Patent ID: 8509456
Filing Date: 2013-08-13
Classification: H03G

Abstract:
1. A level adjustment circuit configured to adjust the level of an audio signal, comprising: at least one or more filters, each of which is configured to receive an input audio signal, and to pass a band set for the respective filter; at least one or more variable gain amplifiers, each of which is provided to a corresponding aforementioned filter, and each of which is configured to amplify an output signal of the corresponding filter; an adder configured to sum the input audio signal and the output signals of the aforementioned at least one or more variable gain amplifiers; and a control unit configured to monitor the level of the output signal of each of the aforementioned at least one or more variable gain amplifiers, and to control the gain of each of the aforementioned at least one or more variable gain amplifiers according to the level thus monitored, wherein the control unit comprises: a selector configured to receive signals output from the aforementioned at least one or more variable gain amplifiers, and to select one from among the output signals thus received; a comparator configured to compare the signal thus selected by the selector with a predetermined threshold value, and to generate level data which represents the comparison result; at least one or more gain setting units, each of which is provided to a corresponding one of the aforementioned at least one or more variable gain amplifiers, and each of which comprises a peak hold circuit configured to hold the value of the level data when the level data generated for the corresponding variable gain amplifier becomes a predetermined level at least once, and configured to set the gain of the corresponding variable gain amplifier according to an output signal of the peak hold circuit, wherein the selector is configured to select, in sequence and in a time sharing manner, at least one or more output signals set beforehand from among the signals output from the aforementioned at least one or more variable gain amplifiers, and wherein the periods for which the selector selects the output signals of the variable gain amplifiers differ in increments of the pass bands of the filters that correspond to the variable gain amplifiers.