An acoustic-electric transducer includes a connection part that has a first connection point able to contact a first contact in a terminal for processing the electrical signal, and a second connection point able to contact a second contact having a potential lower than the potential of the first contact, a microphone that transduces a sound inputted from an external source into an electrical signal, a changeover switch that switches between a non-mute state where the electrical signal is outputted to the terminal and a mute state where the electrical signal is not outputted to the terminal, and a current control circuit that makes a current flow between the first contact and the second contact until a predetermined time passes from the time when the connection part is connected to the terminal and reduces the current flowing between the first contact and the second contact after the predetermined time passes, the current control circuit being provided between the changeover switch and the connection part.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority to the Japanese Patent Application number 2019-113442, filed on Jun. 19, 2019. The contents of this application are incorporated herein by reference in their entirety.

BACKGROUND OF THE INVENTION

The present invention relates to an acoustic-electric transducer for transducing a sound into an electrical signal.

Conventionally, a headset with a switch to mute an audio output from a microphone is known (see, for example, Japanese Unexamined Patent Application Publication No 2003-188967).

A terminal capable of connecting an acoustic-electric transducer such as a microphone or a headset has a connection detection function for detecting that the acoustic-electric transducer is connected. This connection detection function is for detecting the connection of the acoustic-electric transducer by detecting a change in a voltage due to a current flowing through the acoustic-electric transducer when a plug of the acoustic-electric transducer is connected.

However, in a conventional circuit configuration, the current does not flow if the acoustic-electric transducer in the mute state is connected to the terminal, and the terminal cannot detect that the microphone is connected by using the connection detection function. Therefore, even if the microphone or the headset is connected to the terminal, the terminal does not detect them.

BRIEF SUMMARY OF THE INVENTION

The present invention focuses on these points, and an object of the present invention is to provide an acoustic-electric transducer that allows the terminal to detect that the acoustic-electric transducer is connected even if the acoustic-electric transducer in the mute state is connected to the terminal.

An acoustic-electric transducer of an aspect of the present invention is an acoustic-electric transducer for transducing a sound into an electrical signal that includes a connection part that has a first connection point able to contact a first contact in a terminal for processing the electrical signal, and a second connection point able to contact a second contact having a potential lower than the potential of the first contact, an acoustic-electric transducing part that transduces a sound inputted from an external source into an electrical signal, a changeover switch that switches between a non-mute state where the electrical signal is outputted to the terminal and a mute state where the electrical signal is not outputted to the terminal, and a current control circuit that makes a current flow between the first contact and the second contact until a predetermined time passes from the time when the connection part is connected to the terminal and reduces the current flowing between the first contact and the second contact after the predetermined time passes, the current control circuit being provided between the changeover switch and the connection part.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, the present invention will be described through exemplary embodiments of the present invention, but the following exemplary embodiments do not limit the invention according to the claims, and not all of the combinations of features described in the exemplary embodiments are necessarily essential to the solution means of the invention.

An Outline of an Acoustic-Electric Transducer1

FIG. 1shows a configuration of an acoustic-electric transducer1according to the embodiment. The acoustic-electric transducer1is a device for transducing a sound into an electrical signal and is, for example, a microphone device. The acoustic-electric transducer1may be other devices such as a headset that is attached to a user's head. The acoustic-electric transducer1may further include a speaker for transducing an electrical signal generated by the terminal2into a sound.

The terminal2is, for example, a game device, an audio device, a communication device, a smart phone, or a computer. The acoustic-electric transducer1is attachable to/detachable from the terminal2, and outputs a transduced electrical signal to the terminal2while the acoustic-electric transducer1is connected to the terminal2. The terminal2processes an electrical signal inputted from the acoustic-electric transducer1. For example, the terminal2transduces the inputted electrical signal into a sound or transfers the inputted electrical signal to other devices.

A Configuration of the Acoustic-Electric Transducer1

FIG. 2shows a configuration of the acoustic-electric transducer1and the terminal2. The acoustic-electric transducer1includes a sound input part10, a changeover switch11, a cable12, a connection part13, and a current control circuit14.

The sound input part10has a microphone101which is an acoustic-electric transducing part that transduces the sound inputted from the outside into the electrical signal. The microphone101is, for example, an electret condenser microphone.

