Class-D amplifier

Abstract

A class-D amplifier includes: an operational amplifier and capacitors, which constitute an integrator for integrating a difference between a plus-sided input signal and a minus-sided input signal which constitute analog input signals; delay circuits for delaying a phase of a triangular wave by a desirable very small angle; resistors, which constitute a synthesizing circuit for synthesizing an output of the integrator, the triangular wave, and outputs of the delay circuits with each other; comparators for comparing outputs of the synthesizing circuit with each other; AND circuits which constitute a buffer for inputting outputs of the comparators; and resistors feeding back an output of the buffer to an input side of the integrator.

Description

technical field [0001] The present invention relates to class D amplifiers. Background technique [0002] A class D amplifier performs power amplification with a pulse width modulated (PWM) input signal, and is used to perform power amplification of audio signals. A conventional Class D amplifier arrangement has an integrator to integrate the analog input signal, a comparator to compare the output signal of the integrator with a predetermined triangular waveform, and a buffer (pulse amplifier) ​​to amplify the output of the comparator signal to output a pulse signal. In this conventional Class D amplifier, the pulse signal output from the buffer is fed back to the input of the integrator. Next, the output signal of the buffer is filtered by a low-pass filter formed by an inductor and a capacitor to obtain an analog signal for driving a load such as a loudspeaker. [0003] A conventional PWM amplifier arrangement has a comparator to compare an analog input signal with a tr...

AI Technical Summary

Problems solved by technology

However, the conventional pulse width modulation amplifier in Patent Publication 1 described above has a problem that it needs a transformer to convert the impedance and cut off the DC voltage, which may require a large-sized device and increase the cost at the same time

Moreover, there is another problem in the pulse width modulation amplifier described in Japanese Patent Laid-Open No. 56-27001: Since the comparator compares the input signal with a simple triangular waveform, the distortion of the output signal is severe.

As a result, the digital amplifying circuit described in Japanese Patent Application Laid-Open No. 2000-500625 has a problem that since the digital amplifying circuit cannot be arranged to provide an analog circuit, an analog input signal cannot be amplified while maintaining better linearity

However, the circuit for compensating output switching distortion is constructed by providing only such a digital circuit as a logic circuit, so this conventional amplifying circuit cannot amplify an analog input signal with better linearity

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