Wall-plug efficiency analysis of semi-active piezoelectric shunt damping systems

Analysis of the wall-plug efficiency, i.e. the ratio of reflected and absorbed acoustic power over the total electric input power, of semi-active vibration control devices based on the principle of the active piezoelectric shunt damping is presented. The vibration suppression element in the considered vibration control device consists of a piezoelectric actuator, which is connected to the active synthetic impedance shunt circuit that emulates a negative capacitance. Two types of power amplifiers can be used in the implementation of the synthetic impedance: linear (class B, AB) and switching (class D). Using both implementations of the synthetic impedance, a decrease in the transmissibility of vibration by about 30 dB in narrow frequency ranges around 500 Hz, 700 Hz, 900 Hz, and 1.1 kHz has been achieved. The mechanical input power transferred from the source of vibration to the vibration control system, the electric power flow from the piezoelectric actuator to the active shunt impedance, and the wall-plug input electric power were measured. It was demonstrated that the wall-plug input electric power of the vibration control device can be reduced by more than 90% by implementing the switching power stage in the synthetic impedance. Strengths and weaknesses of the two aforementioned implementations of the synthetic impedance shunt circuit in the semi-active vibration control device are analyzed. The key factor in the analysis is the wall-plug efficiency. Principles that can enhance the wall-plug efficiency of the device are discussed.