Piezo Drivers

Piezoelectric effect describes the relation between a mechanical stress and an electrical voltage in solids. It occurs in piezoelectric materials such as crystals or ceramics. This effect is also reversible; an applied mechanical stress will generate a voltage and an applied voltage will change the shape of the solid by a small amount. These properties lead to useful applications such as sensors, ultrasonic transducers, motors, etc.

Piezo stacks are capacitive loads. They can be modeled as a capacitor in the testing circuit. Therefore, the impedance of a hydrophone can be given by the following equation:

Usually, when driving a Piezo stack, it should be DC biased. For example, the following is a block diagram of driving multiple (8) model TS18-H5-202 Piezo Stacks (manufactured by Piezo Systems, Inc.) at the same time. The advantage of driving multiple Piezo stacks at once is the high testing efficiency.  It requires quite some power from the driver (usually are power amplifiers), especially at high frequencies due to their low impedances. (According to The Ohm’s Law, the current goes through the Piezo stack can be calculated with the following equation.)

Figure 1: Block Diagram of Driving Multiple model TS18-H5-202 Piezo Stacks

There are a lot of manufacturers making Piezo drivers. The table below shows a few main products currently available in the market. Some of the companies specialize at high power Piezo driving, such as Amp-Line Corp. located at New York, USA. Their products are suitable for testing or driving piezo elements that require high voltage or/and high current. The output power of their products can go up to 1200 watts, while the output voltage can be as high as 354 V rms. (1000 V p-p). The frequency range and output voltage range can also be custom made according to the specific requirements.

Table 2: Piezo Driving Products and Manufacturers

Figure 2: Image of Amp-Line High Power Piezo Driver (Wideband AC Power Amplifier)