JPH06104664A - Power amplifier ic for audio signal - Google Patents

Abstract

PURPOSE:To realize the audio use power amplifier IC having less number of external terminals while keeping its function. CONSTITUTION:An external terminal 4 for a passive filter connecting to a smoothing circuit 20 is used for an output terminal for a fault detection signal A. Thus, number of external terminals is reduced. Furthermore, a standby control signal B and a muting control signal C equivalent to conventional signals are generated by receiving a tri-state control signal via an external terminal 3 and using comparators 301, 302 to compare the control signal with reference values 301a, 302a respectively. Thus, number of external terminals is reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an audio power amplifier IC, and more particularly to an output for driving a speaker or the like used in an audio circuit of an audio device such as a tape recorder or an audiovisual device such as a so-called television. The present invention relates to an audio power amplifier IC that amplifies an audio signal to generate a signal.

[0002]

2. Description of the Related Art Since a power amplifier which is responsible for power amplification has a large amount of heat generation, it is often formed as an IC by itself.
The C package requires high heat resistance and heat dissipation.
Furthermore, the audio power amplifier has a shorted output
Anomaly detection function that detects an abnormal condition such as an overheat condition due to an overload such as a ground fault, a power saving function that saves power consumption in the power amplifier (standby function), a mute function that temporarily suppresses acoustic output (mute) Function) etc. are also required.
FIG. 2 shows an example of a conventional audio power amplifier IC having these functions.

Here, 1 to 8 are external terminals of the IC,
The terminal 1 receives the audio signal from the outside, the terminal 2 receives the muting control signal C from outside to instruct whether to mute, and the terminal 3 receives the standby control signal B from outside to instruct whether to save power. On the other hand, a passive filter such as a capacitor is connected to the outside of the terminal 4, a power supply voltage Vcc is received from the outside at the terminal 5, a signal is output from the inside of the IC to the outside of the terminals 6 and 7, and an external terminal to the ground GND Connected by.

Further, 10 is a power amplifier which amplifies the audio signal received through the terminal 1 and outputs it from the terminal 7, and 11 is a transmission state and a non-transmission state of the audio signal according to the muting control signal C. A mute circuit which performs the above-mentioned mute function by switching, 12 is a first stage circuit of the power amplifier 10, 13 is an output stage circuit of the power amplifier 10, and 20 is a smoothing circuit which generates a stabilizing voltage from the power supply voltage Vcc received via the terminal 5. A circuit, 30 is an abnormality detection circuit that detects an abnormal state of the power amplifier 10 and generates an abnormality detection signal A, which is output to the outside through the terminal 6.

The smoothing circuit 20 steps down the power supply voltage Vcc to generate a stabilized voltage, but requires a passive filter outside through the terminal 4 in order to stabilize the generated voltage. This passive filter is, for example, a circuit including a smoothing capacitor as a main component and a resistor or a diode adapted to the smoothness, and removes ripples of the received voltage. The smoothing circuit 20 also supplies this stabilized voltage to the power amplifier 10 and the like. Among the circuits that receive the supply of the stabilized voltage, for example, the first-stage circuit 12 and the like operate in the active region of the transistor, and thus constantly consume power. Therefore, in order to achieve the power saving function, the smoothing circuit 20 receives the standby control signal B and stops the supply of the stabilized voltage.

When this IC is incorporated in an audio circuit, the power supply voltage Vcc is supplied, the standby control signal B is released, and the muting control signal C is also released.
The audio signal input via the terminal 1 is amplified by the power amplifier 10 and output via the terminal 7 to an external speaker or the like. In this state, when the mute switch of the device or its remote controller (remote controller) is pressed and the muting control signal C is input due to this, the mute circuit 11 interrupts the transmission of the audio signal. Then, the acoustic output is temporarily suppressed. Then, when the mute switch is pressed again to release the muting control signal C, the mute circuit 11 restarts the transmission of the audio signal, and the sound output is immediately restored.

When the power switch of the device or its remote controller is pressed to instruct its operation to stop, most current audio devices, especially so-called televisions, do not completely turn off the power of all circuits, and the cathode ray tube and the like. Power is maintained in some circuits that require preheating. Therefore, each circuit has a power saving function according to the characteristics of the parts and the like, and fine control is performed. In such a case, the standby control signal B is sent to each circuit in the device that requires power saving operation. Also in the case of this IC, when the standby control signal B is input, the smoothing circuit 20 stops the supply of the stabilization voltage in response to this. Then, the power consumption of the IC is suppressed to an extremely low level. Then, when the power switch is pressed again and the standby control signal B is released, the smoothing circuit 20 resumes the supply of the stabilization voltage, the power amplifier 10 becomes operable immediately, and the muting control signal C is also released. If so, sound output is performed.

