hello every one can anybody tell me what is the purpose of Vr1 and D5 in the circuit and why they are connected in this pattern and how it works in smps design for +12V, 5v with 1A output
and what is the purpose of TNY ic and what is the purpose of optocoupler to trigger the TNY ic
here is the attachment
A bipolar transistor requires some sort of saturation-prevention circuit (i.e. Baker Clamps) to reduce the storage time. That increases static loses, and nevertheless the switching will never be as fast as a Mosfet.
Google or look up Youtube videos on the technique.
Your top post, you will ahve seen by now, shows diodes needed to prevent fet overvoltage due to leakage inductance discharging into the drain node. Its called a "Primary clamp"
Above power supply is not an ASIC design because power supply is a fly back topology for different application but the IC TNY27 can be call as ASIC design because this IC specifically designed for fly back converter