KR20010028823A - Switching circuit for voice output in multi band telecommunication set - Google Patents

Abstract

PURPOSE: A switch circuit for a voice output in a multiple band terminal is provided to construct a switching circuit by using field effect transistors. CONSTITUTION: The first band switch(100) is turned on/off by a selection signal. The first band switch(100) equips the first and the second field effect transistor(T1,T2) to which an N channel and a P channel field effect transistor are connected in parallel, in order to connect an output signal of a GSM(Global System For Mobile) CODEC(COder And DECoder) with a speaker. The second band switch(200) is turned on/off by a selection signal. The second band switch(200) equips the third and the fourth field effect transistor(T3,T4) to which the N channel and the P channel field effect transistor are connected in parallel, in order to connect an output signal of a CDMA(Code Division Multiple Access) CODEC with the speaker. A selector(300) equips an inverter(10), and outputs the selection signal for controlling the transistors(T1-T4) on the basis of a band selection signal. A resistor(R1) is located on a path connected to the speaker, and constantly keeps a difference between signals outputted from the transistors(T1-T4) and ground levels.

Description

SWITCHING CIRCUIT FOR VOICE OUTPUT IN MULTI BAND TELECOMMUNICATION SET}

The present invention relates to a switching circuit for outputting a voice signal in a terminal using a plurality of codecs, and more particularly to a circuit capable of outputting a voice with minimal loss.

In general, when a control unit (MAIN CONTROL UNIT) does not support multiple bands in a communication device and other devices using multiple bands, a codec (CODEC: CODER & DECODER: hereinafter referred to as a "codec") is individually assigned to each band. Should be designed as That is, the controller can output voice using a single codec in a terminal that supports multiple bands, but when the controller cannot support multiple bands, the controller that can operate each band and each codec corresponding thereto are used. Doing.

In this case, a switch circuit for connecting a voice signal output from each codec to a speaker is required for the voice output.

For example, in a dual band (DUAL BAND) terminal supporting GSM (GLOBAL SYSTEM FOR MOBILE) (hereinafter referred to as "GSM") and CDMA (CODE DIVISION MULTIPLE ACCESS: "CDMA") at the same time If used, the codec for supporting voice is also used redundantly. Therefore, a switch circuit for switching the voice signal output from the GSM codec or the CDMA codec to the speaker is required according to the band selected.

On the other hand, in the case of a terminal using a single codec, the operation of the speaker does not reduce the output volume since the signal output from the codec is directly input to the speaker to output voice. However, when an analog switch using a conventional transistor is used to connect a codec and a speaker in a terminal having a plurality of codecs, the voltage driving the speaker is lowered because the impedance of the switch is high. That is, the output volume of the speaker drops. In general, conventional analog switches have a resistance of 2Ω, which is lowered to about 3/4 to 7/8 of the original sound.

Due to the above reasons, in order to increase the dropped volume, an audio amplifier must be additionally used. In this case, there is a problem that more power is consumed to operate the audio amplifier. In addition, the use of an analog switch and an audio amplifier occupies a lot of mounting space of a printed circuit board (PCB), and noise is also amplified together, causing noise to be mixed in the original sound.

Accordingly, an object of the present invention is to provide a switching circuit capable of operating at low impedance during speech output in a terminal using a dual codec.

In order to achieve the above object, the present invention is a circuit for voice output of a terminal having a GS codec and a CD codec, an inverter for receiving and inverting a band selection signal, the gate end of the band A first field effect transistor having a selection signal, a drain stage connected to the GS M codec, a source stage connected to a speaker, and a gate terminal received an output signal of the inverter, and a drain stage connected to the speaker; A third field effect transistor having a source terminal connected to the GS codec, a gate terminal receiving an output signal of the inverter, a drain terminal connected to the CDM codec, and a source terminal connected to the speaker; A field effect transistor and a gate terminal receive the band selection signal, and a source terminal is connected to the CD codec. A stage has a fourth field effect transistor connected to the speaker, one end is connected to the input terminal of the speaker, the other end is a resistor connected to the ground.

1 is a switch circuit diagram having a parallel structure for outputting voice in a terminal having two codecs according to an embodiment of the present invention.

2 is a circuit diagram for outputting voice in a terminal having two codecs according to another embodiment of the present invention.

3 is a circuit diagram for outputting voice in a terminal having two codecs according to another embodiment of the present invention.

4 is a switch circuit diagram using an N-channel transistor according to another embodiment of the present invention.

