JPH0818347A - Power save circuit - Google Patents

Abstract

PURPOSE:To provide the power save circuit which is operated with low power consumption without problems, which cause the occurrence of pop sounds and the malfunction, by a simple circuit constitution at the time when the muting operation is performed and the normal operation of an output amplifier circuit is unnecessary. CONSTITUTION:A muting circuit 1, an output amplifier control circuit 2, and an output amplifier circuit 3 are provided. The input signal of sounds or the like is inputted to the muting circuit 1 from a signal input terminal 12, and the output is amplified by the output amplifier circuit 3 and is outputted from a signal output terminal 01 to a loudspeaker 10 or the like. During the muting operation, a control signal for mute control is inputted from a mute input terminal I1 to the muting circuit l and the output amplifier control circuit 2, and the output of the output amplifier control circuit 2 reduces the bias voltage of the output amplifier circuit 3, and the operation current of a current source of the output amplifier circuit 3 is limited to considerably reduce the current consumption.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an audio output circuit for audio equipment and video equipment such as headphone stereos, video cameras, mobile phones, and mobile TVs, and more particularly to signal transmission including a mute (also called muting) circuit. The present invention relates to a power save circuit of a circuit.

[0002]

2. Description of the Related Art Conventionally, when an operation is stopped or paused during recording or reproduction of a recorded one, an abnormal noise (pop) caused by a sudden change of a signal is generated by a circuit configuration shown in FIG. 4 or 5 which will be described later. Sound) was generated from the speaker 10. In the example shown in FIG. 4, the mute circuit 1 and the output amplifier circuit 3 are main components, and the signal input I2 is input to the mute circuit 1 by an input device such as a microphone, and the mute circuit operation by the mute control signal is performed. At times, the signal level of the input signal is attenuated so that no pop sound is produced from the output side, but the operating current of the output amplifier circuit 3 is not reduced.

Further, in the example shown in FIG. 5, the mute circuit 1
And an output amplifier control circuit 2 and an output amplifier circuit 3 as main elements. The signal input I2 is input to the mute circuit 1 and attenuates the signal level of the signal input when the mute circuit operates by the mute control signal. The pop sound is prevented from coming out from the output side, and the operation of the output amplifier stage is stopped so that the current consumption due to the operation of the output amplifier circuit 3 can be reduced.

[0004]

However, in the circuit configuration as described above, when a device such as a headphone stereo or a video camera is used as a power source of a battery, the mute circuit for the signal input I2 as shown in FIG. 4 is used. With a circuit configuration that only attenuates by 1, the output amplifier circuit 3 which consumes a large amount of current continues to operate in the same manner as when not performing the mute operation and consumes the current. Is abruptly consumed and the operable time is shortened.

Further, in the circuit configuration in which the operation of the output amplifier circuit 3 is also stopped at the time of the mute operation as shown in FIG. 5, the current consumption is greatly reduced and the operable time of the battery is extended, but the output amplifier circuit 3 There is a problem that when the operation of is stopped or restarted, a pop sound is generated due to a rapid transient change of the output of the output amplifier circuit 3 or a malfunction of other circuits is caused.

Therefore, the present invention solves these problems, and when the mute circuit 1 is operating and the operation of the output amplifier circuit 3 is unnecessary, pop noise and malfunction do not occur even though the circuit configuration is simple, and An object of the present invention is to provide a current consumption reduction circuit (power save circuit) with low current consumption.

[0007]

In order to solve the above-mentioned problems, a power save circuit according to a first aspect of the present invention includes a mute circuit for attenuating an input signal such as a sound according to a mute control input during a mute operation. A signal transmission circuit including an output amplifier circuit for amplifying a signal from the mute circuit to drive a speaker and the like, and an output amplifier control circuit for controlling an operating current of the output amplifier circuit The amplifier control circuit is characterized by controlling the output amplifier circuit so as to reduce the operating current of the output amplifier circuit.

A power save circuit according to a second aspect of the present invention is characterized in that the operation current of the output amplifier circuit is reduced by cutting off a part of the operation current source of the output amplifier circuit. Is. The power save circuit according to claim 3 reduces the operating current of the output amplifier circuit by limiting the bias voltage of the operating current source of the output amplifier circuit to such an extent that the operating voltage level can be determined. It is characterized by.

