Theoretical and Empirical Verification of Electrical Impedance Matching Method for High-Power Transducers

In our prior study, a systematic approach was used to devise Langevin transducers for high-power applications where the energy efficiency was not considered in the design criteria. In this paper, the impedance matching methods are thus proposed to evaluate what matching topology is appropriate for their use. Both the series inductor scheme and low pass filter composed of a series inductor and shunt capacitor are examined as matching circuits. According to MATLAB simulation, the resonance frequency is seen at 36.79 kHz due to a series L circuit, and its associated impedance is reduced by 70.45% from that of its non-matching condition. The measured resonance frequency is 36.77 kHz and the corresponding impedance is decreased by 59.52%. Furthermore, the acoustic pressure is measured to determine the effect of the matching circuit on the transducer’s actual behavior. The transducer with a series L circuit shows more efficient matching results, 2.28 kPa of positive acoustic pressure is emitted without matching and 3.35 kPa is emitted with a series L element, respectively. As a result, this study demonstrates how to evaluate the influence of matching circuits by using our customized approach rather than commercial SPICE programs, as well as how to experimentally verify the acoustic behavior of high-power Langevin transducers.

Realization of a Photovoltaic Fed Sparse Alternating Current (AC)-Link Inverter

In this paper, a soft-switched alternating current (AC)-link buck-boost inverter with a reduced number of switches, referred to as a sparse AC-link buck-boost inverter, was designed and implemented for a photovoltaic (PV) interface. Important features of the sparse configuration included a lower number of switches, lower failure rates, compactness, and cost-effectiveness. The link was composed of a low reactive rating series inductor/capacitor pair. Significant merits of the AC-link buck-boost inverter are a zero voltage turn on and a soft turn off of the switches, resulting in minimum voltage stress on the switches and negligible switching losses. In this paper, 10 switches were used instead of 20 switches as are used in existing buck-boost inverter topology. The reduction in the number of switches did not change the principle of operation of the sparse configuration; hence, it remains the same as that of the original configuration. The pulse width modulation (PWM) technique was used for gating the switches. The inverter operation was validated and implemented for PV interface using a microcontroller.