| 摘要 |
PROBLEM TO BE SOLVED: To provide a parametric speaker which has high amplifier driving efficiency and can be made small in size. SOLUTION: This parametric speaker is provided with a level comparator 3 for comparing signal levels between an electric signal in an audio frequency band and a carrier signal in an ultrasonic frequency band to generate a modulated signal of pulse width corresponding to an input signal level in the audio frequency band from the carrier signal, a signal controller 4 for generating a switching signal for opening/closing connection to power supply voltage in a period corresponding to the pulse width of the pulse width modulated signal, a compensator 8 for selecting connection of a capacitive element in accordance with an impedance characteristic of a radiator 7, an inductance 9 for connecting the compensator 8 and the radiator 7, and a pulse width modulation amplifier 5 for driving the radiator 7 with an electric signal amplified in accordance with the input signal level in the audio frequency band by opening/closing connection to the power supply voltage on the basis of the switching signal and performing resonance by the inductance 9 and the capacitive element of the compensator 8 or the capacitive radiator 7. COPYRIGHT: (C)2006,JPO&NCIPI |
