Hi,

Why does Power Integrations not do a Half Bridge controller instead of HiperTFS?....Half bridge can give you a higher duty cycle, higher even than the extended duty of the HyperTFS..

Half bridge only has to switch half the Bus. Half Bridge is better at refreshing the bootstrap capacitor. Half bridge transformer can be smaller than Two Transistor Forward transformer.

Why did Power integrations pick Two transistor forward over Half Bridge?

Was it the case of going into peak current mode when overloaded, and then unbalancing the rail splitter capacitors?