Panasonic Intellectual Property Management Co., Ltd.

Panasonic Corporation

Seigo Ozaki

Tsuyoshi Haga

Mingxue Zhang

Kazuhiro Watanabe

Kazuhiro Uchida

Hirotsugu Kawata

Rintaro Sukegawa

A sound processing device includes an amplifier, a current detector, and a controller. The amplifier amplifies a sound signal to drive a loudspeaker. The current detector detects a value of an electric current flowing into the amplifier. The controller controls whether to supply power to the amplifier based on a predicted current value and the current detected by the current detector. The predicted current value is predicted in accordance with a volume setting and a level of the sound signal.

Sound processing device, sound control device, and sound control method

Disclosed is a technique for reducing noise superimposed on an output signal while keeping loop gain constant without increasing the circuit scale and without changing the transfer function of the amplifier apparatus (frequency characteristics of gain and phase). According to the technique, there are included a power-supply voltage control unitfor detecting the amplitude level Sof an input audio signal Sand outputting power with a voltage value indicated by target set voltage value information Vs corresponding to this amplitude level S, and a PWM modulation unitincluding a PWM converterfor converting the pulse width of the input audio signal Sand a correction unit for correcting the signal modulated by the PWM converter. The PWM modulation unitcorrects the pulse width of a PWM signal Smodulated by the PWM converterso that the correction unit will cancel out a change in amplification gain of a power amplification unitaccording to the target set voltage value information Vs.

Amplifier apparatus

Because of input of a digital signal, PWM-input, separately excited, class-D amplifier systems are less prone to be affected by noise than in the conventional case that an analog signal is input. Since a ramp wave that is synchronized with a PWM signal is used as a comparison clock, no beats occur between a PWM clock and a reference clock, making is possible to provide a class-D amplifier system which exhibits a large S/N ratio. Furthermore, the fact that an external clock can be varied provides another advantage that no beat noise occurs even in a set that is disposed close to a radio receiver.

Amplifier and audio device provided with amplifier

An amplifier is capable of reducing the quantization error caused by conversion accuracy in an A/D converter circuit and, particularly, capable of improving the S/N ratio and distortion rate when an input audio signal is small. In an amplifier () using a voltage variable power supply () as a power supply to follow an input audio signal level (S) to the amplifier () in order to increase or decrease the level of supply voltage supplied to a power amplifier stage (), when the level of source power of the power amplifier stage () is changed, the voltage level of a reference voltage supplied to an A/D converter () of a negative feedback circuit is controlled.

Amplifier using voltage variable power supply

A controllerthat conducts various controls corresponding to input information selects target voltage information and target dead time information corresponding to input audio signal level information from data table information, outputs the target voltage information to a variable power supply unit, and outputs the target dead time information associated with the target voltage information to a dead time generator, to thereby set an output supply voltage and a dead time corresponding to an input audio signal level in a half bridge circuit. Accordingly, there can be provided a class D amplification device that can minimize the dead time and reduce distortion while suppressing the amount of heat generation caused by a through-current.

Class D amplification device

A supply voltage controllerincludes a simplified envelope creating unitthat calculates an envelope of an input audio signal according to an input audio signal from an external device, creates a supply voltage control signal so that a waveform of the supply voltage control signal follows a waveform of the envelope, and outputs the supply voltage control signal to a voltage variable power supplya constant time before the input audio signal is amplified by the amplifier. Accordingly, an amplifying device can be provided which can reduce the distortion of the output signal not depending on a change in the slew rate of the voltage variable power supplyand suppress the deterioration of power efficiency.

Growing community of inventors

Kanagawa, Japan

Seigo Ozaki