Analysis and Design of an Input-Series Two-Transistor Forward Converter for High-Input Voltage Multiple-Output Applications
Abstract
In this paper, an input-series two-transistor forward converter is proposed and investigated, which is aiming at the high-input voltage multiple-output applications. In this converter, all of the switches are operating synchronously, and the input voltage sharing (IVS) of each series-module is achieved automatically by the coupling of primary windings of the common forward integrated transformer. The active IVS processes are analyzed based on the model of the forward integrated transformer. Through the influence analysis when the mismatches in various series-modules are considered, design principles of the key parameters in each series-module are discussed to suppress the input voltage difference. Finally, a 96W laboratory-made prototype composed of two forward series-modules is built, and the feasibility of the proposed method and the theoretical analysis are verified by the experimental results.
EXISTING SYSTEM:
For the input-series converters, the most important issues are to ensure their input voltage sharing (IVS). To achieve IVS, many special control strategies are proposed and introduced in the input-series converters, which have been the most widely investigated. However, in these input-series converters, a dedicated IVS controller must be used, which results in the increasing complexity of the associated control and the decreasing reliability of the whole system. The multiple-output converters are usually designed for the medium or low power applications, therefore, the simplicity and high-reliability of the whole system are very important. To simplify the circuit system, some input-series converters without any special IVS controller have been investigated. In these converters, the basic common-duty-ratio control strategy is adopted, and IVS can be achieved automatically. For example, a forward converter is implemented in, the flyback converters are investigated, and the full-bridge converters are presented. However, due to the connection structure in their output circuits, these converters are not suitable for the multiple-output applications. The input-series converters with a common integrated transformer have also been presented, which can be used in the multiple-output applications. The typical investigations are as follows.
PROPOSED SYSTEM:
In this paper, an input-series multiple-output two-transistor forward converter is proposed and investigated based on the structure. The proposed converter is suitable for the high-input voltage multiple-output applications, which is the same as the converter. However, the active IVS of the proposed converter is achieved by the coupling of each primary winding of the forward integrated transformer, which occurs both in the stages when the switches are turning on and off. Therefore, compared to the converter, the active IVS can be achieved both in the stages when the switches are turning on and off. Furthermore, in the proposed converter, the voltage of each switch is equal to the input voltage of each series-module, so voltage balancing of the switches can also be achieved, which is another advantage compared to the converter. The rest of this paper is organized as follows. In section II, the proposed converter is introduced, and its active IVS processes when the switches are turning on and off are analyzed respectively. In section III, the input voltage differences are analyzed when the tolerance features of the key parameters are considered and when the series-modules are operating asynchronously, from which design principles of the key parameters are discussed
CONCLUSION
In this paper, aiming at the high-input voltage multiple-output applications, an input-series two-transistor forward converter is proposed and investigated. In this converter, a common forward integrated transformer is adopted, and all of the switches are operating synchronously. Firstly, the active IVS processes are analyzed both in the stage when the switches are turning on and in the stage when the switches are turning off. The analysis shows that when the input voltage difference appears, active IVS of this converter can be achieved by the coupling of primary windings of the forward integrated transformer, and IVS can be achieved more speedily as the equivalent leakage inductance of the forward integrated transformer decreases. Secondly, the input voltage differences are discussed in the real conditions, and it shows that the input voltage differences will increase as the differences in various series-modules increase, which can be improved when the values of the equivalent excitation inductance and the input filter capacitor increase. Therefore, design principles of key parameters are obtained. Finally, the feasibility and validity of the proposed converter and the theoretical analysis are verified by the experimental results obtained from a 96W laboratory-made prototype.
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