Power Conversion Device

Abstract

To provide a technology that can contribute to making it easier to exert the output capacity of a power conversion device as desired (for example, to use it so that the junction temperature approaches the upper limit value) without losing sight of the purpose of suppressing the junction temperature of a switching element from exceeding the upper limit value. [Solution] A temperature sense diode is mounted on each of a plurality of switching elements, and a signal generator 3 detects the forward voltage of each temperature sense diode and generates a respective detection signal. Then, the switching of each switching element is controlled based on each detection signal. The controller that controls the switching of each switching element stores the upper limit of the junction temperature of each switching element, and a correlation function between the duty ratio of each detection signal and the temperature corresponding to the forward voltage of each temperature sense diode.

Description

[Technical Field]

[0001] The present invention relates to a technique applicable to a power conversion device such as an inverter. [Background technology]

[0002] For example, in a power conversion device such as an inverter that outputs multiple phase AC power, the desired power conversion is performed by switching control (on / off control) of multiple switching elements (e.g., IGBTs) provided in the power conversion device, but this can lead to temperature rise depending on the operating conditions of the switching elements.

[0003] If the junction temperature of the switching element exceeds an upper limit (temperature limit) due to the temperature rise described above, the switching element may be damaged (thermal breakdown), etc. In such a case, it is desirable to appropriately control the output of the power conversion device (for example, to limit the torque command or output current for a load such as a motor) and prevent the junction temperature of the switching element from exceeding the upper limit.

[0004] For example, Patent Document 1 discloses a configuration having a temperature sensor (temperature sensor indicated by reference numeral 10 in Patent Document 1) provided in a switching element group of an inverter, a signal generating unit (drive IC indicated by reference numeral 20 in Patent Document 1) that detects the voltage output (forward voltage of the diode) of the temperature sensor which changes depending on the temperature of the switching element group and generates a detection signal, and a control unit (control unit indicated by reference numeral 30 in Patent Document 1) that estimates and controls the temperature of the inverter based on the detection signal (detection signal having a pulse width according to the forward voltage). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6428547 Summary of the Invention [Problem to be solved by the invention]

[0006] In each element of the switching element group as described above, errors due to temperature characteristics may occur to a certain extent. Also, errors due to temperature characteristics may occur in the voltage output of a temperature sensor simply provided in the switching element group as in Patent Document 1, or in the detection signal generated based on the voltage output.

[0007] Therefore, it has been considered to control the output of the power conversion device by taking into consideration the error due to the temperature characteristics as described above, but there is a risk that the output of the power conversion device will be restricted more than necessary, which means that it may be difficult to fully utilize the output capacity of the power conversion device (the output capacity within the range where the junction temperature of the switching element does not exceed the upper limit).

[0008] The present invention has been made in consideration of the technical problems described above, and aims to provide a technology that can contribute to making it easier to demonstrate the output capacity of a power conversion device as desired (for example, to use it so that the junction temperature approaches the upper limit value) without losing sight of the purpose of suppressing the junction temperature of a switching element from exceeding the upper limit value. [Means for solving the problem]

[0009] One aspect of the power conversion device of the present invention comprises a plurality of switching elements, each equipped with a temperature sensing diode; a plurality of signal generating units provided corresponding to the temperature sensing diode of each of the switching elements, which detect the forward voltage of the temperature sensing diode and generate a detection signal; and a control unit which controls the switching of each of the plurality of switching elements based on the detection signal generated by each of the signal generating units.

[0010] The detection signal of each signal generating unit is a signal having a pulse width with a duty ratio D corresponding to the forward voltage of the temperature sensing diode corresponding to the detection signal, and the control unit stores the upper limit value of the junction temperature of each of the multiple switching elements, and coefficients a and b of the following equation (1), which is a correlation function between the duty ratio D in the detection signal of each signal generating unit and the temperature T corresponding to the forward voltage of the temperature sensing diode.

[0011] The control unit controls the switching of each of the switching elements so that the temperature T derived by substituting the duty ratio D in the detection signal of each of the signal generating units into the following formula (1) does not exceed the upper limit value, and a and b in the following formula (1) are coefficients derived in advance by the control unit performing switching control on each of the switching elements. T(℃)=a×(duty ratio D(%))+b……(1).

[0012] Another aspect is a device comprising a plurality of switching elements each equipped with a temperature sensing diode, a plurality of signal generating units provided corresponding to the temperature sensing diode of each of the switching elements and configured to detect the forward voltage of the temperature sensing diode and generate a detection signal, and a control unit configured to control the switching of each of the plurality of switching elements based on the detection signal generated by each of the signal generating units.

