JP2003142956A - Switching amplifier device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow a protecting circuit of a switching amplifier device to be automatically reset. SOLUTION: The device is equipped with a switching means 15 which can obtains a pulse signal for speaker driving according to an inputted audio waveform, a protecting means 15a which stops the switching operation of the switching means 15 when abnormality of the input or output of the switching means 15 is detected, detecting means 21 and 22 which detect the protecting means 15a stopping the switching operation, and a control means 20 which resets the protecting operation by the protecting means 15a and restarts outputting a pulse signal by the switching means 15 when the detecting means 21 and 22 detect the switching operation being stopped.

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 device for amplifying an audio signal for driving a speaker, and in particular, directly drives a switching means with a signal modulated by a PWM (Pulse Width Modulation) method or the like. And a switching amplifier device for performing power amplification.

[0002]

2. Description of the Related Art Conventionally, various power amplifier devices for amplifying an audio signal for driving a speaker have been commercialized. As one type of power amplifier device that amplifies this audio signal, a so-called digital power amplifier device that amplifies the audio signal by directly switching the power supply with a signal obtained by modulating the input digital audio signal has been developed. ing. In the case of this digital power amplifier device, for example, PWM that is pulse width modulated (PWM) based on the input digital audio signal
Wave (hereinafter, this PWM wave is referred to as a PWM signal) is generated, the power source stabilized by this PWM signal is switched at high speed, the switched power source is supplied to a filter, and an audio signal component is extracted. Is performed to obtain a speaker drive signal.

The PWM signal is a signal whose pulse width is modulated according to the magnitude of the waveform level of the analog audio signal, and the PWM signal controls ON / OFF of the switching means (power switch) for switching the power supply. Is.

Then, the power source switched by the PWM signal by the switching means is supplied to the low-pass filter to cut the high frequency components and extract the components of the audio signal band, thereby outputting the speaker corresponding to the power source voltage. An amplified signal for driving is obtained.

[0005]

By the way, in the case of such a digital power amplifier device, some kind of protection circuit is required in the switching means for obtaining the amplified signal for driving the speaker. That is, for example, when the speaker connection terminal is short-circuited by some kind of metal, or when some noise is mixed in the power supply supplied to the switching means or static electricity is generated, the switching means is directly affected by them. Therefore, it is necessary to provide a protection circuit and stop the operation of the switching means when these abnormalities occur.

However, when this protection circuit operates, the amplifier operation of the input audio signal is completely stopped, resulting in a so-called silent state. In the conventional digital power amplifier device, in order to recover from this silent state, if there is a reset button, the user needs to operate the reset button, and if there is no reset button, the power amplifier device It was necessary to turn the power on again.

As described above, in the case of the conventional digital power amplifier device, it is impossible to recover from the operating state of the protection circuit unless the user manually operates it.
There was a troublesome problem.

From the user's point of view, since the input audio signal has a silent signal waveform, the output of the speaker is in a silent state or the protection circuit of the power amplifier device is activated. Therefore, it is difficult to quickly determine whether the speaker output is in a silent state, and it is usually impossible to know without looking at the situation to some extent, and it is difficult for the user to take prompt action. .

As described above, in the case of the conventional protection circuit of the digital amplifier device, once the protection circuit is activated, it takes time to restore the protection circuit. Therefore, it is not necessary to activate the protection circuit. It was necessary to devise a structure.
Specifically, for example, by installing a large shield case inside the amplifier device or adding a noise countermeasure capacitor or diode to the circuit, it is possible to reduce the influence of external noise. However, due to such measures, there is a problem that the manufacturing cost of the digital amplifier device is increased.

The present invention has been made in view of the above circumstances, and an object thereof is to automatically restore a protection circuit of an amplifier device using a switching element.

[0011]

According to the present invention, there is provided switching means for obtaining a pulse signal for driving a speaker based on an input audio signal waveform, and switching of the switching means when an abnormal input or output of the switching means is detected. A protection means for stopping the operation, a detection means for detecting the stop of the switching operation by the protection means, and a pulse by the switching means for resetting the protection operation by the protection means when the detection means detects that the switching operation is stopped. And a control means for restarting signal output.

According to the present invention, when the protection means operates, the control means automatically executes the operation of resetting the protection operation, and the output of the pulse signal for driving the speaker by the switching means is restarted. .

