PI-DDS频率跟踪技术在超声电源中的应用

Design of Ultrasonic Power Based on PI-DDS Frequency-tracking Strategy

针对传统超声电源采用模拟锁相电路进行频率跟踪时,存在锁相范围窄、元器件一致性差、在负载突变时易失锁等缺点。在此提出了一种将数字PI控制器和数字频率直接合成(DDS)技术相结合的复合控制方法,对其设计方法、工作原理进行了阐述。实验结果表明,该方法可很好地跟踪负载谐振的变化,使开关器件工作在软开关状态,显著地减小了功率器件的开关损耗,提高了电源效率。

Traditional frequency-tracking technique of ultrasonic power often adopts analog phase-locked loop circuit.But it has some defectss,uch as the narrow locked-in range,poor consistency of components and the tendency to lose phase-locked with a sudden change in load.Thereforet,his paper proposes a composed control strategy which combines digital PI controller with direct digital synthesis（DDS）technique,and the working principle and design method are given.The ex-perimental results show that the ultrasonic power using PI-DDS control strategy has good characteristics of frequency-tracking.For this reasont,he inverter works in the soft-switching statuss,ignificantly reduces switching losses and improves the efficiency of the power supply.