ABSTRACT
The flyback power stage is a popular choice for single and multiple output dc-to-dc converters at power
levels of 150 Watts or less. Without the output inductor required in buck derived topologies, such as the
forward or push-pull converter, the component count and cost are reduced. This application note will review
the design procedure for the power stage and control electronics of a flyback converter. In these isolated
converters, the error signal from the secondary still needs to cross the isolation boundary to achieve
regulation. By using the UC3965 Precision Reference with Low Offset Error Amplifier on the secondary
side to drive an optocoupler and the UCC3809 Economy Primary Side Controller on the primary side, a
simple and low cost 50 Watt isolated power supply is realized.
