Series-Input-Connected Flyback-Forward Converter with Enlarged Duty Cycle

In this paper, a structure consisting of combination of a flyback and a forward converter capable of making the power switch conduct at wide duty cycle, is presented. The configuration suggested employs sub-converters having their inputs combined in series with each other. In a forward converter, the maximum duty cycle by conventional manner becomes insufficient to utilize the isolation transformer, optimally. Under such condition, it becomes more important to extend the duty cycle, further. Bearing its importance and need in mind, present scheme is employed. By combining a forward with a flyback sub-converter in such a way that the inputs to both the sub- converters are in series, very wide switch duty cycle is obtained. The sub-converters are named as modules, and these are combined with their inputs connected in series with each other. A forward sub-converter is essentially a main module while flyback module is treated as auxiliary module. The configuration consisting of two modules is proposed and examined for the establishment of the results. The duty cycle for the switch has been extended to the expected level. For the validation of the performance, a 24 W, 24 V converter is presented.