JP2001112084A - Forced air cooling device for speaker driver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To properly cool a power amplifier 12 while suppressing the noise of a cooling fan device 26 in an audio unit 10 where the power amplifier 12 driving the speaker 11 is cooled by cooling air from the cooling fan device 26. SOLUTION: A CPU 14 detects the output level Lo of the power amplifier 12 and the temperature To of the power amplifier 12 on the basis of an input Li from an output level detection terminal 13 and an input Ti from a thermister 19. The CPU 14 calculates the output Vo that increases number of revolutions of a DC motor 27 as the Lo increases when the Ti is within the range of 50-95 deg.C on the basis of the Lo and provides the output Vo to a driver 25. The driver 25 supplies a fan drive current corresponding to the Vo to the cooling fan device 26, which drives the air 28 at the number of revolutions corresponding to the fan drive current.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a forced air cooling device for a speaker driving device provided in, for example, audio equipment.

[0002]

2. Description of the Related Art Audio equipment equipped with a speaker may be equipped with a cooling fan for forcibly air-cooling a power amplifier for driving a speaker.

[0003]

In a conventional forced air cooling device for a speaker driving device, the temperature of the speaker driving power amplifier and the output level of the speaker driving power amplifier are detected, and the cooling fan of the cooling fan is detected based on the detected values. Although the rotation speed is controlled, the control only turns on / off the operation of the cooling fan or, at most, switches the rotation speed of the cooling fan between high speed and low speed. Also,
In some cases, the wind noise of the cooling fan is a noise for the user.

It is an object of the present invention to provide a solution that overcomes the above-mentioned problems.

[0005]

A forced air cooling device for a speaker driving device according to the present invention includes a speaker driving power amplifier (12) for supplying a driving current to a speaker (11), and a speaker driving power amplifier (12). Temperature detecting means for detecting the temperature of
(19), output level detecting means (13) for detecting the output level of the speaker driving power amplifier (12), output level detecting means
A fan drive current generator (14, 25) for generating a fan drive current related to the output of (13), and a fan drive current generator
A cooling fan (26) driven by the fan driving current (14, 25) to generate cooling air to the speaker driving power amplifier (12). When the temperature of the speaker driving power amplifier (12) is within a predetermined range (hereinafter, referred to as a “first predetermined temperature range”), the fan driving current generation unit
(14, 25) is supplied to the cooling fan (26) so that the amount of cooling air generated by the cooling fan (26) increases continuously as the size of the output level detecting means (13) increases. Is output.

The speaker (11) may be provided in the same housing as the speaker driving power amplifier (12), or may be provided in a separate housing from the speaker driving power amplifier (12). . For example, in an audio system, speakers (1
1) is provided in the speaker box, and the speaker driving power amplifier (12) is provided in the amplifier. The fan drive current generator (14, 25) includes, for example, a CPU (14) and a driver (25) that converts a digital value input from the CPU (14) into a drive current of an analog value and outputs the drive current to the cooling fan (26). ). The cooling fan (26) is usually of a rotary type driven to rotate by an electric motor, and the amount of air generated by the cooling fan (26) is proportional to the rotation speed of the cooling fan (26). The cooling fan (26) is not limited to a rotary fan, but may be a cross-flow fan fan. The temperature detecting means (19) is, for example, a thermistor (19).

The temperature of the speaker driving power amplifier (12) detected by the temperature detecting means (19) may be the temperature of the speaker driving power amplifier (12) itself, or the speaker driving power amplifier (12). It is assumed that the temperature around the speaker driving power amplifier (12) closely related to the temperature of the speaker itself may be detected. The first predetermined temperature range of the speaker driving power amplifier (12) refers to, for example, the speaker driving power amplifier (1).
This is the temperature range during normal operation in 2).

