I am designing a flyback converter based on the UC3844 chip. As a starting point, I went through an eval board that is given in the Microsemi website. The schematic of the design is as shown below -
The document is eval board doc Now, the isolation transformer has an auxillary winding, which can be used to power the IC.
If the auxxiliary winding s used to power the IC, why use R19 ? How is the auxilliary winding serving any purpose here ?