Study On Ripple-based Controlled SIDO CCM Buck Converter

With the development of portable devices and light-emitting diode(LED)lighting,it is increasingly demanding for the volume,cost and efficiency of power supplies.Single-inductor multiple-output(SIMO)DC-DC converter with only one inductor is a preferred candidate to provide multiple outputs with reduced circuit volume,cost and improved effciency.Therefore,it has attracted much attention recently.This paper takes the single-inductor dual-output(SIDO)Buck converter operating in continuous conduction mode(CCM)as research object,and focuses on its ripple-controlled techniques,cross regulation,stability and application in multiple-output LED driver.PCM controlled SIDO CCM Buck converter has more inductor current borderlines and more complex operation modes as it has one more reference current of inductor current than that of PCM Buck converter.In order to analyze the effect of circuit parameters on stability of PCM controlled SIDO CCM Buck converter,inductor current borderlines and operation modes are analyzed comprehensively based on the difference of reference currents.The 1-D discrete iterative model of each operation mode and a unified 1-D discrete iterative model of the converter are established used by discrete iterative modeling approach.Basded on this,the effect of the difference of reference currents,initial inductor current and input voltage on the stability of PCM SIDO Buck converter has been discussed using bifurcation diagrams and Lyapunov exponents.Besides,the stability boundary of the difference of reference currents,stability region of initial inductor current,and stability boundary of input voltage are derived.As capacitor current can reflect the load variation more quickly than peak current,a capacitor current ripple(CCR)controlled SIDO CCM Buck converter is proposed to reduce cross regulation of PCM controlled SIDO CCM Buck converter.The operation principle and operation modes of CCR controlled SIDO CCM Buck converter are presented.The small signal model of the converter is established using state space averaging approach,and then cross reugaltions existing in CCR and PCM controlled SIDO CCM Buck converter are comparative analyzed based on cross regulation transfer functions.Besides,the discrete iterative model of CCR controlled SIDO CCM Buck is established.The dynamic behaviors of the converter are revealed by bifurcation diagram and eigenvalue loci.The effect of the variation of control parameters on the stable load range and the effect of the variation of one load on the stable range of the other load are investigated by bifurcation diagram.Based on this,the stability boundaries and stability regions of loads are given.A capacitor current and capacitor voltage ripple(CCVR)controlled SIDO CCM Buck converter is proposed to extend the stable load range and suppress cross regulation.The operation principle and operation modes of CCVR controlled SIDO CCM Buck converter are presented.The discrete iterative model of CCVR controlled SIDO CCM Buck is established,and then stable load ranges of CCVR and CCR controlled SIDO CCM Buck converter are comparative analyzed by bifurcation diagrams.Furthermore,the small signal model of the converter is established using state space averaging approach,and then cross reugaltions existing in CCVR and CCR controlled SIDO CCM Buck converter are comparative analyzed based on cross regulation transfer functions.SIDO DC-DC converter is applied to LED driver in recent years.In this paper,PCM controlled SIDO CCM Buck LED driver is proposed.The operation principle of PCM controlled SIDO CCM Buck LED driver is presented.The small signal model of the driver is established using state space averaging approach,and the open loop control-to-output transfer functions,control-to-inductor current transfer functions,loop gains transfer functions,and cross regulation transfer functions are obtained.On the basis of open loop control-to-output transfer functions and loop gains transfer functions,the control parameters are designed.Besides,the cross regulation of one output to the other output of proposed driver is investigated using bode plots of cross regulation transfer functions with variation of reference currents and control parameters.Finally,experiment circuits are designed to verify the validity of the theoretical analysis.