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DESCRIPTION JP2008005009

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DESCRIPTION JP2008005009
Abstract: A signal amplification device capable of improving detection of an electrical short
related to an output device and preventing destruction of a signal amplifier due to the electrical
short is provided. A voltage division ratio determined by a resistance value (impedance) of an
output device (speaker 17) and a resistance value of a resistor (resistor R1 and resistor R2) is
detected as a detected voltage, and an output is made based on the detected voltage. It is
determined whether or not an electrical short has occurred in the device, and the switching
circuit (SP relay 13) is switched from off to on only when it is determined that no electrical short
has occurred. [Selected figure] Figure 1
Signal amplifier
[0001]
The present invention relates to a signal amplification device, and more particularly to a signal
amplification device such as an audio amplifier.
[0002]
In general, many electronic components (for example, speakers and the like) are driven by a
signal amplifier constituted by an IC (semiconductor integrated circuit).
In such a signal amplification device, for example, when the speaker terminal is short-circuited
due to some cause, this drive current exceeds the safe operation level, and the IC constituting the
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output amplifier, particularly the transistor for power amplification is overheated. May be
destroyed. Therefore, it is common to detect the drive current of such an electronic component,
and to detect this when it exceeds a preset safe power value, and to provide a protection circuit
for operating the safety circuit.
[0003]
FIG. 3 is a diagram showing the configuration of a conventional signal amplification apparatus
200. As shown in FIG. As shown in FIG. 3, the signal amplification device 200 includes a power
SW (switch) 11, a microcomputer 12, an SP relay 13, a primary relay 14, a transformer 15, an
amplifier unit 16 as a signal amplifier, and a speaker 17 as an output device. It is done.
[0004]
The power switch 11 is a switch for turning on / off the microcomputer 12 and is configured to
be switchable by an operation from the user.
[0005]
The microcomputer 12 includes an arithmetic device such as a CPU (Central Processing Unit),
and detects an electrical short (short) of the amplifier unit 16 based on an input voltage input
from a level shift circuit 161 described later.
Further, the microcomputer 12 performs on / off control of the SP relay 13 and the primary
relay 14.
[0006]
The amplifier unit 16 includes a transistor Q1 (Nch final transistor), a transistor Q2 (Pch final
transistor), a transistor Q3, an emitter resistor RE1, an emitter resistor RE2, a resistor R4, a
resistor R5, and a level shift circuit 161. There is.
[0007]
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The primary relay 14 is controlled by the microcomputer 12 so as to connect the AC primary
power supply (not shown) and the transformer 15 when in the on state.
The collectors of the transistors Q1 and Q2 are connected to the feeding end of the transformer
15, respectively. Emitter resistors RE1 and RE2 are connected in series between the emitters of
the transistors Q1 and Q2. A signal from an external signal source (not shown) is input to the
terminals of the transistors Q1 and Q2.
[0008]
One end of the SP relay 13 is connected between the emitter resistor RE1 and the emitter
resistor RE2. The SP relay 13 is controlled by the microcomputer 12 and connects the output
end of the amplifier unit 16 and the input end of the speaker 17 when in the on state.
[0009]
The resistor R4 is connected between the emitter of the transistor Q1 and the base of the
transistor Q3. The collector of the transistor Q3 is connected to the microcomputer 12 through
the level shift circuit 161, and the emitter of the transistor Q3 is connected to the emitter of the
transistor Q2. Further, one end of a resistor R5 is connected between the resistor R4 and the
base of the transistor Q3, and the other end is connected between the emitters of the transistors
Q2 and Q3.
[0010]
Hereinafter, the operation of the above-described signal amplification device 200 will be
described. First, when the power SW 11 is turned on, the microcomputer 12 turns on the SP
relay 13 and turns on the primary relay 14 after a predetermined time (for example, 4 sec). Next,
when power is supplied to the amplifier unit 16 through the primary relay 14 and the
transformer 15, the microcomputer 12 electrically outputs the voltage to the amplifier output
based on the voltage value input from the level shift circuit 161 of the amplifier unit 16. It is
determined whether a short circuit has occurred.
