Often the inductance value is selected to electrically resonate with the capacitance of the transducer (buzzer) at the acoustic resonance of the transducer. Low resistor values decrease electrical efficiency while damping the mechanical (acoustical) resonance of the transducer, which of course reduces the acoustic efficiency.įigure 2 Substituting an inductor for R2 improves the piezo driver’s output and efficiency. The RC time constant should be short relative to the period of the resonant frequency of the transducer. The resistor R2 serves to discharge the capacitance of the transducer. The voltage across the transducer cannot be greater than the supply voltage, which places an upper limit on the acoustic output. The simplest piezo drive circuit consists of a transducer and a switching transistor ( Figure 1). Before we look at the new approach, let’s look at some of the most commonly-used piezo-acoustic designs and their drawbacks. In contrast, this Design Idea shows how the acoustic output of a piezoelectric transducer can be increased while minimizing the parts count and cost. Most of them involve rather complicated circuitry that drives up the total solution cost such as boosting the low-voltage logic power supply to a higher voltage or using an H-bridge topology.
There have been many different ideas presented for increasing the acoustic output of a piezo buzzer or ultrasonic transducer. This design shows how a piezoelectric transducer's acoustic output can be increased while minimizing the parts count and cost.
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