TWI420919B - Volume adjusting system - Google Patents

Description

Volume adjustment system

The invention relates to a volume adjustment technology, in particular to a volume adjustment system.

At present, electronic devices such as mobile phones and portable music playback devices include an audio driving circuit for driving sound generating devices such as speakers and headphones to sound. Generally, the audio drive circuit includes a digital to analog converter and an amplifier. The digital to analog converter receives the digital audio signal and converts it into an analog signal. The amplifier amplifies the analog signal and provides it to the sound producing device to sound.

In practical applications, sound generating devices such as speakers or headphones have a maximum output volume limit. If the maximum output volume limit is exceeded, a broken sound will occur. This kind of broken sound is often confusing for the user and may damage some highly sensitive components.

In view of this, it is necessary to provide a volume adjustment system that prevents the occurrence of breakage.

A volume adjustment system is configured to receive an audio signal output by an audio input device, adjust the audio signal, and transmit the audio signal to an audio output device. The volume adjustment system comprises: a constant current level bias circuit, a control circuit and a volume processing circuit. The DC level bias circuit is configured to apply a DC bias current to the input AC audio signal to obtain an AC audio signal having a DC component. The control circuit is used according to When the audio signal intensity output by the audio input device exceeds a predetermined value, a corresponding control signal is generated. The volume processing circuit processes the audio signal output by the DC level bias circuit according to the control signal, so that the volume of the audio signal output by the volume processing circuit is within the volume output range allowed by the audio output device.

In the above volume adjustment system, in the case of generating a broken sound, a suitable amount of gain is output by the control circuit, and the audio signals output by the left channel and the right channel of the audio input device are subjected to gain processing, so that the volume is processed. The volume of the circuit output is within the volume range of the audio output device, avoiding the occurrence of breaks.

100‧‧‧Volume adjustment system

12‧‧‧DC level bias circuit

122‧‧‧First reverse summing and amplifying circuit

1221‧‧‧ Input to the amplifier circuit

1222‧‧‧Output of the amplifier circuit

124‧‧‧Second reverse summing amplifier circuit

14‧‧‧Control circuit

142‧‧‧Amplitude detection and amplification circuit

144‧‧‧Discharge circuit

144a‧‧‧The first branch of the discharge circuit

1441‧‧‧ Input of the first branch

1442‧‧‧Output of the first branch

146‧‧‧ trigger circuit

146a‧‧‧The first branch of the trigger circuit

1461‧‧‧ Input of the first branch of the trigger circuit

1462‧‧‧Output of the first branch of the trigger circuit

16‧‧‧Volume processing circuit

162‧‧‧Left channel gain control circuit

1621‧‧‧Amplification circuit

1621a‧‧‧Input of the amplifier circuit

1621b‧‧‧Output of the amplifier circuit

1622‧‧‧Switch circuit

1622a‧‧‧The first branch of the switching circuit

1623‧‧‧ input of the first branch of the switching circuit

1624‧‧‧ Output of the first branch of the switching circuit

164‧‧‧Right channel gain control circuit

20‧‧‧Audio input device

30‧‧‧Audio output device

1 is a circuit block diagram of a volume adjustment system in accordance with a preferred embodiment of the present invention.

2A and 2B are circuit diagrams of the volume adjustment system of Fig. 1.

The invention will be further described in detail below with reference to the accompanying drawings.

In order to further explain the volume adjustment system of the present invention, the following embodiments will be described in detail with reference to the accompanying drawings.

Referring to FIG. 1 , a volume adjustment system 100 is provided for receiving an audio signal input by an audio input device 20 , and adjusting the audio signal to be transmitted to an audio output device 30 . The automatic adjustment of the volume of the audio output device 30 prevents the audio signal output from the audio output device 30 from being broken. Specifically, the audio signal output by the audio input device 20 may be mono or multi-channel. In this embodiment, two channels are taken as an example, that is, a left channel (LC) output signal is included. Right channel (RC) output signal.

