| The isolated DC-DC converter can realize the transformation of voltage level. And the bi-directional DC-DC converter is able to realize the bi-directional flow of energy. With more and more widespread applications of the battery and super capacitor on the fields of rail transport, new energy and other fields, the requirements for the efficient bi-directional isolated charger are urgent increasingly. Cosidering these, this paper performed in-depth study aiming at the basic theory, design method and control strategy of isolated phase shifted full bridge bi-directional DC-DC converter.Firstly, the working principles and control modes of the isolated full-bridge phase-shift bi-directional DC-DC converter under two charge-discharge modes were elaborated. Then, the corresponding operation situations of this bi-directional DC-DC converter were discussed, such as soft realization conditions, duty-cycle loss problems and rectifying circuit commutation situation under the charging mode. Meanwhile, the synchronous rectifier, and switch tube’s voltage spike problems which is caused by transformer leakage inductance under the discharging mode have been also introduced.Secondly, aiming at the existing problems of full-bridge phase-shift bi-directional DC-DC converter during charge and discharge mode, the method of using auxiliary current source networks to achieve soft switching and cancelling resonant inductor in the charging mode were presented. And lots of simulations were performed to verificate the feasibility of this method.Thirdly, based on the technical indicators determined by the existing experimental conditions, paremater calculation and device selection were performed for the each elements of the main circuits and auxiliary circuits in bi-directional DC-DC converter.The converter’s main circuit includes high-frequency transformer, energy storage filtering inductor, auxiliary inductance and capacitance, output filtering capacitor, power switchs, etc. The converter’s auxiliary circuit includes sampling circuit, control circuit, driving circuit and protection circuit.Finally, on the basis of the theoretical analysis of the charging and discharging mode, an experimental platform of an 500W isolated full-bridge phase-shift bi-directional DC-DC converter was set up. And the corresponding experiments were carried out to verify the effectiveness of theoretical analysis. The experiment results show that the soft switch can be achieved well during the charging mode, and the voltage spike of switch can be solved during the discharge mode. |
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