JPH09289281A - Circuit for sensing temperature of transistor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a temperature sensing circuit of a power amplifier transistor with long-time high reliability which effectively prevents breakdown of a power amplifier transistor by eliminating delay of a temperature detection time of a power transistor. SOLUTION: A temperature detection switch 1 is fixed immediately on a power amplifier transistor 2 by direct thermal connection through heat conductive paint 4 and the power amplifier transistor 2 is prevented from being broken by detecting temperature rise of the power transistor 2 by the temperature sensing switch 1 without delay. Furthermore, the heat conductive paint 4 is covered with a silicon coating material 5 for preventing heat conductivity of the heat conductive paint 4 from lowering affected by air and accurate temperature sensing is made possible for a long time, thus obtaining long-time high reliability.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transistor temperature detection circuit, and more particularly to a temperature detection circuit for detecting a temperature rise of a power amplification transistor during transmission by a transmitter.

[0002]

2. Description of the Related Art FIG. 2 shows an example of the configuration of a transmitter to which the present invention is applied. This transmitter includes an external transmission signal input unit 10, a control circuit 20, and a power amplifier 30.

A transmission signal is input to the external transmission signal input section 10 from the outside, and the transmitter starts transmission by this transmission signal. This transmission signal from the outside is input to the control circuit 20, and the control circuit 20 controls the transmission / reception of the power amplifier 30 by the transmission signal from the outside. Control circuit 2
By controlling the transmission on / off from 0, the power amplifier 30 enters the transmission state or the reception state (transmission off). Power amplifier 3
0 has a temperature detection switch 1 therein, and the temperature detection switch 1 detects the temperature of the power amplifier 30,
When the temperature detection switch 1 becomes high temperature, the control circuit 20
The temperature detection signal is output to. The control circuit 20 controls transmission on / off by the temperature detection signal from the temperature detection switch 1 to protect the circuit.

FIG. 3 shows a conventional arrangement of the temperature detection switch and the power amplification transistor inside the power amplifier 30 of the transmitter.

The temperature detecting switch 1 and the power amplifying transistor 2 are provided on the transistor radiator 3 so as to be separated from each other. Transistor radiator 3
Is for radiating heat from the power amplification transistor 2 which becomes high in temperature during transmission.

Next, the operation of the protection circuit against the temperature rise of the power amplification transistor 2 will be described. When the power amplifier 30 enters a transmission state due to a transmission signal from the outside and the temperature of the power amplification transistor 2 in the power amplifier 30 rises, heat is transmitted to the temperature detection switch 1 via the transistor radiator 3 and the temperature detection switch 1 is heated. Raise the temperature. When the temperature detection switch 1 reaches a predetermined high temperature, a temperature detection signal is output from the temperature detection switch 1 to the control circuit 20, and the control circuit 20 outputs a signal of transmission stop to the power amplifier 30 and the transmitter. Stops sending.

However, in the conventional configuration shown in FIG. 3, since the temperature detection switch 1 is mounted on the transistor radiator 3 and there is a distance between the temperature detection switch 1 and the power amplification transistor 2, the temperature detection switch 1 has a thermal resistance. When the temperature detection time is delayed and the temperature detection switch 1 reaches a predetermined high temperature and outputs a temperature detection signal, the temperature of the power amplification transistor 2 has already risen above the predetermined temperature. There was a risk that the amplification transistor 2 would be damaged. In particular, when the power amplification transistor 2 is not sufficiently in contact with the transistor radiator 3, there is a problem that the temperature of the power amplification transistor 2 cannot be correctly detected, and the same transistor is likely to be damaged.

In order to solve such a problem, the present inventors have devised a temperature detecting circuit as shown in FIGS. 4 and 5.

FIG. 4 shows the power amplifier 3 of the transmitter shown in FIG.
FIG. 5 shows an arrangement previously devised by the inventors of the temperature detection switch and the power amplification transistor inside 0, and FIG. 5 is a sectional view taken along line XX of FIG.

The temperature detecting switch 1 is mounted on the power amplifying transistor 2 through a heat conductive paint 4 so as to be directly thermally coupled thereto. Therefore, even if the transmitter is in the transmitting state and the temperature of the power amplification transistor 2 rises, the thermal resistance of the transistor radiator 3 can be ignored, and the delay in the temperature detection time by the temperature detection switch 1 can be eliminated. it can. As described above, since the temperature detection switch 1 is directly thermally attached to the power amplification transistor 2, the power amplification transistor 2 is not particularly in contact with the power amplification transistor 2 even when the power amplification transistor 2 and the transistor radiator 3 are not sufficiently in contact with each other. The temperature of can be detected correctly.

[0011]

However, when the temperature detecting circuit is used for a long period of time, the present inventors deteriorate heat conduction due to aging of the heat conductive paint 4, and as a result, accurate temperature detection is possible. We have found that there is a problem that it disappears, and in some cases, it also leads to damage to the power amplification transistor.

Therefore, an object of the present invention is to solve the above-mentioned problems caused by aging and to provide a temperature detection circuit for a power amplification transistor, which has high long-term reliability.