By the way, if the line of the sound output is short-circuited or grounded in the middle, the power amplifier 10 is overloaded, the IC is overheated, and it may be damaged in some cases. In such a case, the abnormality detection circuit 30
Is an abnormal state of the power amplifier 10, for example, the output stage circuit 13
Of the power amplifier 10 is detected and the abnormality detection signal A indicating the abnormal state of the power amplifier 10 is output to the outside via the terminal 6. Then, an external controller or the like which has received this abnormality detection signal sends, for example, a standby control signal B to this IC. In response to this, the operation of the power amplifier 10 is stopped in order to prevent inconvenience such as damage to the IC.

[0009]

As described above, such a conventional audio power amplifier IC has an abnormality detecting function, a power saving function, a muffling function, and the like. Therefore, in addition to the terminal for the amplification function, which is the basic function of the power amplifier, an abnormality detection signal output terminal, a standby control signal input terminal, and a muting control signal input terminal are also required. However, audio power amplifier IC
Since high heat resistance and heat dissipation are required, a material with a large heat capacity is used for the package. For example, there is a package in which a copper substrate is incorporated, and the cost ratio in this case may be higher in the package than in the IC chip body. Further, it is difficult to reduce the size and the pitch of the external terminals from the viewpoints of securing the strength for supporting the radiation fins and the need to pass a large current. Due to these factors, even if the chip body of the IC becomes small, the package does not become small if the number of external terminals of the IC is large.

Therefore, the audio power amplifier IC, which has various functions as described above and requires many external terminals for control signals and detection signals, has a high manufacturing cost due to a high package cost. , Is a problem. An object of the present invention is to solve such a problem of the conventional technique, and to realize an audio power amplifier IC having a small number of external terminals while maintaining its function.

[0011]

The first structure of the audio power amplifier IC of the present invention which achieves the above object is to provide an audio power amplifier incorporating a power amplifier for amplifying and outputting a received audio signal. In the IC, a smoothing circuit that generates a stabilized voltage by applying a stepped down voltage of a power supply voltage to a passive filter connected to the outside through an external terminal and supplies the stabilized voltage to the power amplifier, and the power amplifier. An abnormality detection circuit that detects an abnormal state of and outputs an abnormality detection signal, and when the abnormality detection signal is output, the voltage applied to the external terminal has a voltage value different from the step-down voltage. The external output terminal serves as an output terminal that indicates an abnormal state.

A second configuration of the audio power amplifier IC of the present invention which achieves the above object is an audio power amplifier IC having a built-in power amplifier for amplifying and outputting a received audio signal. A normal operation state in which amplified output is performed, a muting state in which the audio signal is not amplified or the output is not performed, and a power saving state in which power consumption in the power amplifier is saved are sorted in order of decreasing value (or A corresponding first control signal is input via an external terminal, and the value of the first control signal is intermediate between the power saving state instruction value and the muting state instruction value. A second reference value intermediate between the indication value of the muting state and the indication value of the normal operation state, the value of the first control signal being compared with a first reference value of And a second control signal is generated when the value of the first control signal is smaller than the first reference value (or larger than the first reference value), and the value of the first control signal is Is smaller than the second reference value (or larger than the second reference value), a comparator circuit for generating a third control signal, and a stabilizing voltage from the power supply voltage when receiving the second control signal. And a smoothing circuit for bringing the power amplifier into the power saving state by not supplying the generated stabilizing voltage to the power amplifier, and the power amplifier for the audio signal when receiving the third control signal. To a muting state by setting the transmission path leading to the power amplifier to a non-transmission state or suppressing amplification in the power amplifier. Is shall.

[0013]

In the audio power amplifier IC of the present invention having the first structure, the external terminal to which the passive filter is connected also serves as the output terminal of the abnormality detection signal. Therefore, a terminal dedicated to the abnormality detection signal is unnecessary, and the number of external terminals can be reduced. In the audio power amplifier IC of the second configuration of the present invention, the control signal for instructing the power saving state and the control signal for instructing the mute state (muting state) are input through one external terminal. Therefore, it is not necessary to assign a dedicated terminal to each of these control signals. This can also reduce the number of external terminals.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an audio power amplifier IC of the present invention will be described below with reference to the block diagram of FIG. Where 1,3,4,5,7,8
Is an external terminal of the IC, the terminal 1 receives an audio signal from the outside, the terminal 3 receives a control signal from the outside (hereinafter, an external control signal), and the terminal 4 has a passive filter such as a capacitor connected to the outside. An abnormality detection signal is output, terminal 5 receives power supply voltage Vcc from the outside, terminal 7 outputs an amplified signal of the audio signal to the outside, and terminal 8 is connected to ground GND externally.

