JPH07226633A - Protective device for power amplifier - Google Patents

Abstract

PURPOSE:To perform protection against the burning damage of a power amplifier itself and thermal injuries to a human body by detecting an abnormal heat generating state generated at the time of the fault of the air cooling fan of the power amplifier and the fault of a power supply circuit to a fan motor. CONSTITUTION:When a control circuit 3 for driving a fan fails, the output (c) of an abnormal heat generating detection circuit 9 can be 'H' when the signal level detection input (a) from a signal level detection circuit 8 of the abnormal heat generating detection circuit 9 is 'H' and the output (b) of a motor voltage detection circuit is 'L'. At the time, it is predicted that the abnormal heat generating state is attained since the fan is not rotated in a state where the fan is to be rotated, a signal level attenuation circuit 6 is controlled, an input signal level is attenuated and the heat generation of the power amplifier 1 is reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal protection device for a power amplifier equipped with a fan motor, and more specifically, it detects a signal output level of the power amplifier and a motor terminal voltage of the fan motor, and detects an abnormality in the logical product. The present invention relates to a power amplifier protection device having a function of detecting a heat generation state and attenuating an output signal level of a power amplifier when an abnormality occurs to reduce heat generation.

[0002]

2. Description of the Related Art In recent years, power amplifiers have tended to be miniaturized, and the heat generated by the power amplifier has been kept to a minimum. It is important to consider protection against thermal injury to the human body due to, and it is required to realize this with a simple circuit configuration.

An example of the above-mentioned conventional power amplifier protection device will be described below with reference to the drawings. Figure 2
FIG. 4 is a block diagram showing a circuit configuration of a conventional power amplifier protection device. In the figure, a signal attenuator circuit 6 for attenuating an input signal to the power amplifier is connected to the input side of the power amplifier 1, and a fan motor drive control circuit 3 is connected to the output side of the power amplifier 1 to drive the fan motor. A fan motor 2 having a fan for cooling the power amplifier 1 by air cooling is connected to the control circuit 3 for use. Further, the fan motor 2 is connected with a fan abnormality detection circuit 4 for detecting a failure of the fan motor 2. The output of the fan abnormality detection circuit 4 and the temperature detector 5 that detects the temperature of the power amplifier 1 is connected to the signal attenuation circuit 6.

In this prior art, the fan abnormality detection circuit 4 limits the output of the power amplifier 1 by controlling the signal attenuating circuit 6 to increase the degree of attenuation when the fan motor 2 fails or the like. The fan abnormality detection circuit 4 operates to suppress the heat generation of the power amplifier.
The temperature detector 5 detects the temperature of the power amplifier 1 by using a thermistor or the like in order to protect the power amplifier 1 from being burned or thermal injury to a human body when the device itself fails.
When the temperature is abnormal, a control signal is output to the signal attenuating circuit 6 to increase the degree of attenuation of the signal attenuating circuit 6.

[0005]

However, in the above-mentioned conventional power amplifier protection device, there are large variations in the characteristics of the temperature detector itself, and in addition, technical studies including the mounting method of the temperature detection element are difficult. It had a problem that it was difficult.

The present invention has been made to solve the above-mentioned conventional problems, and can be simply constructed without using a temperature detector, and is provided with a protection circuit against burnout due to heat generation and thermal injury to a human body. It is an object of the present invention to provide a power amplifier protection device.

[0007]

To achieve the above object, a power amplifier protection device of the present invention comprises a power amplifier, a signal attenuating circuit for attenuating the input of the power amplifier,
A fan motor having an air-cooling fan for air-cooling the power amplifier, a fan motor drive control circuit that drives the fan motor by detecting the output signal level of the power amplifier, and a signal that detects the signal level of the output signal of the power amplifier The abnormal heat generation state is detected from the logical product of the level detection circuit, the motor voltage detection circuit that detects the motor voltage of the fan motor, and the output of the signal level detection circuit and the output of the motor voltage detection circuit to determine the degree of attenuation of the signal attenuation circuit. It has a configuration including an abnormal heat generation detection circuit that is largely controlled.

[0008]

According to the present invention, in the above structure, the abnormal voltage detection circuit detects only the logical output of the output signal level detection of the power amplifier and the logical output of the power supply voltage of the fan motor at an arbitrary signal level to detect the abnormality of the power amplifier. When the heat generation state can be detected and the power amplifier may generate heat due to its output, the attenuation of the signal attenuator circuit is controlled to attenuate the input signal to the power amplifier and reduce the output of the power amplifier. It acts to suppress fever.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a power amplifier protection device according to the present invention will be described below with reference to FIG. Figure 1
FIG. 3 is a block diagram showing a circuit configuration of a power amplifier protection device according to the present invention. In the figure, a signal attenuator circuit 6 for attenuating an input signal to the power amplifier is connected to the input side of the power amplifier 1, and a fan motor drive control circuit 3 is connected to the output side of the power amplifier 1. A fan motor 2 having a fan for cooling the power amplifier 1 with air is connected to the drive control circuit 3. Further, the fan motor 2 is connected with a fan abnormality detection circuit 4 for detecting a failure of the fan motor 2.

On the other hand, a signal level detection circuit 8 is further connected to the output of the power amplifier 1, and a motor voltage detection circuit 7 is connected to the connection point between the output of the fan motor drive control circuit 3 and the fan motor 2 to output a signal. The output of the level detection circuit 8 is supplied to the terminal a of the abnormal heat generation detection circuit 9 and the motor voltage detection circuit 7
Is connected to the terminal b of the abnormal heat generation detection circuit 9.
The outputs of the fan abnormality detection circuit 4 and the abnormal heat generation detection circuit 9 are connected to the signal attenuation circuit 6.

