Why no Bode Plots or stability analysis with SMPS design tool?

[grizedale]

Hello,

The following offline SMPS design tool offers to do a design of an offline flyback, when the specifications are input by the user....

Power Supply WebDesigner Design Tool - Flyback Design & Simulation - In Minutes at No Expense | Fairchild Semiconductor


...but there is no mention of the phase or gain margin of the designed SMPS, so what is the point of it.?

What use is an SMPS if you do not know if its going to have sufficient gain and phase margins?

 

[mtwieg]

Most people who want tools are more concerned with things like transformer design, efficiency, ripple, etc... open loop parameters, basically. Most people don't think of stability as anything other than a yes/no question, so this program probably just spits out a foolproof stable feedback loop. Most people wouldn't be interested in bode plots or phase margins or whatever.

As for why, keep in mind that these manufacturer-provided programs generally exist to draw customers for the products they sell. You have to buy the hardware from them, but not the stability analysis, so they have no incentive to provide it.

 

[atripathi]

I agree with MTWIEG, often feedback loop design is considered independent of SMPS design (read power circuit design). Also feedback loop design is not that straight forward.

 

[grizedale]

i see what you mean but powerint.com offer bode plots with their equivalent tool.

Feedback loop is not that difficult once you have the correct expression for the transfer functions.

...once you do have those functions, its simply a case of adding Error amplifier transfer function to Power stage and modulator transfer function, and youve done the best part of it........and that is not difficult.....just check for correct gain and phase margin

The difficult bit is deriving the transfer function for the topology.....but standard functions are available...