision bifurcation with variations of the ESR is studied;meanwhile, the inhibition effect of output capacitor equivalent series resistance (ESR) on low-frequency oscillation is presented. Based on the above analysis, a capacitor current pulse skipped modulation (CC-PSM) technology is proposed; the energy transfer principle of CC-PSM controlled buck converter is analyzed. The control pulse of CC-PSM is generated by the comparison between the sampled capacitor current and preset peak reference current, and thus the range of inductor current ripple is limited. Results show that CC-PSM effectively eliminates the low-frequency oscillation in CCM buck converter under classical PSM when the ESR is low. Finally, the experimental results validate the correctness of theory and simulation analysis.
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