Development Of 600W 28VDC/360VDC Push-pull Forward Converter And Research On Bias-magnetic

It is required to research a 600W 28VDC/360VDC converter as prepositive set of Static inverter in a certain project. Based on comparison of different DC/DC converter, Push-Pull Forward converter (PPF) is selected as main system prototype.The analysis of PPF's operation principle is introduced in detail in this paper. Further more, the effect on the circuit operation is also analysed, which caused by clamping capacitance and different transformer leakage inductance value.Comparing with usual Push-Pull converter, the bias-magnetic can be retrained due to the clamping capacitance. But bias-magnetic can not be avoided. In this paper, the bias-magnetic of PPFC and the parameters effect on the bias-magnetic are all studied. Firstly, the bias-magnetic principle of ambipolar converter and some basic relations are analysed under two different conditions (different Von and different Ton). And that the bias-magnetic is direct ratio with relative V-S difference, and is inverse ratio with circuit resistance. Then a thorough analysis to the bias-magnetic of PPFC is made. The retraining effects of the main parameters(include clamping capacitance C, output filter inductor Lf , load R, the leakage inductor Ls and source winding resistance r) are studied under the conditions of different Von ,different Ton and different winding parameters . Then a conclusion can be drew , that the smaller Lf and the bigger r are, the better the bias-magnetic is restrained and C has a best value to retrain the bias-magnetic. This conclusion is useful to optimize the converter. Then it is proposed that the effects of retraining bias-magnetic and reducing the voltage stress of MOSFET should be both considered in selecting the clamping capacitance.At last, the prototype of 600W 28VDC/360VDC converter is designed and implemented, the efficiency of which is 90%. Aiming at the excessive high peak voltage, a simple lossless solution is adopted and a good effect is gained. Base on this, the bias-magnetic experiment of PPF converter is carried out.