Transistor circuit and power conversion circuit

Abstract

A transistor circuit (2) comprises: a plurality of transistors (4) which are electrically connected in parallel to each other and each have a collector (10), an emitter (12), and a base (14), and in each of which conduction between the collector (10) and the emitter (12) is controlled in accordance with a current input to the base (14); and a plurality of temperature measuring resistors (6) which each exhibit a resistance value gradually increasing in proportion to a gradual increase in the temperature, are each electrically connected to the base (14) of the corresponding transistor (4), and are disposed so as to be able to transfer heat to the transistors (4).

Description

Transistor circuit and power conversion circuit

[0001] The present invention relates to a transistor circuit and a power conversion circuit.

[0002] 2. Description of the Related Art Transistor circuits are known that include a plurality of transistors electrically connected in parallel with one another (see, for example, Patent Document 1).

[0003] JP 2019-113340 A

[0004] When a relatively large current needs to flow in a device or the like incorporating the above-mentioned transistor circuit, there are cases where a current exceeding the rated current of each transistor is supplied to the entire transistor circuit. In this case, under normal conditions, the current supplied to the entire transistor circuit is diverted to each transistor, so that a current less than the rated current flows through each transistor.

[0005] However, due to variations in the characteristics of individual transistors, a specific transistor among multiple transistors connected in parallel may overheat abnormally. When this occurs, the collector-emitter voltage of that specific transistor drops, causing an increase in the current flowing between the collector and emitter of that specific transistor. This can cause the specific transistor to overheat further, further increasing the current flowing between the collector and emitter of that specific transistor, a phenomenon known as thermal runaway. Then, a current exceeding the rated current flows concentratedly through the thermal runaway transistor, potentially damaging that transistor.

[0006] The present invention is intended to solve the above-mentioned problems, and an object of the present invention is to provide a transistor circuit and a power conversion circuit that can suppress the occurrence of thermal runaway.

[0007] A transistor circuit according to a first aspect of the present invention comprises a plurality of transistors electrically connected in parallel to each other, each having a collector, an emitter, and a base, and in which conduction between the collector and the emitter is controlled in accordance with the current input to the base; and a plurality of resistance temperature detectors, each of which gradually increases in resistance value in proportion to a gradual increase in temperature of each of the plurality of transistors, the resistance temperature detectors being electrically connected to the base of each of the plurality of transistors and being arranged so as to be able to transfer heat to each of the plurality of transistors. When a specific transistor among the plurality of transistors abnormally heats up, the resistance value of the specific resistance temperature detector gradually increases in proportion to the gradual increase in temperature of the specific resistance temperature detector electrically connected to the base of the specific transistor, thereby causing a portion of the current flowing through the specific transistor to be diverted to transistors other than the specific transistor.

[0008] According to this aspect, multiple resistance temperature detectors are electrically connected to the bases of the multiple transistors, respectively. The resistance value of each of the multiple resistance temperature detectors gradually increases in proportion to a gradual increase in temperature. Therefore, if a specific transistor among the multiple transistors connected in parallel generates abnormal heat, the resistance value of the specific resistance temperature detector electrically connected to the base of the specific transistor gradually increases in proportion to the gradual increase in temperature of the specific resistance temperature detector. This gradual increase in the resistance value of the specific resistance temperature detector gradually reduces the current input to the base of the specific transistor, thereby gradually reducing the current flowing between the collector and emitter of the specific transistor. As a result, a portion of the current that would otherwise be concentrated in the specific transistor due to abnormal heat is diverted to other transistors electrically connected in parallel to the specific transistor, thereby ensuring equal current flow through all transistors. Therefore, even if a current exceeding the rated value of each transistor is supplied to the entire transistor circuit, thermal runaway in each transistor can be prevented.