The changeover switch11switches between a non-mute state where a sound-transduced electrical signal is outputted to the terminal2and a mute state where the sound-transduced electrical signal is not outputted to the terminal2. The changeover switch11conducts in the non-mute state and the acoustic-electric transducer1can receive power from the terminal2. In the non-mute state, the electrical signal generated by the microphone101is inputted to the terminal2via the changeover switch11, the cable12, and the connection part13. The changeover switch11is non-conductive in the mute state and the power from the terminal2is not supplied to the acoustic-electric transducer1. Therefore, in the mute state, the microphone101does not transduce the electrical signal even if the sound from an external source is received.

The cable12connects the acoustic-electric transducer1and the terminal2. The cable12transmits, to the terminal2, the electric signal transduced from the sound by the microphone101.

The connection part13is, for example, a connector plug provided at a tip end of the cable12. The connection part13has a first connection point131and a second connection point132. The first connection point131contacts a first contact A of a connector jack provided to the terminal2, and the second connection point132contacts a second contact B. The connection part13complies with, for example, the plug-in power standard and receives the power from the terminal2. The first contact A is, for example, a metal terminal connected to a power supply (Vcc) of the terminal2. The second contact B is, for example, a metal terminal connected to a ground of the terminal2. Therefore, a potential of the first contact A is higher than the potential of the second contact B.

The current control circuit14is a circuit that makes a current flow between the first contact A and the second contact B until a predetermined time passes from the time when the acoustic-electric transducer1is connected to the terminal2. The predetermined time is a time that is longer than the minimum time required for the terminal2to determine whether the acoustic-electric transducer1is connected, and is a time determined by the time constant of the current control circuit14. The current control circuit14is provided between the changeover switch11and the connection part13. The current control circuit14has a capacitor141, an electronic switch142, a resistor143(corresponding to a first resistor), and a resistor144(corresponding to a second resistor).

The capacitor141is arranged between the first connection point131and a gate terminal G of the electronic switch142. The capacitor141is charged by the power supplied from terminal2.

The electronic switch142is, for example, a field effect transistor. A drain terminal D of the electronic switch142is electrically connected to the first connection point131via the resistor143. Further, a source terminal S of the electronic switch142is electrically connected to the second connection point132. A voltage of the gate terminal G of the electronic switch142increases until the capacitor141is completely charged. As a result, a potential difference between the gate terminal G and the source terminal S increases, and a state between the drain terminal D and the source terminal S of the electronic switch142becomes a conductive state.

The voltage of the gate terminal G decreases after the capacitor141is completely charged, and the state between the drain terminal D and the source terminal S of the electronic switch142becomes a non-conductive state. As a result, the electronic switch142reduces the current flowing between the first contact A and the second contact B after the predetermined time passes from the time when the connection part13is connected to the terminal2. Since the time required for the state between the drain terminal D and the source terminal S to change from the conductive state to the non-conductive state depends on capacitance of the capacitor141, the predetermined time is determined by the capacitance of the capacitor141.

Due to the state between the drain terminal D and the source terminal S of the electronic switch142becoming the non-conductive state, the current control circuit14enters a high impedance state and does not affect other circuits. The current based on the sound inputted to the microphone101flows between the first contact A and the second contact B in this state.

The resistor143is arranged between (i) the first connection point131and the changeover switch11and (ii) the drain terminal D of the electronic switch142. The resistor143prevents a short circuit from occurring between the first contact A and the second contact B when the state between the drain terminal D and the source terminal S of the electronic switch142is conductive. The resistor144is provided between the second connection point132and the capacitor141. The resistor144increases the potential of the gate terminal G in accordance with the magnitude of the current flowing during a time from when the acoustic-electric transducer1is connected to the terminal2until the predetermined time passes. As a result, the potential of the gate terminal G changes in accordance with the amount of charge of the capacitor141.

A Configuration of the Terminal2

Next, a configuration of the terminal2will be described with reference toFIG. 2. The terminal2includes a resistor201, an amplifier202, a voltage detection circuit203, an audio processing circuit204, and a control part205.

The voltage detection circuit203detects the voltage of the first contact A. The voltage detection circuit203provides notification about the detected voltage of the first contact A to the control part205. The amplifier202amplifies the electrical signal transduced from the sound by the microphone101. The audio processing circuit204, for example, executes a process of outputting the sound based on the electrical signal inputted from the amplifier202to a speaker or executes a process of transmitting the electrical signal through a communication line.