The volume adjustment system 100 includes a constant current level bias circuit 12, a control circuit 14, and a volume processing circuit 16.

An input of the DC level bias circuit 12 is coupled to the audio input device 20, and an output is coupled to the volume processing circuit 16. Generally, the audio signal input by the audio input device 20 is an AC audio signal, and the DC level bias circuit 12 is configured to apply a DC bias voltage to the input AC audio signal to obtain an AC audio signal having a DC component.

An input of the control circuit 14 is coupled to the audio input device 20, and an output is coupled to the volume processing circuit 16. The control circuit 14 is configured to generate a control signal according to the audio signal input by the audio input device 20.

The volume processing circuit 16 includes a left channel gain control circuit 162 and a right channel gain control circuit 164. The volume processing circuit 16 processes the audio signal output by the DC level bias circuit 12 according to the control signal. The volume of the audio signal output by the volume processing circuit 16 is within the volume output range allowed by the audio output device 30. An output of the volume processing circuit 16 is coupled to the audio output device 30 such that an audio signal passing through the volume processing circuit 16 passes through the audio output device 30 to output a sound.

2A and 2B, the DC level bias circuit 12 includes a first reverse summing circuit 122 and a second reverse summing circuit 124. The input of the first inverse summing and amplifying circuit 122 is connected to the left channel output of the audio input device 20, and the output terminal is connected to the left channel gain control circuit 162. The input of the second reverse summing and amplifying circuit 124 is connected to the right channel output of the audio input device 20, and the output terminal is connected to the right channel gain control circuit 164.

Specifically, the first reverse summing and amplifying circuit 122 includes a first amplifier U1, a first resistor R1, a second resistor R2, and a third resistor R3. An input 1221 of the first inverse summing and amplifying circuit 122 is coupled to a left channel output of the audio input device 20. The forward input terminal of the first amplifier U1 is grounded, and the negative input terminal is connected to the input end of the first reverse summing and amplifying circuit 122 by the first resistor R1, and the second resistor R2 is coupled to the first resistor R1. The output of the first amplifier U1 is connected, and the third resistor R3 is also connected to the positive voltage terminal U.

The structure of the second reverse summing and amplifying circuit 124 is substantially the same as that of the first reverse summing and amplifying circuit 122, except that the input end of the second reverse summing and amplifying circuit 124 and the audio input device 20 The right channel output is connected. In this embodiment, the positive and negative power terminals of the first amplifier U1 are respectively applied with voltages of +12V and -12V. The resistances of the first resistor R1, the second resistor R2, and the third resistor R3 are both 10KΩ.

The control circuit 14 includes an amplitude detecting and amplifying circuit 142, a discharging circuit 144 and a trigger circuit 146.

The amplitude detecting and amplifying circuit 142 is configured to detect a negative voltage peak of the audio signal input by the audio input device 20, and convert the negative voltage peak into a positive voltage peak and output the voltage to the discharging circuit 144. Specifically, the amplitude detecting and amplifying circuit 142 includes a second amplifier U2, a first diode D1, a second diode D2, and a third diode D3. The cathode of the first diode D1 is connected to the left channel output of the audio input device 20, and the cathode of the second diode D2 is connected to the right channel output of the audio input device 20. The anodes of the first diode D1 and the second diode D2 are connected to the negative input terminal of the second amplifier U2 by a fourth resistor R4. The negative input terminal of the second amplifier U2 is further connected to the output terminal via a fifth resistor R5, the forward input terminal of the second amplifier U2 is grounded, the anode of the third diode D3 and the discharge battery The roads 144 are connected. The first diode D1 and the second diode D2 are in an off state when an audio signal of a positive voltage is input, that is, the amplitude detection and amplification circuit 142 can only receive and receive a negative voltage audio signal. So that the signal can be processed later. The third diode D3 ensures a positive voltage output and prevents backflow. In this embodiment, the positive and negative power terminals of the second amplifier U2 are respectively applied with voltages of +12V and -12V. The resistance of the fourth resistor R4 is 3KΩ, and the resistance of the fifth resistor R5 is 12KΩ.

