#Piezo sounder drivers#
#Piezo sounder driver#

The schematic drawn below is one possible implementation of a resonant piezo transducer drive circuit. In this application the two elements that store and transfer the energy are the inductor and the parasitic capacitor. One characteristic of a resonant circuit is that energy is stored and transferred alternately between two elements. Yet another option for driving a piezo transducer is to create a circuit that utilizes the parasitic capacitance present in the transducer buzzer and a discrete inductor to form a resonant circuit.

#Piezo sounder driver#

Full-bridge driver with piezo buzzer load Resonant Piezo Transducer Drive Circuit

#Piezo sounder drivers#

Many versions of both half-bridge and full-bridge drivers are available as inexpensive integrated circuits and are often used to drive electric motors. This increased drive voltage results in a louder output sound from the buzzer while using the same supply voltage. The advantage of using a full-bridge driver is that the voltage applied to the buzzer is twice the voltage as compared to a basic driver or half-bridge driver. Two half-bridge drivers driven out of phase are known as a “full-bridge” driver and can be used with the buzzer connected between the outputs of the two half-bridge drivers. This form of driver with push-pull buffers is commonly referred to as a “half-bridge” driver. The changes to the buffer configuration mentioned in the previous section will require the drive circuit for the buffers to be more complex, which may not be desired when implementing a solution with discrete components. Reversing the position of the BJT buffers or utilizing FETs as buffers Half-Bridge and Full-Bridge Drive Circuits Both buffer configurations are outlined below. This circuit can also be constructed with FETs instead of BJTs as the buffer components. The problem of the reduced voltage applied to the buzzer can be addressed by reversing the positions of the BJT buffers in the initial buffered driver. Basic driver circuit with two buffer transistors As in the basic driver circuit, the buzzer and circuit behave the same regardless of whether the one buzzer terminal is connected to the +V supply or to ground. A drawback of this circuit is that the addition of the two buffer transistors reduces the voltage applied to the buzzer by about two diode drops, or roughly 1.2 Volts. The addition of two buffer transistors, as shown in the circuit below, can reduce the power loss present in the basic driver circuit detailed previously by allowing for a higher impedance reset resistor to be used. Basic piezo transducer drive circuit Adding Buffers to a Basic Piezo Transducer Drive Circuit It should be noted that the buzzer and circuit behave the same regardless of whether the one buzzer terminal is connected to the +V supply (as shown in the schematic) or to ground. However, it can be hampered by the fact that the voltage applied to the buzzer is limited to the supply voltage (+V) and the reset resistor dissipates power. The main advantage of this circuit is it only requires a few, inexpensive parts.

One of the most basic piezo transducer drive circuits is composed of an electronic switch, such as an FET or BJT, and a reset resistor as shown in the circuit below. It is also important to note that a transducer buzzer requires an external excitation signal, whereas an indicator buzzer, which contains an internal oscillator, only requires a supply voltage to operate. The amount of deformation and the resultant noise volume caused by the deformation are related to the voltage applied across the piezo material. However, as a quick refresher, a piezoelectric device is constructed of a material that physically deforms when a voltage is applied across the device. The basics of piezoelectric transducer buzzers are described in greater detail in CUI Devices’ Buzzer Basics blog post. This blog outlines the working principles of piezo transducers, common design techniques for increasing audio output, and the advantages and limitations of each. There are several ways to affect the audio output of a piezo buzzer based upon the design of the driver circuit. In most applications the reason for utilizing a piezoelectric transducer buzzer is to create a loud sound, where the amplitude of the sound produced by a buzzer is dependent upon both the specific buzzer selected and the signal used to drive the buzzer. How Do I Maximize the Sound of a Piezo Transducer Buzzer?