Other Parts Discussed in Thread: UCC28704, UCC28C42
I’m working on the design of an offline flyback power supply generating ~140VDC and capable of supplying ~ 20mA of current. Efficiency is not a great concern and the output voltage doesn’t need to be too tightly regulated but I would like the solution to be small and simple. My first thought was to use a flyback controller with an internal FET (since it is low power) and primary side regulation to keep the component count down. The UCC28910/11 seemed to be a good fit but when I try to use this device in webench the output voltage is limited to 25V. Is this limitation intended because the VDS of the internal FET (700V) is not high enough to support the 140V output reflected back through the transformer?
Playing around with Webench some more I found that the only primary side regulation option that it would suggest for a 140V output is a UCC28704 which uses an external FET - Is the UCC28704 my best bet?