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a diagram showing the overall configuration of a digital power amplifier device 10 of this example. In FIG. 1, only one-channel processing configuration is shown for the sake of simplicity of description, but it is actually configured to process audio signals of multiple channels such as two channels.

The digital power amplifier device 10 of this example is
A digital audio signal obtained from an external audio signal source (not shown) at the terminal 11 is supplied to the gain control unit 12 for gain adjustment, and the gain-adjusted digital audio signal is supplied to the digital sigma converter 13 Then, it is converted into 1-bit type digital audio data, and the converted 1-bit type digital audio data is supplied to the signal processing unit 14 to generate a PWM signal for driving the switching element.

The PWM signal generated by the signal processing unit 14 is supplied to the switching amplification unit 15, and the stabilized DC power supply supplied from the power supply circuit 18 is turned on / off based on the PWM signal to supply power. The audio signal component is superimposed on. The switching amplification unit 15 of this example is configured by an integrated circuit, and a field effect transistor is used as a switching element included in the switching amplification unit 15, for example. The signal switched by the switching amplifier 15 is supplied to a low-pass filter (LPF) 16 to remove high frequency components generated by switching to extract only audio signal components, and the extracted audio signal components are output to a speaker. The drive signal is supplied to the speaker device 1 connected to the speaker connection terminal 17, and the speaker device 1 outputs audio (voice) at a predetermined volume.

The switching element is designed to always perform a switching operation except when a protection circuit 15a, which will be described later, is operating. For example, a pulse signal having a constant frequency is output even in a silent state. Is done. By removing the high frequency component corresponding to the switching frequency in the low-pass filter 16, only the audio signal component is supplied to the speaker device side. For example, the switching element is configured to generate a pulse signal of about 250 KHz, and the low-pass filter 16 removes the signal component of about 250 KHz, so that an audio signal component in a so-called audible band (for example, up to about several tens kHz) is generated. The signal is output from the speaker connection terminal 17.

Further, the digital power amplifier device 10
Is provided with an operation unit 19 including various operation keys and a volume knob for adjusting volume, and the CPU 20 determines the operation status of the operation unit 19 so that the CPU 20 performs various controls such as volume adjustment. There is.

Here, the switching amplification section 15 of the present example.
Has a built-in protection circuit 15a. Protection circuit 15a
Detects an abnormality in the power supply input from the power supply circuit 18 to the switching amplification section 15, an abnormality in the input PWM signal, an abnormality in the output switched by the switching element (short circuit, etc.), and when detecting the abnormality, all channels are detected. The switching operation of the switching element is stopped so that the output from the switching amplification section 15, that is, the output of the speaker drive signal from the speaker connection terminal 17 is stopped.

The protection circuit 15a is adapted to reset the protection operation when the protection operation is executed by a reset signal supplied from the CPU 20.

The CPU 20 determines whether or not the protection circuit 15a is activated to stop the switching operation of the switching element, so that the switching amplifier 15 is provided.
Is configured to determine the output of That is, the output of the switching element of any one channel in the switching amplification unit 15 is smoothed by the low-pass filter 21, and the output of the low-pass filter 21 is converted into the analog signal of the CPU 20.
The data is supplied to the digital converter 22, converted into data corresponding to the voltage value, the data converted by the analog / digital converter 22 is judged in the CPU 20, and the protection circuit 15a is based on the judged data. A reset signal is output to. The output of the reset signal here is to temporarily supply a low level signal "L" to the protection circuit 15a as a reset signal, and the high level signal "H" is sent from the CPU 20 to the protection circuit 15a except when resetting. Is supplied. The determination process of outputting the reset signal will be described later.

The low-pass filter 21 has a characteristic different from that of the low-pass filter 16 provided on the speaker connection terminal 16 side. That is, the switching amplifier 15
It is a filter that has different voltage values when the switching element therein is performing the switching operation and when it is not performing the switching operation. Specifically, for example, a low-pass filter with a cut-off frequency of about 3 Hz is used to convert the pulse signal modulated by the PWM signal into direct current.

FIG. 2 is a diagram showing in more detail the configuration relating to the protection operation of the digital amplifier device 10 of this example. In FIG. 2, the switching amplification unit 15 is shown as a configuration for processing signals of two channels, and includes a switching element 15L for the left channel and a switching element 15R for the right channel. The output signals switched by the switching elements 15L and 15R for the respective channels are passed through the low-pass filters 16L and 16R for the respective channels, and the speaker connection terminal 17 is provided.
Supply to L and 17R. Low-pass filters 16L, 16
R is a filter that removes high frequency components generated by switching. The speaker connection terminals 17L and 17R for the left and right channels are connected to the speaker device 1 for each channel.
L and 1R are connected.

