US-20260128719-A1 - METHOD FOR ADAPTIVELY ADJUSTING START-UP TIME OF AUDIO AMPLIFIER AND ASSOCIATED SYSTEM ON CHIP

US20260128719A1US 20260128719 A1US20260128719 A1US 20260128719A1US-20260128719-A1

Abstract

An audio amplifier chip includes an audio amplifier, a current providing circuit, a detection circuit, and a control circuit. The audio amplifier is arranged to drive a speaker, wherein the audio amplifier has multiple differential input terminals, and a direct current (DC) blocking capacitor is coupled to one of the multiple differential input terminals. The current providing circuit is arranged to provide at least one current for charging the DC blocking capacitor. The detection circuit is coupled to a node located between the one of the multiple differential input terminals and the DC blocking capacitor, and is arranged to detect whether an external resistor of the audio amplifier chip exists according to an input voltage from the node, in order to generate a detection result. The control circuit is arranged to determine a start-up time of the audio amplifier according to the detection result.

Inventors

Isaac Y. Chen

Assignees

ELITE SEMICONDUCTOR MICROELECTRONICS TECHNOLOGY INC.

Dates

Publication Date: 20260507
Application Date: 20241106

Claims (20)

1 . An audio amplifier chip, comprising: an audio amplifier, arranged to drive a speaker, wherein the audio amplifier has multiple differential input terminals, and a direct current (DC) blocking capacitor is coupled to one of the multiple differential input terminals; a current providing circuit, arranged to provide at least one current for charging the DC blocking capacitor; a detection circuit, coupled to a node located between the one of the multiple differential input terminals and the DC blocking capacitor, and arranged to detect whether an external resistor of the audio amplifier chip exists according to an input voltage from the node, in order to generate a detection result; and a control circuit, arranged to determine a start-up time of the audio amplifier according to the detection result.
2 . The audio amplifier chip of claim 1 , wherein the detection circuit comprises: a comparator circuit, arranged to perform a comparison operation upon the input voltage and a threshold voltage, in order to generate a comparison result, wherein the detection result depends on the comparison result.
3 . The audio amplifier chip of claim 2 , wherein in response to the comparison result indicating that the input voltage is greater than the threshold voltage, the detection result indicates that the external resistor exists.
4 . The audio amplifier chip of claim 2 , wherein the detection circuit further comprises: at least one resistor-capacitor (RC) constant circuit, arranged to receive the input voltage, and extract a previous input voltage according to the input voltage for acting as the threshold voltage.
5 . The audio amplifier chip of claim 1 , wherein the control circuit comprises: multiple start-up time generating circuits, arranged to generate multiple start-up times; and a multiplexer circuit, arranged to: receive the multiple start-up times from the multiple start-up time generating circuits; receive the detection result from the detection circuit as a selection signal; and perform a selection operation upon the multiple start-up times according to the selection signal, in order to generate a selected start-up time for acting as the start-up time of the audio amplifier.
6 . The audio amplifier chip of claim 5 , wherein the multiple start-up times comprise a first start-up time and a second start-up time, the first start-up time is greater than the second start-up time, and in response to the detection result indicating that the external resistor exists, the multiplexer circuit selects the first start-up time as the selected start-up time.
7 . The audio amplifier chip of claim 5 , further comprising: a switching circuit, wherein the switching circuit is coupled between the multiple differential input terminals, and the control circuit is further arranged to generate a switching control signal and an enabling signal according to the selected start-up time for controlling switching of the switching circuit and enabling the current providing circuit, respectively, in order to control the start-up time of the audio amplifier as the selected start-up time.
8 . The audio amplifier chip of claim 1 , wherein the at least one current comprises a first current and a second current, a current value of the first current is greater than a current value of the second current, and after the DC blocking capacitor is charged by the second current, the detection circuit is further arranged to detect whether an external driver is ready to drive the audio amplifier chip according to the input voltage within a time interval, in order to generate the detection result.
9 . The audio amplifier chip of claim 8 , wherein the detection circuit comprises: a comparator circuit, arranged to perform a comparison operation upon the input voltage and a threshold voltage, in order to generate a comparison result, wherein the detection result depends on the comparison result.
10 . The audio amplifier chip of claim 9 , wherein after the DC blocking capacitor is charged by the second current, in response to the comparison result indicating that the input voltage not being greater than the threshold voltage within the time interval, the detection result indicates that the external driver is ready to drive the audio amplifier chip.
11 . The audio amplifier chip of claim 9 , wherein only after the detection result indicates that the external driver is ready to drive the audio amplifier chip, the current providing circuit provides the first current for charging the DC blocking capacitor, and the detection circuit starts to detect whether the external resistor exists according to the input voltage.
12 . A method for adaptively adjusting a start-up time of an audio amplifier, wherein a speaker is driven by the audio amplifier, the audio amplifier is comprised in an audio amplifier chip, and the method comprises: charging a direct current (DC) block capacitor by at least one current, wherein the DC block capacitor is coupled to one of multiple differential input terminals of the audio amplifier; detecting whether an external resistor of the audio amplifier chip exists according to an input voltage from a node, in order to generate a detection result, wherein the node is located between the one of the multiple differential input terminals and the DC blocking capacitor; and determining the start-up time of the audio amplifier according to the detection result.
13 . The method of claim 12 , wherein the step of detecting whether the external resistor exists according to the input voltage from the node, in order to generate the detection result comprises: performing a comparison operation upon the input voltage and a threshold voltage, in order to generate a comparison result, wherein the detection result depends on the comparison result.
14 . The method of claim 13 , wherein in response to the comparison result indicating that the input voltage is greater than the threshold voltage, the detection result indicates that the external resistor exists.
