Continuous Conduction Mode Single Inductor Multiple-output Step-down Dc-dc Converter

Many electronic products need multiple independent power supplies, such as digital cameras, personal digital assistants, mobile phones and so on. They require high efficient power management system. The main study of this paper is the crosstalk problem between the output branches for the buck single-inductor multiple-output DC-DC converter working in continuous conduction mode, and the control methods of reducing the couple between the output branches. The method is use the inverse matrix of the transfer function as compensation function.The introduction of this paper describes the realization of multi-output power management system in several ways, and then shows the single-inductor multi-output DC-DC converter can be work in three operating modes:discontinuous-conduction mode (DCM), pseudo-continuous-conduction mode(PCCM),continuous-conduction mode(CCM).Then, the second chapter firstly analyzes the general single output buck DC-DC converters, and then analyzes to multi-output converter, discover the buck single-inductor multiple-output converters, boost single-inductor multiple-output converter and buck-boost Single-inductor multiple-output converter have the same function:both can product the output high and low output at the same time. However, there are some differences for the three converters:buck single-inductor multiple-output converter not all the output can be greater than the supply voltage; boost single-inductor multiple-output converter not all the output can be less than the supply voltage; buck-boost single inductor multiple-output converter has no special requirements.ChapterⅢfirst analyzes the four output single-inductor converter slip coupling. And then study a general multi-input multi-output (MIMO) system control method. To simplify the system, this paper uses small-signal Analysis when the state is approximate to steady the steady-state to building a first-order constant coefficient matrix transfer function, and then uses this inverse matrix of the constant coefficient matrix as the compensation function of the single-inductor multiple-output DC-DC converter.Chapter IV analyzes the influence of the body diode of the MOS transistor for the single-inductor multiple-output DC-DC converters, and then designs a special PMOS transistor which bulk can be controlled to connect with source or drain of the PMOS, last explains the whole digital control system implementation.Chapter V is mixed signal simulation. The simulation results well verify some of the derivation in the second chapter and prove that the control method of the inverse matrix of the transfer functions to reduce coupling between the output has good results.