Yamaha Corporation

Takeshi Togawa

Masao Noro

Toshiro Mayuzumi

A class D amplifier includes a self-oscillating class D amplification circuit that is driven by an output current signal; and a voltage-current converting circuit that outputs an output current signal in response to an input signal voltage and an output signal voltage from a feedback signal voltage.

Class D amplifier

An amplifying device includes a self-excited class D amplifier circuit and a band elimination filter. The self-excited class D amplifier circuit includes a modulation circuit that is configured to apply self-oscillating pulse modulation to an audio signal. The modulation circuit is configured to receive, from a signal generation circuit, a supply of a synchronizing signal with which the self-oscillation synchronizes. The band elimination filter is configured to reduce components that belong to a frequency band including a frequency of the synchronizing signal, in an output signal from the self-excited class D amplifier circuit.

Amplifying device

An amplifying device includes a first amplifier, a voltage-limiting circuit, a second amplifier, a first controller, and a second controller. The first amplifier is configured to amplify an input signal. The voltage-limiting circuit is configured to limit a voltage of an output signal from the first amplifier to within a limit range. The second amplifier is configured to amplify an output signal from the voltage-limiting circuit. The first controller is configured to control the limit range in accordance with a current supplied to a load from the second amplifier. The second controller is configured to decrease an amplification factor of the first amplifier in a state in which the voltage-limiting circuit limits the voltage of the output signal from the first amplifier.

Amplifying device and controlling method therefor

A self-oscillating class D amplifier includes an integration circuit configured to integrate an input signal and output a result of the integration as an integrated signal, a comparator configured to receive the integrated signal at an inverting input terminal and output a pulse width modulation signal by comparing voltages of a non-inverting input terminal being grounded and the inverting input terminal, a switching circuit configured to power-amplify the pulse width modulation signal output from the comparator, a low-pass filter configured to extract an amplified output signal from the power-amplified pulse width modulation signal, a first feedback circuit configured to feed back the output signal of the low-pass filter to the inverting input terminal of the comparator, and a second feedback circuit configured to feed back the output signal of the low-pass filter to the integration circuit.

Self-oscillating class D amplifier

The invention is provided with a first class-D amplifying unit for amplifying an inputted audio signal and supplying the amplified signal to a positive side of an audio output terminal, a second class-D amplifying unit for amplifying an inputted audio signal inverted in an inverting unit and supplying the amplified signal to a negative side of the audio output terminal, wherein, in a first mode, the first and second class-D amplifying units are activated and outputs of the first and second class-D amplifying units are kept equal to or less than a first current value, and wherein, in a second mode, the first class-D amplifying unit is activated, the second class-D amplifying unit is inactivated, the negative side of the audio output terminal is grounded, and output of the first class-D amplifying unit is kept equal to or less than a second current value larger than the first current value.

Class-D power amplifier

A class-D power amplifier includes a switching power source section, a synchronization signal generation section and a class-D power amplifying section. The synchronization signal generation section takes out of the switching power source section a clock signal having a second frequency which is 'n' times of a first frequency. The class-D power amplifying section includes a comparator which compares an input signal with a feedback signal, a second switching section which switches a power source fed from the synchronization signal generation section, a filter section which smoothes an output signal from the second switching section, and a combining section which combines a delayed output signal with a clock signal from the synchronization signal generation section to generate the feedback signal. The class-D power amplifying section is adjusted so as to cause self-oscillating operation at a frequency substantially identical with the second frequency, when a level of the output signal from the filter section is low.

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Anjo, Japan

Takeshi Togawa