TW201505025A - Audio playing apparatus and bursting sound elimination method - Google Patents

Abstract

A bursting sound elimination method for use in an audio playing apparatus is provided. The audio playing apparatus comprises a pulse-width modulation (PWM) audio output unit, a digital-to-analog circuit, and an audio amplifier for processing an analog audio signal sequentially. The method comprises the following steps of: determining whether a power failure condition occurs; when the power failure condition occurs, generating a power-failure detection signal having a high logic level; and when the power-failure condition occurs, connecting outputs of the PWM audio output unit and the audio amplifier to the ground to prevent generating bursting sounds on a speaker connected to the audio playing apparatus.

Description

Audio playback device and popping elimination method

The present invention relates to audio processing, and more particularly to an audio playback device and a popping cancellation method that can utilize a second-order pop-up cancellation circuit to eliminate pops during power down.

In a general audio playback device, when a power failure occurs, a popping sound is often generated in the speaker, which may reduce the user's feeling. In a conventional audio playback device, usually only a first-order pop-up cancellation circuit is provided in the front stage of the audio processing (for example, at the output of a pulse width modulation (PWM) sound source output unit) to solve the problem of popping. However, the audio signal is transmitted step by step in the audio playback device. If the popping sound is removed only in the front stage, the audio signal of the powered down image may still be sequentially transmitted to the subsequent stage of the audio processing (for example, an audio amplifier). The output), which causes a popping sound on the speaker. Therefore, there is a need for an audio playback device having a pop-up cancellation circuit to solve the above-described popping problem.

The present invention provides a pop-up cancellation method for an audio playback device, wherein the audio playback device includes a pulse width modulation (PWM) sound source output unit, a digital analog converter, and an audio amplifier for sequentially processing a class of analog audio. Signal, the method includes: determining whether the audio playback device has a power failure a situation occurs; when the power-off condition occurs, a power-off detection signal having a high logic level is generated; and when the power-off condition occurs, the PWM sound source output unit and the audio are generated according to the power-off detection signal The output of the amplifier is grounded to avoid popping at the one of the connected speakers in the audio playback device.

The invention further provides an audio playback device, comprising: a pulse width modulation (PWM) sound source output unit for converting a class of analog audio signals into a left channel digital pulse signal and a right channel digital pulse signal; An analog converter for converting the left channel digital pulse signal and the right channel digital pulse signal into a first left channel audio signal and a first right channel audio signal; an audio amplifier for Amplifying the amplitudes of the first left channel audio signal and the first right channel audio signal to generate a second left channel audio signal and a second right channel audio signal for playing on a speaker; a unit, configured to determine whether the audio playback device has a power-off condition, wherein when the power-off condition occurs, one of the power-off detection signals output by the power-off determination unit is a high logic level; a first pop a cancellation circuit coupled between the PWM sound source output unit, the digital analog converter, and the power failure determination unit, wherein when the power failure condition occurs, the first pop cancellation circuit is based on the The detection signal grounds the left channel digital pulse signal and the right channel digital pulse signal to cancel the popping sound; and a second popping elimination circuit coupled between the audio amplifier, the speaker and the power failure determining unit, When the power-off condition occurs, the second pop-up cancellation circuit grounds the second left channel audio signal and the second right channel audio signal according to the power-off detection signal to eliminate popping.

100‧‧‧Audio playback device

110‧‧‧PWM source output unit

120‧‧‧Digital Analog Converter

130‧‧‧Audio Amplifier

140‧‧‧Power failure judgment unit

150‧‧‧First popping elimination circuit

160‧‧‧second pop-up cancellation circuit

190‧‧‧Speaker

141‧‧‧AC detection circuit

142‧‧‧AC input circuit

143‧‧‧ State logic circuit

111‧‧‧ Left channel digital pulse signal

112‧‧‧Right channel digital pulse signal

121, 131‧‧‧ left channel audio signal

122, 132‧‧‧right channel audio signal

151‧‧ ‧ diode

152-153, 161-164‧‧‧Optoelectronics

AC_DETOUT‧‧‧Power failure detection signal

AC_DETIN, AC_VRMS‧‧‧ voltage input signal

V _CC ‧‧‧ voltage

L1, L2, R1, R2, A, B, C‧‧‧ nodes

R1, R2‧‧‧ resistance

C1‧‧‧ capacitor

Vth1‧‧‧ voltage threshold

VRMS_OK, AC_65‧‧‧ status signal

1 is a functional block diagram showing an audio playback device in accordance with an embodiment of the present invention.

2 is a schematic diagram showing a power-off determination unit 140 according to an embodiment of the present invention.

Figure 3 is a flow chart showing a pop-up cancellation method in accordance with an embodiment of the present invention.

The above described objects, features and advantages of the present invention will become more apparent from the description of the appended claims.