Here, in this example, the signal obtained at one pole of the output of the switching element 15R of one channel (the right channel in FIG. 2) is fed to the low-pass filter 2
Analog / digital converter 2 in CPU 20 via 1
2 is configured to be supplied. Low pass filter 2
As described above, 1 is a filter having a cutoff frequency of about 3 Hz. Here, for example, the resistor R1 and the diode D1 are connected in series, and one end of the resistor R2, one end of the capacitor C1, and the cathode of the diode D2 are connected between the diode D1 and the input of the converter 22. The other end of the resistor R2, the other end of the capacitor C1, and the anode of the diode D2 are connected to the ground side to configure a low-pass filter.

By passing through the low-pass filter 21 having such a configuration, the output of the low-pass filter 21 becomes a voltage of 0.8 V or more when the switching element normally performs the switching operation. Therefore, when the switching operation by the switching element is stopped, the voltage is set to be substantially 0V, which is less than 0.8V. That is, when the switching element is normally performing the switching operation, a pulse signal of about 250 kHz is output from the switching element as shown in FIG. 3A, for example. This pulse signal waveform changes depending on the audio signal waveform, but the basic frequency of the pulse signal is the same even in the case of a silent audio signal. In this example, the pulse signal is passed through the low-pass filter 21 to have a voltage of 0.8 V or higher. On the other hand, when the switching element stops the switching operation, as shown in FIG.
As shown in, the voltage is a constant voltage such as 0V.

Then, the CPU 20 determines whether the output of the analog / digital converter 22 is data of 0.8 V or more.

Next, the control processing based on the output data of the analog / digital converter 22 in the CPU 20 will be described with reference to FIG.
This will be described with reference to the flowchart in FIG.

When the CPU 20 shifts from the main routine (step S10) to the subroutine for starting the determination processing of the operating state of the protection circuit (step S11), it reads the output data of the analog / digital converter 22,
The output voltage value of the low-pass filter 21 is determined and stored (step S12). Then, it is determined whether the voltage value determined at this time is less than 0.8 V (step S13).
When it is not less than 0.8 V (that is, when it is 0.8 V or more), this subroutine is ended (step S1).
6) Return to the main routine of step S10. After that, in a cycle of about 10 ms, the process shifts to a subroutine for determining the operating state of the protection circuit in step S11.

When it is determined in step S13 that the voltage value is less than 0.8V, it is determined whether the voltage value determined and stored in the previous subroutine is less than 0.8V (step S14). ). Here, when the previously determined voltage value is 0.8 V or more, the process proceeds to step S16 to end this subroutine, and returns to the main routine of step S10. And step S1
When it is judged to be less than 0.8V in the judgment of 4,
In step S15, the reset signal is set to the low level signal "L" for 10 ms, and then the high level signal "H"
Then, the process returns to step S16 to end this subroutine.

The low level signal "L" for 10 ms in step S15 is supplied to the protection circuit 15a as a reset signal, so that the protection circuit 15a is reset and the protection circuit 15a operates to perform the switching operation. Then, the switching operation of the switching elements 15L and 15R that have stopped is restored, and the output of audio from the connected speaker device is restarted.

By the CPU 20 performing the control operation in this way, when the output voltage of the low-pass filter 21 is detected to be less than 0.8 V twice continuously at about 10 ms intervals, the switching amplification section 15 is provided. Internal protection circuit 15a
Is activated, the reset signal is supplied to the protection circuit 15a, the protection operation by the protection circuit 15a is reset, and the switching operation in the switching amplification unit 15 is restarted. It Therefore, when the protection circuit operates due to a temporary factor such as power supply noise, the protection circuit automatically recovers about 10 ms after the operation. Therefore, the audio output from the speaker device when the protection circuit is activated is temporarily interrupted for only a short time, and the user does not need to operate the reset button or turn the power of the amplifier device off and on again. .

Further, when the protection circuit operates in this way, it is automatically restored after a lapse of a short time, so that the amplifier device can tolerate a temporary output stop during this short time. In this case, it is not necessary to spend much cost for noise countermeasures by the shield plate and the capacitor, and the manufacturing cost of the amplifier device can be reduced.