[0013]

According to the present invention, the temperature detecting switch is directly thermally coupled to the power amplifying transistor by the heat conductive paint so as to detect the temperature rise of the power amplifying transistor without delay. At the same time, a temperature detecting circuit for a transistor is provided, characterized in that the heat conductive paint is covered with a silicone coating material.

In the present invention, the temperature detection switch is directly thermally coupled to the power amplifying transistor to detect the temperature rise of the power amplifying transistor without delay, so that the power amplifying transistor is effectively destroyed. Can be prevented. Further, since the temperature detection switch is directly thermally coupled to the power amplification transistor in this way, the temperature of the power amplification transistor can be correctly detected even when the power amplification transistor is not sufficiently in contact with the radiator. It is possible to effectively prevent damage to the power amplification transistor.

Further, since the heat conductive paint is used to directly thermally couple the temperature detecting switch to the power amplifying transistor, the heat conduction between the temperature detecting switch and the power amplifying transistor is good and easy. Can be joined.

Since the heat conductive paint is covered with the silicone coating material, it is possible to prevent the heat conductive paint from being deteriorated due to the influence of air. As a result, the heat conductivity of the heat conductive paint is prevented from changing over time, accurate temperature detection is possible for a long period of time, damage to the power amplification transistor can be prevented, and a long-term reliable power amplification transistor is provided. Temperature detection circuit is provided.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Next, an embodiment of the present invention will be described.

FIGS. 1 and 4 are diagrams for explaining the arrangement of an embodiment of the present invention of a temperature detection switch and a power amplification transistor inside the power amplifier 30 of the transmitter shown in FIG. 4 is a perspective view showing the internal arrangement of the power amplifier 30 of the present embodiment, FIG. 1A is a sectional view taken along line XX of FIG. 4, and FIG. 1B is a side view.

In the present embodiment, the temperature detection switch 1 is directly thermally coupled and mounted directly above the power amplification transistor 2 via the heat conductive paint 4. Therefore, even if the transmitter is in the transmitting state and the temperature of the power amplification transistor 2 rises, the thermal resistance of the transistor radiator 3 can be ignored, and the delay in the temperature detection time by the temperature detection switch 1 can be eliminated. it can. As described above, since the temperature detection switch 1 is directly heat-coupled and mounted directly above the power amplification transistor 2, even when the power amplification transistor 2 and the transistor radiator 3 are not sufficiently in contact with each other, the power amplification transistor 2 The temperature of 2 can be correctly detected, and damage to the power amplification transistor 2 can be effectively prevented.

Further, since the temperature detecting switch 1 is directly thermally coupled to the power amplifying transistor 2, the heat conductive paint 4 applied between the temperature detecting switch 1 and the power amplifying transistor 2 is used. , Temperature detection switch 1
And the power amplification transistor 2 have good heat conduction and can be easily joined.

Since the heat conductive paint 4 is covered with the silicone coating material 5, the heat conductive paint 4
Is prevented from being deteriorated in thermal conductivity under the influence of air. As a result, the thermal conductivity of the thermally conductive coating material 4 is prevented from changing over time, accurate temperature detection is possible for a long period of time, and damage to the power amplification transistor 2 can be prevented.

[0022]

According to the present invention, since the temperature detection switch is directly thermally coupled to the power amplification transistor by the heat conductive paint, the temperature rise of the power amplification transistor and the temperature detection time of the temperature detection switch are delayed. It can be eliminated, and damage to the transistor can be effectively prevented.

Further, since the heat conductive paint is covered with the silicone coating material, it is possible to prevent the heat conductive paint from being deteriorated due to the influence of air.
As a result, the thermal conductivity of the thermal conductive paint is prevented from changing over time, accurate temperature detection is possible for a long period of time, and damage to the power amplification transistor can be prevented, ensuring long-term reliable power amplification. A transistor temperature detection circuit is provided.

[Brief description of drawings]

FIG. 1 is a diagram for explaining an embodiment of the present invention, FIG. 1A is a cross-sectional view showing an internal arrangement of a power amplifier of the present embodiment, and is a cross-sectional view taken along line XX of FIG. 4 and FIG. 1B. Is a side view.

FIG. 2 is a diagram showing a configuration of a transmitter to which the present invention is applied.

FIG. 3 is a perspective view showing an internal arrangement of a conventional power amplifier.

FIG. 4 is a perspective view for explaining an embodiment of the present invention and an internal arrangement of the power amplifier previously devised by the present inventors.

5 is a cross-sectional view for explaining the internal arrangement of the power amplifier previously devised by the present inventors and is a cross-sectional view taken along line XX of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Temperature detection switch 2 ... Power amplification transistor 3 ... Transistor radiator 4 ... Thermal conductive paint 5 ... Silicone coating material 10 ... External transmission signal input section 20 ... Control circuit 30 ... Power amplifier

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Satoshi Nakamura 3-14-20 Higashi-Nakano, Nakano-ku, Tokyo Kokusai Electric Co., Ltd.

Claims (1)

[Claims] 1. A temperature detecting switch is directly thermally coupled to a power amplifying transistor by a heat conductive paint to detect a temperature rise of the power amplifying transistor without delay, and the heat conductive paint is made of silicone. A transistor temperature detection circuit characterized by being covered with a coating material.