[0009] In addition, a power conversion circuit according to a second aspect of the present invention comprises a plurality of power conversion devices electrically connected in parallel to each other, each having an input terminal, an output terminal, and a voltage setting terminal for setting a voltage output from the output terminal; and a plurality of resistance temperature detectors, each of which gradually increases in resistance value in proportion to a gradual rise in temperature, the resistance temperature detectors being electrically connected to the voltage setting terminals of each of the plurality of power conversion devices and being arranged so as to be able to transfer heat to each of the plurality of power conversion devices.When a specific power conversion device among the plurality of power conversion devices abnormally heats up, the resistance value of the specific resistance temperature detector gradually increases in proportion to the gradual rise in temperature of the specific resistance temperature detector electrically connected to the voltage setting terminal of the specific power conversion device among the plurality of resistance temperature detectors, thereby causing a portion of the current flowing to the specific power conversion device to be diverted to other power conversion devices other than the specific power conversion device.

[0010] According to this aspect, multiple resistance temperature detectors are electrically connected to the voltage setting terminals of the multiple power conversion devices, respectively. The resistance values ​​of each of the multiple resistance temperature detectors gradually increase in proportion to a gradual rise in temperature. As a result, if a specific power conversion device among the multiple power conversion devices connected in parallel experiences abnormal heat generation, the resistance value of the specific resistance temperature detector electrically connected to the voltage setting terminal of the specific power conversion device gradually increases in proportion to the gradual rise in temperature of the specific resistance temperature detector. This gradual increase in the resistance value of the specific resistance temperature detector gradually reduces the voltage output from the output terminal of the specific power conversion device. As a result, a portion of the current that would otherwise be concentrated in the specific power conversion device due to abnormal heat generation is diverted to the other power conversion devices electrically connected in parallel to the specific power conversion device, thereby ensuring equal current flow through all the power conversion devices. Therefore, even if a current exceeding the rated value of each power conversion device is supplied to the entire power conversion circuit, thermal runaway in each power conversion device can be suppressed.

[0011] A transistor circuit or the like according to one embodiment of the present invention can suppress the occurrence of thermal runaway.

[0012] 1 is a diagram showing a configuration of a transistor circuit according to a first embodiment; FIG. 2 is a diagram showing a configuration of a transistor circuit according to a second embodiment; FIG. 3 is a diagram showing a configuration of a power conversion circuit according to a third embodiment; and FIG. 4 is a diagram showing a circuit example of a DC-DC converter according to a third embodiment.

[0013] Hereinafter, the embodiments will be specifically described with reference to the drawings.

[0014] The embodiments described below are all comprehensive or specific examples. The numerical values, shapes, materials, components, component placement and connection configurations, steps, and step order shown in the following embodiments are merely examples and are not intended to limit the scope of the claims. Furthermore, among the components in the following embodiments, components that are not described in the independent claims that represent the highest concepts are described as optional components.

[0015] In addition, the drawings are not necessarily strict illustrations, and the same reference numerals are used to designate substantially the same components in the drawings, and redundant explanations are omitted or simplified.

[0016] (First Embodiment) [1. Configuration of Transistor Circuit] The configuration of a transistor circuit 2 according to the first embodiment will be described with reference to Fig. 1. Fig. 1 is a diagram showing the configuration of a transistor circuit 2 according to the first embodiment.

[0017] 1, the transistor circuit 2 includes a plurality of transistors 4 (4a, 4b, 4c), a plurality of resistance temperature detectors 6 (6a, 6b, 6c), and a plurality of adjustment resistors 8 (8a, 8b, 8c). The transistor circuit 2 is mounted in, for example, various household or industrial appliances.

[0018] Each of the plurality of transistors 4 is an NPN bipolar transistor, and has a collector 10, an emitter 12, and a base 14. In each transistor 4, conduction between the collector 10 and the emitter 12 is controlled in accordance with the current input to the base 14.

[0019] The plurality of transistors 4 are electrically connected in parallel to one another. That is, the collectors 10 of the plurality of transistors 4 are electrically connected to one another, and the emitters 12 of the plurality of transistors 4 are electrically connected to one another. In this embodiment, three transistors 4 are electrically connected in parallel to one another, but this is not limiting, and two or four or more transistors 4 may be electrically connected in parallel to one another.