Further, in the case of this example, as shown in steps S13 and S14 of the flow chart of FIG.
Since the voltage of the switching output is judged twice continuously at intervals, it is possible to avoid the influence of a malfunction due to a temporary false detection and to reliably detect the operation of the protection circuit.

In the example shown in the flow chart of FIG. 4, the reset signal is supplied to the protection circuit when the switching output is in the stopped state twice consecutively. However, after the reset signal is supplied, the reset signal is supplied. The reset signal may not be supplied when the protection circuit operates continuously. The flowchart of FIG. 5 is a diagram showing a processing example in this case.

Explaining the operation of the flowchart of FIG. 5, the CPU 20 executes the main routine (step S1).
0), the process proceeds to a subroutine for starting the process of determining the operating state of the protection circuit (step S11), the output data of the analog / digital converter 22 is read, and the output voltage value of the low-pass filter 21 is determined and stored ( Step S12). Then, the voltage value determined at this time is
It is determined whether the voltage is less than 0.8 V (step S13). 0.
When it is not less than 8 V (that is, when it is 0.8 V or more), this subroutine is ended (step S16), and the process returns to the main routine of step S10. Then about 10
At a cycle of ms, the process proceeds to a subroutine for determining the operating state of the protection circuit in step S11.

If it is determined in step S13 that the voltage value is less than 0.8V, it is determined whether the voltage value determined and stored in the previous subroutine is less than 0.8V (step S14). ). Here, when the previously determined voltage value is 0.8 V or more, the process proceeds to step S16 to end this subroutine, and returns to the main routine of step S10. The processing up to this point is the same as the processing shown in the flowchart of FIG.

Then, in the determination of step S14, 0.8
When it is determined that the voltage value is less than V, the process proceeds to step S17, and the determined voltage value is 0.8 V continuously for 10 times or more.
Judge whether it was less than. In this determination, if the determined voltage value is less than 0.8 V for 10 consecutive times or more, the process proceeds to step S16 to end this subroutine, return to the main routine of step S10, and perform the reset operation. Not performed. Then, in step S17, the number of times the determined voltage value is continuously less than 0.8 V is 1
When it is determined that the number of times is less than 0, the process proceeds to step S15, the reset signal is set to the low level signal "L" for 10 ms, and then the process is returned to the high level signal "H", and then the process proceeds to step S16. Finish the subroutine.

By performing the processing as shown in the flow chart of FIG. 5, even if the reset operation is performed and the protection operation is reset by the protection circuit, if the protection operation is immediately performed again, the protection operation is performed. The reset operation is no longer performed, the protection circuit is activated and the switching operation remains stopped.

If the protection operation is immediately performed even after such a reset, it is assumed that the cause of the activation of the protection circuit has not been removed, and in that case, the cause of the activation of the protection circuit (for example, the speaker). The user can restore the operation of the protection circuit as in the conventional case by removing the short circuit of the connection terminal) and then pressing the reset button or turning the power on again.

In the above-described embodiment, the PWM signal pulse-width-modulated based on the 1-bit digital audio data is generated to control the switching of the power switch.
The present invention can also be applied to various types of switching amplifier devices that obtain an amplified signal by controlling switching with other pulse-modulated signals such as the ration modulation system.

Further, in the above-described embodiment, the amplifier device is configured as a single unit for driving the connected speaker device based on the input audio signal. However, an audio signal source such as a reproducing device and a speaker device are integrated. It goes without saying that the present invention can be applied to the amplifier section of a converted audio device.

Further, in the above-described embodiment, the low-pass filter (corresponding to the low-pass filter 16 in FIG. 1) for removing the high frequency component generated by switching is provided between the switching amplifier and the speaker connection terminal. However, if a similar low-pass filter is connected to the speaker device side to be connected, or if it is not necessary to remove high frequencies due to the characteristics of the speaker device, the output low-pass filter may be omitted. good.

[0043]

According to the present invention, the operation of automatically resetting the protection operation is executed even if the protection means is activated.
Therefore, when the protection measure is activated by the input of temporary noise etc., it will be silent only for a short time while the protection measure is operating, and it will be automatically performed without the user performing the recovery operation. Then, it becomes possible to effectively prevent the silent state from continuing due to the activation of the protection means due to the power supply noise or the like.