[0013] The detection signal of each signal generating unit is a signal having a pulse width with a duty ratio D corresponding to the forward voltage of the temperature sensing diode corresponding to the detection signal, and the control unit stores the upper limit value of the junction temperature of each of the multiple switching elements, and coefficients a and b of the following equation (1), which is a correlation function between the duty ratio D in the detection signal of each signal generating unit and the temperature T corresponding to the forward voltage of the temperature sensing diode.

[0014] The control unit controls the switching of each of the switching elements so that the temperature T derived by substituting the duty ratio D in the detection signal of each of the signal generating units into the following equation (1) does not exceed the upper limit value, and a and b in the following (1) are values ​​derived by deriving the duty ratios Dα and Dβ of the detection signal generated by detecting the forward voltage of the temperature sensing diode when the temperature sensing diode is heated to different temperatures Tα and Tβ in advance, and substituting the duty ratios Dα and Dβ into the following equations (2) and (3). T(℃)=a×(duty ratio D)+b ……(1) Tα(℃)=a×(duty ratio Dα)+b ……(2) Tβ(℃)=a×(duty ratio Dβ)+b……(3). [Effects of the Invention]

[0015] As described above, the present invention can contribute to making it easier to demonstrate the output capacity of the power conversion device as desired (for example, to use it so that the junction temperature approaches the upper limit value) without losing sight of the purpose of suppressing the junction temperature of the switching element from exceeding the upper limit value. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a schematic configuration diagram for explaining a power conversion device 1 according to an embodiment. [Figure 2] FIG. 2 is a schematic configuration diagram for explaining an example of a switching element SW. [Figure 3] 3 is a diagram showing the characteristics of a temperature sensing diode d, a signal generating section 3, and a duty ratio D in the power conversion device 1. FIG. [Figure 4] FIG. 2 is a flow diagram showing an example of deriving coefficients a and b in equation (1). DETAILED DESCRIPTION OF THE INVENTION

[0017] The power conversion device according to the embodiment of the present invention is completely different from a configuration in which the power conversion device is controlled simply by the voltage output of a temperature sensor provided in a switching element group or a detection signal generated based on the voltage output.

[0018] That is, in this embodiment, a temperature sensing diode is mounted on each of a plurality of switching elements, the forward voltage of each temperature sensing diode is detected to generate a respective detection signal (a signal having a pulse width with a duty ratio corresponding to the forward voltage of the temperature sensing diode), and the switching of each switching element is controlled based on each detection signal.

[0019] The control unit that controls the switching of each switching element stores the upper limit of the junction temperature of each switching element and a correlation function (for example, the correlation function shown in equation (1) described below) between the duty ratio (D) of each detection signal and the temperature (T) corresponding to the forward voltage of each temperature sense diode.The control unit controls the switching of each switching element so that the temperature (T) derived by substituting the duty ratio (D) of the detection signal of each signal generating unit into the correlation function does not exceed the upper limit of the junction temperature.

[0020] With this configuration, the junction temperature of each switching element is estimated via the corresponding temperature sensing diode, and the switching of each switching element is controlled based on the estimated value, which makes it easier to suppress the influence of errors due to the temperature characteristics of each switching element, and also makes it easier to suppress the influence of errors due to the temperature characteristics of the voltage output of each temperature sensing diode and the temperature characteristics of the detection signal generated based on the voltage output.

[0021] This prevents the output of the power conversion device from being restricted more than necessary, making it easier to utilize the output capacity of the power conversion device as desired (up to the upper limit of the junction temperature), which makes it easier to expand the operable range of the power conversion device.

[0022] The power conversion device of this embodiment can be configured to estimate the junction temperature of each switching element via each temperature sensing diode as described above and control the switching of each switching element based on the estimated value, and various design modifications are possible. That is, the design can be modified by appropriately applying common technical knowledge in various fields (for example, the power conversion device field, the temperature sensor field, the signal generation field, etc.) and by appropriately referring to prior art documents, etc. as necessary.

[0023] In the following embodiments, detailed descriptions of similar contents will be omitted as appropriate by using the same reference numerals and terms, for example.

[0024] Example <Main configuration of power conversion device 1> 1 and 2 are schematic diagrams illustrating a power conversion device 1 according to this embodiment. The power conversion device 1 is an inverter or the like capable of outputting multi-phase (three-phase in FIG. 1) AC power, and is housed in a housing not shown.

