| Power converter is an important part of realizing electrical energy conversion. Its core part is switch. Switches existed voltage and current spikes at the time of turn-on and turn-off.Thus, this caused a series of problems, such as switching losses and EMI. Higher switch frequency and more serious problems. So how to solve these problems is of importance for the realization of high frequency in power converter.High frequency loss on power converter hampered the improvement of operating frequency. Through consulting literature materials, it is found that the efficient approach to solve switching dissipation is to use soft switching technique. Soft switching technique, that is switches complete turn-on or turn-off when zero voltage or zero current state. These damages can be limited or avoided.First, four kinds of soft switching circuit were analyzed. Quasi-resonant circuit, resonant DC link, phase-shifted full-bridge Zero-Voltage Switching PWM circuit and Zero-Voltage Transition PWM circuit included. Study on the application of soft switching units in typical power converters. Phase-shifting full-bridge is selected as the study object. Connecting parallel capacitor to the leading-leg, diodes in series with the lagging-leg. In the circuit topology, using with enhanced PWM control policy to adjust the turn-on time of switch.Which realizes Zero-Voltage Switching for the leading leg and Zero-Current Switching for the lagging leg.Then, based on the requirement of the converter, components are calculated in details,every single part of the function modules are designed. Its simulation analysis is made by Saber software, rationality of method of parameter design is validated.Finally, on the base of detail analysis and digital simulation of this converter work,creating the experiment platform based on the circuit topology. The results of simulation and practical application prove that the converter has fine soft-switch effect and strong restraint function to the voltage and current spikes. |
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