The discharge circuit 144 is configured to perform a voltage division process on the positive voltage peak output from the amplitude detecting and amplifying circuit 142. Specifically, the discharge circuit 144 includes a first capacitor C1 and four branches. One end of the first capacitor C1 is connected to the cathode of the third diode D3, and the other end is grounded. For the sake of brevity, only the specific circuit structure of one of the four branches, that is, the first branch 144a, will be specifically described below. The first branch 144a includes an input terminal 1441 and an output terminal 1442, and a sixth resistor R6 and a seventh resistor R7 sequentially connected in series between the input terminal 1441 and the ground potential. Specifically, the input terminal 1441 is connected to the cathode of the third diode D3 in the amplitude detecting and amplifying circuit 142, and the serial connection of the sixth resistor R6 and the seventh resistor R7 constitutes an output end 1442, which is connected to the trigger. Circuit 146. The other branches of the discharge circuit 144 have substantially the same structure as the first branch 144a, and the four branches are different in that the resistances of the sixth resistors R6 in the respective branches are different from each other. The first capacitor C1 is used to accumulate voltage for voltage division in the discharge circuit 144 and to trigger the trigger circuit 146. In the present embodiment, the capacitance of the first capacitor C1 is 22 uF. The resistance of the sixth resistor R6 of the four branches of the discharge circuit 144 is sequentially increased to 5.9 KΩ, 8.45 KΩ, 11.8 KΩ, and 15.8 KΩ, respectively. The resistance of the seventh resistor R7 of the four branches of the discharge circuit 144 is 10 KΩ.

The trigger circuit 146 is configured to not use the intensity of the audio signal passing through the discharge circuit 144. Simultaneously, a corresponding control signal that drives the volume processing circuit 16 is generated. The trigger circuit 146 includes four branches of the same structure. The four branches of the flip-flop circuit 146 are respectively connected to the four branches of the discharge circuit 144. For the sake of brevity, only one of the four branches, that is, the specific circuit structure of the first branch 146a, will be specifically described below. The first branch 146a includes an input terminal 1461 and an output terminal 1462, and a comparator A, an eighth resistor R8 and a second capacitor C2 connected to the input terminal 1461 and the output terminal 1462. The input end 1461 of the first branch 146a is coupled to the output 1442 of the first branch 144a of the discharge circuit 144. The forward input of the comparator A and the input of the first branch 146a of the trigger circuit 146 The terminal 1461 is connected, the negative input terminal is connected to the positive voltage terminal U, the negative power terminal of the comparator A is grounded, and one end of the eighth resistor R8 is connected to the positive power terminal of the comparator A, the second One end of the capacitor C2 is grounded, and the other end of the eighth resistor R8, the other end of the second capacitor C2, and the output end of the comparator A are commonly connected to the output end of the first branch 146a. Comparator A in each branch has a trigger voltage value, and the comparator A is triggered after the intensity of the audio signal input from the input terminal 1461 reaches the trigger voltage value. Wherein, the second capacitor C2 functions as a voltage regulator. In the present embodiment, the positive and negative power terminals of the comparator A are applied with voltages of +12 V and 0, respectively. The capacitance of the second capacitor C2 is 0.1 uF. The resistance of the eighth resistor R8 is 4.7 KΩ. In this embodiment, the voltage connected to the positive voltage terminal U is +3.3V.

The left channel gain control circuit 162 performs gain processing on the left channel output audio signal output from the DC level bias circuit 12 according to the control signal outputted by the trigger circuit 146. Specifically, the left channel gain control circuit 162 includes an amplifying circuit 1621 and a switching circuit 1622.

