KR20040019222A - An audio input selecting circuit of a monitor using a general purpose analog multiplexer - Google Patents

Abstract

PURPOSE: A circuit for selecting audio input of a monitor by using a universal multiplexer is provided to simplify a control program of a microcontroller unit, thereby reducing the manufacturing cost. CONSTITUTION: An input signal selector(30) includes a multiplexer receiving a plurality of audio signals from an external audio signal source and a selecting signal from a control unit(34) for selecting and outputting a specific audio signal. A tone control unit(31) has one end combined with an output terminal of the input signal selector and an input terminal of an output unit(33), and the other end grounded for converting a tone of the specific audio signal. An amplifying unit(32) includes an amplifier amplifying the specific audio signal to be the sufficient size for driving an output device of the output unit. The output unit includes the output device outputting the amplified audio signal in a sound wave of audio frequency. The control unit includes a microcontroller unit controlling the input signal selector and the amplifying unit.

Description

AUDIO INPUT SELECTING CIRCUIT OF A MONITOR USING A GENERAL PURPOSE ANALOG MULTIPLEXER}

The present invention relates to an audio input selection circuit of a monitor using a general-purpose multiplexer, and more particularly, in an audio input selection circuit of a monitor receiving audio signals from a plurality of audio signal sources, complicated programming is required due to unnecessary functions. It relates to a reliable and simple circuit configuration of the audio input selection circuit of a monitor implemented by employing a general-purpose multiplexer instead of a dedicated preamplifier IC.

In the field of monitors, the role of the past monitors was merely to output the video signal transmitted from the video signal source to the screen. However, as multimedia progresses, a TV function is implemented in a monitor, and a computer monitor with a speaker on the monitor appears one after another, so that a computer user may be able to output audio even without a separate PC speaker. It became.

In addition, not only a single audio signal source such as a computer sound card is input as an audio signal input to the monitor, but also various types of audio inputs such as audio input of a VTR and audio input of a TV, as well as audio input from a computer sound card. Monitors have also emerged that allow multiple audio inputs from devices.

However, such a monitor capable of inputting a plurality of audio signals requires a circuit for selecting a signal to be output from various input signals, that is, an audio input selection circuit. Although the desired signal can be selected as a mechanical switch, it is common to adopt an electronic switch rather than a mechanical switch in order to solve the problem of spatial constraints on the monitor and increase durability.

In order to implement such an audio input selection circuit, a conventional preamplifier IC for controlling an audio signal is used. The dedicated IC includes an audio signal selection function, a pre-amplifier function, a tone control function, Various functions such as volume control function can be implemented. However, among these various functions, functions other than the audio signal selection function and the preamplifier function, that is, the tone control function and the volume control function, are almost unnecessary functions. This is because the tone control function or the volume control function is generally performed by the main amplifier and the controller connected to the dedicated IC rather than the dedicated IC including the preamplifier. In addition, in order to control the dedicated IC, a control program must be written even for the unused portion, which increases the capacity of the control program, wastes development manpower and time, and causes errors in the program as the capacity of the program increases. In addition, the probability of occurrence is increased, and the physical configuration of the audio output circuit of the monitor itself is also complicated.

Accordingly, there has been a steady demand for the invention of a monitor having an audio signal input selection circuit that allows a user to select a desired input signal from among a plurality of audio signal inputs without a dedicated preamplifier IC having unnecessary functions.

SUMMARY OF THE INVENTION The present invention has been made in response to the above-mentioned request. The present invention implements an audio signal input selection circuit using a general-purpose multiplexer to simplify the configuration of the audio output circuit of the monitor and to simplify the audio output control program. It is an object of the present invention to provide an audio input selection circuit of a monitor.

1 is a configuration diagram of an audio input selection circuit of a monitor according to the prior art;

2 is a configuration diagram showing the interior of the preamplifier 10 shown in FIG. 1 in more detail;

3 is a configuration diagram of an audio input signal selection circuit of a monitor using a general-purpose multiplexer according to the present invention;

4 is a block diagram illustrating in detail an audio input selection circuit of a monitor using a general-purpose multiplexer according to the present invention shown in FIG.

