Patent ID: 7973429

Claim:
An apparatus comprising: a first DC/DC converter including a first conversion circuit for converting a power supply voltage from a main power supply to a first output voltage, a first driving circuit for driving the first conversion circuit based on a first pulse wave modulated signal, a thinning circuit for removing portions of a first wave signal to form a thinned wave signal, and a first pulse width modulation circuit for performing pulse width modulation on the thinned wave signal to generate the first pulse wave modulated signal; a second DC/DC converter including a second conversion circuit for converting a power supply voltage from a main power supply to a second output voltage, a second driving circuit for driving the second conversion circuit based on a second pulse wave modulated signal, and a second pulse width modulation circuit for performing pulse width modulation on a second wave signal to generate the second pulse wave modulated signal; a speaker driving circuit for generating a speaker driving signal based on the first output voltage and the second output voltage; and a speaker for generating a sound based on the speaker driving signal.