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[0011]
Here, when the amplifier output is shorted, a voltage is generated in the emitter resistors RE1
and RE2 to turn on the transistor Q3, and the microcomputer 12 detects the occurrence of the
short via the level shift circuit 161. In this case, the microcomputer 12 stops the output to the
speaker and the power supply to the amplifier unit 16 by turning off the SP relay 13 and the
primary relay 14, thereby preventing the destruction of the amplifier unit 16 (transistors Q1 and
Q2). It is supposed to
[0012]
Also, in the conventional audio apparatus, with the signal level of the audio signal input to the
power amplifier (amplifier section) lowered by the muting means, the DC offset between the
differential outputs in the power amplifier is detected, and the detection result is Based on this, a
technology for stopping control of the operation of the power amplifier has been proposed (see,
for example, Patent Document 1). Japanese Patent Application Publication No. 2004-56547
[0013]
However, in the above-mentioned prior art, even when an electrical short circuit occurs in the
speaker, when the amplifier output is small, the voltage generated in RE1 and RE2 is also low,
and the generated voltage can be detected as an abnormality. It may not be possible. In this case,
the protection function for the amplifier unit does not work, and there is a possibility that the
amplifier unit may be destroyed by overheating or the like.
[0014]
An object of the present invention is to provide a signal amplification device capable of
improving detection of an electrical short related to an output device and preventing destruction
of a signal amplifier due to the electrical short.
[0015]
In order to solve the above problems, the invention according to claim 1 is characterized in that:
a signal amplifier for amplifying a signal input from the outside; an output device for outputting
an amplified signal amplified by the signal amplifier; An internal power supply for applying a
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predetermined voltage between the switching circuit and the output device via a resistor, and a
resistance value of the output device and the resistance A detection unit that detects a voltage
division ratio determined by the resistance value of the switch as a detection voltage, a
determination unit that determines whether or not an electrical short has occurred in the output
device based on the detected detection voltage, And control means for switching the switching
circuit from off to on when it is determined by the determining means that no electrical short has
occurred.
[0016]
Furthermore, in the invention according to claim 2, in the invention according to claim 1, the
clocking means for clocking time is provided, and the judging means is until the predetermined
time is clocked by the clocking means. It is characterized in that the detection voltage is
determined.
[0017]
Furthermore, the invention according to claim 3 is the invention according to claim 1 or 2,
further comprising: an internal power supply switching circuit which turns on / off voltage
application from the internal power supply, and the control means comprises the switching
circuit. It is characterized in that the internal power switch circuit is switched from off to on
before turning on.
[0018]
Furthermore, the invention according to claim 4 is the invention according to any one of claims 1
to 3, further comprising: notification means, wherein the control means is determined to be a
short circuit by the determination means. It is characterized in that the notification means is
controlled to notify the outside.
[0019]
According to the present invention, it is possible to determine whether or not an electrical short
has occurred in the output device based on the resistance value of the output device, so that the
detection of the electrical short according to the output device can be improved. it can.
In addition, since the amplified signal from the signal amplifier is output to the output device
only when it is determined that an electrical short has not occurred in the output device,
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destruction of the signal amplifier due to the electrical short of the output device can be
prevented. it can.
[0020]
Hereinafter, the best mode for carrying out the present invention will be described in detail with
reference to the drawings.
However, the scope of the invention is not limited to the illustrated example.
[0021]
FIG. 1 is a functional block diagram showing an embodiment of a signal amplification apparatus
100 to which the present invention is applied.
The same reference numerals are given to elements common to the configuration of FIG. 3
described above, and the detailed description thereof will be appropriately omitted.
Hereinafter, the configuration of the signal amplification device 100 will be described.
