Patent ID: 8630148

Claim:
A method comprising: charging a reactive load; selectively holding the reactive load in a first energy state by maintaining a first switching element and a second switching element in an open position, the first energy state comprising a first DC voltage having a first polarity; detecting a current in the reactive load with a controller; permitting the reactive load to change from the first energy state to a second energy state by switching the first switching element to a closed position and then switching the first switching element to the open position in response to the detected current in the reactive load being substantially zero, the second energy state comprising a second DC voltage having a second polarity opposite the first polarity; selectively holding the reactive load in the second energy state by maintaining the first switching element and the second switching element in the open position; and permitting the reactive load to change from the second energy state to the first energy state by switching the second switching element to a closed position and then switching the second switching element to the open position in response to the detected current in the reactive load being substantially zero, wherein the reactive load generates an acoustic wave during transitions between the first and second energy states.