The design of flyback converters is quite a demanding task that requires SMPS engineers to cope with several problem areas such as magnetics, control loop analysis, power devices, as well as regulations concerning safety, EMC and the emerging standby consumption requirements. Lots of variable are involved and complex tradeoffs are necessary to meet the goal. In this scenario, the high-voltage monolithic switchers of the L6590 family greatly simplify the task and, at the same time, allow to build robust and cost-effective low-power systems. In this application note, after a review of flyback topology, a step-by-step design procedure of an offline single-output flyback converter will be outlined. As an example, the design of the test board will be carried out in details.