JP2012015953A - Speaker amplifier and electronic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a speaker amplifier, used in an electronic apparatus having a speaker serving as both a receiver and a sounder, with a simple circuit configuration capable of preventing the speaker from outputting excess sound volume to a user even when a limiter function breaks down, and an electronic apparatus.SOLUTION: A multiplexed protection circuit with a simple circuit configuration including a limiter circuit 17 for limiting an output signal level and an output-signal-level abnormality detection circuit 22 for detecting an abnormality of the output signal level detects the abnormality of the output signal level output from a speaker 32. Each protection circuit prevents the simultaneous faults of the limiter circuit 17 and the output-signal-level abnormality detection circuit 22 by operating on the basis of a threshold voltage output from each of independent reference voltage generation circuits 24a, 24b. Further, a threshold-voltage-level abnormality detection circuit 23 detects an abnormality of the threshold voltage.

Description

  The present invention relates to a speaker amplifier and an electronic device. In particular, when a reception speaker output speaker (receiver) and a ring tone output speaker (sounder) are used as a single speaker, an excessive volume is output from the speaker. The present invention relates to a speaker amplifier and an electronic device having a protection function for preventing the noise.

  In many electronic devices that incorporate a speaker, the volume output from the speaker is restricted in order to prevent the user from outputting an excessive volume from the speaker. An example of this can be found in the standard EN50332-2: 2003 by the European Electrotechnical Commission. For example, even in a cellular phone device that is used close to the user, consideration is given to preventing an excessive volume from being output from a speaker to a user.

  In a conventional mobile phone device, in order to prevent a loud ringing tone from being output from a speaker when a user puts his ear close to the speaker, a sounder that requires a large volume, In general, receivers that are designed so that a large volume of sound is difficult to output are arranged separately. However, recent mobile phone devices are becoming smaller and it is becoming difficult to secure a space for mounting the receiver and the sounder separately, and mounting the receiver and the sounder separately increases the cost. It is also a factor. If the receiver and the sounder can be shared by a single speaker while maintaining safety, the mounting area and cost can be greatly reduced.

Against this background, an increasing number of electronic devices share a receiver and sounder with a single speaker. Many of such electronic devices are equipped with an output signal level limiting (limiter) function for limiting the level of an output signal so that an excessive volume is not output from a speaker.
For example, Patent Document 1 discloses a mobile phone device that uses a receiver and a sounder as a single speaker and has ringtone volume limiting means. This mobile phone device limits the speed at which the volume is increased when the output volume continuously exceeds the reference volume.

  Patent Document 2 discloses a received sound volume limiting circuit. This circuit rectifies and smoothes the drive signal of the receiver, compares the average value for each predetermined time with a threshold value, and subtracts the excess level from the received voice data to limit the volume.

JP 2002-185571 A JP-A-7-235975

In the inventions disclosed in Patent Documents 1 and 2 described above, it is possible to prevent an excessive sound volume from being output from the speaker to the user when the sound volume limiting circuit is operating normally. However, when the volume limiting circuit fails, the limiter function does not operate normally, and a large volume may be output from the speaker.
Therefore, in view of the above problems, the present invention is a speaker amplifier and an electronic device that are used in an electronic device in which a receiver and a sounder are combined with a single speaker, and the limiter function fails in a simple circuit configuration. It is an object of the present invention to provide a speaker amplifier and an electronic device that can prevent an excessive sound volume from being output from a speaker even if it exists.

In order to achieve the above object, a speaker amplifier and an electronic apparatus according to the present invention are configured as follows.
A first speaker amplifier according to the present invention is a speaker amplifier for driving a single speaker that serves as both a receiver as a reception sound output speaker and a sounder as a ringtone output speaker, A reference voltage generating means for generating a first threshold voltage that is a level and a second threshold voltage that is higher than the level of the first threshold voltage, and a first voltage generated by the reference voltage generating means Output signal level limiting means for limiting the level of the output signal output to the loudspeaker so as not to exceed the threshold voltage level; and the second threshold voltage level generated by the reference voltage generating means Output signal level abnormality detecting means for detecting an abnormal state in which the signal level exceeds.

  According to the speaker amplifier, the output signal level limiting unit limits the level of the output signal so as not to exceed the level of the first threshold voltage generated by the reference voltage generating unit. Thereby, it is possible to output a stable received sound while preventing an excessive sound volume from being output from the speaker to the user. Further, the output signal level abnormality detecting means detects that the output signal level is in an abnormal state exceeding the second threshold voltage. As a result, even if the output signal level limiting means breaks down, it is possible to take measures such as stopping the driving of the speaker before an excessive volume is output from the speaker to the user. On the contrary, even if the output signal level abnormality detecting means fails, if the output signal level limiting means operates normally, it is possible to prevent the user from outputting an excessive volume from the speaker. It becomes. When the output signal level limiting means is operating normally, the output signal level is limited so as not to exceed the first threshold voltage level, and the second threshold voltage level is the first threshold voltage level. Since the level is higher than the threshold voltage level, the output signal level does not exceed the second threshold voltage level. Therefore, the output signal level abnormality detecting means makes an abnormality determination only when the output signal level limiting means fails. Therefore, when the protection circuit detects an abnormal state excessively, the driving of the speaker is frequently stopped. It becomes possible to avoid being done.

In the second speaker amplifier according to the present invention, the output signal level limiting means limits the level of the output signal in a time shorter than a time in which the output signal level abnormality detecting means detects the abnormal state. And
According to the above-described speaker amplifier, the output signal level limiting means limits the magnitude of the output signal earlier than the output signal level abnormality detecting means detects the abnormal state. As a result, the output signal level abnormality detection means makes an abnormality determination only when the limiter circuit fails. Therefore, when the protection circuit detects an abnormal state excessively, the driving of the speaker is frequently stopped. It becomes possible to avoid doing.

