JPH01191505A - Heat balance device for parallel transistor - Google Patents

Abstract

PURPOSE:To uniformize the heat of transistors(TR) connected in parallel by feeding back the temperature of each case of the TRs connected in parallel to a gate exciting circuit so as to decrease the gate exciting level as the temperature increases. CONSTITUTION:As the heat of, e.g., TRs 11-13 increases, temperature sensors 21-23 corresponding to the TRs 11-13 detect the increased heat. Gate exciting circuits 31-33 decrease the exciting level of a gate G of the TRs 11-13 in response to the state of the temperature sensors 21-23 or a control signal being the result of temperature detection from the temperature sensors 21-23. With the exciting level decreased, the ON-resistance of the TRs 11-13 is increased thereby decreasing the current flowing to the TRs 11-13. Thus, the ON-resistance lose of the TRs 11-13 is decreased and the heat of the TRs 11-13 is decreased. Thus, the heat of the TRs connected in parallel is uniformized.

Description

TECHNICAL FIELD The present invention relates to a heat balance device for parallel transistors, and more particularly to a heat balance device for parallel transistors used in a power amplifier of a medium wave broadcasting device.

Conventional technology Conventionally, parallel-connected FETs (Field Effe
ct Transistor; field effect transistor) and 5IT (Static Induction Tr)
Regarding the thermal balance of transistors such as static induction transistors, there is no thermal runaway because the temperature coefficient of the on-resistance of the transistor is positive, and the entire system connected in parallel is in a state of thermal equilibrium, so there is nothing to worry about. It had not been done.

However, when the entire system connected in parallel is in a thermal equilibrium state, the amount of heat generated by each transistor is not balanced, and the amount of heat generated varies depending on the variation in the characteristics of each transistor.

Therefore, the heat resistance of the entire system connected in parallel is dominated by the transistor that generates the largest amount of heat in the system, resulting in a disadvantage that the heat reduction performance of the system as a whole deteriorates.

OBJECTS OF THE INVENTION An object of the present invention is to provide a heat balance device for parallel transistors that can equalize the amount of heat generated by transistors connected in parallel.

1. A heat balance device for parallel transistors according to the present invention includes transistor elements connected in parallel, and excitation control means for controlling the excitation state of each of the transistors according to the temperature of each of the transistor elements. It is characterized by having the following.

Example Hereinafter, the present invention will be explained in detail using the drawings.

FIG. 1 is a circuit diagram of an embodiment of a parallel transistor heat balance device according to the present invention. In the figure, a parallel transistor heat balance device according to an embodiment of the present invention includes transistors 11, 12 and 13, and temperature sensors 21, 22.
and 23, and gate excitation circuits 31, 32 and 33.

Transistors 11, 12, and 13 are connected in parallel and have a drain D, a gate G, and a source S, respectively.

The temperature sensor 21 detects the temperature of the transistor 11. Further, the temperature sensor 22 detects the temperature of the transistor 12. Furthermore, temperature sensor 2
3 detects the temperature of the transistor 13.

The gate excitation circuits 31, 32 and 33 activate the gates 1-1 of the corresponding transistors 11, 12 and 13, respectively, according to the temperature detection results of the corresponding temperature sensors 21, 22 and 23, respectively.
This changes the excitation level input to G.

In such a configuration, when the amount of heat generated by a transistor increases, the temperature sensor corresponding to the transistor detects it. The gate excitation circuit reduces the excitation level of the gate G of the transistor according to a control signal that is a temperature detection result from the temperature sensor or the state of the temperature sensor. As the excitation level decreases, the on-resistance of the transistor increases and the current flowing through the transistor decreases. This reduces on-resistance loss in the transistor and reduces the amount of heat generated by the transistor.

On the other hand, when the amount of heat generated by a transistor decreases, the temperature sensor corresponding to that transistor detects this. The gate excitation circuit increases the excitation level of the gate G of the transistor in accordance with a control signal that is a temperature detection result from the temperature sensor or the state of the temperature sensor. As the excitation level increases, the on-resistance of the transistor decreases, and the current flowing through the transistor increases. This increases the amount of heat generated by the transistor.

Next, a specific example of the temperature sensor will be explained using FIG. Figure 2 shows a circuit when a thermistor is used as the temperature sensor, and parts equivalent to those in Figure 1 are indicated by the same symbols.
In the figure, thermistors 41, 42 and 43 are connected as temperature sensors between the gate G and source S of the corresponding transistor, respectively. In this case thermistor 41.42
and 43 are fixed to the gates of the respective transistors. Further, 51, 52 and 53 are gate series resistances.

Thermistors 41, 42 and 43 are NTC (Negati
ve Ten+perature Coefficie
nt (negative characteristic) A thermistor whose resistance value decreases as the temperature rises. Therefore, the excitation level input from the gate excitation circuits 31, 32 and 33 to the respective gates G of the transistors 11, 12 and 13 can be changed by the thermistors 41, 42 and 43 and the gate series resistors 51, 52 and 53. This makes the amount of heat generated by the transistors 11, 12 and 13 uniform.

In such a configuration, when the amount of heat generated by the transistor increases, the resistance value of the thermistor decreases, and the excitation level decreases. Then, the on-resistance of the transistor increases,
The current flowing through the transistor is reduced. This reduces the on-resistance loss in the transistor and reduces the amount of heat generated by the transistor.

On the other hand, as the amount of heat generated by the transistor decreases, the resistance value of the thermistor increases and the excitation level increases. As a result, the on-resistance of the transistor decreases, and the current flowing through the transistor increases.

As a result, the on-resistance loss in the transistor increases, and the amount of heat generated by the transistor increases.6 In other words, in the present invention, a temperature sensor is provided for each of the transistors connected in parallel, and the By changing the excitation level to the gate of the transistor, the amount of heat generated by the transistor is made uniform.

As explained above, the present invention takes advantage of the fact that the on-resistance of a transistor depends on the voltage between the gate and source, and feeds back the temperature of each case of transistors connected in parallel to the gate excitation circuit. When the temperature rises, the gate excitation level is reduced, thereby making it possible to equalize the amount of heat generated by the transistors connected in parallel.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a parallel transistor heat balance device according to an embodiment of the present invention, and FIG. 2 is a circuit diagram showing an example in which a thermistor is used as the temperature sensor of FIG. 1. Explanation of symbols of main parts 11.12.13...Transistor 21.22
．． 23...Temperature sensor 31.32.33...
...Gate excitation circuit Figure 1 Figure 2

Claims (1)

[Claims] (1) A heat balance device for parallel transistors, comprising transistor elements connected in parallel, and excitation control means for controlling the excitation state of each of the transistor elements according to the temperature of each of the transistor elements.