The operation of the power amplifier protection device configured as described above will be described below. First, the fan motor drive control circuit 3 detects the output signal of the power amplifier and controls the air-cooling fan to rotate when the output of the power amplifier is large. In other words, when the output of the power amplifier is large, the heat generated by the power amplifier is large, so the fan motor 2
Rotate to cool the power amplifier. The fan is controlled to stop when there is no signal generated by the power amplifier and the output signal level is low. This is a design consideration so that the wind noise that is generated when the fan rotates does not disturb the ears of the user. Further, the fan abnormality detection circuit 4 detects a motor terminal opening, a short circuit, and a fan lock in preparation for a failure of the fan motor,
When the fan motor 2 is abnormal, a detection signal is output to the signal attenuating circuit 6 to attenuate the signal level to the power amplifier 1 to suppress heat generation of the power amplifier 1. However, in the conventional circuit configuration, there is a problem that the signal attenuation circuit 6 cannot be controlled when the fan abnormality detection circuit 4 itself fails. Therefore, in the conventional example of FIG. Although the temperature detector 5 is provided to attenuate the signal level at the time of abnormal heat generation, in the present invention, the motor voltage detection circuit for detecting the terminal voltage applied to the fan motor 2 in addition to the conventional fan abnormality detection circuit 4 is used. 7
The above problem was solved by providing the signal level detection circuit 8. Assuming that the fan drive control circuit 3 may fail and the original control may not be performed in FIG. 1, the signal level detection input a from the signal level detection circuit 8 of the abnormal heat generation detection circuit 9 is “H”. If the input b from the motor voltage detection circuit 7 to the abnormal heat generation detection circuit 9 is "H" in the signal output state in which the fan should rotate, the output c of the abnormal heat generation detection circuit 9 becomes "L". . At this time, the fan is judged to be operating normally and the signal is not attenuated. Next, in the same state, when the output b of the motor voltage detection circuit is "L", the output c of the abnormal heat generation detection circuit 9
To "H". At this time, since the fan does not rotate in a state where the fan should rotate, it can be predicted that an abnormal heat generation state occurs. Therefore, the signal level attenuation circuit 6 attenuates the signal level to suppress heat generation of the power amplifier 1.
It protects the power amplifier 1 from burning and thermal injury to the human body.

The detection logic value of the abnormal heat generation detection circuit is not limited to the above example. As a result, when the output signal of the power amplifier is large and the fan motor is not driven, the attenuation of the signal attenuation circuit is reduced. There is no problem if the logic works so that the value becomes large. As described above, according to the present embodiment, since the abnormal heat generation state of the power amplifier 1 can be detected without using a temperature detector such as a thermistor, it is possible to easily use general-purpose circuit components without using a temperature detection element. The circuit can easily configure the power amplifier 1 and a protection device against thermal injury to the human body. Further, a temperature detecting element such as a thermistor required technical know-how in variations in characteristics and mounting method, but according to the present invention, it is possible to design relatively easily.

[0013]

As described above, in the structure using the conventional thermistor or the like, technical know-how of the mounting method of the temperature detecting element is required, and the temperature experiment is repeated to grasp the variation of the temperature detecting element. However, according to the per-amplifier protective device of the present invention, the output of the signal level detection circuit for detecting the level of the output signal of the power amplifier and the voltage of the fan motor are detected. The abnormal heat generation detection circuit that detects the abnormal heat generation state from the logical product of the output of the motor voltage detection circuit and controls the attenuation degree of the signal attenuator circuit to a large extent even if the fan abnormality detection circuit is damaged. It is possible to prevent burnout and damage to the human body due to its heat generation, and a protective device with a simple configuration using only general-purpose circuit parts without using a temperature detector. Can be formed, can the design of a desk,
The effect of saving the design work is great.

[Brief description of drawings]

FIG. 1 is a block diagram of a power amplifier protection device according to an embodiment of the present invention.

FIG. 2 is a block diagram of a conventional power amplifier protection device.

[Explanation of symbols]

 1 Power Amplifier 2 Fan Motor 3 Fan Motor Drive Control Circuit 4 Fan Abnormality Detection Circuit 6 Signal Attenuation Circuit 7 Motor Voltage Detection Circuit 8 Signal Level Detection Circuit 9 Abnormal Heat Generation Detection Circuit

Claims (2)

[Claims] 1. A power amplifier, a signal attenuating circuit for attenuating an input of the power amplifier, a fan motor having an air-cooling fan for air-cooling the power amplifier, and an output signal level of the power amplifier is detected to detect the output signal level. A fan motor drive control circuit for driving a fan motor, a signal level detection circuit for detecting a signal level of an output signal of the power amplifier, a motor voltage detection circuit for detecting a motor voltage of the fan motor, and the signal level detection A power amplifier protection device having an abnormal heat generation detection circuit for detecting an abnormal heat generation state from a logical product of an output of a circuit and an output of the motor voltage detection circuit and largely controlling the degree of attenuation of the signal attenuation circuit. 2. The protection of the power amplifier according to claim 1, wherein the abnormal heat generation detection circuit controls the attenuation degree of the signal attenuation circuit to be large when the output signal level of the power amplifier is large and the fan motor terminal voltage is small. apparatus.