The amplifying circuit 1621 includes an input end 1621a, an output end 1621b, and a connection A third amplifier U3, a ninth resistor R9 and a tenth resistor R10 are connected between the input terminal 1621a and the output terminal 1621b. The input terminal 1621a of the amplifying circuit 1621 is connected to the output terminal 1222 of the first inverse summing and amplifying circuit 122. The output terminal 1621b of the amplifying circuit 1621 is connected to the audio output device 30. The forward input terminal of the third amplifier U3 is grounded, and the negative input terminal is connected to the input end 1621a of the amplifying circuit 1621 by the ninth resistor R9, and the tenth resistor R10 and the third amplifier U3 are connected. The outputs are connected.

The switch circuit 1622 includes four branches, and the four branches of the switch circuit 1622 are respectively connected to the four branches of the trigger circuit 146. For the sake of brevity, only the specific circuit structure of one of the four branches, that is, the first branch 1622a, will be specifically described below. The first branch 1622a includes an input terminal 1623, an output terminal 1624, and a controllable switch K and an eleventh resistor R11 connected between the input terminal 1623 and the output terminal 1624. The input 1623 of the first branch 1622a is coupled to the output 1462 of the corresponding branch of the trigger circuit 146a, and the output 1624 is coupled to the negative input of the third amplifier U3. The input end of the controllable switch K is connected to the output end 1621b of the amplifying circuit 1621 by the eleventh resistor R11, the output end is connected to the negative input end of the third amplifier U3, and the control end is connected to the first end. The output 1623 of the branch 1622a is connected. The other branches of the switch circuit 1622 are substantially identical in structure to the first branch 1622a of the switch circuit 1622. The branches of the switch circuit 1622 differ in the resistance of the eleventh resistor R11 in each branch. Can be the same or different. In the present embodiment, the positive and negative power terminals of the third amplifier U3 are respectively applied with voltages of +12 V and -12 V. The resistance values of the ninth resistor R9 and the tenth resistor R10 are both 10 KΩ, and the resistance value of the eleventh resistor R11 of the four branches of the switch circuit 1622 is sequentially decreased, which are 90 KΩ, 72 KΩ, 56 KΩ, and 42 KΩ, respectively.

The right channel gain control circuit 164 performs gain processing on the audio signal output from the right channel output from the DC level bias circuit 12 according to the control signal outputted by the trigger circuit 146. Specifically, the structure of the right channel gain control circuit 164 is substantially the same as the left channel gain control circuit 162. The difference is that the input terminal of the amplifying circuit 1621 in the right channel gain control circuit 164 is connected to the output terminal of the second inverse summing amplifying circuit 124.

In practical applications, the signals passing through the left and right channel gain control circuits 162 and 164 need to pass through a capacitor that can filter out the DC signal, and the signal is restored to be enabled by the audio output device 30 (eg, a speaker). Output.

It can be understood that the audio signal output by the audio input device 20 can be divided into a left channel output and a right channel output, and only one channel is output, corresponding to an audio signal output by the audio input device 20, and the volume adjustment system 100 is DC. The level biasing circuit 12 only needs to include a reverse summing and amplifying circuit, and the amplitude detecting and amplifying circuit 142 only needs to include a diode connected to the audio input device 20, and the volume processing circuit only needs to include one channel gain control. Circuit.