[0009]

With the structure of the power save circuit according to the present invention, when the output amplifier circuit 3 does not need to perform the normal operation as in the mute operation, the output amplifier circuit 3 has a simple circuit structure but does not output. The operation current of the output amplifier circuit 3, which consumes the most current, is limited by the operation of the amplifier control circuit 2, and the current consumption of portable devices such as tape recorders and video recorders that use batteries is greatly reduced to greatly increase the operation time. Output amplifier circuit 3
There is an effect that it is possible to eliminate the problem that a pop sound is generated or a malfunction occurs due to a sudden change in the output voltage when the operation of is stopped or restarted.

[0010]

Embodiments of the present invention will now be described in detail with reference to FIGS. Throughout the drawings, the same or similar circuit elements are designated by the same reference numerals throughout the specification. FIG. 1 shows a configuration of a current consumption reduction circuit (power save circuit) according to an embodiment of the present invention. A mute circuit 1 for attenuating an input signal such as voice according to a mute control input during a mute operation, and the mute circuit 1 Output amplifier circuit 3 for amplifying the above signal into a signal capable of driving the speaker 10, and an output amplifier control circuit 2 for controlling the output amplifier circuit 3 so as to reduce the operating current of the output amplifier circuit 3 during the mute operation. Is the main circuit element. A signal such as voice obtained from an input device such as a microphone is input from the signal input terminal I2, and is output from the signal output terminal O1 to the speaker 10 via the mute circuit 1 and the output amplifier circuit 3. Mute circuit 1 and output amplifier control circuit 2
A control signal for a mute operation is externally input to each of them via the mute control input terminal I1, and the output of the output amplifier control circuit 2 is the constant current sources 5 and 6 of the amplifier section 4 constituting the output amplifier circuit 3. Of these, only the current source 5 for large current is connected via a switch. The current sources 5 and 6 of the output amplifier circuit 3 operate together in the normal operation without performing the mute operation. However, during the mute operation, the mute control input I1 is added to the output amplifier control circuit 2 to output a signal from the output amplifier control circuit 2. Due to this, the large current source 5 out of the current sources 5 and 6 of the output amplifier circuit 3 stops operating,
Since only the low-current source 6 is controlled so as to continue to operate, the operating current of the output amplifier circuit 3 is limited and the current consumption is reduced.

FIG. 2 shows another embodiment of the present invention in which a mute circuit 1, an output amplifier control circuit 2 and an output amplifier circuit 3 are main circuit elements. A signal such as voice is input from the signal input terminal I2, and is output from the signal output terminal O1 to the speaker 10 via the mute circuit 1 and the output amplifier circuit 3. Mute circuit 1 and output amplifier control circuit 2
A control signal is input to each of them via a mute control input terminal I1, and an output from the output amplifier control circuit 2 is connected as a bias voltage of a current source 7 of an amplifier section 4 forming an output amplifier circuit 3. During normal operation without mute operation, a bias voltage is applied to the current source 7 of the output amplifier circuit 3 so as to obtain a sufficient output current for driving the speaker in the output amplifier circuit 3, and a mute control input during mute operation. I1 is added to the output amplifier control circuit 2, and the signal from the output amplifier control circuit 2 reduces the bias voltage of the current source 7 of the output amplifier circuit 3 to such an extent that the operating state of the output amplifier circuit 3 can be maintained. Limits the operating current of.

FIG. 3 shows an example of an implementation circuit of the power save circuit having the configuration shown in FIG. The power save circuit has a mute circuit 1, an output amplifier control circuit 2, and an output amplifier circuit 3 as main circuit elements, and further applies a signal input I2 as an input terminal, a mute control input I1, and a bias voltage to the power save circuit. Bias input I3 for controlling the constant current of the power save circuit I
4, a constant current input I5 for controlling the bias voltage of the output amplifier circuit 3, and a signal output O1 as an output terminal
It has and.

The structure and function of each block will be described below. The mute circuit 1 includes transistors 11, 12,
An input circuit section 13 and 14 and a resistor 1a for inputting and attenuating a signal together with an input amplifier circuit 8 to be described later, and a mute circuit 1 including resistors 1e and 1f.
A mute control input I1 connected to the base of the transistor 19 via the resistor 8c, and a mute control input I1 connected to the base of the transistor 19 via a resistor 8c. An input amplifier control voltage circuit for giving a control voltage O2 for determining the operating current of the control circuit portion of the circuit 1, the transistor 23 which is current mirror connected to the transistor 20, the transistors 24 and 25, and the resistor 1d. Section, a control voltage circuit section for providing a voltage for determining an operating current of an input circuit section including a transistor 16, a transistor 15 and a resistor 1b which are current-mirror connected to the transistor 18, and a current mirror connection to the transistor 18. Controlled by the output amplifier control circuit 2 consisting of a transistor 17 And a current output circuit for supplying a flow O4.

