Electronic Driver – Piezo Motors
As with electromagnetic motors, a complete and useable piezo motor assembly consists of three parts: the electronic drive, the electrical-mechanical transducer (motor) itself, and the output linkage.
For electromagnetic motors, the drive function requires sourcing and dipping current into the electromagnetic coils, which is usually done using power semiconductors. These power devices are controlled by drivers that turn them on and off at the correct times with appropriate slew rates, and they must source the required current into their highly inductive loads. The voltage that is applied to the output stage is needed to force the current into the coils, but it is the current that provides the electromagnetic force for the motor coils.
For piezo motors, the situation is very different. Instead of driving current, the driver must supply a relatively high voltage to create the electric field, and current is the secondary factor accompanying this applied voltage.
The piezo drive scenario is the complement of the electromagnetic drive, where current drive is needed and voltage is a consequence; here, voltage is what is needed, and current is the consequence. The piezo driver must supply the needed voltage (not current) into a capacitive (not inductive) load, and it must control and modulate this voltage to force the desired crystal elongation. In other words, current is the independent parameter and voltage is reliant on parameter for conventional motors, but for piezo motors, the situation is the opposite.