软开关DC/AC变换器原理分析及谐振环节参数设计

On Better Design of LongLife SoftSwitching DC/AC Converters

导出了ＤＣ／ＡＣ变换器谐振直流环节电压波形可靠回零所依赖的最小初始条件和谐振开关所需的最小导通时间ｔ１ｍｉｎ。证明了电机负载电感Ｌ２及电阻Ｒ２对系统谐振特性影响较小，可用一恒流源代替的结论。讨论了谐振频率及谐振参数的选取方法，给出了谐振频率ω，谐振参数Ｌ、Ｃ，谐振电感初始预充电电流ＩＬ０及谐振峰值电压ＶＣｍａｘ之间的关系曲线。

Two factors tend to lower the life of DC/AC converters: (1) high transient voltage, (2) high switching frequency. Softswitching DC/AC converters overcome conspicuously these two shortcomings of ordinary DC/AC converters. Our design attempts to prolong significantly the life of longlife softswitching DC/AC converter. Fig.1 shows schematically the equivalent circuit of our design. The inverse bridge is at I x and our design allows its voltage to be kept very close to zero at instant of switchon and instant of switchoff and reach the nominal voltage of 540 V during operation. Thus the permissible high frequency of the converter can be raised from 10 kHz to 40 kHz for obtaining still better performance. Simulation results given in Fig.4 show that a relatively large value of inductance L should be selected for resonant inductor L so that the resonant peak voltage V C max can be decreased and the efficiency of the softswitching converter can be increased.