[0022]
As shown in FIG. 1, the signal amplification device 100 includes a power switch (switch) 11, a
microcomputer 12, an SP relay 13, a primary relay 14, a transformer 15, an amplifier unit 16, a
speaker 17, an impedance measurement power supply 18, a resistor R1, A relay 19 for
impedance measurement, a resistor R2, a resistor R3, and an LED (Light-Emitting Diode) 20 as
notification means are provided.
The amplifier unit 16 has the same configuration as that of FIG. 3 described above.
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[0023]
The impedance measurement power supply 18 applies a predetermined voltage between the
speaker side terminal of the SP relay 13 and the speaker 17 via the resistor R1, the impedance
measurement relay 19 and the resistor R2. In the present embodiment, the impedance
measurement power supply 18 is a DC power supply that supplies the power divided by the
transformer 15. However, the present invention is not limited to this aspect. For example, the
power from the primary power supply may be an impedance measurement power supply. The
power supply 18 may be directly supplied with power, or may be an AC power supply.
[0024]
The impedance measuring relay 19 connected between the resistor R1 and the resistor R2 is
controlled by the microcomputer 12 to connect one end of the resistor R1 and one end of the
resistor R2 when in the on state. ing.
[0025]
The microcomputer 12 detects a voltage division ratio determined by the impedance of the
speaker 17 and the resistance value of the resistors R1 and R2 as a detection voltage from
between the resistor R2 and the speaker 17.
[0026]
Then, the microcomputer 12 determines whether or not the detected voltage detected is equal to
or less than a predetermined threshold (voltage value). When the detected voltage is equal to or
less than the threshold, the microcomputer 12 determines that a short circuit occurs in the
speaker 17.
In this case, the microcomputer 12 lights the LED 20 to notify the occurrence of a short to the
outside.
On the other hand, when it is determined that the short circuit does not occur in the speaker 17,
the SP relay 13 is switched from off to on, and the amplification signal amplified by the amplifier
unit 16 is output from the speaker 17. In addition, the value of the threshold value which is an
index of short detection of the speaker 17 is assumed to be stored in advance in storage means
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such as a ROM (not shown) built in the microcomputer 12. Although the voltage value set as the
threshold value can be arbitrarily set, it is preferable to set based on the value of the detection
voltage detected at the normal time.
[0027]
Further, the microcomputer 12 has a clocking means (not shown) for clocking time of a crystal
oscillator or the like, and the judgment of the above-mentioned detection voltage is performed
until the predetermined time is clocked by this clocking means. Here, the predetermined time
which is an index of the passage of time can be arbitrarily set (for example, 4 sec), and is stored
in advance in storage means such as a ROM (not shown) built in the microcomputer 12 It is
assumed that As described above, by performing the determination of the detection voltage while
the predetermined time is counted, the determination of the voltage detection can be reliably
performed before the SP relay 13 is turned on.
[0028]
One end of the LED 20 is connected to the microcomputer 12 via the resistor R3, and the other
end is grounded. The LED 20 is turned on / off according to the control of the microcomputer
12. In the present embodiment, the LED is used as the notification unit. However, the present
invention is not limited to this. For example, a voice output device such as a buzzer or a
communication device capable of transmitting a notification signal to an external device may be
used.
[0029]
Hereinafter, the operation of the signal amplification device 100 will be described with reference
to FIG. FIG. 2 is a flow chart showing the procedure of the short circuit inspection process at the
time of activation of the signal amplification device 100. It is assumed that the SP relay 13, the
primary relay 14, and the impedance measuring relay 19 are all in the off state as a precondition
of this process.
[0030]
First, when the power switch 11 is operated and the microcomputer 12 is turned on (step S11),
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the microcomputer 12 switches the primary relay 14 from off to on (step S12) and switches the
impedance measuring relay 19 from off to on Then, a predetermined voltage is applied to the
speaker 17 from the impedance measurement power supply 18 (step S13).