<Name of main drawing reference>

10, 20 ... preamplifier 11 ... amplifier

12 ...... Output section 13 ...... Control section

210 ... Input selector 220 ... Volume control

230 ... Voice control section 30, 40 ... Input selection section

31, 41 ... Voice control section 32, 42 ... Amplification section

33,43 ...... Output section 34,44 ...... Control section

401 ...... Selection signal

In order to achieve the above object, the audio input selection circuit of the monitor using the general-purpose multiplexer according to the present invention is an input signal selection unit, a tone control unit coupled to the input signal selector, and is coupled to the tone control unit An amplifying unit, an output unit coupled to the amplifying unit, a control unit coupled to the input signal selector and the amplifying unit,

The input signal selector receives a plurality of audio signals (each audio signal is composed of a pair of left / right signals) input from the external audio signal source to the input signal selector and a selection signal from the controller. It includes a multiplexer for selecting and outputting a specific audio signal from a plurality of audio signals,

The tone control unit includes a resistor and a capacitor connected in series, one end of which is coupled to an output terminal of the input signal selection unit and an input terminal of the output unit, and the other end of which is grounded to convert a tone of the audio signal. ,

The amplifier includes an amplifier for amplifying the audio signal output from the tone control unit to a predetermined size sufficient to drive the output device of the output unit,

The output unit includes an output device such as a speaker for outputting the audio signal amplified by the amplifier in sound waves of an audible frequency,

The control unit may include a micro control unit for controlling operations of the input selector and the amplifier.

Hereinafter, with reference to the drawings will be described in more detail.

In the present specification, a case in which a maximum of four audio signal sources are connected to four channel audio input selection circuits, that is, four input terminals will be described as an example.

1 is a configuration diagram of an audio input selection circuit of a monitor according to the prior art.

The audio input selection circuit of the monitor according to the prior art comprises a preamplifier 10, an amplifier 11, an output 12 and a controller 13.

FIG. 2 is a diagram illustrating the interior of the preamplifier 10 shown in FIG. 1 in more detail.

As described above, the preamplifier of the audio input selection circuit of the monitor according to the prior art is composed of a dedicated preamplifier IC, the dedicated preamplifier IC is the input selector 210, the volume control unit 220 and the tone control unit ( 230, and each of the input selector 210, the volume controller 220, and the tone controller 230 is connected to and controlled by the micro control unit.

The operation principle of the audio input signal selection circuit according to the prior art is as follows.

That is, each connection terminal from the first input terminal to the fourth input terminal is given a unique register value, and when an audio signal source is connected to each input terminal, the micro control unit (MCU) By I2C communication (inter integrated-circuit communication) by setting and resetting the corresponding register value of each input terminal of the preamplifier, only the audio signal source connected to the desired input terminal can be accepted.

Thereafter, the volume control unit 220 similarly adjusts the volume by amplifying only the audio signal for the corresponding register value to a predetermined level by I2C communication, and in the tone control unit 230 as well by the corresponding register value by I2C communication. Only the audio signal for the amplification according to the frequency band will be able to adjust the tone.

However, since the signal primarily amplified in the preamplifier is finally insufficient to drive the speaker of the output unit, it is necessary to amplify it again to a sufficient level in the main amplifier, and the main amplifier also needs a volume control function.

If so, the preamplifier does not need to include a volume control section, but since the control program must be programmed for the volume control section that is unnecessary because of the conventional IC, a dedicated IC is used. Increased, and development manpower was wasted.

3 is a configuration diagram of an audio input signal selection circuit of a monitor using a general-purpose multiplexer according to the present invention.

As shown in FIG. 3, the audio input selection circuit of the monitor using the general-purpose multiplexer according to the present invention includes an input selector 30, a tone control unit 31, an amplifier 32, an output unit 33, and a microcontroller. Unit 34.

4 is a block diagram illustrating in detail an audio input selection circuit of a monitor using a general-purpose multiplexer according to the present invention shown in FIG.

The principle of an operation of selecting a specific audio signal in the input selector 40 is as follows.