The control part205is, for example, a Central Processing Unit (CPU) and controls respective parts of the terminal2. If the voltage detected by the voltage detection circuit203is equal to or greater than a threshold, the control part205determines that the acoustic-electric transducer1is not connected to the terminal2, and if the voltage detected by the voltage detection circuit203is less than the threshold, the control part205determines that the acoustic-electric transducer1is connected to the terminal2. The threshold is set below the maximum value assumed as the voltage of the first contact A within the predetermined time from the time when the acoustic-electric transducer1is connected to the terminal2. For example, the control part205switches between an on state and an off state of a microphone (not shown) built in the terminal2on the basis of the voltage of the first contact A detected by the voltage detection circuit203.

A Voltage Change Due to a Connection of the Acoustic-Electric Transducer1

FIGS. 3A and 3Bshow a change in voltage when the acoustic-electric transducer1is connected to the terminal2. Vcc inFIGS. 3A and 3Bis a power supply voltage of the terminal2.FIG. 3Ashows a voltage between the gate terminal G and the source terminal S of the electronic switch142.FIG. 3Bshows the voltage of the first contact A detected by the voltage detection circuit203. A time T1inFIG. 3indicates a time at which the acoustic-electric transducer1is connected to the terminal2.

As shown inFIG. 3A, the voltage between the gate terminal G and the source terminal S of the electronic switch142increases due to the power supply from the terminal2starting at the time T1. As a result, the state between the drain terminal D and the source terminal S becomes conductive, and so the current flows between the first contact A and the second contact B. As the capacitor141accumulates the charge due to the current flowing in, an inter-terminal voltage of the capacitor141gradually increases. Therefore, the potential appearing on the gate terminal G side gradually lowers, the voltage between the gate terminal G and the source terminal S gradually decreases, and the electronic switch142at a time T2enters the non-conductive state.

As shown inFIG. 3B, the voltage of the first contact A (i.e., the voltage of the first connection point) starts decreasing from Vcc at the time T1when the acoustic-electric transducer1is connected to the terminal2, and increases after the electronic switch142enters the non-conductive state at the time T2. Thereafter, the voltage of the first contact A reaches Vcc at the time when the current control circuit14enters the high-impedance state.

Variations

Although the above description has exemplified a case where the electronic switch142is the field effect transistor, the electronic switch142may be an NPN bipolar transistor. In this case, the gate terminal, the source terminal, and the drain terminal of the field-effect transistor inFIG. 2correspond to a base terminal, a collector terminal, and an emitter terminal of the NPN bipolar transistor.

Further, the above description has exemplified the configuration in which the current control circuit14controls the current flowing between the first contact A and the second contact B with the electronic switch142, but the configuration of the current control circuit14is not limited thereto. The current control circuit14may include a processor that operates by executing software, for example. In this case, the processor, activated by the current supplied from the terminal2, may reduce the impedance of the circuit provided between the first contact A and the second contact B to make the current flow between the first contact A and the second contact B. The processor increases the impedance of the circuit provided between the first contact A and the second contact B to interrupt the current after the predetermined time passes.

Effects of the Acoustic-Electric Transducer1

According to the acoustic-electric transducer1according to the present embodiment, the current control circuit14makes the current flow between the first contact A and the second contact B until the predetermined time passes from the time when the connection part13is connected to the terminal2. Therefore, the control part205of the terminal2can determine, on the basis of the voltage detected by the voltage detection circuit203, whether the acoustic-electric transducer1is connected. Further, the current control circuit14reduces the current flowing between the first contact A and the second contact B after the predetermined time passes, and enters the high-impedance state. Therefore, the current control circuit14does not affect characteristics of the electrical signal generated by the microphone101.

The present invention is explained on the basis of the exemplary embodiments. The technical scope of the present invention is not limited to the scope explained in the above embodiments and it is possible to make various changes and modifications within the scope of the invention. For example, all or part of the apparatus can be configured to be functionally or physically distributed and integrated in arbitrary units. Further, new exemplary embodiments generated by arbitrary combinations of them are included in the exemplary embodiments of the present invention. The effect of the new embodiment caused by the combination has the effect of the original embodiment together.