JPS5812404A - Amplifying device - Google Patents

Abstract

PURPOSE:To prevent the thermal destruction, etc., of a circuit due to the temperature rise in a device, by detecting the temperature in the device and then attenuating the output of an amplifier in accordance with the detected temperature. CONSTITUTION:Once detecting the temperature in a device exceeding preset temperature T0, a temperature detecting circuit 6 supplies a driving signal to a switch driving circuit 7. This signal permits a driving circuit 7 to place a switch 8 on the side of an attenuator 9. Consequently, a signal applied to an input terminal 1 is supplied to an amplifier 2 through an attenuator 9. Then, an output signal attenuated by the attenuation amount of the attenuator 9 appears at an output terminal 3, and the self-heating value in the device is reduced accordingly to reduce the temperature rise in the device. Thus, the thermal destruction, etc., of a circuit in the device is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an amplifying device for amplifying audio signals, etc., and is concerned with various problems that occur due to the heat generated within the device, such as burns due to an excessive rise in the temperature of the outer shell of the device, or damage to the inside of the device. The purpose is to prevent the temperature inside the device from increasing further by detecting the temperature inside the device and attenuating the output of the amplifier according to the temperature, in order to resolve thermal damage to each circuit. It is.

FIG. 1 shows a conventional amplifying device. In FIG. 1, 1 is an input terminal, 2 is an amplifier such as a power amplifier, 3 is an output terminal, 4 is a load, and 6 is a temperature compensation circuit.

Generally, when power is supplied from the amplifier 2 to the load 4, a current corresponding to the power flows into the load 4 through the amplifier 2, and heat is generated in the device including the amplifier 2 together with the load 4. Most of this is caused by Joule heat generated by current flowing through the resistor inside the amplifier 2 and heat due to copper loss in the power transformer. This heat increases the temperature inside the device.

Therefore, in the conventional amplifier device, the temperature compensation circuit 6
The amplifier 2 is designed to operate normally even if the internal temperature of the device increases.

However, if the amplifier 2 is driven at a high input for a long period of time, if another device is placed on top of the device, or if the device is placed in a small storage box, the first
In this case, due to self-heating inside the device, the second and third
In this case, the temperature inside the device exceeds the compensation range of the temperature compensation circuit 6 due to poor diffusion of heat generated within the device to the surroundings, and when the temperature inside the device rises, each circuit in the device becomes thermally unstable. There is a very high risk that accidents such as damage to the equipment, excessive rise in the temperature of the outer shell of the equipment, and burns may occur.

The present invention provides an amplification device that solves these conventional problems.

An embodiment of the present invention will be described below with reference to FIG.

In FIG. 2, parts having the same functions as those in FIG. 1 are given the same reference numerals, and explanations thereof will be omitted.

The temperature detection circuit 6 detects that the internal temperature T of the device is equal to the preset temperature T0. It is detected that the value exceeds the threshold value, and a drive signal is given to the switch drive circuit 7. This signal causes the switch drive circuit 7 to drive the switch 8 through the attenuator 9.
gllll3, so that the signal applied to the input terminal 1 is input to the amplifier 2 through the attenuator 9. As a result, an output signal that is attenuated by the attenuation amount of the attenuator 9 is generated at the output terminal 3, and the amount of self-heating within the device is reduced by that amount, reducing the temperature rise within the device. . Therefore, burns and thermal damage to each circuit within the device can be prevented.

The effect is shown in Figure 3. The horizontal axis t is time, and the vertical axis T is the temperature inside the device. Curve 10 (dashed line) represents the conventional temperature change, and curve 11 (solid line) represents the temperature change according to the above embodiment. To is the detected temperature of the temperature detection circuit 6 set in advance, T1 is the saturation temperature inside the device according to the conventional method, and T
2 is the saturation temperature inside the device in the above embodiment, and Ti is the initial temperature inside the device, that is, the room temperature.

