CN102237095A - Audio frequency coding/decoding chip output circuit - Google Patents

Abstract

The invention relates to an audio frequency coding/decoding chip output circuit, which comprises an audio frequency coding/decoding chip, an audio frequency amplification chip electrically connected with the audio frequency coding/decoding chip and a noise absorbing circuit which is electrically connected between the audio frequency coding/decoding chip and the audio frequency amplification chip and can be used for reducing a noise signal; the noise absorbing circuit comprises a voltage detection circuit and a switch circuit; and when the voltage detection circuit detects that an input voltage signal of the audio frequency coding/decoding chip comprises a high-potential switching on/off signal, the voltage detection circuit triggers the switch circuit and the audio frequency amplification chip is grounded by the switch circuit, so that the interference of noise in the output voltage signal is avoided.

Description

Audio codec/decoder chip output circuit

technical field

The invention relates to an output circuit, in particular to an output circuit of an audio encoding/decoding chip.

Background technique

The computer is usually equipped with an audio codec/decoder chip that provides audio output, and is used for mutual conversion of audio signals and sounds between various peripheral devices. Traditional audio encoding/decoding chips are directly electrically connected to peripherals with audio output functions, such as speakers and earphones. However, when the computer is turned on or off or reset, the analog signal output pin of the audio codec/decoder chip will have a sudden change in high and low potential, and the potential of the output analog signal will directly rise from 0V to 2.5V. Therefore, it will affect the connected peripherals, for example, it will generate a lot of noise at the output of the speaker.

Contents of the invention

In view of the above, it is necessary to provide an output circuit of an audio encoding/decoding chip that can eliminate noise during audio output.

An audio encoding/decoding chip output circuit, comprising an audio encoding/decoding chip, an audio amplification chip electrically connected to the audio encoding/decoding chip, and an audio amplifier chip electrically connected to the audio encoding/decoding chip and the audio A noise absorption circuit that can reduce noise signals between amplifying chips, the noise absorption circuit includes a voltage detection circuit and a switch circuit, when the voltage detection circuit detects that the input voltage signal of the audio encoding/decoding chip contains When the switch signal is high potential, the voltage detection circuit opens the switch circuit, and the audio amplifier chip is grounded through the switch circuit, thereby avoiding the interference of noise in the output voltage signal.

Compared with the prior art, the audio encoding/decoding chip output circuit of the present invention detects the input voltage signal of the audio encoding/decoding chip through the voltage detection circuit, and detects that the input voltage signal contains a high potential switch signal , or a reset signal of low potential, the gate circuit opens the switch circuit, and the audio amplifier chip is grounded through the switch circuit, thereby avoiding the interference of noise in the output voltage signal.

Description of drawings

FIG. 1 is a block diagram of an output circuit of an audio encoding/decoding chip in a preferred embodiment of the present invention.

FIG. 2 is a circuit diagram of an on/off signal detection circuit of the voltage detection circuit in FIG. 1 .

FIG. 3 is a circuit diagram of a reset signal detection circuit of the voltage detection circuit in FIG. 1 .

Explanation of main component symbols

Audio codec/decoder chip 100

Left channel analog output port 101

Right channel analog output port 102

Noise absorbing circuit 200

Voltage detection circuit 210

Switch signal detection circuit 211

Reset signal detection circuit 212

Gate circuit 220

Control signal input terminal 221, 222

Output terminal 223, 303

Switch circuit 230

Audio amplifier chip 300

Left channel analog input terminal 301

Right channel analog input terminal 302

Horn 400

Comparator A1, A2

FET Q1, Q2

Resistance R1～R6

Detailed ways

Please refer to FIG. 1 , the preferred embodiment of the audio encoding/decoding chip output circuit of the present invention includes an audio encoding/decoding chip 100 , a noise absorption circuit 200 , an audio amplifier chip 300 and a speaker 400 . The audio encoding/decoding chip 100 includes a left channel analog output terminal 101 and a right channel analog output terminal 102 . The noise absorption circuit 200 includes a voltage detection circuit 210 , a gate circuit 220 and a switch circuit 230 . The audio amplifier chip 300 includes a left channel analog input terminal 301 , a right channel analog input terminal 302 and an output terminal 303 . When the voltage detection circuit 210 detects that the input voltage signal of the audio encoding/decoding chip 100 includes a high-potential switch signal or a low-potential reset signal, the voltage detection circuit 210 controls the gate circuit 220 to open the The switch circuit 230 is described above. The audio amplifying chip 300 is grounded through the switch circuit 230 , thereby avoiding the noise in the output voltage signal from interfering with the speaker 400 . The switch circuit 230 includes switches S1, S2 and resistors R1, R2. The left channel analog output terminal 101 is grounded sequentially through the switch S1 and the resistor R1, and the right channel analog output terminal 102 is grounded sequentially through the switch S2 and the resistor R2. The left channel analog output terminal 101 is also electrically connected to the left channel analog input terminal 301 via a switch S1, and the right channel analog output terminal 102 is also electrically connected to the right channel analog input terminal via a switch S2 302. The output end 303 is electrically connected to the speaker 400 .

