The TNY253 and TNY254 switch at 44 kHz to minimize EMI and to allow a simple snubber clamp to limit DRAIN spike voltage. At the same time, they allow use of low cost EE16 core transformers to deliver up to 5 W. The TNY253 is identical to the TNY254 except for its lower current limit,which reduces output short-circuit current for applications under 2.5 W. TNY255 uses higher switching rate of 130 kHz to deliver up to 10 W from the same low cost EE16 core for applications such as PC standby supply. An EE13 or EF13 core with safety spaced bobbin can be used for applications under 2.5 W. Absence of a bias winding eliminates the need for taping/margins in most applications,when triple insulated wire is used for the secondary. This simplifies the transformer construction and reduces cost.