Flyback leakage inductance in sandwich winding

[ivan_mateo]

Hi everyone,

From my knowledge, when the primary winding split to two winding and if secondary windinds wound between these two primary, leakage inductance needs to decrease and parasit capacitance needs to increase. But when I tried to wound my flyback transformer, the result is oppoiste, leakage is increased and par. cap. is decrease. The transforformer has multiple output and input 24v and outputs 5V, 16V, +-15V and 24 volt. Primary windings 8 turn.

 

[FvM]

From my knowledge, when the primary winding split to two winding and if secondary windinds wound between these two primary, leakage inductance needs to decrease and parasit capacitance needs to increase.

Generally true, quatitative analysis can be found in literature, e.g. the Properties of Windings chapter in Snelling Soft Ferrites. The effect can be also analyzed in FEM modelling.

In your setup, each secondary winding has its specific leakage inductance, depending on the winding order. The same with capacitance. To answer specifically, we need to know the geometries of compared transformers.

 

[opampsmoker]

Do both primary halves extend evenly across the whole bobbin width?
Did you wind a "non-sandwiched" comparison transformer, or are you just postulating>

 

[ivan_mateo]

Do both primary halves extend evenly across the whole bobbin width?
Did you wind a "non-sandwiched" comparison transformer, or are you just postulating>

No, when primary split two winding, it not extend across whole bobbin width. It covers only half of widht.

 

[opampsmoker]

You need to have full layers to get good coupling