15 . The method of claim 13 , further comprising: extract a previous input voltage according to the input voltage for acting as the threshold voltage.
16 . The method of claim 12 , further comprising: generating multiple start-up times; and performing a selection operation upon the multiple start-up times according to the detection result, in order to generate a selected start-up time for acting as the start-up time of the audio amplifier.
17 . The method of claim 16 , wherein the multiple start-up times comprise a first start-up time and a second start-up time, the first start-up time is greater than the second start-up time, and in response to the detection result indicating that the external resistor exists, the first start-up time is selected as the start-up time of the audio amplifier.
18 . The method of claim 16 , wherein the audio amplifier chip further comprises a switching circuit and a current providing circuit, the switching circuit is coupled between the multiple differential input terminals, the current providing circuit provides the at least one current for charging the DC blocking capacitor, and the method further comprises: generating a switching control signal and an enabling signal according to the selected start-up time for controlling switching of the switching circuit and enabling the current providing circuit, respectively, in order to control the start-up time of the audio amplifier as the selected start-up time.
19 . The method of claim 12 , wherein the at least one current comprises a first current and a second current, a current value of the first current is greater than a current value of the second current, and the method further comprises: after the DC blocking capacitor is charged by the second current, detecting whether an external driver is ready to drive the audio amplifier chip according to the input voltage within a time interval, in order to generate the detection result.
20 . The method of claim 19 , wherein the step of after the DC blocking capacitor is charged by the second current, detecting whether the external driver is ready to drive the audio amplifier chip according to the input voltage within the time interval, in order to generate the detection result comprises: performing a comparison operation upon the input voltage and a threshold voltage, in order to generate a comparison result, wherein the detection result depends on the comparison result.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is related to an audio amplifier, and more particularly, to an audio amplifier chip that can adaptively adjust a start-up time of the audio amplifier, and an associated method. 2. Description of the Prior Art An audio amplifier may receive differential audio inputs through direct current (DC) blocking capacitors and charge the DC blocking capacitors in a charging mode. When there is a need for fast charging, if an external resistor coupled between the DC blocking capacitor and the audio amplifier exists for adjusting the gain of the audio amplifier, resistor-capacitor (RC) time constants between differential input terminals of the audio amplifier may be different and/or a voltage difference between the differential input terminals may be large, which may cause POP problems (i.e., pop noise). As a result, a start-up time of the audio amplifier is usually delayed. Some existing audio amplifiers, however, require a faster start-up time (e.g., audio amplifiers that drive Artificial Intelligence (AI) speakers), and delaying the start-up time for these audio amplifiers may cause further problems. As a result, a novel audio amplifier chip that can detect whether an external resistor exists and thereby adjust a start-up time of an audio amplifier is urgently needed. SUMMARY OF THE INVENTION It is therefore one of the objectives of the present invention to provide an audio amplifier chip that can adaptively adjust a start-up time of an audio amplifier, and an associated method, in order to address the above-mentioned issues. According to an embodiment of the present invention, an audio amplifier chip is provided. The audio amplifier chip comprises an audio amplifier, a current providing circuit, a detection circuit, and a control circuit. The audio amplifier is arranged to drive a speaker, wherein the audio amplifier has multiple differential input terminals, and a DC blocking capacitor is coupled to one of the multiple differential input terminals. The current providing circuit is arranged to provide at least one current for charging the DC blocking capacitor. The detection circuit is coupled to a node located between the one of the multiple differential input terminals and the DC blocking capacitor, and is arranged to detect whether an external resistor of the audio amplifier chip exists according to an input voltage from the node, in order to generate a detection result. The control circuit is arranged to determine a start-up time of the audio amplifier according to the detection result. According to an embodiment of the present invention, a method for adaptively adjusting a start-up time of an audio amplifier is provided, wherein a speaker is driven by the audio amplifier, and the audio amplifier is comprised in an audio amplifier chip. The method comprises: charging a DC block capacitor by at least one current, wherein the DC block capacitor is coupled to one of multiple differential input terminals of the audio amplifier; detecting whether an external resistor of the audio amplifier chip exists according to an input voltage from a node, in order to generate a detection result, wherein the node is located between the one of the multiple differential input terminals and the DC blocking capacitor; and determining the start-up time of the audio amplifier according to the detection result. One of the benefits of the present invention is that, by the method and an associated audio amplifier chip proposed by the present invention, a start-up time of an audio amplifier can be adaptively adjusted according to different scenarios (e.g., existence of external resistors of the audio amplifier chip). In this way, an optimized balance between the start-up time and the POP problems (i.e., pop noise) can be achieved, and the audio amplifier chip of the present invention can be applied to different types of speakers (e.g., speakers with/without the external resistors). In addition, the method and the audio amplifier chip of the present invention can further detect whether an external system on chip (SoC) driver is ready to drive the audio amplifier chip, and the audio amplifier chip is prevented from being started until the external SoC driver is ready. In this way, the potential POP problems may be further avoided. These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of an audio amplifier chip according to an embodiment of the present invention. FIG. 2 is a diagram illustrating a detection circuit according to an embodiment of the present invention. FIG. 3 is a diagram illustrating a control circuit according to an embodiment of the present invention. FIG. 4 is a timing diagram illustrating volta