Design-oriented analysis of cross-regulation in single-inductor dual-output Buck-boost DC-DC converters

In single-inductor multiple-output converters, the multiplexing of the inductor at each output port will inevitably lead to severe cross-regulation effect. This paper aims to investigate the steady state performance and transient state cross-regulation in the single-inductor multiple-output DC-DC converters. A ripple-based averaged model is proposed to describe the inherent cross-regulation characteristics of single-inductor dual-output (SIDO) Buck-Boost DC-DC converter by considering the three piecewise ripple of the inductor current. Then, the steady state performance analysis is carried out to show the cross-coupling effect on the power distribution relationship and voltage gains of the two output ports. Furthermore, the nonlinear modal series representation is derived to describe the transient behavior of SIDO converter under different load disturbances. More significantly, based on the nonlinear modal analysis, the cross-regulation factors are proposed to evaluate the influence of some key circuit parameters on the transient state cross-regulation. It is found that increasing k_p2 may improve the transient cross-regulation performance of the output voltages, but non-ideal factor V_F has little influence on the transient cross-regulation. This provides much design-oriented information to suppress the cross-regulation and optimize the transient performance of the SIDO converter. Finally, the effectiveness of the above analysis is verified by the experimental results. This paper proposes one design-oriented analysis method to investigate the cross-regulation in the SIDO DC-DC converters based on the ripple-based averaged model. Firstly, the steady state analysis is carried out to show the cross-coupling effect on the power distribution of the two output ports. Then, according to the nonlinear modal analysis, the cross-regulation factors are defined to identify the key parameters for the transient cross-regulation, which provides some design-oriented information to suppress the cross-regulation.