自激式LLC谐振变换器

LLC谐振变换器可以在全负载范围内实现开关管的零电压开关和二次侧整流二极管的零电流开关,变换效率高。当它工作在谐振频率时,输出电压与负载无关。根据此特点,提出一种LLC谐振变换器的自激驱动方法,采用电流互感器并联电感的方式检测谐振电感电流,从而获得开关管的驱动信号,为了提高开关速度,对驱动电路进行了进一步的改进。针对启动电流过冲的问题,采用一种改进的LLC谐振变换器拓扑。该变换器适用于对输出电压精度要求不高的应用场合,相对于采用专用控制芯片的控制方式,自激驱动方法还具有成本低和体积小的优点。

A Self-Oscillating LLC Resonant Converter

The LLC resonant converter can realize zero-voltage-switching for the switches and zero-current-switching for the rectifier diodes over the full load range,thus a high efficiency is achieved.The output voltage is independent of the load when LLC resonant converter operates at the resonant frequency.Based on this characteristic,this paper proposes a self-oscillating drive circuit for LLC resonant converter.The driving signals of the switches are obtained by the current transformer parallel with a inductor,which is used to sense the resonant inductor current,and the driving circuit is improved to speed up switching.For restraining the current overshoot during the start up period,an improved LLC resonant converter topology is used.The self-oscillating LLC resonant converter has the advantages of reduced cost and size compared with the converter with specific control chip,and it is suitable for the applications where the regulation of the output voltage is not strictly required.