Referring to FIGS. 1 to 3 , the voltage detection circuit 210 includes a power-on/off signal detection circuit 211 and a reset signal detection circuit 212 . The on/off signal detection circuit 211 and the reset signal detection circuit 212 are respectively used to detect the on/off and reset signals of a computer, and the voltage detection circuit 210 outputs control signals according to the detected on/off and reset signals to the gate circuit 220 . The switch signal detection circuit 211 includes a comparator A1, an N-channel field effect transistor Q1 and resistors R3-R5. The inverting input terminal of the comparator A1 receives a DC voltage VCC through the resistor R3, and the inverting input terminal of the comparator A1 is also grounded through the resistor R4. The inverting input terminal of the comparator A1 is used to receive the switch signal. The non-inverting input terminal of the comparator A1 receives a reference voltage. The output end of the comparator A1 is electrically connected to the gate of the field effect transistor Q1. The source of the field effect transistor Q1 is grounded. The drain of the field effect transistor Q1 receives the DC voltage VCC through the resistor R5. The drain of the field effect transistor Q1 is used to output the control signal.

The reset signal detection circuit 212 includes a comparator A2, an N-channel field effect transistor Q2 and a resistor R6. The inverting input terminal of the comparator A2 receives the reset signal. The non-inverting input terminal of the comparator A2 receives the reference voltage. The output terminal of the comparator A2 is electrically connected to the gate of the field effect transistor Q2. The source of the field effect transistor Q2 is grounded via the resistor R6. The source of the field effect transistor Q2 is used to output the control signal. The collector of the field effect transistor Q2 receives the DC voltage VCC. The gate circuit 220 includes an OR gate, and the OR gate includes control signal input terminals 221 , 222 and an output terminal 223 . The control signal input terminals 221 and 222 are respectively electrically connected to the drain of the field effect transistor Q1 and the source of the field effect transistor Q2 to receive the control signal. The OR gate outputs a drive signal at the output terminal 223 to control the opening and closing of the switches S1 and S2 according to the received control signal.

During operation, the voltage signal from the computer system is input to the audio encoding/decoding chip 100 , and the switch signal detection circuit 211 detects the voltage signal input to the audio encoding/decoding chip 100 . When the on/off signal detection circuit 211 detects that the voltage signal from the computer system includes a high potential on/off signal, the potential of the inverting input terminal of the comparator A1 is higher than the potential of the non-inverting input terminal. The output terminal of the comparator A1 outputs a low potential. The field effect transistor Q1 is turned off, and its drain outputs a high potential control signal. And when the reset signal detecting circuit 212 detects that the voltage signal from the computer system includes a low potential reset signal, the potential of the inverting input terminal of the comparator A2 is lower than the potential of the non-inverting input terminal. The output terminal of the comparator A2 outputs a high potential. The field effect transistor Q2 is turned on, and its drain outputs a high potential control signal. Therefore, no matter whether the voltage detecting circuit 210 detects a high-potential switch signal or a low-potential reset signal, it will output a high-potential driving signal after the logical operation of the OR gate. At this time, the switches S1 and S2 are in an open state under the action of the driving signal, thus completely isolating the audio encoding/decoding chip 100 and the audio amplifying chip 300 . At the same time, the analog input terminal 301 of the left channel and the analog input terminal 302 of the right channel are grounded through resistors R1 and R2 respectively. When the user performs the power on/off or reset operation, the noise in the power on/off and reset signals will not interfere with the audio amplifier chip 300 , which avoids popping interference on the output signal of the speaker 400 .

Only the switch signal detection circuit 211 does not detect the switch signal in the voltage signal from the computer system, and the reset signal detection circuit 212 also does not detect the voltage signal from the computer system When the signal is reset, the field effect transistor Q1 is turned on, and its drain outputs a low potential control signal; the field effect transistor Q2 is turned off, and its drain outputs a low potential control signal. After the logical operation of the OR gate, a low potential driving signal is output. At this time, the switches S1 and S2 are in a closed state under the action of the driving signal, so the audio encoding/decoding chip 100 and the audio amplification chip 300 are electrically connected through the switching circuit 230 . The audio signal output by the audio encoding/decoding chip 100 can be normally output on the speaker 400 after being amplified by the audio amplifier chip 300 .