The third speaker amplifier according to the present invention is characterized in that the output signal level abnormality detecting means detects the abnormal state using a level obtained by integrating the level of the output signal for a predetermined time.
According to the above speaker amplifier, the output signal level abnormality detection means detects an abnormal state using a level obtained by integrating the output signal level over a predetermined time. Thereby, even when instantaneous noise occurs in the output signal, it is possible to reduce the erroneous detection of the abnormal state by the output signal level abnormality detecting means.

The fourth speaker amplifier according to the present invention is characterized in that the output signal level abnormality detecting means outputs an abnormal signal when the abnormal state is detected continuously a predetermined number of times.
According to the above speaker amplifier, even if the output signal level abnormality detecting means detects the abnormal state, the output signal level abnormality detecting means does not output the abnormal signal until the abnormal state is continuously detected. As a result, if there is no excessive volume output from the speaker to the user, such as when instantaneous noise occurs in the output signal, ignore the detection result. It is possible to reduce erroneous detection of abnormal states.

The fifth speaker amplifier according to the present invention is characterized in that the output signal level abnormality detecting means outputs the abnormal signal when the abnormal state is detected a predetermined number of times or more out of a predetermined number of times.
According to the speaker amplifier, the output signal level abnormality detection means does not output an abnormality signal until an excessive audio signal is detected a predetermined number of times within a predetermined number of times. Thereby, it is possible to detect whether or not an excessive sound volume is output from the speaker to the user with a higher probability, and to reduce erroneous detection of an abnormal state.

In a sixth speaker amplifier according to the present invention, the reference voltage generating means includes a first reference voltage generating means for generating the first threshold voltage, and the first reference voltage generating means independently of the first reference voltage generating means. And second reference voltage generating means for generating a second threshold voltage.
According to the above-described speaker amplifier, the first reference voltage generating means outputs the first threshold voltage, and the second reference voltage generating means outputs the second threshold voltage. That is, the first threshold voltage and the second threshold voltage are generated by independent reference voltage generating means. As a result, both the output signal level limiting means and the output signal level abnormality detecting means are simultaneously prevented from malfunctioning due to the failure of the two reference voltage generating means, and the duplication of the protection circuit is more robust. It becomes possible to make it.

A seventh speaker amplifier according to the present invention comprises a third reference voltage generating means for generating a third threshold voltage independently of the reference voltage generating means, and a level of the second threshold voltage being the first threshold voltage. And a threshold voltage level abnormality detecting means for outputting the abnormality signal when a threshold voltage level of 3 is exceeded.
According to the above speaker amplifier, the threshold voltage level abnormality detection means outputs an abnormality signal when the second threshold voltage exceeds the third threshold voltage. As a result, the level of the second threshold voltage becomes higher than usual due to a failure or the like, and the output signal level abnormality detecting means cannot detect the abnormality normally. It is possible to take measures such as stopping the driving of the loudspeaker before a sound volume is output.

The electronic device according to the present invention includes a receiver serving as a receiver for outputting received sound, a single speaker serving as a sounder serving as a speaker for outputting ringtone, and any one of claims 1 to 7 for driving the speaker. The speaker amplifier according to claim 1 and control means for controlling an operating state of the speaker amplifier.
According to the above electronic device, the speaker amplifier built in the electronic device has a simple configuration, but the protection circuit is effectively doubled. Therefore, the control means need only control the operation state of the speaker amplifier such as receiver / sounder mode switching. As a result, it is possible to manufacture an electronic device that uses both a receiver and a sounder as a single speaker with reduced size and cost.

According to the present invention, it is possible to output a received sound while preventing an excessive sound volume from being output from the speaker to the user by the output signal level limiting means. Even when the output signal level limiting means fails, it is possible to take measures such as stopping the driving of the speaker by detecting the output signal level by the output signal level abnormality detecting means.
The output signal level limiting means and the output signal level abnormality detecting means are operated with reference to the threshold voltages generated by the first and second reference voltage generating means that are independent of each other, thereby providing the output signal level limiting means. And the output signal level abnormality detecting means can be prevented from malfunctioning at the same time, and an excessive volume output from the speaker to the user can be prevented. In addition, when a failure occurs such that the threshold voltage used in the output signal level abnormality detection means is at a level that causes an excessive sound volume to be output from the speaker to the user, the threshold voltage level abnormality detection means Based on the determination, measures such as stopping the driving of the speaker can be taken.

As described above, each protection circuit is multiplexed with a simple configuration. For this reason, it is possible to use a single speaker for both the receiver application and the sounder application while maintaining safety, which can contribute to safety, downsizing, and cost reduction of an electronic device such as a mobile phone device.
The output signal level abnormality detecting means limits the output signal level so as not to exceed the threshold voltage level in a time shorter than the time for detecting an abnormal state in which the output signal level exceeds the threshold voltage level. The output signal level abnormality detecting means integrates the output signals for a predetermined time, performs abnormality detection a plurality of times using the level, and outputs an abnormality signal.
As described above, since each protection circuit determines the probability that an excessive volume is output from the speaker to the user, the audio signal output frequently stops due to the influence of noise or the like due to excessive protection operation. Can be avoided.

