Matsushita Electric Industrial Co., Ltd.

Panasonic Corporation

Kiyomi Kimura

Kazuki Adachi

Tetsuro Sugioka

Tsuyoshi Takayama

Kosei Fujisaka

The potential of a smoothing capacitor for a speaker is smoothly changed by controlling the potential with use of a PWM signal and switching between outputting the PWM signal and an actual audio signal, thereby suppressing a pop sound. The scale of circuitry is reduced and cost is lowered by implementing a PWM circuit in a one-chip microcontroller. Noise is eliminated by outputting a pulse that has been divided in the PWM signal generation stage.

Audio signal output control device that suppresses pop sound

In a tone output device, an oscillatoroutputs a clockthat is emitted by a crystal resonator. A multiplication circuitoutputs a clockthat is generated by multiplying the clock. A timing control circuitoutputs a timing signalgenerated based on the clockfor operations of a CPU. The CPUoperates in sync with the timing signal. The DA converteroperates in sync with a signal generated based on the clock. The timing adjustment circuitdetects deviation of the clockfrom the clockresulting from frequency jitter of the clock, and prevents occurrence of clock racing.

Growing community of inventors

Nara, Japan

Kiyomi Kimura