[0020] Each of the multiple resistance temperature detectors 6 is a resistor having a characteristic that its resistance value changes in proportion to changes in temperature of the resistance temperature detector 6, and has a pair of terminals. That is, as the temperature of each resistance temperature detector 6 gradually increases, the resistance value of each resistance temperature detector 6 gradually increases. Note that the proportionality between the temperature and resistance value of the resistance temperature detector 6 does not only mean that there is a strict mathematical proportional relationship between the two, but also means that the resistance value of the resistance temperature detector 6 gradually increases as the temperature of the resistance temperature detector 6 increases. Each of the multiple resistance temperature detectors 6 is made of a metal having the above-mentioned characteristics, such as platinum, nickel, or copper. Alternatively, each of the multiple resistance temperature detectors 6 may be made of an alloy, such as a platinum-cobalt dilute alloy.

[0021] Each of the multiple resistance temperature detectors 6 is electrically connected to the base 14 of each of the multiple transistors 4. Specifically, one terminal of each resistance temperature detector 6 is electrically connected to the base 14 of the transistor 4. As shown by the dashed-dotted line frame in FIG. 1 , each resistance temperature detector 6 is arranged to be able to transfer heat to the transistor 4. As a result, when the transistor 4 generates heat, the heat from the transistor 4 is transferred directly or indirectly to the resistance temperature detector 6. Each resistance temperature detector 6 may be in direct contact with the package of the transistor 4, or may be in contact with the package of the transistor 4 via a heat-conducting member or the like. Alternatively, the resistance temperature detector 6 may be arranged near the package of the transistor 4.

[0022] Each of the plurality of adjusting resistors 8 is a resistor for adjusting the resistance value between the base 14 and collector 10 of the transistor 4 (i.e., the resistance value of the combined resistance of the temperature detector 6 and the adjusting resistor 8), and has a pair of terminals. The plurality of adjusting resistors 8 are each electrically connected in series to the plurality of temperature detectors 6. Specifically, one terminal of each adjusting resistor 8 is electrically connected to the other terminal of the temperature detector 6, and the other terminal of each adjusting resistor 8 is electrically connected to the collector 10 of the transistor 4.

[0023] 1 , the effects obtained by the above-described transistor circuit 2 will be described. When a relatively large current needs to flow in a device or the like incorporating the above-described transistor circuit 2, there are cases where a current exceeding the rated current of each transistor 4 is supplied to the entire transistor circuit 2. In this case, under normal conditions, the current supplied to the entire transistor circuit 2 is diverted to each transistor 4, so that a current less than the rated current flows through each transistor 4.

[0024] However, due to variations in the characteristics of the individual transistors 4, one or more of the multiple transistors 4 may abnormally heat up. Below, we consider the case where, for example, transistor 4a, one of the multiple transistors 4a, 4b, and 4c, abnormally heats up. In this case, heat from transistor 4a is transferred to resistance temperature detector 6a, causing the temperature of resistance temperature detector 6a to gradually rise, and the resistance value of resistance temperature detector 6a to gradually increase. As a result, the current input to base 14 of transistor 4a gradually decreases, and the current flowing between collector 10 and emitter 12 of transistor 4a gradually decreases.

[0025] As a result, part of the current concentrated in the abnormally heated transistor 4a is diverted to each of the other transistors 4b and 4c electrically connected in parallel to the transistor 4a, so that the current flows equally to each of the transistors 4a, 4b, and 4c. Therefore, even if a current exceeding the rated value of each of the transistors 4a, 4b, and 4c is supplied to the entire transistor circuit 2, it is possible to prevent thermal runaway from occurring in each of the transistors 4a, 4b, and 4c.

[0026] (Embodiment 2) The configuration of a transistor circuit 2A according to embodiment 2 will be described with reference to Fig. 2. Fig. 2 is a diagram showing the configuration of a transistor circuit 2A according to embodiment 2. In each embodiment described below, the same components as those in embodiment 1 above are denoted by the same reference numerals, and their description will be omitted.

[0027] 2, in this embodiment, the types of the plurality of transistors 4A (4Aa, 4Ab, 4Ac) of the transistor circuit 2A are different from those in the above-described embodiment 1. Specifically, each of the plurality of transistors 4A is a PNP-type bipolar transistor, and has a collector 10, an emitter 12, and a base 14.

