Electronic Power Amplifiers for Piezo Actuators
Application of piezoelectric actuators
Various forms of piezo actuators include nanopositioning, accustic applications with transducers for sonar systems, constant and switching pneumatic and hydraulic valves as well as injectors for fuel injection. Materials and structures are also versatile. The electric capacities reach from 100 nF up to some 10 μF, the operating voltages from 10 V up to the kV range.
Power amplifier for piezoelectric actuators
There is no ideal piezo power amplifier for all applications, since piezo actuators are operated on switching amplifiers and analog amplifiers. According to their performance and required signal quality, a rough classification of the amplifier categories can be made, however. In case of small performance and high demands for signal quality, analog class A amplifiers are the best choice, for high performance, switching class D amplifiers should be used. Class C amplifiers are in-between, but are limited in their performance. In this respect, the dissipated heat and the required heat sink must also be taken into account. The controlling of the piezo actuator often has to be integrated into the given space of the device. The power amplifier has to be developed for practical application. Should the piezo actuator be as fast as possible? Is an especially precise adjustment required? Is a high-dynamic large signal operation necessary? Does an energy recovery from the piezo actuator make sense? In this case, the only option would be a class D amplifier with inductor. Specifically designed class D amplifiers can also provide the desired signal quality. In addition, specific class D amplifiers will also allow actuator voltages larger than the supply voltage of the amplifier. Controls based on current might also be realized with class D amplifiers.