As the output level of the speaker driving power amplifier (12) increases, the speaker driving power amplifier
(12) and the heat generated from the DC power generation unit (24) increase.
In this way, an optimal amount of cooling air that can prevent the temperature rise of the speaker driving power amplifier (12) is generated with respect to the heat generated from the speaker driving power amplifier (12), and the speaker driving power amplifier (12) is generated. ) Can be cooled and the amount of noise such as wind noise of the cooling fan (26) is maximized.
Can be suppressed.

A forced air cooling device for a speaker driving device according to the present invention includes a speaker driving power amplifier (12) for supplying a driving current to the speaker (11), and an electric device (10) including the speaker driving power amplifier (12). A DC power generation unit (24) that generates DC power for operation of each electric element from an AC power supply, a temperature detection unit (19) that detects the temperature of the DC power generation unit (24), a power amplifier for driving a speaker ( 12) an output level detecting means (13) for detecting an output level, a fan driving current generating section (14, 25) for generating a fan driving current related to an output of the output level detecting means (13), and a fan driving current DC power generator (24) driven by the fan drive current of the generators (14, 25)
A cooling fan (26) for generating cooling air to the cooling fan.
When the temperature of the speaker driving power amplifier (12) is within a predetermined range (hereinafter, referred to as a “first predetermined temperature range”), the fan driving current generation unit (14, 25) controls the cooling fan.
The amount of cooling air generated by (26) is determined by the output level detection means (1
The fan driving current to the cooling fan (26) is output so as to continuously increase as the size of 3) increases.

As the output level of the speaker driving power amplifier (12) increases, the load of the DC power generation unit (24) increases, and the heat generated from the DC power generation unit (24) increases.
Thus, for the heat generated from the DC power generation unit (24),
It is possible to generate a cooling air having an optimal flow rate that can prevent a rise in temperature of the DC power generation unit (24), thereby cooling the DC power generation unit (24) and noise such as wind noise of the cooling fan (26). The amount can be suppressed to the maximum.

According to the forced air cooling device for a speaker drive device of the present invention, the upper limit of the first predetermined temperature range is defined as Tu, and the speaker drive power amplifier (12) and the fan drive current generator (14, 25). When the temperature T of the speaker driving power amplifier (12) is determined to be Tu <T ≦ Ta based on the input to the fan drive current generator (14, 25), the cooling fan
The maximum fan drive current is output to (26) to the cooling fan (26) so that the amount of cooling air from the cooling fan (26) is maximized.

Tu and Tl are respectively 95 ° C. and 50 ° C. in FIG. 2 in the description of the embodiment of the invention described later.
C. Further, Ta and Tb are each 135 ° C. in FIG.
And -20 ° C.

When the temperature of the speaker driving power amplifier (12) rises and Tu <T ≦ Ta, the air volume of the cooling fan (26) is reduced to the output level of the output level detecting means (13). Irrespective of the fact that the maximum is uniformly set, the temperature of the speaker driving power amplifier (12) and / or the DC power generation unit (24), which has become high in temperature, can be quickly lowered. When the output level detecting means (13) fails,
Output level detection means for fan drive current generator (14, 25)
The input of (13) is incorrect, which results in the cooling fan (26)
Power volume for speaker drive
The temperature of (12) may rise and become equal to or higher than Tu, but when the temperature becomes equal to or higher than Tu, the cooling fan (26) reaches the maximum air volume, so even if the output level detecting means (13) fails, Safety is ensured.

According to the forced air cooling device for a speaker driving device of the present invention, the lower limit of the first predetermined temperature range is defined as Tl, and the speaker driving power amplifier (12) and the fan driving current generating units (14, 25). When the temperature T of the speaker driving power amplifier (12) is determined to be Tb <T ≦ Tl based on the input to the fan drive current generator (14, 25), the cooling fan
Stop the operation of (26).

When the temperature of the speaker driving power amplifier (12) is in a sufficiently low temperature range of Tb <T ≦ T1, the cooling fan (26) is independent of the output level of the speaker driving power amplifier (12). ), Unnecessary cooling of the speaker driving power amplifier (12) and / or the DC power generation unit (24) can be prevented.