5 is a switch circuit diagram using a P-channel transistor according to another embodiment of the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. Specific details appear in the following description, which is provided to aid a more general understanding of the present invention, and it should be understood by those skilled in the art that the present invention may be practiced without these specific details. It will be self explanatory. In the following description of the present invention, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

1 is a switch circuit diagram having a parallel structure for outputting voice in a terminal having two codecs according to an embodiment of the present invention.

2 is a circuit diagram for outputting voice in a terminal having two codecs according to another embodiment of the present invention.

3 is a circuit diagram for outputting voice in a terminal having two codecs according to another embodiment of the present invention.

4 is a switch circuit diagram using an N-channel transistor according to another embodiment of the present invention.

5 is a switch circuit diagram using a P-channel transistor according to another embodiment of the present invention.

First, the first embodiment of the present invention will be described below with reference to FIG.

The controller (not shown) selects one of signals output from the plurality of codecs through a switch circuit and outputs a band selection signal for transmitting to the speaker.

The switch circuit includes a first band switch unit 100, a second band switch unit 200, and a selector 300 to switch the voice signal output from the codec according to the band selection signal output from the control unit and transmit the same to the speaker. do.

The first band switch unit 100 includes field effect transistors T1 and T2 connected in parallel, and the field effect transistor is turned on / off according to the selection signal output from the selector 300 so that the first band voice signal GSM Codec output signal) to the speaker.

The second band switch unit 200 includes the field effect transistors T3 and T4 connected in parallel, and the field effect transistors T3 and T4 are turned on / off according to the selection signal output from the selector 300 so that the second band switch unit 200 is turned on. The band voice signal (CDMA codec output signal) is transmitted to the speaker.

The selector 300 outputs a selection signal for controlling the first and second band switch units according to the band selection signal output from the controller.

A detailed circuit configuration according to the above configuration will be described below.

The first band switch unit 100 is turned on or off according to the selection signal, and the first and second field effect transistors T1 and N channel P transistors for connecting the output signal of the GSM codec to the speaker are connected in parallel. T2).

The second band switch unit 200 is turned on or off according to the selection signal, and the third and fourth field effect transistors T3 and N, which are connected in parallel with the N-channel and P-channel field effect transistors for connecting the output signal of the CDMA codec to the speaker, T4).

The selector 300 includes an inverter 10 and controls the transistors T1, T2, T3, and T4 of the first band switch 100 and the second switch 200 based on the band select signal. Outputs a selection signal for

In addition, the configuration according to FIG. 1 includes a resistor R1 positioned on a path leading to a speaker to make the difference between the signal output through the field effect transistors T1, T2, T3, and T4 and the ground level constant. have.

An operation according to the configuration as shown in FIG. 1 will be described below.

When the GSM band is selected, the band select signal goes high. The level of the high signal is such that the field effect transistor is sufficiently SATURATION. At this time, the first and second field effect transistors T1 and T2 are turned on to connect an output signal of the GSM codec to the speaker. However, the third and fourth field effect transistors T3 and T4 are turned off and do not operate.

When the CDMA band is selected, the band selection signal goes low. The low signal is changed into a high signal by the inverter 10, and the level of the signal output from the inverter 10 is such that the field effect transistor is sufficiently SATURATION. At this time, the third and fourth field effect transistors T3 and T4 are turned on to connect the output signal of the CDMA codec to the speaker. However, the first and second field effect transistors T1 and T2 are turned off and do not operate. Typically, the resistance applied to the drain and the source by one field effect transistor is 0.6Ω. Therefore, when field effect transistors are connected in parallel, the resistance becomes 0.3 Ω, which enables low impedance switching. Of course, there is enough current between the drain and the source to drive the speakers.

The configuration of the second embodiment according to FIG. 2 includes an N-channel field effect transistor T1 for turning on or off according to a band selection signal to connect an output signal of a GSM codec to a speaker;

An N-channel field effect transistor T3 for turning on or off according to the inverted selection signal to connect the output signal of the CDMA codec to the speaker;

One end is connected to the input terminal of the speaker and the other end is connected to the ground, and is made of a resistor (R1) to make a difference between the signal output through the field effect transistors (T1, T3) and the ground level.

The operation according to the configuration of FIG. 2 will be described below.