[0031]
Next, the microcomputer 12 detects the voltage division ratio according to the impedance of the
speaker 17 and the resistance value of the resistors R1 and R2 as a detection voltage even when
time counting by the clock means is started (step S14), and this detection voltage Is less than a
predetermined threshold value (step S15).
Here, when it is determined that the value of the detected voltage is equal to or less than the
threshold (step S15; Yes), the microcomputer 12 determines that a short circuit occurs in the
speaker 17, and turns on the LED 20 to generate a short circuit externally. Is notified (step S16).
Subsequently, the microcomputer 12 turns off the impedance measurement relay 19 (step S17),
turns off the primary relay 14 (step S18), and ends the present process.
[0032]
For example, when the applied voltage 5 V of the power supply 18 for impedance measurement,
the resistances of the resistors R1 and R2 are both 10 Ω, and the threshold of the detection
voltage is 0.2 V, the impedance of the speaker 17 having a short is 0.2 Ω. Then, the detection
voltage detected from the voltage division ratio between the impedance of the speaker 17 and
the resistance value of the resistors R1 and R2 is 0.05 V, so that it is determined that a short has
occurred in the speaker 17.
[0033]
On the other hand, when it is determined in step S15 that the detected voltage exceeds the
threshold (step S15; No), the microcomputer 12 determines whether or not the time counted by
the clock means has exceeded a predetermined time, and the predetermined time If it is
determined that the time has not passed (step S19; No), the process returns to step S15 again.
[0034]
If it is determined in step S19 that the predetermined time has elapsed (step S19; Yes), the
impedance measuring relay 19 is turned off (step S20), and then the SP relay 13 is switched from
off to on, whereby the amplifier The amplification signal amplified by the unit 16 is output by the
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speaker 17 (step S21), and the present process ends.
[0035]
In the operation after the above processing, the microcomputer 12 determines whether or not a
short has occurred in the amplifier output based on the voltage value input from the level shift
circuit 161 of the amplifier unit 16, and it is determined that the short has occurred. If it is
determined, the SP relay 13 and the primary relay 14 are turned off to stop the output to the
speaker and the power supply to the amplifier unit 16.
[0036]
As described above, according to the signal amplification device 100 of the present embodiment,
the speaker 17 is used to determine whether or not an electrical short has occurred in the
speaker 17 based on the impedance (resistance value) of the speaker 17. Detection of such
electrical shorts can be improved.
Further, only when it is determined that the electrical short circuit does not occur in the speaker
17, the amplification signal from the amplifier section 16 is output to the speaker 17 so that the
destruction of the amplifier section 16 due to the electrical short circuit of the speaker 17 is
prevented. be able to.
[0037]
The detailed configuration and the detailed operation of the signal amplification device 100 in
the above embodiment can be appropriately modified without departing from the scope of the
present invention.
[0038]
For example, in the above embodiment, the detection signal is determined by the microcomputer
12 for a predetermined time. However, the present invention is not limited to this. When the
short circuit of the speaker 17 is not confirmed, the impedance measurement relay 19 is
immediately turned off. The SP relay 13 may be turned on.
[0039]
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It is a figure showing composition of a signal amplification device to which the present invention
is applied.
It is the flowchart which showed the procedure of the short circuit inspection processing at the
time of starting of the signal amplification device to which the present invention is applied.
It is the figure which showed the structure of the conventional signal amplification apparatus.
Explanation of sign
[0040]
DESCRIPTION OF SYMBOLS 100 Signal amplifier 11 Power SW 12 Microcomputer 13 SP relay
14 Primary relay 15 Transformer 16 Amplifier part Q1 Transistor Q2 Transistor Q3 Transistor
RE1 Emitter resistance RE2 Emitter resistance R4 Resistor R5 Resistor 161 Level shift circuit 17
Speaker 18 Power supply for impedance measurement 19 Impedance measuring relay 20 LED
R1 resistor R2 resistor R3 resistor 200 signal amplifier
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