[0028] In this embodiment, the connections of the plurality of adjustment resistors 8 (8a, 8b, 8c) are different from those in the above-described embodiment 1. Specifically, one terminal of each adjustment resistor 8 is electrically connected to the other terminal of the resistance temperature detector 6, and the other terminal of each adjustment resistor 8 is electrically connected to ground.

[0029] Therefore, in this embodiment as well, the same effects as those in the first embodiment can be obtained.

[0030] (Embodiment 3) [3-1. Configuration of voltage conversion circuit] The configuration of a power conversion circuit 16 according to embodiment 3 will be described with reference to Fig. 3 and Fig. 4. Fig. 3 is a diagram showing the configuration of the power conversion circuit 16 according to embodiment 3. Fig. 4 is a diagram showing an example circuit of a DC-DC converter 18 according to embodiment 3.

[0031] 3, the power conversion circuit 16 includes a plurality of DC-DC converters 18 (18a, 18b), a plurality of resistance temperature detectors 6 (6a, 6b), and a plurality of adjustment resistors 8 (8a, 8b). The power conversion circuit 16 is mounted on various household or industrial devices, for example.

[0032] Each of the multiple DC-DC converters 18 is a power conversion device for converting DC power into DC power and has an input terminal 20, an output terminal 22, a voltage setting terminal 24, and a ground terminal 26. A DC voltage is input to the input terminal 20. The output terminal 22 outputs a DC voltage having a voltage value different from the voltage value of the DC voltage input to the input terminal 20. The voltage setting terminal 24 is a terminal for setting the DC voltage output from the output terminal 22. Specifically, as the resistance value of the resistor electrically connected to the voltage setting terminal 24 (i.e., the combined resistance of the resistance temperature detector 6 a and the adjustment resistor 8 a) increases, the voltage value of the DC voltage output from the output terminal 22 decreases. Note that a specific circuit of each DC-DC converter 18 is configured, for example, as shown in FIG. 4.

[0033] The multiple DC-DC converters 18 are electrically connected in parallel to one another. That is, the input terminals 20 of the multiple DC-DC converters 18 are electrically connected to one another, and the output terminals 22 of the multiple DC-DC converters 18 are electrically connected to one another. In the present embodiment, two DC-DC converters 18 are electrically connected in parallel to one another, but this is not limitative, and three or more DC-DC converters 18 may be electrically connected in parallel to one another.

[0034] Each of the multiple resistance temperature detectors 6 is electrically connected to the voltage setting terminal 24 of each of the multiple DC-DC converters 18. Specifically, one terminal of each resistance temperature detector 6 is electrically connected to the voltage setting terminal 24 of the DC-DC converter 18. As shown by the dashed-dotted line frame in FIG. 3 , each resistance temperature detector 6 is arranged to be able to transfer heat to the DC-DC converter 18. As a result, when the DC-DC converter 18 generates heat, the heat from the DC-DC converter 18 is transferred directly or indirectly to the resistance temperature detector 6. Each resistance temperature detector 6 may be in direct contact with the package of the DC-DC converter 18, or may be in contact with the package of the DC-DC converter 18 via a heat conductive member or the like. Alternatively, the resistance temperature detector 6 may be arranged near the package of the DC-DC converter 18.

[0035] Each of the plurality of adjustment resistors 8 is a resistor for adjusting the resistance value of a resistor electrically connected to the voltage setting terminal 24 (i.e., the combined resistance of the temperature detector 6a and the adjustment resistor 8a), and has a pair of terminals. Each of the plurality of adjustment resistors 8 is electrically connected in series to the plurality of temperature detectors 6. Specifically, one terminal of each adjustment resistor 8 is electrically connected to the other terminal of the temperature detector 6, and the other terminal of each adjustment resistor 8 is electrically connected to ground.

[0036] 3, the effects obtained by the above-described power conversion circuit 16 will be described. When a relatively large current needs to flow in a device or the like equipped with the above-described power conversion circuit 16, there are cases in which a current exceeding the rated current of each DCDC converter 18 is supplied to the entire power conversion circuit 16. In this case, under normal conditions, the current supplied to the entire power conversion circuit 16 is diverted to each DCDC converter 18, so that a current less than the rated current flows through each DCDC converter 18.

