Control Strategy Of Dynamic Matching Transducer To Ultrasonic Power Supply

Ultrasonic power supply is widely used in manufacture, diagnoses and washing area. And ultrasonic transducer is a device to convert electronic power to mechanical oscillation power. In order to make the power supply have the highest efficiency, an inductance should be used to match the transducer for its capacitive load. Series-wound matching is widely used because of its good performance, however, when resonance frequency excursion caused by environment temperature transformation or equipment aging happens, the system will get out of resonate state. The traditional solution is frequency tracking but the matching inductance isn't working at resonance frequency which will cause power lost and over heated,at last results in its limited use in industry. As a conclusion that in order to have a high efficiency, only change working frequency of the inverter is not enough, the matching inductance value should be changed according to the working frequency too.To eliminate the shortcomings due to choosing a fixed resonant frequency for matching inductance parameters of an ultrasonic transducer, the modeling as well as theoretic analysis for the dynamic matching relations between inductance parameters and coupled frequency are introduced in this paper. After some analysis and comparison, an alterable inductance based on flux control is chosen to be the matching inductance.Applying the model and the coupled resonance theory for choosing matching inductance dynamically, an experimental inverter based on DSP TMS320F2812 used in the ultrasonic power supply is designed. The results of experiments and emulations have shown that the inductance value can be changed linearly and continuously, coordinated with DPLL and PS-PWM, the novel matching method mentioned above is provided with advantages. Compared to the traditional matching method with a fixed frequency, the new ultrasonic power can always work at high outputting current.