The audio encoding/decoding chip output circuit of the present invention detects the input voltage signal of the audio encoding/decoding chip 100 through the voltage detection circuit 210, and detects that the input voltage signal includes a high-potential on/off signal, or a low-potential When the signal is reset, the gate circuit 220 opens the switch circuit 230, and the audio amplifier chip 300 is grounded through the switch circuit 230 to avoid the interference of noise in the output voltage signal.

Claims (9)

1. An audio coding/decoding chip output circuit, comprising an audio coding/decoding chip and an audio amplification chip electrically connected to the audio coding/decoding chip, characterized in that: the audio coding/decoding chip and audio A noise absorption circuit that can reduce noise signals is also connected between the amplification chips. The noise absorption circuit includes a voltage detection circuit and a switch circuit. When the voltage detection circuit detects the input voltage of the audio coding/decoding chip When the signal contains a high-potential switch signal, the voltage detection circuit turns on the switch circuit, and the audio amplifier chip is grounded through the switch circuit, thereby avoiding the interference of noise in the output voltage signal. 2. The audio encoding/decoding chip output circuit as claimed in claim 1, characterized in that: the audio encoding/decoding chip output circuit also includes a gate circuit, when the voltage detection circuit detects that the audio encoding/decoding When the input voltage signal of the chip includes a high-potential switch signal or a low-potential reset signal, the voltage detection circuit controls the gate circuit to open the switch circuit. 3. audio coding/decoding chip output circuit as claimed in claim 1, is characterized in that: described switch circuit comprises a first switch, a second switch, a first resistance and a second resistance, and described audio coding The /decoding chip includes a left channel analog output terminal and a right channel analog output terminal, the left channel analog output terminal is grounded through the first switch and the first resistor in turn, and the right channel analog output terminal is grounded through the first resistor in turn. The second switch and the second resistor are grounded. 4. audio code/decoder chip output circuit as claimed in claim 3, it is characterized in that: described audio amplifier chip comprises a left sound channel analog input end, a right sound channel analog input end and an output end, and described left The channel analog output terminal is also electrically connected to the left channel analog input terminal via a first switch, and the right channel analog output terminal is also electrically connected to the right channel analog input terminal via a second switch. The output end of the amplification chip is electrically connected to a speaker. 5. The audio coding/decoding chip output circuit as claimed in claim 2, characterized in that: said voltage detection circuit comprises a switch signal detection circuit and a reset signal detection circuit, said switch signal detection circuit The circuit and the reset signal detection circuit are respectively used to detect the on/off and reset signals, and the voltage detection circuit outputs a control signal to the gate circuit according to the detected on/off and reset signals. 6. The audio coding/decoding chip output circuit as claimed in claim 5, characterized in that: the switch signal detection circuit includes a first comparator, a first field effect transistor and a third resistor, the The inverting input terminal of the first comparator receives the switch signal, the non-inverting input terminal of the first comparator receives a reference voltage, and the output terminal of the first comparator is electrically connected to the first field effect transistor the gate of the first field effect transistor, the source of the first field effect transistor is grounded, the drain of the first field effect transistor receives a DC voltage through the third resistor, and the drain of the first field effect transistor outputs the control signal . 7. The audio coding/decoding chip output circuit as claimed in claim 6, wherein the reset signal detection circuit includes a second comparator, a second field effect transistor and a fourth resistor, and the first The inverting input terminal of the second comparator receives the reset signal, the non-inverting input terminal of the second comparator receives the reference voltage, and the output terminal of the second comparator is electrically connected to the second field effect transistor. gate, the source of the second field effect transistor is grounded via a fourth resistor, the drain of the second field effect transistor receives the DC voltage, and the source of the second field effect transistor outputs the control signal . 8. audio coding/decoding chip output circuit as claimed in claim 7, is characterized in that: described gate circuit comprises an OR gate, and described OR gate comprises a first control signal input end, a second control signal input end and an output terminal, the first and second control signal input terminals are respectively electrically connected to the drain of the first field effect transistor and the source of the second field effect transistor to receive the control signal, and the OR gate Outputting a drive signal at the output terminal according to the received control signal to control the opening and closing of the first and second switches. 9. The audio encoding/decoding chip output circuit according to claim 7, characterized in that: said first and second field effect transistors are N-channel field effect transistors.

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