1 is a block diagram showing a configuration of a speaker amplifier 10 according to the present invention. 3 is a block diagram showing a configuration of a limiter circuit 17. FIG. It is a graph which shows the output signal level output from the limiter circuit 17 at the time of receiver mode. 4 is a flowchart showing an algorithm of gain adjustment sequence control executed by a gain adjustment unit 41. 3 is a block diagram showing a configuration of an output signal level abnormality detection circuit 22. FIG. 3 is a graph showing signal levels inside an output signal level abnormality detection circuit 22; It is a flowchart which shows the algorithm of the output signal level abnormality determination sequence control which the sequencer 54a performs. 3 is a block diagram showing a configuration of a threshold voltage level abnormality detection circuit 23. FIG. It is a flowchart which shows the algorithm of threshold value abnormality determination sequence control.

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. In each drawing referred to in the following description, components equivalent to those in the other drawings are denoted by the same reference numerals.
(Configuration of speaker amplifier 10)
With reference to FIG. 1, a configuration of a speaker amplifier 10 according to the present invention built in a mobile phone device will be described as an example of an electronic apparatus that also serves as a single speaker for receiver use and sounder use. FIG. 1 is a block diagram showing a configuration of a speaker amplifier 10 according to the present invention.

  A speaker amplifier 10 shown in FIG. 1 includes a control signal input / output terminal 11, a control unit 12, a receiver mode audio signal input terminal 13, a sounder mode audio signal input terminal 14, a speaker output terminal 15, a signal path switch 16, and an output. Signal level limiting (limiter) circuit 17, receiver mode speaker drive unit 18, sounder mode speaker drive unit 19, threshold voltage setting pin 20, constant current source 21a, resistance element 21b, output signal level abnormality detection circuit 22, threshold voltage A level abnormality detection circuit 23 and a reference voltage generation circuit 24 are provided.

The control signal input / output terminal 11 is a terminal for connecting the main control unit 31 and the speaker amplifier 10 for overall control of the mobile phone device and inputting / outputting control signals.
The control unit 12 communicates with the main control unit 31 such as a mobile phone device, and internally holds various setting information including a receiver mode for driving as a reception sound output speaker and a sounder mode for driving as a ring tone output speaker. Then, the overall operation of the speaker amplifier 10 such as power on / off of each unit and switching of the signal path is controlled in an integrated manner.

  When an abnormal signal ER indicating that some abnormality has been detected is notified from any part of the speaker amplifier 10, the control unit 12 powers off the receiver mode speaker drive unit 18 and disconnects the signal path switch 4. For example, a necessary measure is taken to prevent an excessive volume output from the speaker 32 to the user. For example, it is also possible to generate a flag signal for notifying the main control unit 31 such as a mobile phone device that an abnormality has occurred.

In the present embodiment, only an abnormal state including an event in which an excessive volume is output from the speaker 32 serving as a receiver and a sounder in the receiver mode is handled, and other abnormal states are not handled.
The receiver mode audio signal input terminal 13 is a terminal for inputting an audio signal output from the receiver mode audio signal output unit 33 of the mobile phone device in the receiver mode.

The sounder mode audio signal input terminal 14 is a terminal for inputting an audio signal output from the sounder mode audio signal output unit 34 of the mobile phone device or the like in the sounder mode.
The speaker output terminal 15 is a terminal for connecting the speaker amplifier 10 and the speaker 32 built in the mobile phone device together with the speaker amplifier 10.

  The signal path changeover switch 16 is a switching element for changing the audio signal input terminal in response to an instruction from the control unit 12 for switching between the receiver mode and the sounder mode. In the receiver mode, the signal path switch 16 connects the receiver mode audio signal input terminal 13 and the limiter circuit 17, and the audio signal input from the receiver mode audio signal input terminal 13 is input to the limiter circuit 17. In the sounder mode, the signal path selector switch 16 connects the sounder mode audio signal input terminal 14 and the limiter circuit 17, and the audio signal input from the sounder mode audio signal input terminal 14 is input to the limiter circuit 17. The

  The limiter circuit 17 observes the level of the audio signal input from the receiver mode audio signal input terminal 13 and the sounder mode audio signal input terminal 14, and generates an excessive volume from the speaker 32 connected via the speaker output terminal 15. Adjust the gain so that is not output. Thereby, the limiter circuit 17 limits the level of the audio signal so that the level of the audio signal output from the limiter circuit 17 does not exceed the level of the first threshold voltage VL1 that is a predetermined level.

The receiver mode speaker drive unit 18 is powered on in the receiver mode based on an instruction from the control unit 12, amplifies the audio signal output from the limiter circuit 17 with a predetermined gain, and outputs the amplified audio signal to the speaker. Output from terminal 15. In addition, the receiver mode speaker driver 18 is powered off in the sounder mode.
The sounder mode speaker drive unit 19 is powered on in the sounder mode based on an instruction from the control unit 12, amplifies the audio signal output from the limiter circuit 17 with a predetermined gain, and outputs the amplified signal from the speaker output terminal 15. The sounder mode speaker drive unit 19 is powered off in the receiver mode.

  It is possible to drive the speaker 32 by using a single circuit in both the receiver mode and the sounder mode. However, since the required sound volume is different between the receiver mode and the sounder mode, the speaker 32 is used. The driving capability required for the circuit to be driven is different. Therefore, in this embodiment, an example using a speaker drive unit optimized for each mode is presented.

