Voltage/Current Sensing Technique Cuts Flyback Converter Costs

摘要

In usb and low-power adapters, resonant flyback converters can be utilized for the design, without the need of a regulator opto feedback network by sensing the output through the transformer turns ratio. In these cost-sensitive applications, removing this feedback circuitry can reduce the cost of the design. In low-power USB and offline wall adapters, quasi-resonant and discontinuous current mode flyback converter topologies are a popular choice due to their low parts count and relatively low cost. However, to increase profitably in the adapter market, power supply manufacturers continuously are working on ways to reduce design cost. This article discusses a voltage and current sensing technique (Fig. 1) that removes the need for an optoisolator and an adjustable precision shunt regulator like the TL431 feedback network.