In the above embodiment, the attenuator 9 is inserted on the input side of the amplifier 2, and the attenuator 9 is connected or separated depending on the temperature inside the device. Similar effects can be obtained by using the apparatus shown in FIG. Below is Figure 4.

The operating principle and effects will be explained using FIG. 6. However, in FIGS. 4 and 6, parts having the same functions as those in FIGS. 1 and 2 are denoted by the same reference numerals, and explanations thereof will be omitted. Further, the temperature compensation circuit 6 is also omitted from illustration as it is included in the amplifier 2.

In FIGS. 4 and 6, 12 is a first feedback circuit that returns part of the output to the input, and 13 is an input/output terminal of the amplifier 2 that replaces the first feedback circuit 12 after the temperature detection circuit 6 operates. This is a second feedback circuit inserted between the two.

In the conventional negative feedback amplifier shown in FIG. 4, if the open loop gain is Kinuta and the amount of feedback is β1, the overall gain A1 of this amplifier is as follows.

Open loop gain A of the amplifier. is theoretically infinite, so
A1 takes its limit and is determined only by the feedback amount β1 of the feedback circuit 12.

On the other hand, in the case of FIG. 6, which is the second embodiment of the present invention,
Similarly to FIG. 2, the temperature T inside the device is set to a certain temperature T.
. When the temperature detection circuit 6 detects that the temperature has exceeded the temperature, it provides a drive signal to the switch drive circuit 7, and the switch drive circuit 7 drives the switch 8 based on this signal, and the feedback circuit is switched from the first feedback circuit 12 to the first feedback circuit 12. Switch to the feedback circuit 13 of No. 2.

The overall gain A2 at this time is expressed as in equation (2). However, in order to attenuate the output and prevent temperature rise, the following conditional expression must be satisfied.

A2〈A1 ,・,β〉β・・・・・・・・・(
41 Under this condition, when the negative feedback amplifier is operated, the internal temperature T of the device becomes the set temperature T. 'j &: When the temperature exceeds the temperature T2, the operation of the temperature detection circuit 6 lowers the overall gain of the amplifier and prevents the temperature T inside the device from rising any further.As a result, at a temperature T2 lower than the conventional saturation temperature T1, It is possible to saturate the temperature inside the device and prevent burns and thermal damage to the circuit.

It goes without saying that the switch 8 shown in FIGS. 2 and 6 automatically returns to its original state when the internal temperature of the apparatus falls below the set temperature T0. In addition, in the embodiments shown in FIGS. 2 and 6, the circuits are switched at a predetermined temperature within the device. The input, output, gain, etc. of the amplifier may be changed continuously according to the temperature inside the device.

As described above, the present invention detects the temperature inside the device, and when the temperature inside the device rises, the detection output is used to attenuate the output of the amplifier. It is possible to solve various problems and realize a safe and high-performance amplifier. .

[Brief explanation of drawings]

Fig. 1 is a block diagram showing a conventional amplifier device, Fig. 2 is a block diagram showing a first embodiment of the present invention, Fig. 3 is a characteristic diagram showing the temperature characteristics inside the device of the above embodiment, and Fig. 4 6 is a block diagram of a conventional negative feedback amplifier, and FIG. 6 is a block diagram showing a second embodiment in which the present invention is applied to a negative feedback amplifier. 1...Input terminal, 2...Amplifier, 3
...Output terminal, 4...Load, 6...
... Temperature compensation circuit, 6 ... Temperature detection circuit, 7
...Switch drive circuit, 8...Switch, 9...Attenuator, 12°13...1st. Second feedback circuit. -1 Name of agent Patent attorney Medium
Toshio O and 1 other base 1 Zuguruma 21! 1 Chest 3 Figure 411 2 15 Figure

Claims (1)

[Claims] An amplifier device comprising: a temperature detection circuit for detecting a temperature inside the device; and means for attenuating the output of an amplifier by using the output of the temperature detection circuit when the temperature inside the device rises.