The LM5157x/LM5158x device is a wide-input range, non-synchronous converter with an integrated power MOSFET. The commonly supported configurations include Boost, Flyback and SEPIC topologies. This report focuses on designing the LM5157x/LM5158x as a primary side regulated (PSR) flyback converter. The design procedure is generic on selecting suitable components of the PSR flyback converter for the given application specification. The LM5175EVM-FLY evaluation module is used as the example to illustrate the design procedure, and the circuit performance results are also presented in the LM5157EVM-FLY User's Guide. For typical applications the LM5157/58 Flyback Controller Quick Start Calculator can also be used to efficiently complete the calculations described in this report.
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The typical design procedures and calculations to implement an isolated nonsynchronous flyback controller operating in continuous conduction mode are presented in this report. The design example produce multiple output voltage rails for typical applications of the 3-phase inverter gate driver bias supplies. The converter can provide a regulated output of 10 V at 250 mA from an input of 8 V to 16 V, and three isolated and cross-regulated 20-V rails at 75 mA, 75 mA, and 150 mA, respectively.