1 is a functional block diagram showing an audio playback device in accordance with an embodiment of the present invention. As shown in FIG. 1, the audio playback device 100 includes a pulse width modulation (PWM) sound source output unit 110, a digital analog converter (DAC) 120, an audio amplifier 130, a power failure determining unit 140, and a first A pop-up cancellation circuit 150 and a second pop-up cancellation circuit 160. The PWM sound source output unit 110 is configured to convert a class of analog audio signals into a left channel digital pulse wave signal 111 and a right channel digital pulse wave signal 112, and the digital analog converter 120 converts the left channel digital pulse wave signal. The right channel digital pulse signal 112 is converted into a left channel audio signal 121 and a right channel audio signal 122, respectively. The audio amplifier 130 amplifies the amplitudes of the left channel audio signal 121 and the right channel audio signal 122 to generate a left channel audio signal 131 and a right channel audio signal 132, respectively. Furthermore, the left channel audio signal 131 and the right channel audio signal 132 generated by the audio amplifier 130 can be further connected to a speaker (that is, a load) 190 for playing.

When the audio playback device 100 is suddenly powered down, the signals 111, 112, 121, 122, 131 or 132 may have an abnormal audio waveform, which in turn causes a popping sound to be heard on the speaker 190. Therefore, the present invention is connected to the first pop-up cancel circuit 150 and the second pop-up cancel circuit 160 at the output end of the PWM sound source output unit 110 and the output end of the audio amplifier 130, respectively, so that the audio playback device 100 is powered off or the voltage is not supplied. The sound can be eliminated before the sound is played in advance by the speaker.

2 is a schematic diagram showing a power-off determination unit 140 according to an embodiment of the present invention. In one embodiment, the power-off determination unit 140 of the present invention can receive the AC_DETIN and AC_VRMS voltage input signals and generate an AC_DETOUT output signal via an AC detection circuit 141, as shown in FIG. When the input signal disappears (meaning that the power is off or the AC_VRMS is less than the reference voltage), the AC_DETOUT output signal of the AC detection circuit 141 is raised to a high logic level and remains at a low logic level at other times. 65% in Fig. 2 means that the AC detecting circuit 141 determines whether the AC_VRMS (root mean square voltage value) of the current AC voltage is 65% of the normal AC rms voltage value of the full amplitude (for example, 110 V). That is, the voltage threshold Vth1), thereby generating a status signal of AC_65. The AC detection circuit 141 further compares the AC_VRMS rms voltage value with a reference voltage to generate a VRMS_OK status signal. Next, the state logic circuit 143 determines a status signal such as AC_65 and VRMS_OK to determine whether its output AC_DETOUT is a high logic level.

It should be noted that the above-described power-off determination unit 140 can be implemented by the IC circuit of the SONYCXA3810M, but the present invention is not limited thereto, and various circuits that can be used to detect power-off can be used in the present invention.

Referring to FIG. 1 again, the first pop-up cancellation circuit 150 is coupled between the PWM sound source output unit 110, the digital analog converter 120, and the power-off determination unit 140. When the output AC_DETOUT of the power-off determination unit 140 is at a high logic level, the diode 151 in the first pop-up cancel circuit 150 is forward-conducting, thereby turning on the transistors 152 and 153. At this time, the potentials of the nodes L1 and R1 are all reduced to the ground, which means that the left channel digital pulse signal 111 and the right channel digital pulse signal 112 can be grounded instantaneously when the power failure occurs.

The second pop-up cancellation circuit 160 is coupled between the audio amplifier 130, the speaker 190, and the power-off determination unit 140. When the output AC_DETOUT of the power-off determination unit 140 is at a low logic level, that is, the audio playback device 100 is in a normal power supply state, the diode 151 is open at this time, and the bases of the transistors 152 and 153 are both Pulled to ground, the transistors 152 and 153 will not turn on at this time. In other words, when the audio playback device 100 is in the normal power supply state, the left channel digital pulse signal 111 and the right channel digital pulse signal 112 can be normally output to the digital analog converter 120.

When the output AC_DETOUT of the power-off determination unit 140 is a high logic level, the transistor 161 (NPN transistor) in the second pop-up eliminating circuit 160 is turned on, so that the voltage of the node C is a small proportional voltage of the voltage VCC. Therefore, it is a low voltage level. At this time, the transistor 162 (PNP transistor) is turned on, and the node A and the node B are at a high voltage level, thereby turning on the transistors 163 and 164 (both NPN transistors). Therefore, at this time, the nodes L2 and R2 are pulled to the ground, thereby preventing the left channel audio signal 131 and the right channel audio signal 132 output by the audio amplifier 130 from generating a popping sound on the speaker 190.

When the output of the power-off determination unit 140 is AC_DETOUT is low logic When the level is on, the transistor 161 is not turned on. At this time, the voltage of the base of the transistor 162 is close to VCC, so the transistor 162 is not turned on. Therefore, the voltage levels of the bases of the transistors 163 and 164 are close to ground, so the transistors 163 and 164 are not turned on. In other words, when the audio playback device 100 is in the normal power supply state, the left channel audio signal 131 and the right channel audio signal 132 output by the audio amplifier 130 are not grounded, and can be normally output to the speaker 190 for playback.