According to the forced air cooling device for a speaker driving device of the present invention, the speaker driving power amplifier (12) is controlled based on the input from the speaker driving power amplifier (12) to the fan driving current generator (14, 25). Temperature T is T ≦ Tb or T> T
a, the speaker drive power amplifier (1
2) The operation of the DC power generation unit (24) is stopped.

Stopping the operation of the speaker driving power amplifier (12) and / or the DC power generation unit (24) means that the operation of the electric device (10) equipped with the forced air cooling device for the speaker driving device is completely controlled. As a result of the stop, the operation of the speaker driving power amplifier (12) and / or the DC power generation unit (24) is stopped. In the case of such a complete stop, when the fan drive current generation unit (14, 25) includes a microprocessor, the fan drive current generation unit (14, 25) is activated at the next startup of the electric device (10). Then, the protection is stopped, such as storing the data of the program being processed so as not to cause a problem, and then the operation is stopped.

T ≦ Tb and T> Ta are, for example, impossible states as the temperature of the speaker driving power amplifier (12), and the input from the temperature detecting means (19) is unreliable.
This means that the temperature of the speaker driving power amplifier (12) cannot be detected. In such a case, the speaker driving power amplifier (12) and / or the DC power generation unit (24)
By stopping the operation of, safety can be ensured.

According to the forced air cooling device for a speaker driving device of the present invention, when the temperature detecting means (19) fails, the input terminal from the temperature detecting means (19) in the fan drive current generating section (14, 25) is connected. It is designed to be pulled to near ground or near supply voltage.

When the temperature detecting means (19) is out of order, the fan driving current generating unit may be operated due to short-circuit or disconnection of the temperature detecting means (19).
At (14, 25), the input terminal from the temperature detecting means (19) is pulled almost to the ground voltage or almost to the supply voltage. Accordingly, the fan drive current generation unit (14, 25) determines that the temperature T of the speaker drive power amplifier (12) is T ≦ Tb or T> Ta.
Therefore, the power amplifier (12) for driving the speaker and / or the DC power generation unit (24) is stopped, and safety is ensured.

According to the forced air cooling device for a speaker drive device of the present invention, the fan drive current generator (14, 25) sets the fan drive current to the maximum or zero when the output fails. I have.

In the event of an output failure of the fan drive current generator (14, 25), the output terminal of the fan drive current generator (14, 25) is pulled substantially to the supply voltage or the ground voltage, and The fan driving current from the sections (14, 25) to the cooling fan (26) becomes maximum or zero. When the fan drive current is maximized, the air volume of the cooling fan (26) is maintained at the maximum, and safety is ensured. Further, when the fan driving current becomes 0, the operation of the cooling fan (26) is stopped, whereby the temperature of the speaker driving power amplifier (12) rises and finally reaches T
a, the power amplifier (12) for driving the speaker and / or
Alternatively, the operation of the DC power generation unit (24) is stopped, and safety is ensured.

According to the forced air cooling device for a speaker drive device of the present invention, the fan drive current generator (14, 25) controls the fan drive based on the moving average value of the output level detected by the output level detection means (13). And a moving time for calculating a moving average value when the output level detected by the output level detecting means (13) rises is set to be longer than the reference value Ra.

The wind noise or the like caused by the operation of the cooling fan (26) becomes noise for the user who hears the sound from the speaker.
When the output level of the speaker driving power amplifier (12) increases, it means that the volume from the speaker (11) is about to increase. If the volume from the speaker (11) is appropriately large with respect to noise such as wind noise, the noise will be almost inaudible to the user due to the masking effect. Therefore, when the volume from the speaker (11) is about to increase, the moving time for calculating the moving average value when the output level detected by the output level detecting means (13) rises is set larger than the reference value Ra. The increase in the air volume of the cooling fan (26), that is, the increase in the noise, is appropriately delayed from the increase in the volume from the speaker (11), so that the user can be prevented from hearing disturbing noise.