The threshold voltage setting pin 20 is a terminal for connecting the constant current source 21a and the resistance element 21b and outputting the second threshold voltage VL2 higher than the level of the first threshold voltage VL1.
The constant current source 21a uses the reference voltage output from the reference voltage generation circuit 24 to generate a reference current that is a basis for generating the second threshold voltage VL2.
The resistance element 21b is an element connected to generate the second threshold voltage VL2 that is higher than the level of the first threshold voltage VL1. The second threshold voltage VL2 is determined by the reference current output from the output signal level abnormality detection circuit 22 to the threshold voltage setting pin 20 and the resistance value of the resistance element 21b. The resistance element 21b is not limited to a fixed resistance and may be a variable resistance.

A circuit composed of the constant current source 21a and the resistance element 21b functions as a reference voltage generation circuit for generating the second threshold voltage VL2.
Note that the second threshold voltage VL2 needs to be set appropriately according to the characteristics of the speaker 32 and the application of the system in which the speaker amplifier 10 is mounted. In this embodiment, the output signal level abnormality detection circuit 22 outputs a predetermined reference current to the second threshold setting pin 20, and the resistance element 21b having an appropriate resistance value between the threshold voltage setting pin 20 and the ground point. Is connected to the threshold voltage setting pin 20, the second threshold voltage VL2 can be generated. According to this method, the level of the second threshold voltage VL2 can be easily adjusted by selecting the single resistance element 21b.

  A specific example in which the second threshold voltage VL2 is set assuming the characteristics of the speaker 32 and the like will be described. For example, the electroacoustic conversion efficiency of the speaker 32 is 110 dBA / 100 mV, and the excessive amount for the user is 120 dBA. At this time, the voltage of the speaker output terminal 15 corresponding to this volume increases from 100 mV to 10 dB to 316 mV. Therefore, if the operating point of the speaker output terminal 15 is 1.2 V, the second threshold voltage VL2 should be 1.2 V + 316 mV = 1.516 V or less. If the current output from the constant current source 21a is 10 μA, the resistance value of the resistance element 21b connected to the threshold voltage setting pin 20 may be 1.516 V / 10 μA to 150 kΩ.

  The output signal level abnormality detection circuit 22 detects whether or not the level of the audio signal output from the speaker 32 is excessive based on the second threshold voltage VL2 output to the threshold voltage setting pin 20. When the output signal level abnormality detection circuit 22 detects that the level of the audio signal is such that an excessive volume is output from the speaker 32 to the user, the abnormality signal ER is notified to the control unit 12. .

  The threshold voltage level abnormality detection circuit 23 determines whether the level of the second threshold voltage VL2 is higher than the third threshold voltage VL3 with reference to the third threshold voltage VL3 output from the reference voltage generation circuit 24. Is detected. If there is an abnormality in the level of the second threshold voltage VL2, the output signal level abnormality detection circuit 22 cannot detect the abnormality. Therefore, the threshold voltage level abnormality detection circuit 23 has a level of the second threshold voltage VL2. When an abnormality is detected, an abnormality signal ER is notified to the control unit 12.

  The reference voltage generation circuit 24 includes two reference voltage generation circuits, reference voltage generation circuits 24a and 24b. The reference voltage generation circuit 24a is used to limit the output signal level in the limiter circuit 17 and the reference voltage necessary for operating each circuit other than the output signal level abnormality detection circuit 22 and the threshold voltage level abnormality detection circuit 23. The first threshold voltage VL1 is generated. The reference voltage generation circuit 24b uses the reference voltage necessary for operating the output signal level abnormality detection circuit 22 and the threshold voltage level abnormality detection circuit 23, and the threshold voltage level abnormality detection circuit 23 as a determination threshold. The third threshold voltage VL3 is generated. In the reference voltage generation circuit 24 according to the present embodiment, each part operating on the basis of the reference voltage output from the reference voltage generation circuit 24 and the first threshold voltage VL1 to the third threshold voltage threshold voltage VL3 simultaneously fails. In order to reduce the probability, the reference voltage and the first threshold voltage VL1 to the third threshold voltage threshold voltage VL3 are output from two independent reference voltage generation circuits. Further, an independent third reference voltage generation circuit can be used to generate another threshold voltage.

(Operation in sounder mode)
Here, the operation of the speaker amplifier 10 in the sounder mode will be described.
When receiving an instruction from the main control unit 31 to switch to the sounder mode, the control unit 12 powers on the necessary units. The signal path switch 16 switches the electrical connection state so that the sounder mode audio signal input terminal 14 and the input side of the limiter circuit 17 are connected. Further, since the receiver mode speaker driving unit 18 is powered off and the sounder mode speaker driving unit 19 is powered on, the speaker 32 is driven by the sounder mode speaker driving unit 19 via the speaker output terminal 15.

  In the present embodiment, in the sounder mode, the protection function for preventing the user from outputting an excessive volume from the speaker 32 is not functioned, and the protection function is functioned only in the receiver mode. For this reason, the output signal level abnormality detection circuit 22 and the threshold voltage level abnormality detection circuit 23 are powered off. For the limiter circuit 17, the preamplifier 40 is operated with a constant gain. If it is necessary to control the magnitude of the output signal for reasons other than preventing the loud sound from being output from the speaker 32 to the user, for example, to protect the speaker 32, the gain is adjusted. It may be operated.

(Operation in receiver mode)
The operation of the speaker amplifier 10 in the receiver mode will be described.
When receiving an instruction to switch to the receiver mode from the main control unit 31 such as a mobile phone device, the control unit 12 powers on the necessary units. The signal path switch 16 switches the electrical connection state so that the receiver mode audio signal input terminal 13 and the input side of the limiter circuit 17 are connected. Since the receiver mode speaker driving unit 18 is powered on and the sounder mode speaker driving unit 19 is powered off, the speaker 32 is driven by the receiver mode speaker driving unit 18 via the speaker output terminal 15.