Further, when the audio playback device 100 has a power failure or a voltage instability, the audio playback device 100 of the present invention has first and second order pop-up cancellation circuits (for example, a first pop-up cancellation circuit, respectively). The 150 and the second pop-up canceling circuit 160) can respectively pull the audio signals of different nodes in the audio processing path to the ground, thereby avoiding the situation that the noise signal generated by the power-off in the front stage is transmitted to the subsequent stage and the noise is transmitted. It is also possible to directly pull the output audio signal of the latter stage to the ground directly, and avoid the popping sound generated by the speaker playing the noise.

Figure 3 is a flow chart showing a pop-up cancellation method in accordance with an embodiment of the present invention. In step S310, the power-off determination unit 140 determines whether the audio playback device 100 has a power-off condition. In step S320, when the power-off condition occurs, the power-off determination unit 140 generates a power-off detection signal having a high logic level. In step S330, when the power-off condition occurs, the PWM sound source output unit and the output of the audio amplifier are grounded according to the power-off detection signal to prevent the audio playback device from generating a popping sound on the connected one of the speakers. For example, referring to the embodiment of FIG. 1 , when the power failure condition occurs, the power-off detection signal output by the power-off determination unit 140 is a high logic level, and the first pop-up cancellation circuit 150 can use the PWM sound source. The output of the output unit (for example, the left channel digital pulse signal 111 and the right channel digital pulse signal 112) is grounded, and the second pop-up cancellation circuit The output of the audio amplifier 130 (e.g., the left channel audio signal 131 and the right channel audio signal 132) may be grounded to avoid popping at the speaker 190.

The present invention has been disclosed in the above preferred embodiments, and is not intended to limit the scope of the present invention. Any one of ordinary skill in the art can make a few changes without departing from the spirit and scope of the invention. The scope of protection of the present invention is therefore defined by the scope of the appended claims.

100‧‧‧Audio playback device

110‧‧‧PWM source output unit

120‧‧‧Digital Analog Converter

130‧‧‧Audio Amplifier

140‧‧‧Power failure judgment unit

150‧‧‧First popping elimination circuit

160‧‧‧second pop-up cancellation circuit

190‧‧‧Speaker

111‧‧‧ Left channel digital pulse signal

112‧‧‧Right channel digital pulse signal

121, 131‧‧‧ left channel audio signal

122, 132‧‧‧right channel audio signal

151‧‧ ‧ diode

152-153, 161-164‧‧‧Optoelectronics

AC_DETOUT‧‧‧Power failure detection signal

V _CC ‧‧‧ voltage

L1, L2, R1, R2, A, B, C‧‧‧ nodes

Claims (8)

An audio playback device includes: a pulse width modulated sound source output unit for converting a type of analog audio signal into a left channel digital pulse signal and a right channel digital pulse signal; a digital analog converter for The left channel digital pulse signal and the right channel digital pulse signal are converted into a first left channel audio signal and a first right channel audio signal; an audio amplifier for the first left channel audio signal And amplifying the amplitude of the first right channel audio signal to generate a second left channel audio signal and a second right channel audio signal for playing on a speaker; and a power failure determining unit for determining the audio signal Whether a power-off condition occurs in the playback device, wherein when the power-off condition occurs, one of the power-off detection signals output by the power-off determination unit is a high logic level; a first pop-up cancellation circuit coupled to the a pulse width modulated sound source output unit, the digital analog converter, and the power failure determining unit, wherein when the power failure occurs, the first popping cancel circuit is based on the power failure detecting No. the left channel digital pulse signal and the right channel digital pulse signal are grounded to cancel the popping sound; and a second popping cancel circuit is coupled between the audio amplifier, the speaker and the power failure determining unit, wherein When the power-off situation occurs, the second pop-up cancellation circuit grounds the second left channel audio signal and the second right channel audio signal according to the power-off detection signal to eliminate popping. The audio playback device of claim 1, wherein the power failure detection unit outputs the power failure detection signal when the power failure condition does not occur. It is a low logic level. The audio playback device of claim 2, wherein the first pop-up canceling circuit and the second pop-up canceling circuit do not operate when the power-off condition does not occur. The audio playback device of claim 1, wherein the power failure determining unit calculates a rms voltage of one of the input AC power sources of the audio playback device, wherein the rms voltage is less than a reference At the time of voltage, the power-off determination unit sets the power-off detection signal to a high logic level. A pop-up canceling method for an audio playback device, wherein the audio playback device comprises a pulse width modulated sound source output unit, a digital analog converter and an audio amplifier for sequentially processing an analog audio signal, the method comprising: determining Whether the audio playback device has a power-off condition; when the power-off condition occurs, generating a power-off detection signal having a high logic level; and when the power-off condition occurs, according to the power-off detection signal The pulse width modulated tone source output unit and the output of the audio amplifier are grounded to avoid popping at the one of the connected speakers of the audio playback device. The method for eliminating pops according to claim 5, further comprising: generating the power-off detection signal having a low logic level when the power-off condition does not occur. The pop-up canceling method of claim 5, wherein the output of the pulse width modulated sound source output unit and the audio amplifier is not grounded when the power-off condition does not occur. The method for eliminating popping according to claim 5, further comprising: calculating a rms voltage of one of the input AC power sources of the audio playback device; and when the rms voltage is less than a reference voltage, The power-off detection signal is set to a high logic level.