Discontinuous Current Mode Operation of Two-Phase Interleaved Boost Dc-dc Converter with Coupled-inductor

Abstract

A two-phase interleaved boost dc-dc converter with an inversely coupled inductor in a discontinuous current mode (DCM) is analyzed by the equivalent inductance method. Coupling effects on the circuit statuses are described, and a forced conduction of the power diode or reverse-paralleled diode of MOSFET is caused by coupling. As a result, three major circuit statuses are figured out according to the physical relationship between the input-output voltage ratio and the coupling-coefficient, and their condition boundaries are used to classify the DCM operation modes. Then, considering the load  (duty cycle) variation, ten DCM operation modes are comprehensively analyzed. The analysis can be used to make an easy prediction of operation modes, and extended to the analysis of an interleaved buck converter or buck/boost bidirectional converter with a coupled-inductor in DCM. At last, a 300 W prototype is built and tested in the lab to verify the analysis. 

PROPOSED  SYSTEM:

This paper analyzed the DCM operation modes of a two-phase interleaved boost dc-dc converter with a coupled-inductor. First, based on a qualitative and quantitative analysis of the equivalent inductance of the winding current, the circuit statuses are classified into three major conditions, which just depend on the physical relations of the coupling-coefficient and the input-output voltage ratio. Then, ten DCM operation modes are described in detail considering the variation of load (duty cycle), which structure all the possible operation modes in a map. The corresponding boundary of each operation mode is presented for the prediction of the converter operation. The analysis and classification can also be extended to an interleaved buck converter or buck/boost bidirectional converter with a coupled-inductor in DCM.

EXISTING SYSTEM:

Due to the discontinuous current in each winding and  mutual effects caused by the coupled-inductor in multiple phases, DCM produces more circuit statuses in one switching cycle than CCM, and it means more operation modes under different conditions. Some publications have examined behaviors and operation modes of the multi-phase interleaved boost converter with a coupled inductor in DCM. Reference focuses on the current ringing of a multi-phase interleaved boost dc-dc converter in DCM and has a limited analysis of its operation modes. Reference analyzes some key dc performances of an interleaved boost dc-dc converter with a coupled-inductor in three DCM and two CCM operation modes, separately, including dc voltage gain, input current ripple, inductor current ripple and output voltage ripple. Reference provides a more comprehensive analysis of DCM operation modes for a two-phase interleaved boost converter with a discrete or coupled-inductor, of which ten DCM operation modes and their boundary conditions are analyzed. However, the operation modes are presented directly with a flowchart, and one possible operation mode occurred under a relatively weak coupling condition (Mode 5 as shown in this paper) is missing. Reference analyzes the operation modes of dual interleaved buck and boost converters with an inter-phase transformer, and presents eight converter sub-circuits and seven DCM major operation regions according to the relationship of the voltage ratio against to the duty cycle. However, the operation modes are classified according to circuit analysis and simulations, and their relationship are rarely explained. Although available researches have presented a mass of operation modes and their  boundary conditions, the physical reasons why a converter has those modes and what kind of relationship those modes have are not described clearly enough. Moreover, most analysis is based on a strong coupled inductor, so some operation modes under a relatively weak coupling condition may be missed

CONCLUSION

The two-phase interleaved boost dc-dc converter with coupled-inductors is analyzed in detail based on the fundamental circuit statuses. From the analysis of equivalent  inductances of DCM operation modes, it is found out that  under specific conditions determined by the relations between the input-output voltage ratio and the coupling-coefficient, the sign of the equivalent inductance is changed and the power diode or reverse-paralleled diode will conducts under force. This coupling effects on the circuit statuses are independent of the converter load (duty cycle), and their condition boundaries can be used to classify the DCM operation modes. As a result, three major operation regions are introduced, and ten DCM operation modes as well as their key waveforms and boundary conditions under varied input-output voltage ratios and loads (duty cycles) are analyzed comprehensively. Since the classification was based on the physical parameters of the converter and its operation conditions, the operation mode under a given condition can be predicted easily. The analysis can also be extended directly to the interleaved buck converter with coupled-inductors in DCM.

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