  The limiter circuit 17 adjusts the gain and outputs the audio signal so that the level of the audio signal does not exceed the first threshold voltage VL1. The output signal level abnormality detection circuit 22 monitors the signal level of the speaker output terminal 15 for an excessive audio signal being output with reference to the second threshold voltage VL2. The threshold voltage level abnormality detection circuit 23 monitors whether the second threshold voltage VL2 exceeds the third threshold voltage VL3.

(Configuration of limiter circuit 17)
Next, the configuration of the limiter circuit 17 will be described with reference to FIG. FIG. 2 is a block diagram showing the configuration of the limiter circuit 17.
The limiter circuit 17 shown in FIG. 2 includes a preamplifier 40 and a gain adjustment unit 41.
The preamplifier 40 amplifies and outputs the audio signal input with the gain instructed by the gain adjustment unit 41.
The gain adjustment unit 41 observes the level of the audio signal output from the preamplifier 40 and adjusts the gain of the preamplifier 40 so that the output signal level does not exceed the first threshold voltage VL1. The gain adjustment unit 41 performs gain adjustment sequence control for adjusting the gain of the preamplifier 40 so that an excessive sound volume is not output from the speaker 32 to the user in the receiver mode. Continue adjusting the gain of the preamplifier 40.

(Operation of limit circuit 17)
Next, the operation of the limit circuit 17 when the audio signal level is increased in the receiver mode will be described with reference to FIG. FIG. 3 is a graph showing the output signal level output from the limiter circuit 17 in the receiver mode.
FIG. 3 shows how the output signal level that exceeds the first threshold voltage VL1 in the receiver mode is gradually limited by the limiter circuit 17 so as not to exceed the first threshold voltage VL1.

  As the input signal level input from the preamplifier 40 of the limiter circuit 17 increases, the output signal level output from the preamplifier 40 also increases. When the output signal level exceeds the first threshold voltage VL1, the gain adjustment unit 41 decreases the gain of the preamplifier 40 so that the magnitude of the output signal does not exceed the first threshold voltage VL1. Thereby, when the limiter circuit 17 is operating normally, the level of the output signal is limited so as not to exceed the level of the first threshold voltage VL1. For this reason, the amplitude of the output signal is limited between VL1 to VREF− (VL1−VREF) with reference to the reference voltage VREF.

  The first threshold voltage VL1 is set lower than the second threshold voltage VL2 used by the output signal level abnormality detection circuit 22 for abnormality determination. As a result, when the limiter circuit 17 is operating normally, the level of the output signal does not exceed the level of the second threshold voltage. Therefore, since the output signal level abnormality detection circuit 22 makes an abnormality determination only when the limiter circuit 17 fails, the protection circuit detects an abnormal state excessively and the driving of the speaker is frequently stopped. Can be avoided.

However, in the response time TR1 until the operation of limiting the output signal level output from the limiter circuit 17 so as not to exceed the first threshold voltage VL1 is completed, the output signal level instantaneously becomes the second threshold voltage. It is possible to exceed VL2. However, if the response time TR1 is such that the user cannot recognize that an excessive volume is output from the speaker 32, the protection function is sufficient.
The response time TR1 of the limiter circuit 17 is also set shorter than the response time TR2 of the output signal level abnormality detection circuit 22 until the output signal level abnormality detection circuit 22 evaluates the magnitude of the output signal and makes a determination. . Thereby, the protection function by the output signal level abnormality detection circuit 22 can be prevented from operating more frequently.

(Gain adjustment sequence control algorithm executed by the gain adjustment unit 41)
Next, an algorithm for gain adjustment sequence control executed by the gain adjustment unit 41 will be described with reference to FIG. FIG. 4 is a flowchart showing an algorithm for gain adjustment sequence control executed by the gain adjustment unit 41.
As shown in FIG. 4, first, the gain adjustment unit 41 outputs an instruction to the preamplifier 40 so as to amplify the input signal with the gain of the normal operation (step S101). The gain adjustment unit 41 determines whether the output signal level output from the preamplifier 40 exceeds the first threshold voltage VL1 (step S102). If the output signal level of the preamplifier 40 does not exceed the first threshold voltage VL1 (NO in step S102), the gain adjustment unit 41 instructs the preamplifier 40 to amplify the input signal with the normal operation gain. While continuing to output, the process returns to step S101 to continue monitoring the output signal level.

When the output signal level of the preamplifier 40 exceeds the first threshold voltage VL1 (YES in step S102), the gain adjustment unit 41 sets the current gain so that the output signal level does not exceed the first threshold voltage VL1. An instruction is started to be output to the preamplifier 40 so as to amplify the input signal with that gain (step S103). Thereafter, until the output signal level falls below the first threshold voltage VL1, the gain adjustment unit 41 returns to step S102 and continues to output an instruction to adjust the gain of the preamplifier 40.
When the output signal level of the preamplifier 40 does not exceed the first threshold voltage VL1 again (NO in step S102), the gain adjustment unit 41 amplifies the input signal with the gain of the normal operation. Continue to output instructions.

  When a failure occurs in the limiter circuit 17 itself, the limiter circuit 17 cannot limit the output signal level so as not to exceed the first threshold voltage VL1. As a result, the output signal level may continuously exceed the second threshold voltage VL2. However, before an excessive volume is output from the speaker 32 to the user, the output signal level abnormality detection circuit 22 detects this, notifies the controller 12 of the abnormality signal ER, and stops driving the speaker 32. Take measures such as

(Configuration of output signal level abnormality detection circuit 22)
Next, the configuration of the output signal level abnormality detection circuit 22 will be described with reference to FIG. FIG. 5 is a block diagram showing a configuration of the output signal level abnormality detection circuit 22.
The output signal level abnormality detection circuit 22 shown in FIG. 5 includes a rectifier circuit 51, an integration circuit 52, a comparator 53, and an output signal level abnormality determination sequence control unit 54.
The rectifier circuit 51 is a circuit for rectifying the signal at the speaker output terminal 15 with reference to the reference voltage.

