KR19990038905A - Hand-free signal conversion circuit - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hand-free signal conversion circuit, and more particularly, to a circuit for converting an analog signal and a digital signal to each other in order to wirelessly transmit and receive a PCM data signal between a hand-free and a terminal of an automobile. An A / D and D / A converter 14 connected to the CODEC chip IC1 and the echo canceller chip IC2, and a + terminal is connected to the rear end of the CODEC chip IC1, and the-terminal A comparator 22 serving as a reference voltage, a flip flop FF having a clock terminal CLK connected to a rear end of the comparator 22, and an output terminal Q of the CODEC chip IC1 and the flip flop FF. And an inverting buffer (82, 84) and an inverting buffer (92, 94, 96) connected to the bus line 50 of the A / D and D / A converter 14 And a buffer 18, 98, a non-inverting buffer 82 and an inverting buffer 92, 94, 96, 98 of the buffer 18, and A / D and D Provides a hand-free signal conversion circuit including the IrDA 20 and the microprocessor 16 through which the PCA data signal is transmitted to and from the / A converter 14, so that the analog signal is cut off when it is lower than the reference voltage to prevent noise. The PCM data signal, which can be removed and is a digital signal, relates to a hand-free signal conversion circuit which can transmit / receive wirelessly with a terminal, thereby increasing convenience in use.

Description

Hand-free signal conversion circuit

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hand-free signal conversion circuit. In particular, in order to wirelessly transmit and receive a PCM data signal between a hand-free and a terminal of an automobile, an analog signal and a digital signal are converted to each other to transmit and receive a PCM data signal to a microprocessor and The signal relates to a hand free signal conversion circuit which is passed and blocked by a reference voltage.

Conventionally, in order to use a terminal such as a mobile phone as a telephone without disturbing the operation of the vehicle, the terminal is mounted on a cradle installed in the middle of the right side of the driver's seat, and a curl cord connected to the hand free is connected to the contact terminal below the terminal. Insert was used.

The configuration of such a hand-free will be described with reference to FIG. 1.

1 is a block diagram of a conventional hand free.

The microphone 10 is used by plugging into a sunshade in front of a car cumulus seat and converts a voice signal into an electrical signal, a microphone amplifier 12 that amplifies the electrical signal, and an electrical signal amplified by the microphone amplifier 12. And a comparator 22 for comparing the electrical signal received through the curl code from the terminal with a reference voltage, an analog switch 24 for forming a contact when the electrical signal is higher than the reference voltage, and dropping the contact when the electrical signal is higher than the reference voltage, and the analog switch ( 24) a preamplifier 26 for amplifying the first electrical signal, and a main amplifier 28 for amplifying the second, and a speaker 30 which converts the amplified electrical signal into an audible sound that can be heard by a human ear and sends it out. It is composed.

The electrical signal here is an analog signal and reference numeral 34 is a power supply for supplying power to the above configuration.

As described above, since an analog signal is transmitted and received between the hand-free and the terminal through a wire called a curl code, there is an inconvenience in using the wire cord curl code attached to or detached from the terminal, and there is a problem of poor sound quality. Applicant has previously filed a hand free system capable of transmitting and receiving PCM data signals (Application No. 97-58390).

The pre-applied hand-free system is described with reference to the accompanying drawings as follows.

2 is a block diagram of a hand free filed by the applicant.

Signals are transmitted to and received from the terminal, and the microphone 10, the microphone amplifier 12, the comparator 22, the analog switch 24, the preamplifier 26, the main amplifier 28, the speaker 30, the power supply 34 In the conventional hand-free consisting of a), IrDA 20 of the infrared transmitting and receiving module capable of transmitting and receiving a PCM data signal with the terminal, and equipped with an infrared sensor, a buffer 18 for shaping the input PCM data signal, and An A / D and D / A converter 14 converting analog signals input through the microphone 10 into PCM data and PCM data input through the IrDA 20 into analog signals, and the main amplifier ( 28, an analog switch 25 installed in front of the A / D and D / A converter 14 to prevent howling of the analog signal through the microprocessor 16, and a microprocessor 16 for determining whether the above-described configuration is operated. Characterized in that configured.