[0037] However, due to variations in the characteristics of the individual DC-DC converters 18, one or more of the multiple DC-DC converters 18 may abnormally heat up. Below, consider the case where, for example, the DC-DC converter 18a among the multiple DC-DC converters 18a, 18b, abnormally heats up. In this case, heat from the DC-DC converter 18a is transferred to the resistance temperature detector 6a, gradually increasing the temperature of the resistance temperature detector 6a, and accordingly, gradually increasing the resistance value of the resistance temperature detector 6a. As a result, the resistance value of the resistor electrically connected to the voltage setting terminal 24 of the DC-DC converter 18a (i.e., the combined resistance of the resistance temperature detector 6a and the adjustment resistor 8a) gradually increases, and the DC voltage output from the output terminal 22 of the DC-DC converter 18a gradually decreases.

[0038] As a result, part of the current concentrated in the abnormally heated DCDC converter 18a is diverted to the other DCDC converters 18b electrically connected in parallel to the DCDC converter 18a, so that current flows evenly to all of the DCDC converters 18a, 18b. Therefore, even if a current exceeding the rated value of each DCDC converter 18a, 18b is supplied to the entire power conversion circuit 16, thermal runaway can be suppressed in each DCDC converter 18a, 18b.

[0039] (Other Modifications, etc.) While the transistor circuits and power conversion circuits according to one or more aspects of the present invention have been described based on the above-mentioned embodiments, the present invention is not limited to the above-mentioned embodiments. As long as they do not deviate from the spirit of the present invention, various modifications that a person skilled in the art can make to the above-mentioned embodiments, or configurations constructed by combining components of different embodiments, may also be included within the scope of one or more aspects of the present invention.

[0040] In the third embodiment, the power conversion device is configured by the DC-DC converter 18, but is not limited to this and may be configured by, for example, an AC-DC converter for converting AC power into DC power.

[0041] The transistor circuit and power conversion circuit according to the present invention can be applied to various household or industrial appliances, for example.

[0042] 2, 2A transistor circuit 4, 4a, 4b, 4c, 4A, 4Aa, 4Ab, 4Ac transistor 6, 6a, 6b, 6c resistance temperature detector 8, 8a, 8b, 8c adjustment resistor 10 collector 12 emitter 14 base 16 power conversion circuit 18, 18a, 18b DCDC converter 20 input terminal 22 output terminal 24 voltage setting terminal 26 ground terminal

Claims

1. A transistor circuit comprising: a plurality of transistors electrically connected in parallel with each other, each having a collector, an emitter, and a base, and wherein conduction between the collector and the emitter is controlled in accordance with a current input to the base; and a plurality of resistance temperature detectors, each of which gradually increases in resistance value in proportion to a gradual rise in temperature, the resistance temperature detectors being electrically connected to the base of each of the plurality of transistors and being arranged so as to be able to transfer heat to each of the plurality of transistors; wherein, when a specific transistor among the plurality of transistors abnormally heats up, the resistance value of the specific resistance temperature detector gradually increases in proportion to the gradual rise in temperature of the specific resistance temperature detector electrically connected to the base of the specific transistor, thereby causing a portion of the current flowing through the specific transistor to be diverted to transistors other than the specific transistor.

2. A power conversion circuit comprising: a plurality of power conversion devices electrically connected in parallel with each other, each having an input terminal, an output terminal, and a voltage setting terminal for setting the voltage output from the output terminal; and a plurality of resistance temperature detectors whose resistance value gradually increases in proportion to a gradual rise in their respective temperatures, the resistance temperature detectors being electrically connected to the voltage setting terminals of each of the plurality of power conversion devices and being arranged so as to be able to transfer heat to each of the plurality of power conversion devices, wherein when a specific power conversion device among the plurality of power conversion devices abnormally heats up, the resistance value of the specific resistance temperature detector gradually increases in proportion to the gradual rise in temperature of the specific resistance temperature detector electrically connected to the voltage setting terminal of the specific power conversion device, thereby causing a portion of the current flowing through the specific power conversion device to be diverted to other power conversion devices other than the specific power conversion device.

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