A Bidirectional Voltage-Mode Controlled Converter for Power Distribution in a Low-Power Dual-Output Flyback Converter

The cross-regulation performance of a dual-output flyback converter can be improved by several approaches, but the voltage error on outputs under extreme load conditions is still difficult to mitigate with an effective method. In this article, an additional bidirectional converter is employed in an ac-dc dual-output flyback converter to improve the cross-regulation. Since the two secondary winding currents of the flyback converter can be distributed by the bidirectional converter, the proposed converter has the following properties: 1) the two output voltages are regulated well even under one output at full load and the other at no load; 2) the maximum load current for one output can be up to the sum of the two rated load currents when the other output is at no load; 3) the component current stress on the heavy-load path of the flyback converter is reduced, whereas the efficiency of the whole system is improved; 4) the specifications of the components used in the bidirectional converter only meet the amount of current to be transferred and the output voltages. The experimental results demonstrate that the proposed ac-dc dual-output converter exhibits effective output regulation under all extreme load conditions, even when the difference between the two load currents is up to twice the full load current.