Further, 10 is a power amplifier which amplifies the audio signal received through the terminal 1 and outputs the amplified audio signal to the terminal 7.
Reference numeral 11 denotes a mute circuit that performs the above-described sound deadening function by switching the transmission state and the non-transmission state of the audio signal according to the muting control signal C, 12 is the first stage circuit of the power amplifier 10, and 13 is the power amplifier 10. An output stage circuit, 20 is a smoothing circuit which generates a stabilizing voltage from the power supply voltage Vcc received through the terminal 5 and which has the power saving function described above, and 30 is an abnormality detection signal for detecting an abnormal state of the power amplifier 10. It is an abnormality detection circuit for generating A. Further, 301 and 302 are comparators, 600 is a switch circuit, and these are newly provided, so their roles and connection relationships will be described in detail below.

Comparator 301 generates a standby control signal B from an external control signal received via external terminal 3. Here, this external control signal is basically a three-valued voltage signal, and for example, its voltage value is 3V.
Indicates that the IC should be in the normal signal amplification operation state, indicates that the IC should be in the mute state when 1.5V, and indicates that the IC should be in the power saving state when 0V. . The voltage of this external control signal is compared with a reference voltage 301a of 1V, for example. When the voltage of the external control signal is smaller than the reference voltage 301a, the standby control signal B is sent to the smoothing circuit 20. In response to this, the smoothing circuit 20 stops the supply of the stabilized voltage to the power amplifier 10, so that the power saving function is realized.

The comparator 302 generates a muting control signal C from the above external control signal received via the external terminal 3. To this end, the voltage of this external control signal is compared with the reference voltage 302a. And
When the voltage of the external control signal is smaller than the reference voltage 302a, the muting control signal C is sent to the mute circuit 11. The mute circuit 11 that receives the signal blocks the input of the audio signal to the power amplifier 10, so that the mute function is realized.

Here, the reference voltage 302a is, for example, 2V.
And is set to a voltage higher than the reference voltage 301a. Therefore, the muting control signal is also generated when the standby control signal B is generated, and these control signals are not necessarily independent. That is, when the voltage of the external control signal changes from 0V to 3V, the power saving state, the mute state, and the normal operation state are correspondingly changed. Conversely, when the voltage of the external control signal changes from 3V to 0V, the normal operation state, the mute state, and the power saving state are sequentially changed correspondingly.

However, an audio power amplifier IC
Then, in the state where the circuit from the power-on to the start of operation is unstable, it is more convenient that the muffling function is working rather than the occurrence of pop noise. In the case of reverse power supply, it is still more convenient if the silencing function was working first. Therefore, in the past, separate external terminals, that is, a plurality of external terminals were required for these control signals, but in the present invention, this characteristic can be utilized to reduce the number of external terminals by sharing them. . Moreover, it is possible to improve the operation characteristics.

The switch circuit 600 is, for example, a transistor circuit which is controlled by receiving the abnormality detection signal A from the abnormality detection circuit 30. When the abnormality detection signal A is received, the external terminal 4 is electrically connected to the ground. The electric potential of the external terminal 4 is forcibly set to the ground potential. Here, the step-down voltage from the smoothing circuit 20 is usually applied to the external terminal 4, and a passive filter is connected to the outside in order to stabilize the step-down voltage. This passive filter is, for example, a circuit including a smoothing capacitor as a main component and a resistor or a diode adapted to the smoothness, and removes ripples of the received voltage.

However, this passive filter does not generate a specific voltage by itself, and receives a step-down voltage slightly stepped down from the power source voltage Vcc in a normal state. Therefore, the switch circuit 600 can be connected to the ground potential. Further, the stabilizing voltage from the smoothing circuit 20 is supplied to the power amplifier 10 and the like, but it is better not to supply the stabilizing voltage when the abnormality detection signal A is detected, that is, when the power amplifier 10 is in an abnormal state. The operation of the power amplifier 10 is stopped, which is rather safe. Therefore, when the abnormality detection signal A is detected, the smoothing circuit 20 does not need to operate, and the passive filter connected to the external terminal 4 does not need to operate either. That is, in the case of the audio power amplifier IC, there is no inconvenience even if the potential of the external terminal 4 is set to the ground potential when the abnormality detection signal A is detected. Therefore, it is possible to reduce the number of terminals for outputting the abnormality detection signal, and also use this as a terminal for connecting a passive filter.

When this IC is incorporated in an audio circuit and a power supply voltage Vcc is supplied, its operation is as follows. When the voltage of an external control signal from an external controller or the like changes from 0V to 3V. Standby control signal B
When the muting control signal C is also canceled, the audio signal input through the terminal 1 is amplified by the power amplifier 10 and output through the terminal 7 to an external speaker or the like. In this state, the mute switch on the device or its remote controller is pressed to output 1.5
When V is input, the muting control signal C is generated,
The mute circuit 11 interrupts the transmission of the audio signal.
Then, the acoustic output is temporarily suppressed. When the mute switch is pressed again and the external control signal is returned to 3V, the muting control signal C is released, the mute circuit 11 restarts the transmission of the audio signal, and the sound output is immediately restored.

