How to add feedback for all outputs?

[Zaim]

HI ,

I have working on switched mode power supply design with wide input range (30-300) and I am using on the design many ST components.

I have make my first design using eDesignSuite from ST using Viper37 IC, but I ordered only 2 IC and after that I couldn't find any Viper37 any more in any market, for that I used another IC with separately Moseft outside.

When I designed multiple outputs smps on eDesignSuite it gives me only feedback from only one output as shown on the schematic below.

After make the PCB of the design I test in the lab, and it works very well on no load condition but when I add load (resistors in parallel), the voltage of all the output voltage are decreasing.

I have multiple output from the transformer with only one feedback for 24v output, I think the problem is having only one feedback for all systems for that it is not steady.

I attached my circuit here, may you please show me how can I add feedback for all of my outputs ?

sincerely,

ZAIM

[Peter BENSCH · Accepted solution]

What should the controller be based on when there are several independent variables?

Such a design is definitely a challenge because the overall performance depends on the parameters of the individual components. Here, the transformer is particularly important, where not only the leakage inductance is important, but whose coupling of the individual windings plays a major role. 

There are approaches to link the output voltages in such a way that a common control signal is obtained, but this is always fraught with compromises.

So you will have to deal with the techniques of flyback converters, especially the parameters of the transformers, the eDesignSuite can only support you because of the complexity.

However, if you have optimised the transformer coupling in such a way that the unregulated output voltages no longer fluctuate quite so much, you can finally supplement your design in such a way that the output voltages either lie within a tolerable range or are readjusted with further voltage regulators.

Regards

/Peter