Efficient class-B analog amplifier for a piezoelectric actuator drive

The paper covers a pure analog amplifier design favorable to drive capacitive solid state actuators such as piezoelectric actuators. The research in this field is prompted by the introduction of a new piezoelectric motor (piezoelectric actuator drive - PAD) which employs piezoelectric multilayer actuators, offering mechanical output power of up to 20 W. Due to their static and continuous operation, the actuators of the motor need to be supplied by high-quality, low-frequency, high-voltage, sinusoidal signals. The described circuit is an efficiency-improved class-B amplifier capable of recovering up to 50% of the charge stored in the actuator. The paper begins with a short overview of different amplifier types and their trade-off between signal quality, efficiency and circuit complexity. Starting with a description of the sources of power-loss in a basic class-B amplifier which drives a capacitive actuator, a hybrid design, combining the analog with a switched-mode amplifier, is discussed. The efficiency-improved class-B amplifier is then derived from the hybrid design. Finally, the amplifier is tested in an experiment together with the PAD.