Buck-Boost变换器的能量传输模式及输出纹波电压分析

根据电感电流最小值与输出电流的比较,将Buck-Boost 变换器的能量传输模式(ETM)分为完全电感供能模式(CISM)和不完全电感供能模式(IISM),得出了CISM和IISM的临界条件和临界电感.将电感电流最小值与零和输出电流进行比较,得出Buck-Boost 变换器存在三种工作模式,即CISM、不完全电感供能且连续导电模式(IISM-CCM)和不完全电感供能且不连续导电模式(IISM-DCM).推导出了变换器工作于三种模式时的输出纹波电压表示式,指出对于给定负载、电容和开关频率的Buck-Boost变换器,CISM的输出纹波电压最小且与电感无关,而IISM-CCM和IISM-DCM的输出纹波电压较大且随电感减小而增大.CISM和IISM的临界电感即为使得变换器的输出纹波电压最低的最小电感.文中给出实例,实验结果与理论分析一致,但因未考虑器件参数输出纹波电压略高于理论分析值,实验结果验证了理论分析的正确性.

Energy Transmission Modes and Output Ripple Voltage of Buck-Boost Converters

Comparing the minimum current through the inductor with the output current,the Energy Transmission Modes(ETM) of Buck-Boost converters can be divided into two types,i.e.,the Complete Inductor Supply Mode(CISM) and the Incomplete Inductor Supply Mode(IISM).The critical inductance and critical condition of CISM and IISM are deduced.Comparing the minimum current through the inductor with zero and the output current,a Buck-Boost converter may work in three operating modes,i.e.,CISM,the Incomplete Inductor Supply Mode as well as Continuous Conduction Mode(IISM-CCM) and the Incomplete Inductor Supply Mode as well as Discontinuous Conduction Mode(IISM-DCM).Formulations for output voltage ripple of Buck-Boost converters in three operating modes are deduced,respectively.As for the Buck-Boost converters with certain load,output capacitance and switching frequency,it is pointed out that the output voltage ripple(OVR) in CISM is the smallest and independent of the inductance,and that the OVR in IISM-CCM and IISM-DCM is much larger and increasing with the decreasing of the inductance.It is concluded that the minimum inductance to guarantee the lowest output ripple voltage is the critical inductance between CISM and IISM.The experiment results are in positive to the analysis results.The experiment results of OVR are a little higher than the analysis due to without considering the parasitic elements of the devices.The feasibility of the proposed methods is proved by the experiment results.