For a flyback SMPS, if the output [with feedback] is loaded more, the switching duty cycle goes up.
In this situation, what would happen to voltages on other outputs ?
(They remain constant I guess, but why?? Shouldn't they shoot up?)
Please explain.
Mike
siliconmike skrev:
Your un-regulated output will increase. The way to avoid this is to:
Stack the windings for better coupling (less leakage inductance). Wind =BD primary first, then all the secondaries and wind the last =BD primary winding last Stack the output diodes instead of the output windings Add a bleeder resistor to the un-regulated winding to pre-load the output Use a scheme to not regulate 100% on one winding, but use feedback from the summing of two windings instead
Regards
Klaus
Nope-- the flyback peak has to do with the magnetic field itself. To a reasonable approximation, this field is shared evenly by all windings, so when one drags down the voltage, they all drag down in ratio. :)
Leakage inductance, winding (and wiring) resistance and other effects contribute to reduce regulation by decoupling the windings from each other. If you want one winding better regulated than any other, add feedback to its output (use an op-amp and opto, if isolation is required). Otherwise, the usual route (which also allows full isolation) is to add an additional winding specifically to feed back voltage to the control chip.
Tim
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