The left channel output and the right channel output of the audio input device 20 respectively output an audio signal, and the audio signal passes through the DC level bias circuit 12 and the amplitude detecting and amplifying circuit 142 respectively, and the amplitude detection and After the amplifier circuit 142 and the discharge circuit 144 are processed, if the trigger circuit 146 is unable to obtain a trigger, it indicates that the audio signal does not generate a sound break after being amplified, and the audio signal directly passes through the left and right channel gain control circuits 162. The amplifying circuit 1621 in 164 is output to the output of the audio output device 30. Otherwise, if the intensity of the audio signal exceeds a predetermined value, the amplitude detecting and amplifying circuit 142 detects the peak voltage of the audio signal and outputs the peak voltage to the first capacitor C1, and the branches in the discharging circuit 144 Electricity accumulated in the first capacitor C1 The voltage is divided, and the first capacitor C1 accumulates the voltage to a certain value, and then triggers one or more branches of the corresponding trigger circuit 146 to be turned on, so that the comparator A in the one or more branches outputs a high level. The high level outputted from the comparator A causes the corresponding controllable switch K in the left channel gain circuit 162 and the right channel gain circuit 164 to be turned on, thereby changing the negative input applied to the third amplifier U3. The resistance value between the terminal and the output terminal reduces the amplification factor of the third amplifier U3, and ensures that the left channel output and the right channel output are subjected to gain processing, and the volume output by the audio output device 30 does not break. The phenomenon. In this embodiment, after the first branch of the discharge circuit 144 is triggered, the first branch of the trigger circuit 146 is triggered, and when the corresponding comparator A output is high, the left and right channel gain circuits 162 are controlled. The controllable switch K in the first branch 1622a of the switch circuit 1622 of 164 is turned on, and the audio signal output gain is 90%. By analogy, 80%, 70%, and 60% of the three-level gain can also be achieved.

It can be understood that the output of the audio input device 20 can be one channel or multiple channels, as long as the number of the first diode D1 or the second diode D2 in the amplitude detecting and amplifying circuit 142 is changed correspondingly and The number of gain control circuits in the volume processing circuit 16 is achievable.

It can be understood that if the number of stages of the gain and the amount of gain of each stage are to be changed, the switching circuit in the discharge circuit 144, the trigger circuit 146, the left channel gain circuit 162, and the right channel gain circuit 164 can be increased. The number of branches of 1622 and the corresponding parameters of the components in each branch are implemented.

In the above volume adjustment system, in the case of generating a broken sound, a suitable amount of gain is output by the control circuit, and the audio signal of the left channel output and the right channel output of the audio input device is subjected to gain processing to make the volume The volume of the output of the processing circuit is within the volume range of the audio output device, avoiding the occurrence of breakage.

In summary, the present invention has indeed met the requirements of the invention patent, and has filed a patent application according to law. However, the above is only a preferred embodiment of the present invention, and it is not possible to limit the scope of the patent application in this case. Equivalent modifications or variations made by persons skilled in the art in light of the spirit of the invention are intended to be included within the scope of the following claims.

100‧‧‧Volume adjustment system

12‧‧‧DC level bias circuit

14‧‧‧Control circuit

142‧‧‧Amplitude detection and amplification circuit

144‧‧‧Discharge circuit

146‧‧‧ trigger circuit

16‧‧‧Volume processing circuit

162‧‧‧Left channel gain control circuit

164‧‧‧Right channel gain control circuit

20‧‧‧Audio input device

30‧‧‧Audio output device

Claims (9)