According to the forced air cooling device for a speaker drive device of the present invention, the fan drive current generator (14, 25) controls the fan drive based on the moving average value of the output level detected by the output level detection means (13). And a moving time for calculating a moving average when the output level detected by the output level detecting means (13) falls is a reference value Rb (where Rb ≦
Ra) is set smaller.

When the output level of the speaker driving power amplifier (12) decreases, it means that the volume from the speaker (11) will decrease. Then, speaker (11)
When the sound volume from the output of the cooling fan (26) is set to be smaller than the reference value Rb, the moving time for calculating the moving average value when the output level detected by the output level detecting means (13) rises is set. Can be reduced promptly, that is, the noise can be reduced promptly, and the user can be prevented from hearing disturbing noise as much as possible.

[0027]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram of a forced air cooling device for a speaker driving device in an audio device 10.
The speaker 11 receives a drive current from the power amplifier 12 and generates a sound wave corresponding to the drive current. The output level detection terminal 13 is a connection point of two resistors connected in series to each other between the output terminal of the power amplifier 12 and the ground, and is connected to the input terminal of the CPU 14. The thermistor 19 is arranged at a place where the temperature of the power amplifier 12 can be detected (eg, a radiator, a power transistor, a rectifying diode, etc.), is connected to the ground at one end, and is supplied with power via the resistor 20 at the other end. Connected to voltage 21. The resistor 20 side terminal of the thermistor 19 is connected to another input terminal of the CPU 14. The DC power generation unit 24 converts a commercial AC voltage input from a plug (not shown) into a predetermined DC voltage, and supplies the DC voltage to each electric element of the audio device 10. The CPU 14 converts an analog input from the output level detection terminal 13 and the thermistor 19 into a digital value and performs a predetermined process. The CPU 14 sends a digital value based on the processing result to the driver 25. Driver 25 is C
An analog drive current corresponding to the digital value input from the PU 14 is generated and sent to the DC motor 27 of the cooling fan device 26. The DC motor 27 drives the wing 28 at a rotation speed proportional to the current sent from the driver 25. In this audio device 10, the cooling air generated by the wings 28 is applied to the power amplifier 12 to cool the power amplifier 12,
It is sent to the DC power generation unit 24 instead of the power amplifier 12 to cool the DC power generation unit 24, or
It may be sent to both the DC power generator 12 and the DC power generator 24 to cool both.

FIG. 2 shows the relationship between the detected temperature To detected by the CPU 14 based on the input from the thermistor 19 and the processing mode of the CPU 14. The detected temperature To is as follows: (a) To <−
20 ° C, (b) -20 ° C ≦ To <50 ° C, (c)
50 ° C ≦ To <95 ° C, (d) 95 <To ≦ 135
° C and (e) 135 ° C <To.

(A) and (e) cannot be considered as a real problem. When the input from the thermistor 19 is (a) and (e), the CPU 14 detects the temperature of the power amplifier 12 due to the failure of the thermistor 19 or the like. Is determined to be impossible, and protection processing is performed. Specifically, the CPU 14 performs all measures that can stop the audio device 10 without hindrance, such as immediately terminating the currently executing program, saving data, and the like, and then turning on the power switch (not shown). Is turned off, and the operation of all the electric elements of the audio device 10 including the power amplifier 12 and the DC power generation unit 24 and the operation of the CPU 14 itself are promptly stopped.

In the case of (a), it is determined that it is impossible that two or more failures occur at the same time. That is, the failure is determined to be only the thermistor 18 and the others are determined to be normal. In other words, instead of performing the above-described protection processing as a minimum operation that allows the user to use the audio device 10 without any trouble, the CPU 14 is continuously operated by the cooling fan device 26 as in the case of (c) described later. Speed control may be performed.