[0025] In the case of the power conversion device 1 of FIG. 1, for example, the device mainly comprises a semiconductor module (ASSY) 2 that houses a plurality of chip-shaped switching elements SW (six in FIG. 1) as shown in FIG. 2 in a case 20, a gate drive circuit board 21 that is arranged so as to overlap the case 20 and outputs gate drive signals to each switching element SW, and a control unit (not shown) that controls the current output of the power conversion device 1 (on / off control of the switching elements SW, etc.).

[0026] The case 20 is provided with input conductors 22 and output conductors (three conductors corresponding to the three-phase output current in FIG. 1) 22 that extend through the case 20 in an inward and outward direction, and each is appropriately connected to each switching element SW within the case 20.

[0027] Each switching element SW is equipped with a temperature sensing diode d (for example, mounted on the surface of the chip-shaped switching element SW as shown in FIG. 2). The temperature sensing diode d of each switching element SW changes its forward voltage Vf in response to the ambient temperature T of the temperature sensing diode d (for example, the temperature on the surface of the switching element SW in the case of FIG. 2), and is configured to output the forward voltage Vf to the corresponding signal generating unit 3, which will be described later.

[0028] The forward voltage Vf of such a temperature sensing diode d has a temperature characteristic such as that shown in Fig. 3(A), which means that as the ambient temperature T of the temperature sensing diode d increases, the forward voltage Vf decreases.

[0029] A plurality of signal generating units 3 (six in FIG. 1) are mounted on one end surface 21a of the gate drive circuit board 21 so as to correspond to each switching element SW in the case 20. Each signal generating unit 3 is configured to detect the forward voltage Vf of the temperature sensing diode of the switching element SW in the corresponding case 20 and generate a detection signal based on the detected forward voltage Vf. The detection signal generated as described above is transmitted to the control unit as appropriate.

[0030] An example of a signal generating unit 3 having such a configuration is a configuration similar to the drive IC shown in Patent Document 1 (for example, a configuration in which a comparator, a carrier signal generating unit, a header pulse generating unit, a switch, a sequencer, etc. are integrated into an IC chip, such as the drive IC shown by reference numeral 20 in Figure 1 of Patent Document 1).

[0031] The detection signal generated by the signal generating unit 3 has temperature characteristics such as those shown in Fig. 3(B). Specifically, the detection signal has a pulse width with a duty ratio D corresponding to the forward voltage Vf of the temperature sensing diode d.

[0032] 3A and 3B, the duty ratio D of the detection signal has a linear function characteristic with respect to the forward voltage Vf of the temperature sensing diode d. That is, the duty ratio D of the detection signal and the temperature T corresponding to the forward voltage Vf of the temperature sensing diode d can both be expressed by the correlation function shown in the following equation (1). T(℃)=a×(duty ratio D(%))+b……(1).

[0033] Therefore, the temperature T of the temperature sensing diode d mounted on each switching element SW can be expressed by the correlation function of equation (1). The coefficients a and b in equation (1) can be derived, for example, by appropriately controlling the switching of each switching element SW through a pre-test or the like described below.

[0034] The control unit includes a control circuit board (not shown) on which a CPU, memory, etc. are mounted, and is connected to, for example, the semiconductor module 2 and the gate drive circuit board 21 via signal cables, connectors, etc.

[0035] This control unit is assumed to have stored in advance, for example, through a pre-test of the power conversion device 1 in an offline state, the upper limit value of the junction temperature of each switching element SW and the coefficients a and b of the correlation function of equation (1) corresponding to the temperature T of each temperature sense diode d of each switching element SW, so as to classify them according to each switching element SW.

[0036] For example, when the power conversion device 1 is online, this control unit controls the switching of each switching element SW based on a desired output command (e.g., an output current command, a torque command, etc.) while appropriately receiving detection signals from the signal generating unit 3 corresponding to each switching element SW. Then, the duty ratio D of each received detection signal is substituted into equation (1) for the corresponding switching element SW to derive the temperature T of each temperature sensing diode. Each temperature T derived in this way is compared with the upper limit value of the junction temperature for the corresponding switching element SW.

[0037] For example, if the comparison result indicates that the temperature T is lower than the upper limit (or is relatively close to the upper limit), the switching control being performed may be continued, or the switching control may be controlled to increase the output. On the other hand, if the comparison result indicates that the temperature T is likely to exceed the upper limit (or has already exceeded the upper limit), the switching control may be controlled to suppress the output, thereby reducing the temperature T to prevent damage to the switching elements SW.

