JP3245565B2 - Power saving circuit of microphone amplifier - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power saving circuit of a microphone amplifier using a jack for microphone signal input.

[0002]

2. Description of the Related Art Conventionally, a power saving circuit of a microphone amplifier turns on / off power supply to the amplifier using, for example, a multi-contact microphone jack.

FIG. 3 shows an example of a circuit configuration of a power saving circuit of the microphone amplifier of the first prior art. In FIG. 3 showing a power saving circuit of the microphone amplifier of Conventional Example 1, a microphone jack 21 with switching contacts, a microphone 2 including a plug, a load resistor 3,
Detection resistor 4, power supply switching transistor 5, microphone amplifier 6, capacitor 7, drive power supply 8, protection resistor 1
9 is provided. In the power saving circuit of the microphone amplifier having this configuration, plug-in detection of the microphone is realized.

In the first prior art, the power saving function of the microphone amplifier is configured by using a special type of microphone jack 21. The microphone jack 21 is provided with a switch of a mechanism in which a contact for a control signal of a drive power supply to the microphone amplifier is electrically independent of the contact for the microphone signal and mechanically interlocked.

[0005] In "Acoustic equipment with microjack" of Japanese Utility Model Application Laid-Open No. 61-40092 of Conventional Example 2, a transistor (13 / FIG. 1 attached to the publication) has a base-emitter connection.
It is configured to be inserted as a microphone load.

[0006]

However, in the above-mentioned conventional system, a microphone jack provided with a switch to be applied is more expensive than a general microphone jack having a complicated structure and not having a plug-in detection function. Further, it has the disadvantage that the shape is large and the variety is small. For this reason, there is a problem that becomes an obstacle in improving the efficiency of the configuration, such as lowering the price of the apparatus, reducing the size, and improving the productivity.

In the second prior art, since the base-emitter of the transistor has a non-linear characteristic, a non-linear load is inserted into the microphone in the circuit configuration shown in the second prior art. This is not preferable from the viewpoint of sound signal / electric signal conversion requiring higher fidelity. If the resistance value of the resistor (12 / FIG. 1 attached to the publication) is relatively large enough, the adverse effect is reduced, but there is a problem that it is hard to say that there is no resistance.

An object of the present invention is to provide a more efficient microphone amplifier power saving circuit.

[0009]

In order to achieve the above object, a power saving circuit of a microphone amplifier according to the present invention comprises: a microphone jack having a switching contact provided for a signal input of a predetermined microphone amplifier; A gate circuit provided between the power supply input terminal of the amplifier and the terminal of the drive power supply for driving the microphone amplifier for controlling on / off of the drive power supply, and switching between a gate control terminal of the gate circuit and a microphone jack It is characterized by comprising an inverter circuit element provided between the contact point and a resistor connected between the input terminal of the inverter circuit element and the negative terminal of the driving power supply.

A connection point between the input terminal of the inverter circuit element and the resistor is connected to one switching contact B of the microphone jack, and the other contact A forming open / close with the contact B and a driving power supply. And a resistor connected between the positive terminals of the above.

Further, a capacitor is connected between the contact A and the signal input terminal of the microphone amplifier, and the voltage level of the gate control terminal of the gate circuit is low when the plug is not normally attached to the microphone jack with switching contacts. It is preferable to configure a high impedance between the negative power supply input terminal and the power supply terminal of the microphone amplifier.

Further, an earphone amplifier in which a power supply terminal is connected in parallel between the positive and negative electrodes of the microphone amplifier and the amplifier driving power supply, and a microphone jack with switching contacts have a third contact C, and the signal output of the earphone amplifier is provided. Terminal is contact C
It is good to be connected and constructed.

It is preferable that the output signal of the earphone amplifier can be taken out via a jack compatible with the above-mentioned microphone jack with switching contacts.

[0014]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of a microphone amplifier according to an embodiment of the present invention; 1 and 2, there is shown an embodiment of a power saving circuit of a microphone amplifier according to the present invention. FIG. 1 shows a first embodiment, and FIG. 2 shows a second embodiment.

In FIG. 1, a power saving circuit of a microphone amplifier according to a first embodiment includes a microphone jack 1 having switching contacts, a microphone 2 including a plug, a load resistor 3, a detection resistor 4, a transistor 5, a microphone amplifier 6, Capacitor 7,
A drive power supply 8 and a signal inverter (inverter circuit element) 9 are provided.

The microphone jack 1 has a contact A, a contact B,
It has two circuit connection contacts by contact C. Contact A of these is connected to one end of capacitor 7 and load resistor 3
Is connected to one end. The contact B is connected to one end of the detection resistor 4 and an input of the signal inverter 9. The output of the signal inverter 9 is connected to the base of the transistor 5. The other end of the capacitor 7 is connected to the input terminal of the microphone amplifier 6.

The other end of the load resistor 3 is connected to a positive power supply terminal of the microphone amplifier 6 and a positive electrode of the drive power supply 8.
The other end of the detection resistor 4 is connected to the negative electrode of the drive power supply 8, the emitter of the transistor 5, and the contact C of the microphone jack 1. The collector of the transistor 5 and the negative power supply terminal of the microphone amplifier 6 are connected.

The contact A and the contact B of the microphone jack 1 are
It has a structure that conducts when the microphone 2 is not inserted and becomes non-conductive when inserted. The resistance value of the detection resistor 4 is set to a value sufficiently larger than the resistance value of the load resistor 3.

Hereinafter, an operation example of the present embodiment will be described below. When the microphone 2 is not inserted into the microphone jack 1, the contact A and the contact B of the microphone jack 1 are conductive. At this time, the voltage of the driving power supply 8 is applied to the input of the signal inverter 9 to the detection resistor 4 and the load resistor 3.
Is applied. However, the detection resistor 4
Is sufficiently larger than the resistance value of the load resistor 3, a high-level signal in the logic circuit is applied to the signal inverter 9.