In the case (b), the CPU 14 determines that the cooling of the power amplifier 12 is unnecessary, and outputs 0 to the driver 25.
And As a result, the cooling fan device 26 does not rotate the wing portion 28, and the power amplifier 12 does not receive cooling air from the cooling fan device 26.

In the case (c), the CPU 14 controls the speed of the cooling fan device 26 steplessly. The stepless speed control will be described later in detail.

In the case of (d), the CPU 14
The digital output value to 25 is maximized, whereby the cooling fan device 26 rotates at the maximum rotation speed, and the air volume of the cooling fan device 26 becomes maximum.

The input voltage from the thermistor 19 to the CPU 14 continuously decreases as the temperature of the power amplifier 12 increases. If the input from the thermistor 19 to the CPU 14 is interrupted, such as a short circuit of the thermistor 19 or a disconnection between the input terminal of the CPU 14 and the thermistor 19, the input terminal of the thermistor 19 in the CPU 14 is connected to the ground or the DC power generation unit 24. At about the supply voltage of the CPU 14. When the input terminal of the thermistor 19 in the CPU 14 is at about the ground voltage, the CPU 14
Since it is determined that the temperature of the power amplifier 12 is lower than −20 ° C., the protection processing in the case of (a) is performed, and safety is ensured. When the input terminal of the thermistor 19 in the CPU 14 is at about the supply voltage of the CPU 14 from the DC power generation unit 24, the CPU 14 determines that the temperature of the power amplifier 12 is higher than 135 ° C. The processing of the case is performed.

When the output from the CPU 14 to the driver 25 becomes inappropriate, the output terminal of the CPU 14 to the driver 25 is pulled to the ground or the supply voltage of the CPU 14 from the DC power generation unit 24. When the input terminal of the thermistor 19 in the CPU 14 is at about the ground voltage, the driver
25 sets the drive current to the cooling fan device 26 to 0, whereby the cooling fan device 26 stops the rotation of the wing 28.
As a result, the temperature of the power amplifier 12 rises, and finally,
In the case of (e), protection processing is performed,
Safety is ensured. When the input terminal of the thermistor 19 in the CPU 14 is at about the supply voltage of the CPU 14 from the DC power generation unit 24, the driver 25
The cooling fan device 26 maximizes the drive current to
As in the case of (1), the wing portion 28 is rotated at the maximum rotation speed, and the power amplifier 12 is cooled by the cooling air having the maximum air volume from the cooling fan device 26, thereby ensuring safety.

If the output level detection terminal 13 is short-circuited,
If the input from the output level detection terminal 13 to the CPU 14 is interrupted, such as a disconnection between the input terminal of the PU 14 and the output level detection terminal 13, the input terminal of the output level detection terminal 13 in the CPU 14 may be grounded or DC. The voltage is pulled to about the supply voltage of the CPU 14 from the power generation unit 24. In cases (a) and (e), protection processing is performed, and
In the case of (d), the cooling fan device 26 operates at the maximum air volume, and safety is ensured. In the cases (b) and (c), when the amount of cooling air from the driver 25 is insufficient to cool the power amplifier 12, as a result, the temperature of the power amplifier 12 rises, and finally Is (d) or (e)
In this case, safety is ensured.

