RE: Flybacks from the Ground Up - Part 5: Going Back to Basics & Getting More Than I Bargained For

DAB — Sun, 21 Jan 2024 20:39:08 GMT

Good update Gough.

RE: Flybacks from the Ground Up - Part 5: Going Back to Basics & Getting More Than I Bargained For

jc2048 — Sat, 20 Jan 2024 20:29:46 GMT

The simplified circuits in textbooks are to illustrate the principles. You generally need regulation from the loop control. (I don't think that would apply in quite the same way to inserting a transformer into a buck switching circuit, which I think might be stable, though you'd still want regulation to account for external changes. But I don't know much about that approach, so don't quote me on that.)

Think of the whole thing as a kind of charge pump. Each cycle you pump charge into the output capacitor. For a fixed PWM ratio, unless there is a load constantly removing the charge, the voltage keeps going up. There is one point where your set-up balances and that is where the charge delivered by a particular PWM ratio matches that taken by your load resistor over the whole cycle. That may be happening here or you might be regulating by limiting: if you look closer, it's possible that the output voltage has reached the point where the MOSFET parasitic diode is then avalanching on the primary and stealing the energy away from the secondary - if you put the MOSFET on a good heatsink, you could look at that happening in more detail.

RE: Flybacks from the Ground Up - Part 5: Going Back to Basics & Getting More Than I Bargained For

balajivan1995 — Sat, 20 Jan 2024 15:35:20 GMT

Even though I don't understand most of the bits, your blogs are always a treat to read.