Digital resonant frequency tracking and constant current control for power ultrasonic system via hilbert and cascaded integrator comb filter

In this paper, we propose a Hilbert based resonant frequency tracking (RFT) and cascaded integrator comb (CIC) filter based constant current control for power ultrasonic generator to increase the phase detect accuracy and driving current stability. The Hilbert based RFT and CIC based constant control are all realized on a FPGA in digital domain, which is immune to the temperature drifting effects and parameter mismatches of the analogue components. Besides, the phase accuracy of the improved Hilbert based phase detector (PD) is up to 0.03 ° and RFT loop is up to 0.58°. An 100 W ultrasonic generator is established to verify the proposed algorithms. The experimental results are in consistent with the simulation results. Compared with the existing control methods, the proposed algorithm can reduce the phase overshoot and increase the response speed. The IGBT aluminum wire bonding test demonstrate that, in comparison with existing methods, this method can effectively mitigate the temperature drifting effect of analog devices and also effectively enhance the phase tracking accuracy. The experimental results further indicate that this method can improve the consistency of strength and bonding quality of the wire bonding system during continuous operation.