drive circuit of piezoelectric diaphragm buzzer

The sound source of the piezoelectric buzzer sound element mainly comes from the piezoelectric diaphragm. The piezoelectric vibrating plate is composed of a piezoelectric ceramic plate on which electrodes are printed on both sides, and a metal plate (brass or stainless steel, etc.). The adhesive is used to bond the piezoelectric vibrating plate to the metal sheet.This is what we call a piezo buzzer.

Figure shows the oscillation system of the piezo ceramic bimorph. When a direct current voltage is applied between the two electrodes of the piezoelectric diaphragm, mechanical deformation is caused due to the piezoelectric effect. For a piezoelectric element having a shape distortion, its deformation is extended in the radiation direction.

The piezoelectric vibrating plate is bent in the direction shown in Fig. 2(a), and the metal piezo ceramics are bonded to the piezoelectric vibrating plate does not stretch. On the contrary, when the piezoelectric element contracts, the piezoelectric diaphragm is bent in the direction shown in Fig. 2(b). Therefore, when the alternating voltage is passed through the electrode, as shown in Fig. 2(c), the bending shown in Figs. 2(a) and 2(b) is alternately repeated.

Normally, a piezoelectric diaphragm buzzer is installed in the resonance chamber to generate a high sound pressure (Fig. 4). Using Equation (1) (Hermholtz Formula), the resonant frequency (fcav) of the resonance chamber in Figure 4 can be calculated. Since the piezoelectric diaphragm and the resonance chamber have appropriate resonance frequencies, respectively (f0) and (fcav), it is possible to increase the sound pressure at a specific frequency and obtain a specific bandwidth by controlling the positions of both.