Analysis of leakage-inductance effect in a flyback DC-DC converter using time keeping control

Flyback DC-DC converter is often used as power supply for many electronic systems because of circuit simplicity. We have already presented novel flyback DC-DC converter with improved stability (time keeping controlled flyback converter) by using the technique of keeping inductor current constant (H.Terashi, et al.). This converter behaves as like forward converter without RHPZ (Right Half Plane Zero), therefore the frequency bandwidth of open-loop transfer function from duty ratio to output voltage is wider than conventional flyback converter due to disappearing of RHPZ. We report the static and dynamic analysis about this novel flyback converter with leakage inductance, which become larger in case of a few turn of secondary winding especially. The analysis method is selected with state space averaging method because of obtaining the symbolical solution. The number of state is 5 including the period regarding leakage inductances of primary and secondary stages. According to the results the theoretical data with state space averaging method agree with the experimental one and also the theoretical date with sampled-data method well. And it is confirmed that the leakage inductances act as an equivalent resistance and that static load regulation is deteriorated, but the dynamic response is smoothed due to the increased dumping factor.