When buck boost converter is modified as flyback converter it's not working

[vidhz]

Hi

I tried modifying buck boost converter in MATLAB as flyback converter referring to the book Fundamentals of power electronics by Robert.W.Erickson.
But it is not giving expected output as per the duty ratio. The output voltage depends only on transformer. Please help me with this.

Thank You

 

[tantudaisu]

If output depends only on transformer turns ratio, it means there are no feedback regulations in your simulation circuit.

Primary wiring current ramps up until reaches comparator's (current sense) threshold causing mosfet transistor to turn off. Then voltage on the secondary wiring goes as high as turn ratio allows. Circuit is not controlled.

- tantudaisu -

 

[BradtheRad]

1.

A flyback operates best at a 50 percent duty cycle (or thereabouts). You can adjust this, but within limits.

2.

Even if the transformer primary has the same Henry value as the single coil, they need to be operated at different frequencies.

3.

While your project is in the development stage, try using a full-wave diode bridge at the secondary. This will take advantage of all current flows, in either direction.

Later you can substitute a single diode, when you see which orientation yields maximum current.

 

[vidhz]

I am using PI controller and PWM switching to control it but stil its not under control..How can I control output as per reference??

- - - Updated - - -

Actually I modified a soft switching buck boost converter as flyback converter. Its not giving expected output for duty ratio in open loop. Its not under control in closed loop also.

- - - Updated - - -

Actually I modified a soft switching buck boost converter as flyback converter. Its not giving expected output for duty ratio in open loop. Its not under control in closed loop also.