Series-Input-Connected Structure for Extended Duty Cycle in Forward Converter

Abstract

A wide duty cycle results in large output voltage. More than one converters are combined in series at input side, due to which, the total power delivered to the output side is the sum of powers due to individual converter. This results in enhancement in power handling capability of the structures. This paper describes a family of converters capable of rendering the power switch conduct at wide duty cycle. A wide duty cycle is necessary for battery charging application where its value should be close to unity. The proposed configuration employs different sub-converters having their inputs combined in series with each other. In many cases, especially in a forward converter, the upper limit of duty cycle is required to be as wide as possible. But by conventional methods this can not exceed half of the total which is not sufficient to utilize the power switch, optimally. Under such extreme conditions, it is necessary to extend the duty cycle beyond half. In the present scheme, for this purpose, a forward converter, termed as main module, and other converter(s), termed as auxiliary module(s), is (are) combined in series. The outputs of all modules in the configuration are combined in parallel. Expected combination of converters is presented and for the validation of the performance of the proposed scheme, the results are provided for three module configuration. The switch duty cycle is presented for a converter of 24 W, 24V rating.