At this time, a low-level signal logically inverted by the signal inverter 9 is applied to the base of the transistor 5. Therefore, the transistor 5 is turned off. If the transistor 5 is off, the power supply to the microphone amplifier 6 is cut off and the microphone amplifier 6 enters a non-operation state. Therefore, no power is consumed.

When the microphone 2 is inserted into the microphone jack 1, the contact A and the contact B are separated. At this time, the input of the signal inverter 9 is connected to the negative electrode of the drive power supply 8 by the detection resistor 4. Therefore, a low level is applied to the input terminal of the signal inverter 9. As a result, the transistor 5 is turned on, and the microphone amplifier 6 is energized to be operated.

FIG. 2 is a circuit block diagram showing a configuration example of a second embodiment of the power saving circuit of the microphone amplifier according to the present invention.
2, the power saving circuit of the microphone amplifier according to the second embodiment includes an earphone microphone jack 11, an earphone microphone 12 including a plug, a load resistor 3, a detection resistor 4, a transistor 5, a microphone amplifier 6, a capacitor 7, a driving power source. 8,
It comprises a signal inverter 9 and an earphone amplifier 10.

In FIG. 2 showing a configuration example of the power saving circuit of the microphone amplifier of the second embodiment having the above configuration, the basic configuration is the same as the first embodiment, but the following points are different from the first embodiment. .

The microphone jack 1 in FIG. 1 has been changed to an earphone microphone jack 11, the microphone 2 with a plug has been changed to an earphone microphone 12 with a plug, and an earphone amplifier 10 has been added.

In the second embodiment, the earphone microphone 12
Is inserted, that is, the fact that it is equivalent to the insertion of an earphone is used, and the earphone amplifier 10 is also configured to save power. That is, when the earphone microphone 12 is not inserted, the power supply to the negative electrode side of the transistor 5 and the microphone amplifier 10 becomes high impedance. By increasing the impedance of the power supply circuit, the power supply circuit becomes substantially the same as the power supply cutoff.

The above embodiment is an example of a preferred embodiment of the present invention. However, the present invention is not limited to this, and various modifications can be made without departing from the scope of the present invention.

[0027]

As is apparent from the above description, the power saving circuit of the microphone amplifier according to the present invention is a circuit for turning on / off the power supply between the power input terminal of the microphone amplifier and the terminal of the driving power supply for driving the microphone amplifier. A gate circuit is provided to control turning off, and an inverter circuit element is provided between a gate control terminal of the gate circuit and a switching contact of the microphone jack, and an inverter circuit element is provided between the input terminal of the inverter circuit element and the negative terminal of the driving power supply. Is connected to a resistor.

According to the above configuration, the power supply to the amplifier is controlled on / off according to whether the plug is mounted or not. According to this, the power consumption of the microphone amplifier can be stopped in a state where the microphone is not inserted into the microphone jack, that is, in a state where the microphone amplifier is not energized, so that power saving of the entire device can be achieved. Become.

[Brief description of the drawings]

FIG. 1 is a circuit configuration block diagram illustrating a first embodiment of a power saving circuit of a microphone amplifier according to the present invention.

FIG. 2 is a circuit configuration block diagram showing a second embodiment.

FIG. 3 is a block diagram showing a circuit configuration example of a conventional power saving circuit of a microphone amplifier.

[Explanation of symbols]

 1, 21 Microphone jack with switching contact 2 Microphone including plug 3 Load resistor 4 Detection resistor 5 Transistor 6 Microphone amplifier 7 Capacitor 8 Drive power supply 9 Signal inverter (inverter circuit element) 10 Earphone amplifier 11 Earphone microphone jack 12 Plug Including earphone microphone

Claims (6)

(57) [Claims] A microphone jack with a switching contact for inputting a signal to a predetermined microphone amplifier; and a power supply on / off switch between a power input terminal of the microphone amplifier and a terminal of a driving power supply for driving the microphone amplifier. A gate circuit provided to control turning off; an inverter circuit element provided between a gate control terminal of the gate circuit and a switching contact of the microphone jack; an input terminal of the inverter circuit element and the drive A power saving circuit for a microphone amplifier, comprising: a resistor connected between negative terminals of a power supply. 2. A connection point between the input terminal of the inverter circuit element and the resistor is connected to one switching contact B of the microphone jack, and the other contact A forming a connection / disconnection with the contact B. 2. The power-saving circuit for a microphone amplifier according to claim 1, further comprising a resistor connected between the power supply and a positive terminal of the drive power supply. 3. The power saving circuit for a microphone amplifier according to claim 2, wherein a capacitor is further connected between the contact point A and a signal input terminal of the microphone amplifier. 4. A voltage level of a gate control terminal of the gate circuit is low when a plug is not attached to the microphone jack with a switching contact in a normal state, and a voltage between a negative power supply input terminal and a power supply terminal of the microphone amplifier is high. 4. The structure according to claim 2, wherein the impedance is configured.
The power saving circuit of the microphone amplifier described in the above. 5. The microphone amplifier, an earphone amplifier in which a power supply terminal is connected in parallel between positive and negative electrodes of the microphone amplifier driving power supply, and the microphone jack with a switching contact further includes a third contact C; The power saving circuit of a microphone amplifier according to any one of claims 2 to 4, wherein a signal output terminal of the earphone amplifier is connected to the contact point C. 6. The microphone amplifier power saving circuit according to claim 5, wherein an output signal of the earphone amplifier can be taken out via a jack compatible with the microphone jack with switching contacts.