When the power switch of the device or its remote controller is pressed to give an instruction to stop the operation, the voltage of the external control signal changes from 3V to 0V. In response to this, first, the muting control signal C is generated and the sound is muted, whereby the amplification of noise sound is suppressed, and then the standby control signal B is generated, and the supply of the stabilizing voltage is stopped. Further, the operation of the power amplifier 10 is stopped, the power saving state is set, and the power consumption in the IC is suppressed to an extremely small amount.

Then, when the power switch is pressed again and the voltage of the external control signal changes from 0V to 3V, the standby control signal B is first released in response to this, and the power amplifier which has been supplied with the stabilization voltage. The operation of 10 starts. However, in this state, the muting control signal C is still generated, so that the generation of a noise sound such as a pop sound is suppressed. Next, when the muting control signal C is also released, the audio signal input via the terminal 1 is amplified by the power amplifier 10 and output to an external speaker or the like via the terminal 7.

If the acoustic output line is short-circuited or grounded in the middle, the power amplifier 10 is overloaded and the IC is overheated. In such a case, the abnormality detection circuit 30 detects, for example, an abnormal state of the output stage circuit 13 of the power amplifier 10, and an abnormality detection signal A indicating the abnormal state of the power amplifier 10 is generated. Then, the switch circuit 600 receiving the abnormality detection signal A sets the potential of the external terminal 4 to the ground potential. And
The smoothing circuit 20 stops the supply of the stabilizing voltage to the power amplifier 10.

As a result, the operation of the power amplifier 10 is stopped without passing through an external controller or the like, and I
Inconvenience such as damage to C can be minimized. In this way, the external controller or the like can detect the abnormal state by simply monitoring the potential of the external terminal, and it is sufficient to simply detect the abnormal state. You don't have to.

[0027]

As can be understood from the above description, in the audio power amplifier IC of the present invention, the output terminal of the abnormality detection signal is also used as the filter connection terminal. Further, the standby control signal and the muting control signal are generated from the control signal input via one external terminal. Therefore, it is possible to reduce the number of external terminals without impairing various functions such as an abnormality detection function, a power saving function, and a muffling function in addition to the amplification function. As a result, the package cost can be reduced, which in turn can reduce the manufacturing cost.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of an audio power amplifier IC having the configuration of the present invention.

FIG. 2 is a conventional audio power amplifier IC.
Is an example.

[Explanation of symbols]

 1-8 External terminal 10 Power amplifier 11 Mute circuit 12 First stage circuit 13 Output stage circuit 20 Smoothing circuit 30 Abnormality detection circuit 301,302 Comparator 600 Switch circuit

Claims (2)

[Claims] 1. An audio power amplifier IC incorporating a power amplifier for amplifying and outputting a received audio signal.
A smoothing circuit for generating a stabilized voltage by applying a step-down voltage obtained by stepping down a power supply voltage to a passive filter connected to the outside through an external terminal and supplying the stabilized voltage to the power amplifier; An abnormality detection circuit that detects an abnormal state and outputs an abnormality detection signal, and when the abnormality detection signal is output, the voltage applied to the external terminal is set to a voltage value different from the step-down voltage. An audio power amplifier IC, wherein the external terminal is an output terminal indicating an abnormal state. 2. An audio power amplifier IC having a built-in power amplifier for amplifying and outputting a received audio signal.
In, a normal operation state in which the audio signal is amplified and output, a muting state in which the audio signal is not amplified or the output is not performed, and a power saving state in which power consumption in the power amplifier is saved are set as values. A first control signal for instructing correspondingly in the order of magnitude (or reverse order) is input via an external terminal, and the value of the first control signal is the instruction value of the power saving state and the muting state. Value of the first control signal is compared with a first reference value intermediate between the reference value of the muting state and the reference value of the normal operation state. It is compared, and when the value of the first control signal is smaller than the first reference value (or larger than the first reference value), a second control signal is generated, and the value of the first control signal is According to the second reference value Smaller (or larger than the second reference value)
Sometimes the comparator circuit generates a third control signal, and when the second control signal is received, the power supply voltage does not generate a stabilization voltage or the generated stabilization voltage is not supplied to the power amplifier. A smoothing circuit that puts an amplifier into the power saving state, and a transmission path of the audio signal to the power amplifier is set to a non-transmission state when receiving the third control signal, or amplification by the power amplifier is suppressed. The power amplifier I for audio according to claim 1, further comprising: a mute unit that brings the power amplifier into the muting state.
C.