Designing the voltage feedback loop (refer to Section 3.9)
The voltage feedback loop must be isolated from the input voltage line and the
control IC. An optoisolator must be used. To minimize the drift effect of the
optoisolator an error amplifier is desired on the secondary side. A TL431CP
does this job nicely. The topology of the feedback circuitry is shown in
Figure 3–70.
To improve the effects of poor output cross-regulation, sensing some current
from each positive output greatly improves the behavior of each output in
response to changes in individual loads.
The design of this section begins at the control IC. It is decided to bypass the
error amplifier ...
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