A Study On Combined DC-DC Converter With Naturally Sharing Voltage And Current

With the rapid development of the society and economics, the power system with high capacity, high power density and reliability are strongly desired. With the influence of such background, the combined converters appeared. The problems of sharing voltage and current are usually solved through the current control method and voltage control method respectively. This problems result the reduction of the reliability and the increasing of the cost.In certain conditions, the combined converter can achieve naturally sharing of voltage and current by changing connection method or adopting coupled inductors. Some topology has characteristic of naturally sharing voltage or current without multi-loop control. The control loop of the converters is simple to design. The combined converter with naturally sharing voltage and current is simpler than traditional combined converter with multi-loop control. It has high reliability because sharing of voltage and current rely on the characteristics of the main circuit.This paper studies the input series output parallel (ISOP) combined converter, and pointed out that naturally sharing of output current can be achieved by input voltage sharing. In this paper, a simple control method named common-phase-shifted control is proposed for a phase-shifted full bridge ISOP converter. This control scheme is simple and reliable because no input voltage sharing loop is needed. Based on small signal average model, this paper drew a conclusion that voltage sharing between the two input capacitors can be achieved naturally when the converter working in continuous conduction mode(CCM). By analyzing averaged switch model, this paper point out main reasons which influence input-voltage disturbance. A prototype is build up and experimental results confirmed the theoretical analysis.This paper then studies the input parallel output parallel (IPOP) converters. It point out that paralleled converters can not achieve current sharing without current sharing loop. In this paper, a simple method named cross rectifier is proposed for a IPOP converter. It can be applied to half-bridge or full-bridge converter. Cross rectifier can achieve naturally sharing of current because difference of two models can be compensated by it. As an example, the working principle of half-bridge paralleled converter with cross rectifier is studied carefully. A prototype is build up and experimental results confirmed that naturally sharing of output current can be achieved by cross rectifier.