FIG. 3 is a flowchart of a program for detecting the output level Lo of the power amplifier 12 from the input from the output level detecting terminal 13. This program is 500m
It is implemented by a time interrupt of sec. In S40, the current input Li from the output level detection terminal 13 is read. S
At 41, the current Li and the previous Li (= 500 msec before) are compared, and if current Li ≧ last Li, the process proceeds to S42, and if current Li <last Li,
Proceed to S43. In S42, that is, when Li rises, the average value of Li (= 21 Lis including the current Li) for 10 seconds in the past audio device is set to Lo. In S43, that is, when Li is falling, the past three seconds of Li (=
The average value of the seven most recent Lis including Li this time is defined as Lo. The reason why the moving time of the moving average is longer when rising and shorter when falling is as follows. That is,
The wind noise of the cooling fan device 26 becomes noise for the user who hears the sound from the speaker 11. The case where the output level of the power amplifier 12 increases is the case where the volume from the speaker 11 increases. In such a case, the increase in the volume from the speaker 11 precedes and the increase in the rotation speed of the cooling fan device 26, that is, the increase in the volume of the noise of the cooling fan device 26, is followed by the masking effect. Suppress 26 noises from the user. The case where the output level of the power amplifier 12 decreases is the case where the volume from the speaker 11 decreases. In such a case, the rotation speed of the cooling fan device 26 is reduced, that is, the volume of the noise of the cooling fan device 26 is rapidly reduced, and the noise of the cooling fan device 26 is suppressed from being heard by the user.

FIG. 4 is a flowchart of a program for detecting the temperature To of the power amplifier 12 from the input Ti from the thermistor 19. This program is also executed by a 500 msec time interrupt. In S50, the current input Ti from the thermistor 19 is read. In S51, the current Ti is compared with the previous Ti (= 500 msec before). If they match, the process proceeds to S52, and if they do not match, the program ends. In S52, the detected temperature To is set to the current T
Change to i. Thus, highly reliable To can be obtained.

FIG. 5 is a flowchart of a program for executing the stepless speed control of FIG. This program is
This is performed when To is (c) 50 ° C ≦ To <95 ° C. In S57, the output level Lo of the power amplifier 12 is read from the memory. In S58, the CPU 14
Outputs the digital value Vo to the driver 25 as Vo = a
・ Calculate from Lo + b. Here, a and b are positive numbers. If the range of Lo is Lomin ≦ Lo ≦ Lomax, a and b must be set so that Vo ≧ 0 when Lo = Lomin. Also, Lo =
In the case of Lomax, a and b are preferably set so that Vo causes the cooling fan device 26 to rotate at the maximum rotation speed. Equation of S58: Vo = a · Lo + b
Is an example, and if Vo increases as Lo increases, Vo may be set to a multiple-order function of Lo.
In S59, Vo is output from the CPU 14 to the driver 25. Thus, the cooling fan device 26 rotates at a rotation speed corresponding to Vo, and sends cooling air to the power amplifier 12.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a forced air cooling device for a speaker driving device in audio equipment.

FIG. 2 is a diagram illustrating a relationship between a detected temperature To detected by a CPU through an input from a thermistor and a processing mode of the CPU;

FIG. 3 is a flowchart of a program for detecting an output level Lo of a power amplifier from an input from an output level detection terminal.

FIG. 4 is a flowchart of a program for detecting a temperature To of a power amplifier from an input Ti from a thermistor.

FIG. 5 is a flowchart of a program for executing the stepless speed control of FIG. 2;

[Explanation of symbols]

 Reference Signs List 10 audio equipment (speaker drive device) 11 speaker 12 power amplifier (speaker drive power amplifier) 13 output level detection terminal (output level detection means) 14 CPU (fan drive current generation unit) 19 thermistor (temperature detection means) 24 DC Power generation unit 25 Driver (fan drive current generation unit) 26 Cooling fan device (cooling fan)

Claims (9)