The present invention is a circuit configured to operate the above-mentioned hand-free, among which the important analog signal and the digital signal is converted to each other, PCM data signal is transmitted and received by the microprocessor and the analog signal is passed or blocked by the reference voltage signal of the hand-free It relates to a conversion circuit.

The present invention is a circuit for operating the applicant's pre- filed hand-free, and converts the analog signal and the digital signal to each other to block the analog signal when the lower than the reference voltage to remove noise and the digital signal PCM data signal is It is an object of the present invention to provide a hand-free signal conversion circuit capable of transmitting and receiving wirelessly with a terminal, thereby increasing convenience in use.

In order to achieve the above object, the present invention provides an A / D and D / A converter connected to a microphone amplifier and consisting of a CODEC chip and an echo canceller chip, and a + terminal connected to a rear end of the CODEC chip. Is a reference voltage, a flip-flop having a clock terminal connected to the rear end of the comparator, an analog switch connected to the output terminals of the CODEC chip and the flip-flop, and bus lines of the A / D and D / A converters. IrDA and microprocessor connected to the buffer consisting of an inverting buffer and an inverting buffer, and connected to the inverting buffer and the inverting buffer of the buffer, and to which A / D and D / A converters and standard PCM data signals are transmitted and received. To provide a hand-free signal conversion circuit comprising a.

1 is a block diagram of a conventional hand-free,

2 is a block diagram of a hand free filed by the applicant of the present application;

3 is a signal conversion circuit diagram of a hand-free according to the present invention.

<Description of Symbols for Main Parts of Drawings>

10: microphone 12: microphone amplifier

14: A / D and D / A Converter 16: Microprocessor

18: Buffer 20: IrDA

22: comparator 24: analog switch

26: preamplifier 28: main amplifier

30: speaker 34; Power supply

50: bus line 82, 84: non-inverting buffer

92, 94, 96, 98: inverting buffers R1, R2, R3, R4, R5: resistors

C1, C2: Capacitor D1: Diode

Q1: transistor FF: flip flop

IC1: CODEC Chip IC2: Echo Canceller Chip

Hereinafter, the present invention will be described with reference to the accompanying drawings.

3 is a signal conversion circuit diagram of the hand-free according to the present invention.

First, referring to the basic configuration of the present invention, an A / D and D / A converter 14 connected to the microphone amplifier 12 and configured with a CODEC chip IC1 and an echo canceller chip IC2, and the CODEC chip ( + Terminal is connected to the rear end of IC1),-terminal is a comparator 22 which becomes a reference voltage, a flip-flop FF to which a clock terminal CLK is connected to the rear end of the comparator 22, and the CODEC chip An analog switch 24 connected to the IC1 and the output terminal Q of the flip-flop FF, and to the bus line 50 of the A / D and D / A converters 14, A buffer 18 comprising 82, 84 and inverting buffers 92, 94, 96, and 98, and an inverting buffer 82 and an inverting buffer 92, 94, 96, and 98 of the buffer 18. And an IrDA 20 and a microprocessor 16 to which A / D and D / A converters 14 and standardized PCM data signals are transmitted and received.

In addition to the above-described basic configuration, the resistor R1 and the capacitor C1 are connected to the reset terminal R of the flip flop FF.

Reference numerals R2, R3, R4, and R5 denote resistors, C2 denotes a capacitor, D1 denotes a diode, and Q1 denotes a buffer 18 as a transistor.

The non-inverting buffers 82 and 84 constituting the buffer 18 here are three-state buffers.

Referring to the operation of the circuit having the above-described configuration, when the microprocessor determines whether the terminal and the hand-free can transmit and receive to each other, it is determined that the transmission and reception with each other is possible.

