Modeling Analysis And Control Technique Of Single-inductor Dual-output Switching Converter

Single-inductor multiple-output(SIMO)switching converter with only one inductor is a preferred candidate to support multiple outputs with reduced circuit volume and cost,and provide a good solution for mobile phone,tablet computers and other portable electronic devices which need multiple outputs.Therefore,the research on it is significance.Taking single-inductor dual-output(SIDO)boost converter in continuous conduction mode(CCM)as the research object,the working principle and mode of CCM SIDO boost converter are analyzed in detail.The time averaging equivalent circuit of CCM SIDO boost converter is established,the DC gain of different outputs and transfer functions of main power circuit are derived,then the root cause of cross-regulation between output branches is revealed,which provide a theoretical basis for analyzing the cross-regulation between output branches.The correctness of the modeling results is verified by the frequency domain sweep on simulation circuit.By establishing the closed-loop small signal model of common-mode voltage and differential-mode voltage(CMV-DMV)controlled CCM SIDO boost converter,the closed-loop output impedance and cross-regulation impedance transfer functions are obtained.Then the cross-regulation characteristics in different output voltage levels are discussed by bode diagram in frequency-domain.The research results show that,for CMV-DMV controlled CCM SIDO boost converter,the cross-regulation of high-voltage output to low-voltage output is smaller than the low-voltage output to high-voltage output when the two output voltages are not equal,and the cross-regulation of the first turn-on output branch to the second one is bigger than the second output branch to the first one when the two output voltages are equal.The correctness of the theoretical analysis is proved by simulation and experimental results.A fixed valley current mode(FVCM)variable frequency control technology is proposed.Its working principle and operation sequence are analyzed,and then the relationship between switching frequency,main circuit parameters and valley current reference is obtained.The small signal model of FVCM variable frequency controlled CCM SIDO boost converter is established,and the closed-loop output impedance and cross-regulation impedance transfer functions are obtained.Moreover,transient performance and cross-regulation of traditional common-mode voltage and difference-mode voltage(CMV-DMV)control and FVCM variable control are compared.It is found that,comparing to traditional CMV-DMV controlled SIDO boost converter,FVCM variable frequency controlled SIDO boost converter has improved transient response and reduced output cross-regulation.The validity of the theoretical analysis is proved by simulation and experimental results.