  The integration circuit 52 includes an amplifier 52a, a resistance element 52b, an integration capacitor 52c, and a reset switch 52d, and is a circuit for integrating the output of the rectifier circuit 51 in a predetermined time frame. Based on the signal from the output signal level abnormality determination sequence control unit 54, the integration circuit 52 closes the electrical connection state of the reset switch 52d, thereby resetting the charge integrated in the integration capacitor 52c with the reference voltage. . Note that, instead of the integration circuit 52, a switched capacitor circuit may be used for sampling in accordance with the polarity of the signal at the speaker output terminal 15. Thus, the rectifier circuit 51 can be omitted by configuring the circuit so that the switched capacitor circuit also has a rectification function.

The comparator 53 is a comparison circuit for comparing the output level of the integration circuit 52 with the level of the second threshold voltage VL2. When the voltage of the signal output from the integration circuit 52 becomes higher than the voltage of the second threshold voltage VL2, the comparator 53 outputs a signal whose polarity is inverted to the output signal level abnormality determination sequence control unit 54.
The output signal level abnormality determination sequence control unit 54 includes a sequencer 54a and a counter 54b. The output signal level abnormality determination sequence control unit 54a executes an output signal level abnormality determination sequence control algorithm for determining whether or not an excessive audio signal is continuously output based on the output of the comparator 53, When an excessive audio signal is continuously output, the controller 12 is notified of the abnormal signal ER.
The counter 54b counts the number of times that the output signal level abnormality determination sequence control unit 54a determines that an excessive audio signal is continuously output.

(Operation of output signal level abnormality detection circuit 22)
Next, the operation of the output signal level abnormality detection circuit 22 will be described with reference to FIG. FIG. 6 is a graph showing signal levels inside the output signal level abnormality detection circuit 22.
FIG. 6A is a graph showing the output signal level of the speaker output terminal 15 (the signal level input to the rectifier circuit 51). FIG. 6B is a graph showing the output signal level output from the rectifier circuit 51. FIG. 6C is a graph showing the output signal level output from the integration circuit 52 and the timing of each control process of the integration circuit 52.
The output signal output from the speaker output terminal 15 shown in FIG. 6A is input to the rectifier circuit 51 and rectified by the rectifier circuit 51 with reference to the reference voltage. Then, a rectified signal as shown in FIG. Further, the signal rectified by the rectifying circuit 51 is input to the integrating circuit 52.

  As shown in FIG. 6C, when the sequencer 54a initializes the integration circuit 52 in the integration circuit initialization phase, the integration circuit 52 starts to integrate the output signal output from the rectification circuit 51 for the integration time. Each time this integration time ends, the comparator output acquisition phase is entered. The sequencer 54a receives the output signal integrated by the integration circuit 52 and the second threshold voltage VL2 of the comparator 53 in this comparator output acquisition phase. Get the comparison result. When the voltage of the signal output from the integration circuit 52 becomes higher than the voltage of the second threshold voltage VL2, the sequencer 54a changes the value of the counter 54b. Thereafter, the sequencer 54a repeats the initialization of the integration circuit 52 in the integration circuit initialization phase and integration of the output signal output from the rectifier circuit 51 again.

The method for integrating the output signal from the rectifier circuit 51 is not limited to the method described above. For example, it is possible to integrate the absolute value of the amplitude of the output signal using the rectifier circuit 51, or to integrate the average value of the squares of the output audio amplitude (using the square average value).
The integration time is determined when the sequencer 54a initializes the integration circuit 52 in the integration circuit initialization phase at regular intervals. It is preferable to set the integration time so that the determination accuracy due to instantaneous noise does not deteriorate. However, an excessive volume is surely output from the speaker to the user within that time. It is necessary to set the time so as to prevent the above. In this embodiment, the integration time is assumed to be 1.28 ms.

(Algorithm for sequence control of output signal level abnormality determination executed by sequencer 54a)
Next, an output signal level abnormality determination sequence control algorithm executed by the sequencer 54a will be described with reference to FIG. FIG. 7 is a flowchart showing an algorithm of output signal level abnormality determination sequence control executed by the sequencer 54a.
As shown in FIG. 7, when the sequencer 54a receives an instruction from the control unit 12 to operate in the receiver mode of the speaker amplifier 10, the sequencer 54a resets the value of the counter 54b to 0 (step S201). In addition, the sequencer 54a switches the electrical connection state of the reset switch 52d and resets the integration circuit 52 (step S202). As a result, the entire output signal level abnormality detection circuit 22 is reset.

When the integration circuit 52 is reset, the integration circuit 52 starts integrating the output signal rectified by the rectification circuit 51 during the integration time. The integration time of this output signal is 1.28 ms as described above. The sequencer 54a waits until the integration time is reached (NO in step S203).
Then, when the integration time has elapsed (YES in step S203), the sequencer 54a determines whether the output signal level integrated by the integration circuit 52 is greater than the second threshold voltage VL2 based on the output signal from the comparator 53. Is determined (step 204). If the output signal level integrated by the integration circuit 52 does not exceed the second threshold voltage VL2 (NO in step 204), the sequencer 54a returns to step 201 and repeats the above-described processing. If the output signal level integrated by the integrating circuit 52 exceeds the second threshold voltage VL2 (YES in step 204), the sequencer 54a adds 1 to the counter value held by the counter 54b (step 205). .

