Flyback Converter Control by Inner Supply Voltage Feedback Using Sigma-Delta Converter

This paper proposes a synchronous rectified flyback converter control using inner supply data transmission without optocoupler. Inner supply data transmission allows digital data to be sent from the secondary to the primary side without additional communication lines. Using this data transmission, direct voltage feedback is created without using optocoupler. In this system, inner supply data transmission is done using multiplexing mode of the flyback converter and sigma-delta converter is used to send the data in a continuous way. In order to maintain the bandwidth of the converter even in low bitrate, a dual loop control that utilizes both primary side sensing and inner supply data transmission is proposed. Here primary side sensing is used to keep the bandwidth of the controller high while data transmission is utilized to increase the accuracy of the controller. The experimental results are presented to verify the performance of the proposed system and controller.