That is, in the multiplexer, the number of inputs that can be controlled by the n-bit selection signal (n is a natural number) is generally (2 ⁿ -1).

For example, a four-channel multiplexer, which allows up to four audio inputs, selects a particular input from four inputs and requires a 3-bit select signal to allow audio inputs connected to that input.

In addition, the output of the multiplexer according to the selection signal is as follows.

Selection signal Select channel C0 C1 C2 X Y 00001 0011- 0101- X0X1X2X3 None Y0Y1Y2Y3 None

In the above table, the selection signals X0, X1, X2, and X3 are the left channels of the first input terminal, the second input terminal, the third input terminal, and the fourth input terminal, respectively, and Y0, Y1, Y2, and Y3 are respectively. Means a right channel of the first input terminal, the second input terminal, the third input terminal and the fourth input terminal.

Accordingly, when selecting a desired audio input, the control unit 44 may transmit a 3-bit selection signal 401 for selecting an input terminal to which the corresponding audio signal source is connected to the input selection unit 40.

If C0 is a logic 1 of the 3-bit selection signal 401, all audio signals are cut off. In the case of logic 0, the input terminals as shown in the table above are selected according to the values of the remaining 2 bits of selection signals C1 and C2. It is selected and delivered to the output terminal.

Next, the tone control unit 41 is a resistor and a capacitor connected in series, one end of which is coupled to the output terminal of the input signal selection unit and the input terminal of the output unit, and the other end is grounded to convert the tone of the audio signal. And a capacitor.

In a circuit of frequency f, the combined impedance Z of the resistor of the resistor r and the capacitor of the capacitor c is

Therefore, as the value of r or c is changed, the value of the synthesized impedance z is changed. When the appropriate resistance value and capacitance value are selected according to the characteristics of the speaker to be used, the tone of the audio signal can be adjusted. .

The amplifier 42 is implemented like a general amplifier. In other words, any type of amplifier, such as class A, class B, class AB, or class D, may be an amplifier capable of amplifying an audio signal in any manner, and the amplification gain is applied to the audio signal transmitted from the tone controller 41. By doing so, what is necessary is just enough to drive the speaker which comprises the output part 43. FIG.

The output unit 43 also includes a general speaker. Any speaker capable of converting an audio signal into sound waves may be sufficient, but in the audio input selection circuit of the monitor according to the present invention, since the speaker is mainly embedded in the monitor, it is generally several watts (W) to several tens of watts (W). Some magnetic speaker can be adopted.

The control section 44 comprises a micro control unit for controlling the audio output circuit of the overall monitor. The micro control unit transmits a 3-bit selection signal 401 to the input selector 40, and controls the output of the output unit 42.

As described above, by using the audio input selection circuit of the monitor using the general-purpose multiplexer according to the present invention, the control program of the MCU as compared to the case of using a dedicated preamplifier IC that also needs to create a control program for unnecessary functional elements. This greatly simplifies the system, reduces development time, reduces development time, and reduces the manufacturing cost by simplifying the configuration of the monitor's audio output circuit by using an inexpensive general-purpose multiplexer.

Claims (1)

An input signal selection unit, a tone control unit coupled to the input signal selector, an amplification unit coupled to the tone control unit, an output unit coupled to the amplification unit, the input signal selector and the amplification unit In the audio input selection circuit of a monitor using a general-purpose multiplexer comprising a control unit coupled to, The input signal selector receives a plurality of audio signals (each audio signal is composed of a pair of left / right signals) input from the external audio signal source to the input signal selector and a selection signal from the controller. It includes a multiplexer for selecting and outputting a specific audio signal from a plurality of audio signals, The tone control unit includes a resistor and a capacitor connected in series, one end of which is coupled to an output terminal of the input signal selection unit and an input terminal of the output unit, and the other end of which is grounded to convert a tone of the audio signal. , The amplifier includes an amplifier for amplifying the audio signal output from the tone control unit to a predetermined size sufficient to drive the output device of the output unit, The output unit includes an output device such as a speaker for outputting the audio signal amplified by the amplifier in sound waves of an audible frequency, And the control unit includes a micro control unit for controlling the operation of the input selector and the amplifier.