If the counter 54b has not reached the predetermined value at this time (NO in step 206), the sequencer 54a returns to step 202 and repeats the same processing. When the counter 54b reaches a predetermined value (YES in step 206), the sequencer 54a determines that an excessive audio signal is continuously output, notifies the control unit 12 of the abnormal signal ER, and outputs it. The process of integrating the signal is terminated (step 207).
For example, if the predetermined value that determines the output of the abnormal signal ER in step 206 is four times, an excessive audio signal is continuously output during 1.28 ms × 4 times = 5.12 ms. Therefore, it is considered that an excessive volume may be output from the speaker 32 to the user.

  In the present embodiment, an algorithm for determining that an excessive audio signal is continuously output when the result of the integration average in the time frame of 1.28 ms exceeds the second threshold voltage VL2 for four consecutive times. showed that. In addition, an algorithm for determining that an excessive audio signal is continuously output by exceeding the second threshold voltage VL2 at a frequency exceeding the second threshold voltage VL2, for example, exceeding the second threshold voltage VL2 at least four times out of ten times, An algorithm that determines that an excessive audio signal is continuously output by exceeding the second threshold voltage VL2 four times out of ten times may be used.

  Note that even if a failure occurs in the output signal level abnormality detection circuit 22 itself, the operation of the limiter circuit 17 described above is not affected. For this reason, even if the output signal level abnormality detection circuit 22 itself fails, before the excessive sound volume is output from the speaker 32 to the user, the limiter circuit 17 sets the output signal level to the first threshold voltage VL1. It can be limited not to exceed. However, when the second threshold voltage VL2 is increased so that an excessive volume is output from the speaker 32 to the user due to disconnection or the like of the resistance element 21b connected to the threshold voltage setting pin 20, the output is performed. The signal level abnormality detection circuit 22 cannot detect the abnormality. In this case, before an excessive volume is output from the speaker 32 to the user, the threshold voltage level abnormality detection circuit 23 detects this and notifies the control unit 12 of the abnormality signal ER.

(Configuration of threshold voltage level abnormality detection circuit 23)
Next, the configuration of the threshold voltage level abnormality detection circuit 23 will be described with reference to FIG. FIG. 8 is a block diagram showing a configuration of the threshold voltage level abnormality detection circuit 23.
The threshold voltage level abnormality detection circuit 23 shown in FIG. 8 includes a comparator 60 and a threshold voltage level abnormality determination sequence control unit 61.
The comparator 60 is a comparison circuit for comparing the level of the second threshold voltage VL2 with the level of the third threshold voltage VL3. When the level of the second threshold voltage VL <b> 2 becomes higher than the level of the third threshold voltage VL <b> 3, the comparator 60 outputs a signal whose polarity is inverted to the threshold voltage level abnormality determination sequence control unit 61.

  The threshold voltage level abnormality determination sequence control unit 61 controls the overall operation of the threshold voltage level abnormality detection circuit 23. The threshold voltage level abnormality determination sequence control unit 61 performs threshold abnormality determination sequence control for determining whether the level of the second threshold voltage VL2 exceeds the level of the third threshold voltage VL3 based on the comparator 60. If the level of the second threshold voltage VL2 exceeds the level of the third threshold voltage VL3, the controller 12 is notified of the abnormality signal ER.

(Algorithm for threshold abnormality determination sequence control executed by threshold voltage level abnormality determination sequence control unit 61)
Next, an algorithm for threshold abnormality determination sequence control executed by the threshold voltage level abnormality determination sequence control unit 61 will be described with reference to FIG. FIG. 9 is a flowchart showing an algorithm for threshold abnormality determination sequence control.
As shown in FIG. 9, the threshold voltage level abnormality determination sequence control unit 61 first inputs the second threshold voltage VL2 generated from the constant current source 21a and the resistance element 21b (step S301). Subsequently, the third threshold voltage VL3 output from the reference voltage generation circuit 24b that operates independently of the reference voltage generation circuit including the constant current source 21a and the constant current source 21a is input (step S302). When the threshold voltage level abnormality determination sequence control unit 61 determines that the second threshold voltage VL2 does not exceed the third threshold voltage VL3 (NO in step S303), the process returns to step S301 and repeats the above-described processing. .

If the threshold voltage level abnormality determination sequence control unit 61 determines in step S303 that the second threshold voltage VL2 exceeds the third threshold voltage VL3 (YES in step S303), It is determined that the threshold voltage VL2 is in an abnormal state, the control unit 12 is notified of the abnormal signal ER, and the process is terminated (step 304).
Note that the limiter circuit 17 and the output signal level abnormality detection circuit 22 described above do not have nodes commonly connected to them. For this reason, the probability that these two circuits themselves fail simultaneously is low. However, if the limiter circuit 17 and the output signal level abnormality detection circuit 22 simultaneously malfunction due to a failure of the reference voltage generation circuit 24, an excessive volume may be output from the speaker 32 to the user. Therefore, a configuration for detecting that both the limiter circuit 17 and the output signal level abnormality detection circuit 22 have malfunctioned at the same time is required.

  As a countermeasure, the first threshold voltage VL1 used as a reference by the limiter circuit 17 is generated by the reference voltage generation circuit 24a, and the output signal level abnormality detection circuit 22 is used to generate the second threshold voltage VL2 used as a reference. A constant current is generated by the reference voltage generation circuit 24b. In this way, it is possible to reduce the probability that both the limiter circuit 17 and the output signal level abnormality detection circuit 22 will malfunction simultaneously.

