Flyback Converter 100% duty cycle

The peak input current of the discontinuous flyback converter, with a fixed duty cycle and fixed frequency, is defined by... 

The forward converter (Fig. 10.82) is a variation of the buck converter. It is usually operated in the CCM to reduce the peak currents and does not have the stabihty problem of the flyback converter. The HF transformer transfers energy directly to the output with very small stored energy. The output capacitor size and peak current rating are smaller than they are for the flyback. A reset windingis required to remove the stored energy in the transformer. The maximum duty cycle is about 0.45, which limits the control range. This topology is used for power levels up to about 1 kW. 

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