A volume adjustment system for receiving an audio signal output by an audio input device, adjusting the audio signal and transmitting the audio signal to an audio output device, the volume adjustment system comprising: a constant current level bias circuit for inputting The AC audio signal is applied with a DC bias current to obtain an AC audio signal having a DC component; a control circuit for generating a corresponding control signal according to the audio signal strength output by the audio input device exceeding a predetermined value; The processing circuit processes the audio signal output by the DC level bias circuit according to the control signal, so that the volume of the audio signal output by the volume processing circuit is within a volume output range allowed by the audio output device. The volume adjustment system of claim 1, wherein the control circuit comprises: an amplitude detection and amplification circuit for detecting a negative voltage peak of the audio signal input by the audio input device, and The negative voltage peak is converted into a positive voltage peak; a discharge circuit is used for dividing the positive voltage peak outputted by the amplitude detection and amplification circuit; and a trigger circuit having a trigger voltage value according to the discharge The output value of the circuit is triggered after the trigger voltage value is reached, and a control signal for driving the volume processing circuit is generated. The volume adjustment system of claim 2, wherein the DC level bias circuit comprises at least one reverse summing amplifier circuit, an input end of the at least one reverse summing amplifier circuit and the audio input device The output of at least one channel is connected, and the output is connected to the volume processing circuit. The volume adjustment system of claim 3, wherein the volume is The processing circuit includes at least one gain control circuit corresponding to the reverse summing and amplifying circuit, and the gain control circuit performs gain processing on the audio signal output by the DC level offset circuit according to the control signal output by the trigger circuit. The volume adjustment system of claim 4, wherein the reverse summing and amplifying circuit comprises a first amplifier, a first resistor, a second resistor and a third resistor, the reverse summation amplification An input end of the circuit is connected to an output of the audio input device, a forward input end of the first amplifier is grounded, and a negative input terminal is connected to an input end of the reverse summation amplifying circuit by the first resistor, and The second resistor is connected to the output end of the first amplifier, and is further connected to a positive voltage terminal by the third resistor. The volume adjustment system of claim 5, wherein the amplitude detecting and amplifying circuit comprises a second amplifier, a first diode corresponding to the input, and a second diode, the first The cathode of the diode and the second diode is connected to the output of the audio input device, and the anode is connected to the negative input terminal of the second amplifier by a fourth resistor, and the negative direction of the second amplifier The input terminal is also connected to the output terminal by a fifth resistor, and the forward input terminal of the second amplifier is grounded. The volume adjustment system of claim 6, wherein the discharge circuit comprises a first capacitor and at least one branch, the amplitude detecting and amplifying circuit further comprising a third diode, the first capacitor One end of the discharge is connected to the cathode of the third diode, and the other end is grounded. Each branch of the discharge circuit includes a sixth resistor and a seventh resistor, and the input of each branch of the discharge circuit is The cathodes of the third diode are connected, one end of the sixth resistor of each branch is connected to the input end of the branch, and the other end is connected to the output end of the branch, and the seventh of each branch One end of the resistor is connected to the output of the branch, and One end is grounded, and the resistance of the sixth resistor in each branch of the discharge circuit is different from each other. The volume adjustment system of claim 7, wherein the trigger circuit comprises a branch having the same number of branches as the discharge circuit and corresponding to each branch of the discharge circuit, each branch An input terminal and an output terminal, and a comparator connected to the input terminal and the output terminal, an eighth resistor and a second capacitor, and an output of the corresponding branch of each branch and the corresponding branch of the discharge circuit The terminals are connected, the forward input of the comparator of each branch is connected to the input of the branch, the negative input is connected to the positive voltage terminal, the negative power supply is grounded, and the eighth of each branch is connected. One end of the resistor is connected to the positive power terminal of the comparator in the branch, one end of the second capacitor of each branch is grounded, the other end of the eighth resistor of each branch, the other end of the second capacitor, and the comparator The outputs are connected in common to the output of the branch. The volume adjustment system of claim 8, wherein the gain control circuit comprises an amplifying circuit and a switching circuit, the amplifying circuit comprising a third amplifier, a ninth resistor and a tenth resistor, the amplifying circuit The input end is connected to the output end of the reverse summing and amplifying circuit, the forward input end of the third amplifier is grounded, and the negative input end is connected to the input end of the amplifying circuit by the ninth resistor, and Connected by the tenth resistor to an output of the third amplifier, the switch circuit comprising a branch of the same number of branches as the trigger circuit and corresponding to each branch of the trigger circuit, the switch circuit Each branch includes an input end, an output end, and a controllable switch connected between the input end and the output end and an eleventh resistor, and the input end of each branch and the corresponding branch of the trigger circuit The output of the circuit is connected, the output is connected to the negative input of the third amplifier, and the input of the controllable switch of each branch The eleventh resistor of the branch is connected to the output end of the amplifying circuit, the output end is connected to the negative input end of the third amplifier, and the control end is connected to the output end of the corresponding branch of the trigger circuit. .