[Claims] 1. A speaker driving power amplifier (12) for supplying a driving current to a speaker (11), temperature detecting means (19) for detecting a temperature of the speaker driving power amplifier (12), Output level detection means (13) for detecting the output level of the power amplifier (12), and a fan drive current generation section (14, 25) for generating a fan drive current related to the output of the output level detection means (13) And the speaker drive power amplifier (1) driven by the fan drive current of the fan drive current generator (14, 25).
A cooling fan (26) for generating cooling air to 2), wherein the temperature of the speaker driving power amplifier (12) is within a predetermined range (hereinafter, referred to as a "first predetermined temperature range"). The fan drive current generator (14, 25) is configured such that the amount of cooling air generated by the cooling fan (26) increases continuously as the size of the output level detecting means (13) increases. As described above, the forced air cooling device for a speaker drive device is configured to output a fan drive current to the cooling fan (26). 2. A speaker driving power amplifier (12) for supplying a driving current to a speaker (11), and an electric device (1) including the speaker driving power amplifier (12).
0) a DC power generation unit (24) for generating DC power for operation of each electric element from an AC power supply, and a temperature detection unit for detecting a temperature of the DC power generation unit (24).
(19), an output level detecting means (13) for detecting an output level of the speaker driving power amplifier (12), a fan driving current for generating a fan driving current related to an output of the output level detecting means (13) Generating unit (14, 25), and a cooling fan (26) driven by a fan driving current of the fan driving current generating unit (14, 25) to generate cooling air to the DC power generating unit (24), When the temperature of the speaker driving power amplifier (12) is within a predetermined range (hereinafter, referred to as a “first predetermined temperature range”), the fan driving current generation unit (14, 25) A fan driving current to the cooling fan (26) such that the flow rate of the cooling air generated by the cooling fan (26) increases continuously as the size of the output level detecting means (13) increases. A forced air cooling device for a speaker drive device, wherein the forced air cooling device outputs 3. An upper limit of the first predetermined temperature range is defined as Tu, and the speaker drive is performed based on an input from the speaker drive power amplifier (12) to the fan drive current generator (14, 25). The temperature T of the power amplifier (12) is Tu <T ≦
When it is determined that the current is Ta, the fan drive current generator (1
4, 25) output the maximum fan drive current to the cooling fan (26) to the cooling fan (26) to maximize the amount of cooling air of the cooling fan (26). The forced air cooling device for a speaker drive device according to claim 1 or 2, wherein: 4. A lower limit of the first predetermined temperature range is defined as Tl, and the speaker drive is performed based on an input from the speaker drive power amplifier (12) to the fan drive current generator (14, 25). The temperature T of the power amplifier (12) is Tb <T ≦
When it is determined to be Tl, the fan drive current generator (1
4. The forced air cooling device for a speaker driving device according to claim 1, wherein the cooling fan (26) stops the operation of the cooling fan (26). 5. A temperature T of the speaker driving power amplifier (12) based on an input from the speaker driving power amplifier (12) to the fan driving current generator (14, 25) is T ≦ T.
If it is determined that Tb or T> Ta, the speaker driving power amplifier (12) and / or the DC power generation unit (2
The forced air cooling device for a speaker drive device according to claim 3 or 4, wherein the operation of (4) is stopped. 6. When the temperature detecting means (19) fails, the input terminal from the temperature detecting means (19) in the fan drive current generating section (14, 25) is pulled to a substantially ground voltage or a substantially supply voltage. The forced air cooling device for a speaker drive device according to claim 5, wherein the forced air cooling device is configured to be capable of being driven. 7. The fan drive current generator (14, 25),
The forced air cooling device for a speaker drive device according to any one of claims 1 to 6, wherein the fan drive current is set to a maximum value or 0 at the time of the output failure. 8. The fan drive current generator (14, 25),
A fan drive current is generated based on the moving average value of the output level detected by the output level detecting means (13), and the moving average value when the output level detected by the output level detecting means (13) rises The forced air cooling device for a speaker driving device according to any one of claims 1 to 7, wherein the calculation movement time is set to be longer than the reference value Ra. 9. The fan drive current generator (14, 25),
A fan drive current is generated based on the moving average value of the output level detected by the output level detecting means (13), and the moving average value when the output level detected by the output level detecting means (13) falls is calculated. The travel time for the calculation is the reference value Rb.
The forced air cooling device for a speaker driving device according to any one of claims 1 to 8, wherein the value is set to be smaller than (Rb ≦ Ra).