Alternatively, both the first threshold voltage VL1 and the second threshold voltage VL2 are generated from the reference voltage generation circuit 24a, and the third threshold voltage VL3 that the threshold voltage level abnormality detection circuit 23 uses as a reference is used as the reference voltage generation circuit. It may be generated from 24b. In this case, when the second threshold voltage VL2 is so high that there is a possibility that an excessive volume is output from the speaker 32 to the user due to one failure of the reference voltage generation circuit 24a. The threshold voltage level abnormality detection circuit 23 can detect an abnormality based on the third threshold voltage VL3 generated from the reference voltage generation circuit 24b and notify the control unit 12 of the abnormality signal ER. Further, when one of the reference voltage generation circuits 24b fails, the operation of each circuit of the limiter circuit 17 and the output signal level abnormality detection circuit 22 is not affected by this failure. The level is limited to a level that does not output an excessive volume from the speaker 32 to the user, or the output signal level abnormality detection circuit 22 detects an abnormality and notifies the control unit 12 of the abnormality signal ER. be able to.
As described above, it is possible to suppress the output of excessive sound volume in a multiple manner by multiple countermeasures despite the simple circuit configuration.

(Summary)
According to the present embodiment, it is possible to output a signal while preventing the excessive sound volume from being output from the speaker 32 to the user by the limiter circuit 17. Even when the limiter circuit fails, it is possible to take measures such as stopping the driving of the speaker 32 by detecting the output signal level by the output signal level abnormality detection circuit 22.

The limiter circuit 17 and the output signal level abnormality detection circuit 22 are operated based on the threshold voltages VL1 and VL2 generated from independent circuits, respectively. At the same time, it is possible to prevent an excessive sound volume from being output from the speaker 32 to the user due to malfunction. Further, when a failure occurs such that the second threshold voltage VL2 used in the output signal level abnormality circuit 23 is at a level that causes an excessive sound volume to be output from the speaker 32 to the user, the threshold voltage Based on the determination of the level abnormality detection circuit 23, measures such as stopping the driving of the speaker 32 can be taken.
As described above, each protection circuit has a simple configuration, but multiple protection circuits are provided. For this reason, a single speaker can be used for both the receiver application and the sounder application while maintaining safety.

  ADVANTAGE OF THE INVENTION According to this invention, it utilizes as electronic equipment, such as a mobile telephone apparatus which incorporates the speaker combined with a receiver use and a sounder use, as a speaker amplifier for driving the speaker.

10 …… Speaker amplifier 11 …… Control signal input / output terminal 12 …… Control unit 13 …… Receiver mode audio signal input terminal 14 …… Sounder mode audio signal input terminal 15 …… Speaker output terminal 16 …… Signal path switching Switch 17 …… Output signal level limiting (limiter) circuit 18 …… Receiver mode speaker drive unit 19 …… Sounder mode speaker drive unit 20 …… Threshold voltage setting pin 21a …… Constant current source 21b …… Resistance element 22… ... Output signal level abnormality detection circuit 23 …… Threshold voltage level abnormality detection circuit 24 …… Reference voltage generation circuit 40 …… Preamplifier 41 …… Gain adjustment unit 51 …… Rectification circuit 52 …… Integration circuit 53, 60 …… Comparator 54 ...... Output signal level abnormality determination sequence control unit 61 ...... Threshold voltage level abnormality determination sequence control unit

Claims (8)

A speaker amplifier for driving a single speaker that serves as both a receiver as a speaker for receiving sound output and a sounder as a speaker for ringtone output,
Reference voltage generating means for generating a first threshold voltage that is a predetermined level and a second threshold voltage that is higher than the level of the first threshold voltage;
Output signal level limiting means for limiting the level of the output signal output to the speaker so as not to exceed the level of the first threshold voltage generated by the reference voltage generating means;
Output signal level abnormality detection means for detecting an abnormal state in which the level of the output signal exceeds the level of the second threshold voltage generated by the reference voltage generation means;
A speaker amplifier comprising:   2. The speaker amplifier according to claim 1, wherein the output signal level limiting means limits the level of the output signal in a time shorter than a time during which the output signal level abnormality detecting means detects the abnormal state.   3. The speaker amplifier according to claim 1, wherein the output signal level abnormality detecting means detects the abnormal state using a level obtained by integrating the level of the output signal for a predetermined time.   4. The speaker amplifier according to claim 3, wherein the output signal level abnormality detecting means outputs an abnormal signal when the abnormal state is continuously detected a predetermined number of times.   5. The speaker amplifier according to claim 3, wherein the output signal level abnormality detection means outputs the abnormality signal when the abnormal state is detected more than a predetermined number of times in a predetermined number of times. The reference voltage generating means includes
First reference voltage generating means for generating the first threshold voltage;
Second reference voltage generating means for generating the second threshold voltage independently of the first reference voltage generating means;
The speaker amplifier according to claim 1, further comprising: Independent of the reference voltage generating means, third reference voltage generating means for generating a third threshold voltage;
Threshold voltage level abnormality detection means for outputting the abnormality signal when the level of the second threshold voltage exceeds the level of the third threshold voltage;
The speaker amplifier according to claim 1, comprising: A single speaker that doubles as a receiver as a speaker for receiving sound output and a sounder as a speaker for ringtone output;
The speaker amplifier according to any one of claims 1 to 7, for driving the speaker;
Control means for controlling the operating state of the speaker amplifier;
An electronic device characterized by comprising:

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