| This paper conducts detailed analysis on the main shortcomings of the traditional forward converter, such as hard switching problem and surge voltage of power tubes, provides improvement methods aiming to promote the performance.This novel converter, ZVS interleaved step-up forward converter with auxiliary network, includes a three-winding transformer; circuits on the primary side of transformer are interleaved to decrease the output voltage ripple; LC branch and active-clamping network will provide enough energy to help power MOSFETs to achieve ZVS, absorb the voltage peak and lower the voltage stress; the filter inductance with center tap will help rectifier diodes to eliminate voltage peak.This article analyzes the working modes of the power circuit in detail, which also provides the basis of the necessary conditions of ZVS. Equivalent model of converter is also established to set up exact discrete-time model. By MATLAB simulation tool, the chaos analysis is executed and bifurcation diagrams are acquired, which will show the critical point of the chaos phenomenon of system to direct the choice of parameter of the system.TMS320F2812 DSP chip is selected as the control core of the control circuit, which will accomplish the generation of PWM driving signal, PI close-loop control and power protection. This paper discusses the circuits of driving, protection and close-loop control in detail, and expounds the flow chart of software design.The PSpice software is used to simulate the main circuit, which preliminary verifies the reasonability of theoretical analysis and parameter design. Finally, a 48V/5A converter prototype is manufactured. Main electric waveforms and technical index are acquired, which show the result that, the proposed converter can achieve ZVS, the voltage peak and surge of transformer are restrained, the rectifier diodes can naturally commutate eliminating peak voltage and the indexes are consistent with expectation. The novel converter attains the initial target. |
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