Adaptive pseudo-continuous conduction mode operation schemes and circuit designs for single-inductor multiple-output switching converters

Abstract

As single-inductor multiple-output (SIMO) switching converters proliferate in integrated power management designs, pseudo-continuous conduction mode (PCCM) operation with freewheel switching has been well adopted owing to its effectiveness on cross-regulation, voltage ripple and switching noise issues, especially in heavy load scenarios. However, the technique faces a direct challenge in unbalanced loading conditions. Potential lengthy freewheel switching periods and high I dc current levels could lead to conduction and switching power losses, degrading the efficiency of the converters. To alleviate this problem, this paper presents adaptive PCCM operation schemes with the respective distributed and unified freewheel switching schemes. The optimal freewheel switching durations are achieved in various load conditions by adaptively adjusting the phase durations and freewheel switching I dc current level, thereby reducing the conduction and switching losses effectively. The switching power loss is further reduced by turning on/off the freewheel switch less frequently, without compromising the performance of operation. The proposed schemes have been implemented and verified in digital and analog-based SIMO power converters designed with 130 nm CMOS process.