Patent ID: 7997671
Filing Date: 2011-08-16
Classification: B41J,H04R

Abstract:
1. A piezoelectric speaker driving device applying a driving signal to a piezoelectric speaker and driving the piezoelectric speaker, the piezoelectric speaker driving device comprising: an operational amplifier outputting a difference signal of a signal inputted to an inverting input terminal and an analog driving signal inputted to a non-inverting input terminal, and setting a loop gain; a first pulse width modulator pulse-width-modulating the difference signal outputted by the operational amplifier, and outputting resultant digital signal; a first digital voltage amplifier amplifying a voltage of the digital signal outputted from the first pulse width modulator; a first filter smoothing a digital signal outputted by the first digital voltage amplifier, and supplying a smoothed signal to one polarity of the piezoelectric speaker as a first driving signal; a second pulse width modulator pulse-width-modulating an inverted signal of the difference signal outputted by the operational amplifier, and outputting resultant digital signal; a second digital voltage amplifier amplifying a voltage of the digital signal outputted from the second pulse width modulator; a second filter smoothing a digital signal outputted by the second digital voltage amplifier, and supplying a smoothed signal to another polarity of the piezoelectric speaker as a second driving signal; and a differential amplifier outputting a differential amplification of the first and second driving signals outputted from the first and second filters, and supplying it to the inverting input terminal of the operational amplifier.