Research On Active-clamping ZVZCS Interleaved Step-upforward Converter

With the improvement of science and technology, the power electric equipmentsare developing towards miniaturization, lightweight and high power level. Interleavedforward converter is widely used in industrial applications due to its high power level，low ripple and high reliability. But the problems of hardly achieving soft-switching andoscillation in the traditional circuit restrict its further development. For the typicalproblems, this paper has improvements and design in the topology to improveconverters’performance, based on the step-up interleaved forward converter.The converter proposed in this paper uses an active-clamping net to limit voltageovershoot of the transformer’s primary side and a filter with a center-tapped wind tolimit voltage shocks and duty lost of the transformer’s second side. Developing achopper control strategy to adjust output voltage. Combining simulation and theoreticalanalysis completes the work of modal analysis.Using Pspice do the simulation to obtainthe selection of the prototype’s components to ensure that the selected device’s stress isin a allowable range. The paper establishes a accurate discrete model for the system anduses chaos theory analyze the mathematical model,then combines Matlab simulationobserve the chaos phenomena in the course of different parameters and join guidance ofthe prototype’s components, to make sure the converter can operate in a steady state.The prototype system completes a series of software design including PWMsignals, the output voltage’s PI closed-loop control and a series of hardware circuitsincluding drive circuits,over-voltage and under-voltage detection, input over-currentdetection and protection circuits based on TMS320F2812. The combination of hardwareand software can ensure the converter has higher reliability and better performance.A48V/4A80kHz experimental prototype is designed and produced. Then the paperfinishes work of correcting the prototype’s parameters and testing hardware andsoftware. The test results show that: When the improved converter works, overshoot andvoltage shocks in the original side and the secondary side of the high frequencytransformer have been suppressed effectively; The converter achieves to idealsoft-switch and a smaller ripple factor. These all prove that the active-clamping ZVZCSinterleaved forward converter has significant advantages comparing to the traditionstructure and the overall performance has been improved.