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US 12,401,330 B2Granted
Audio circuit
AssigneeRohm Co., Ltd.
InventorMitsuteru Sakai
Life of this patent
Estimating the term…
Abstract
A class D amplifier circuit receives an analog audio signal with a first reference voltage as its center level, and outputs an output pulse signal having a duty cycle that corresponds to the analog audio signal. A bias circuit generates a second reference voltage having a voltage level obtained as a division of the first reference voltage and the power supply voltage. A periodic voltage generating circuit of the class D amplifier circuit generates a periodic voltage having a triangle waveform or otherwise a sawtooth waveform having an amplitude that corresponds to the second reference voltage.
Claims8
An audio circuit comprising:
- a class D amplifier circuit structured to receive an analog audio signal with a first reference voltage as a center level, and to output an output pulse signal having a duty cycle that corresponds to the analog audio signal;
- and
- a bias circuit structured to generate a second reference voltage having a voltage level obtained by dividing the first reference voltage and a power supply voltage,
- wherein the class D amplifier circuit comprises:
- an integrator structured to receive the analog audio signal and a feedback signal that corresponds to the output pulse signal;
- a periodic voltage generating circuit structured to generate a periodic voltage having a triangle waveform or a sawtooth waveform;
- a Pulse Width Modulation (PWM) comparator structured to compare an output of the integrator with the periodic voltage;
- a bridge circuit structured to receive a supply of the power supply voltage;
- and
- a driver structured to drive the bridge circuit according to an output of the PWM comparator,
- wherein the integrator comprises:
- a first operational amplifier structured to receive the second reference voltage via a non-inverting input terminal;
- a first resistor structured such that the analog audio signal is input to one end thereof, and the other end thereof is coupled to an inverting input terminal of the first operational amplifier;
- and
- a second resistor structured such that the feedback signal is input to one end thereof, and the other end thereof is coupled to the inverting input terminal of the first operational amplifier,
- and wherein the periodic voltage generating circuit generates a periodic voltage having an amplitude that corresponds to the second reference voltage,
- wherein the periodic voltage generating circuit comprises:
- a clock generating circuit structured to generate a first clock signal with an amplitude having a voltage level that is twice that of the second reference voltage;
- and
- a triangle wave generating circuit structured to generate the periodic voltage based on the first clock signal.
17 more elements
An audio circuit comprising:
- a class D amplifier circuit structured to receive an analog audio signal with a first reference voltage as a center level, and to output an output pulse signal having a duty cycle that corresponds to the analog audio signal;
- and
- a bias circuit structured to generate a second reference voltage having a voltage level obtained by dividing the first reference voltage and a power supply voltage,
- wherein the class D amplifier circuit comprises:
- an integrator structured to receive the analog audio signal and a feedback signal that corresponds to the output pulse signal;
- a periodic voltage generating circuit structured to generate a periodic voltage having a triangle waveform or a sawtooth waveform;
- a Pulse Width Modulation (PWM) comparator structured to compare an output of the integrator with the periodic voltage;
- a bridge circuit structured to receive a supply of the power supply voltage;
- and
- a driver structured to drive the bridge circuit according to an output of the PWM comparator,
- wherein the integrator comprises:
- a first operational amplifier structured to receive the second reference voltage via a non-inverting input terminal;
- a first resistor structured such that the analog audio signal is input to one end thereof, and the other end thereof is coupled to an inverting input terminal of the first operational amplifier;
- and
- a second resistor structured such that the feedback signal is input to one end thereof, and the other end thereof is coupled to the inverting input terminal of the first operational amplifier,
- and wherein the periodic voltage generating circuit generates a periodic voltage having an amplitude that corresponds to the second reference voltage,
- wherein the bias circuit comprises:
- a first voltage dividing circuit structured to generate a midpoint voltage that is ½ times the power supply voltage;
- and
- a second voltage dividing circuit structured to divide the first reference voltage and the midpoint voltage,
- wherein the second voltage dividing circuit has a voltage dividing ratio that is equal to a gain of the class D amplifier circuit.
18 more elements
Dependencies are inferred from the claim text.