When the GSM band is selected, the band select signal goes high. The level of the high signal is such that the field effect transistor is sufficiently SATURATION. At this time, the first field effect transistor T1 is turned on to connect the output signal of the GSM codec to the speaker. However, the third field effect transistor T3 is turned off and does not operate.

When the CDMA band is selected, the band selection signal goes low. The low signal is changed into a high signal by the inverter 10, and the level of the signal output from the inverter 10 is such that the field effect transistor is sufficiently SATURATION. At this time, the third field effect transistor T3 is turned on to connect the output signal of the CDMA codec to the speaker. However, the first field effect transistor T1 is turned off and does not operate.

The configuration of the third embodiment according to FIG. 3 includes a P-channel field effect transistor T2 for turning on or off according to a band selection signal to connect an output signal of a GSM codec to a speaker;

A P-channel field effect transistor T4 for turning on or off according to the inverted selection signal to connect the output signal of the CDMA codec to the speaker;

One end is connected to the speaker input terminal, and the other end is connected to ground, and the resistance R1 is provided to make the difference between the signal output through the field effect transistors T2 and T4 and the ground level constant.

An operation according to the configuration of FIG. 3 will be described below.

When the GSM band is selected, the band selection signal goes low. Then, the second field effect transistor T2 is turned on to connect the output signal of the GSM codec to the speaker. However, the fourth field effect transistor T4 is turned off and does not operate.

When the CDMA band is selected, the band select signal becomes HIGH. The high signal is converted into a low signal by the inverter 10. At this time, the fourth field effect transistor T4 is turned on to connect the output signal of the CDMA codec to the speaker. However, the second field effect transistor T2 is turned off and does not operate.

4 and 5 are circuit diagrams for reducing the impedance due to switching by half by connecting each field effect transistor in parallel in the configuration according to FIGS. 2 and 3.

The operation according to FIGS. 4 and 5 is similar to the operation according to FIGS. 2 and 3 described above, and a detailed description thereof will be omitted.

Meanwhile, in the detailed description of the present invention, specific embodiments have been described, but various modifications are possible without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined not only by the claims below, but also by the equivalents of the claims of the present invention.

As described above, the present invention configures a switching circuit using a field effect transistor, so that the switching operation can be performed with low impedance.

Claims (10)

In the circuit for audio output of a multi-band terminal having a codec for each band, A voice signal connected to each of the voice signal output terminals of the codec and having a field effect transistor turned on / off according to a band selection signal and outputted from one of the codecs by an on / off operation of the field effect transistor A switch circuit for transmitting a to a speaker, And a control unit for outputting the band selection signal. The method of claim 1, wherein the switch circuit, A plurality of band switch units having field effect transistors, connected to each of the codecs, for transmitting the voice signals output from each of the codecs to the speaker by turning on / off the field effect transistors; And a selection unit for outputting a selection signal for turning on / off the field effect transistor according to the band selection signal. The method of claim 2, wherein the band switch unit, A switch circuit comprising an N-channel field effect transistor and a channel-effect transistor in parallel. The method of claim 2, wherein the band switch unit, A switch circuit characterized in that a circuit in which two N-channel field effect transistors are connected in parallel. The method of claim 2, wherein the band switch unit, Switch circuit, characterized in that the two channel-effect transistors are connected in parallel. The method of claim 2, wherein the band switch unit, And the N-channel transistor transmits the voice signal to the speaker by being turned on and off by the selection signal. The method of claim 2, wherein the band switch unit, And the channel transistor transmits the audio signal to the speaker by being turned on and off by the selection signal. The method according to any one of claims 2 to 7, wherein the selection unit, And an inverter for inverting and outputting the band selection signal. The method according to any one of claims 1 to 7, And a resistor connected at one end to the input terminal of the speaker and at the other end to the ground. A circuit for voice output of a mobile wireless terminal having a GS codec and a CD codec, An inverter for receiving and inverting a band selection signal; A first field effect transistor having a gate end receiving the band selection signal, a drain end connected to the GS M codec, and a source end connected to a speaker; A second field effect transistor having a gate terminal receiving an output signal of the inverter, a drain stage being connected to the speaker, and a source terminal being connected to the GS codec; A third field effect transistor having a gate terminal receiving an output signal of the inverter, a drain stage being connected to the CDM codec, and a source terminal being connected to the speaker; A fourth field effect transistor having a gate terminal input to the band selection signal, a source terminal connected to the CD codec, and a drain stage connected to the speaker; A switch circuit having one end connected to an input terminal of the speaker and the other end connected to ground.