In this case, the detecting means is composed of a filter means for smoothing the pulse signal output from the switching means and a judging means for judging the output voltage of the filter means. By detecting that the switching operation is stopped when the voltage is detected, it is possible to easily detect that the switching operation is stopped.

Further, the pulse signal for driving the speaker outputted from the switching means is supplied to the speaker by removing the high frequency component by the filter means different from the filter means provided in the detecting means. The characteristics of the filter means can be optimally set, and the detection of the switching operation and the output for supplying the speaker can be performed well.

Further, when the detecting means detects that the switching operation is stopped for a predetermined number of times continuously, the control means resets the protecting operation by the protecting means so that the state in which the protecting operation is performed is continued. Then, the operation of resetting after surely detecting that the current state is performed is executed.

Further, when the resetting is performed when it is detected that the switching operation is stopped for a predetermined number of times in succession, the switching operation is stopped immediately after the resetting. Since the resetting is not performed when the detecting means detects it, the resetting operation is not executed when the factor for operating the protection means continues, and the protection function comes to function effectively.

[Brief description of drawings]

FIG. 1 is a block diagram showing an example of an overall configuration according to an embodiment of the present invention.

FIG. 2 is a configuration diagram showing an example of a configuration of a portion related to a protection operation according to an embodiment of the present invention.

FIG. 3 is a waveform diagram showing an output waveform example of a switching amplification unit.

FIG. 4 is a flowchart showing an example of a returning operation according to the embodiment of the present invention.

FIG. 5 is a flowchart showing an example of a returning operation according to another embodiment of the present invention.

[Explanation of symbols]

1, 1L, 1R ... Speaker device, 10 ... Digital power amplifier device, 11 ... Input terminal, 12 ... Gain control unit, 13 ... Digital sigma conversion unit, 14 ... Signal processing unit, 15 ... Switching amplification unit, 15L, 15R ... Switching element, 16, 16L, 16R ... Low-pass filter, 17, 17L, 17R ... Output terminal, 18 ... Power supply circuit, 19 ... Operation part, 20 ... Central control unit (CP)
U), 21 ... Low-pass filter, 22 ... Analog / digital converter

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Takashi Kumagai             6-735 Kita-Shinagawa, Shinagawa-ku, Tokyo Soni             -Inside the corporation (72) Inventor Ryoichi Katai             6-735 Kita-Shinagawa, Shinagawa-ku, Tokyo Soni             -Inside the corporation F term (reference) 5J091 AA02 AA24 AA41 CA00 CA56                       FA18 GP02 HA19 HA25 HA29                       HA39 KA00 KA33 KA34 KA42                       KA53 KA62 MA20 SA05 TA01                       TA06 TA07 UW01                 5J500 AA02 AA24 AA41 AC00 AC56                       AF18 AH19 AH25 AH29 AH39                       AK00 AK33 AK34 AK42 AK53                       AK62 AM20 AS05 AT01 AT06                       AT07 PG02 WU01

Claims (5)

[Claims] 1. Switching means for obtaining a pulse signal for driving a speaker based on an input audio signal waveform, and stopping the switching operation of the switching means when an abnormality in the input or output of the switching means is detected. Protecting means, detecting means for detecting stop of the switching operation by the protecting means, and when the detecting means detects that the switching operation is stopped, the protecting operation by the protecting means is reset and the switching means And a control means for restarting the output of the pulse signal by the switching amplifier device. 2. The switching amplifier device according to claim 1, wherein the detection means includes a filter means for smoothing a pulse signal output from the switching means, and a determination means for determining an output voltage of the filter means. The switching amplifier device is configured to detect that the switching operation is stopped when the determination means detects the voltage in the state without the pulse signal. 3. The switching amplifier device according to claim 2, wherein a high-frequency component of the speaker driving pulse signal output from the switching unit is removed by a filter unit different from the filter unit included in the detecting unit, Switching amplifier device designed to be supplied to the speaker. 4. The switching amplifier device according to claim 1, wherein the control means resets the protection operation by the protection means when the detection means detects that the switching operation is continuously stopped a predetermined number of times. Switching amplifier device. 5. The switching amplifier device according to claim 4, wherein the control means resets the control means immediately after the reset when the detection means further detects that the switching operation is stopped. Switching amplifier device that does not perform.