The output amplifier control circuit 2 includes a transistor 2
6, 27, 28 and resistors 2a, 2b, 2e, and a conversion circuit section that receives a constant current from another circuit (not shown) at the constant current input I5 and converts it into a voltage, and transistors 29, 30.
And an output amplifier bias circuit section for controlling the bias voltage of the output amplifier circuit 3 including the resistors 2c and 2d. The output amplifier control circuit 2 receives the control current O4 in the mute circuit 1 by the transistor 26 and outputs the output amplifier control voltage O5 to control the bias voltage of the current source 7 of the output amplifier circuit 3.

The output amplifier circuit 3 includes a transistor 41,
42, 43, 44 and an input amplifier circuit section including a resistor 3b, a transistor 45 current-mirror connected to the transistor 44, and transistors 46, 47 diode-connected to the collector side of the transistor 45 and transistors 48, 49, 50, 51. , 52 and an electric current circuit (not shown) connected to the resistors 3c and O7, and an output driver circuit section composed of transistors 53 and 54. The output amplifier circuit 3 receives the output O6 of the input amplifier circuit 8 through the resistor 3a at the base of the transistor 43 and receives the signal output O1 at the resistor 3d.
The output amplifier control voltage O5 is input from the output amplifier control circuit 2 to the bases of the transistors 42 and 48. In the normal operation without the mute operation, the output amplifier control voltage O5 is set to the transistor 42 so that the output current sufficient to drive the speaker is obtained.
And 48, and a voltage of about forward voltage V _F is applied during the mute operation, so that each transistor becomes substantially non-conductive and the current flowing through the output amplifier circuit 3 is greatly reduced. Further, at the time of mute, the voltage of the signal output O1 is held at the output voltage O6 of the input amplifier circuit 8 via the resistor 3d. Therefore, when the operation is restarted, a sudden change in the signal does not occur, and a pop sound or a malfunction is generated. It does not cause.

The input amplifier circuit 8 includes a transistor 81,
An input circuit section including 82, 83, 84 and a resistor 8a;
It is composed of a buffer circuit section composed of transistors 85, 86, 87 and a resistor 8b, and an output driver circuit section of an input amplifier composed of transistors 88, 89. The control voltage O2 from the mute circuit 1 is connected to the base of the transistor 82. , The control input I4 is connected to the base of the transistor 87.
Is connected to the control voltage O3. In the normal operation without the mute operation, the input signal is amplified and output to the output amplifier circuit 3, and in the mute operation, the signal input I2 is attenuated together with the input circuit section of the mute circuit 1 and output to the output amplifier circuit 3.

Although the present embodiment shows an example in which the circuit is composed of bipolar elements, the same effect can be obtained even when the circuit is equivalently composed of MOS elements. Further, a pickup signal may be used as the signal input in addition to the microphone input, and a piezoelectric element or the like may be used as the signal output in addition to the speaker output.

[Brief description of drawings]

FIG. 1 is a configuration example showing a first embodiment of the present invention.

FIG. 2 is a structural example showing another embodiment of the present invention.

FIG. 3 is a circuit diagram showing an actual circuit of the first embodiment of the present invention.

FIG. 4 is a configuration example showing a conventional configuration example.

FIG. 5 is a structural example showing another conventional structural example.

[Explanation of symbols]

1: Mute circuit 2: Output amplifier control circuit 3: Output amplifier circuit 4: Constant current source during normal operation of output amplifier 7: Constant current source during normal operation of output amplifier and mute operation 9: Operation bias of output amplifier Power supply 10: Output device (speaker) Applicant ROHM Co., Ltd.

Claims (4)

[Claims] 1. A mute circuit for attenuating an input signal such as voice according to a mute control input during a mute operation, an output amplifier circuit for amplifying a signal from the mute circuit and driving a speaker, and the output amplifier. In a signal transmission circuit including an output amplifier control circuit for controlling the operating current of the circuit, the output amplifier control circuit controls the output amplifier circuit so as to reduce the operating current of the output amplifier circuit during a mute operation. Characteristic power save circuit. 2. The power save circuit according to claim 1, wherein the operating current of the output amplifier circuit is reduced by cutting off a part of the operating current source of the output amplifier circuit. 3. The power according to claim 1, wherein the operating current of the output amplifier circuit is reduced by limiting the bias voltage of the operating current source of the output amplifier circuit to such an extent that the operating voltage level can be determined. Save circuit. 4. An audio device and a video device using the power save circuit according to claim 1 or 2.