That is, pin 6 of the non-inverting buffer 84 constituting the buffer 18 is in a low state.

In this state, when a call comes in, the terminal outputs a PCM data signal and a clock frequency of 128 kHz and 8 kHz and detects it in the IrDA 20 and sends it to the A / D and D / A converter 14 through the buffer 18.

At this time, each signal is shaped through the inverting buffers 92, 94, 96, and 98 constituting the buffer 18 and transmitted to the A / D and D / A converters 14 through the bus line 50.

The clock frequency motivates the generation of sound in the CODEC chip IC1 and the echo canceller chip IC2, and the PCM data signal is converted into an audible analog signal by the CODEC chip IC1 and the echo canceller chip IC2. This prevents howling from which sound returns.

The analog signal converted by the CODEC chip IC1 is output at pin 3 so that it is in standby at the front of the analog switch 24 or passes through the comparator 22.

If the voltage of the analog signal input to the + terminal of the comparator 22 is higher than the reference voltage of the-terminal, pin 1 of the comparator 11 becomes high and the clock terminal CLK of the flip-flop FF is low. ) Is high and the output terminal Q is also high at low.

At this time, the high state of the output terminal Q is maintained by the time constant of the resistor R1 and the capacitor C1 connected to the reset terminal R, and is reset again after the delay time passes.

When the output terminal Q of the comparator 22 becomes high, the analog signal output from pin 3 of the CODEC chip IC1 passes from pin 1 to pin 2 of the analog switch 24, The preamplifier 26 is transmitted to the preamplifier 26 for primary amplification.

If a small noise enters the + terminal of the comparator 22, this signal is weak and lower than the reference voltage of the-terminal. Therefore, the output terminal Q of the flip-flop (FF) also remains in the state of the CODEC chip (IC1). The analog signal output from pin 3 of) does not pass through the analog switch 24.

In the case of transmission, the analog signal amplified by the microphone amplifier 12 is converted into the PCM data signal of the CODEC chip IC1 of the A / D and D / A converter 14, and is transferred to the echo canceller chip IC2. After howling is prevented, it is output through pin 12 of the echo canceller chip IC2.

As pin 6 of the non-inverting buffer 84 becomes high, the PCM data signal is transmitted to the terminal through the non-inverting buffer 82 connected to the transmission line tx.

As described above, the analog signal and the digital signal are converted to each other, and the analog signal is cut off when it is lower than the reference voltage to remove noise, and the PCM data signal, which is the digital signal, is a circuit that can transmit and receive wirelessly with the terminal.

As described above, the present invention converts an analog signal and a digital signal to each other, and when the analog signal is lower than the reference voltage, the noise can be removed and the PCM data signal, which is a digital signal, can be transmitted and received wirelessly with the terminal. It is a useful invention that can increase the ease of use.

Claims (2)

An A / D and D / A converter 14 connected to the microphone amplifier 12 and consisting of a CODEC chip IC1 and an echo canceller chip IC2, and a + terminal connected to a rear end of the CODEC chip IC1. The terminal is a comparator 22 serving as a reference voltage, a flip flop FF having a clock terminal CLK connected to a rear end of the comparator 22, a CODEC chip IC1 and a flip flop FF. An analog switch 24 connected to an output terminal Q of the first and second bus lines 50 of the A / D and D / A converters 14 and non-inverting buffers 82 and 84 and an inverting buffer ( 92, 94, 96, 98 and a buffer 18, the inverting buffer 82 and the inverting buffer (92, 94, 96, 98) of the buffer 18 is connected to the A / D and D A hand-free signal conversion circuit including an IrDA (20) and a microprocessor (16) through which a / A converter (14) and a formatted PCM data signal are transmitted and received. The hand-free signal conversion circuit according to claim 1, wherein a resistor (R1) and a capacitor (C1) are connected to a reset terminal (R) of the flip flop (FF).