[0038] <An example of how to derive the coefficients a and b in equation (1)> The coefficients a and b in equation (1) can be derived appropriately, for example, in a preliminary test in an offline state of the power conversion device 1, by heating the temperature sensing diodes d of the switching elements SW to different temperatures Tα and Tβ and going through steps S1 to S5 of the flow shown in Fig. 4. In Fig. 4, the temperatures Tα and Tβ are set to 30°C (i.e., approximately room temperature) and 80°C (i.e., a temperature several tens of degrees higher than room temperature), respectively, as an example.

[0039] 4, first, in step S1, the temperature sensing diode d of the switching element SW is heated to 30° C. using a heating device (not shown, for example, a heating device having a sensor capable of measuring the temperature of the temperature sensing diode d). Then, in step S2, the forward voltage Vf of the temperature sensing diode d in the heated state (30° C. state) as described above is detected by the signal generating unit 3, the detection signal generated by the signal generating unit 3 is received by the control unit, and the duty ratio Dα of the detection signal is derived.

[0040] Next, in step S3, the temperature sensing diode d of the switching element SW is heated to 80° C. using the heating device or the like. Then, in step S4, the forward voltage Vf of the temperature sensing diode d in the heated state (80° C.) as described above is detected by the signal generating unit 3, the detection signal generated by the signal generating unit 3 is received by the control unit, and the duty ratio Dβ of the detection signal is derived.

[0041] In step S5, the coefficients a and b are derived by substituting the temperatures Tα and Tβ (i.e., 30°C and 80°C) heated in steps S1 and S3 and the duty ratios Dα and Dβ derived in steps S2 and S4 into the following equations (2) and (3). Tα(℃)=a×(duty ratio Dα)+b ……(2) Tβ(℃)=a×(duty ratio Dβ)+b……(3).

[0042] Although the present invention has been described in detail above only with respect to the specific examples, it will be apparent to those skilled in the art that various modifications are possible within the scope of the technical concept of the present invention, and it is natural that such modifications fall within the scope of the claims.

[0043] For example, in this embodiment, multiple switching elements SW are mounted inside the case 20, but the present invention may also be applied to a power conversion device in which only one switching element SW is mounted inside the case 20 and multiple cases 20 are provided. [Explanation of symbols]

[0044] 1...Power conversion device 2...Semiconductor module 3...Signal generation section SW: Switching element d...Temperature sensing diode

Claims

1. a plurality of switching elements each equipped with a temperature sensing diode; a plurality of signal generating units provided corresponding to the temperature sensing diodes of the switching elements, each generating a detection signal by detecting a forward voltage of the temperature sensing diode; a control unit that controls the switching of each of the plurality of switching elements based on the detection signals generated by each of the signal generating units; Equipped with The detection signal of each signal generating unit is a signal having a pulse width with a duty ratio D according to the forward voltage of the temperature sensing diode corresponding to the detection signal, The control unit includes: an upper limit value of the junction temperature of each of the plurality of switching elements; Coefficients a and b of the following formula (1) which is a correlation function between the duty ratio D in the detection signal of each of the signal generating units and the temperature T according to the forward voltage of the temperature sense diode corresponding to the detection signal: is stored, The control unit controlling the switching of each of the switching elements so that a temperature T derived by substituting the duty ratio D in the detection signal of each of the signal generating units into the following formula (1) does not exceed the upper limit value; In the following formula (1), a and b are coefficients derived in advance by controlling the switching of each of the switching elements by the control unit. A power conversion device characterized by: T (°C) = a × (duty ratio D (%)) + b (1).

2. a plurality of switching elements each equipped with a temperature sensing diode; a plurality of signal generating units provided corresponding to the temperature sensing diodes of the switching elements, each generating a detection signal by detecting a forward voltage of the temperature sensing diode; a control unit that controls the switching of each of the plurality of switching elements based on the detection signals generated by each of the signal generating units; Equipped with The detection signal of each signal generating unit is a signal having a pulse width with a duty ratio D according to the forward voltage of the temperature sensing diode corresponding to the detection signal, The control unit includes: an upper limit value of the junction temperature of each of the plurality of switching elements; Coefficients a and b of the following formula (1) which is a correlation function between the duty ratio D in the detection signal of each of the signal generating units and the temperature T according to the forward voltage of the temperature sense diode corresponding to the detection signal: is stored, The control unit controlling the switching of each of the switching elements so that a temperature T derived by substituting the duty ratio D in the detection signal of each of the signal generating units into the following formula (1) does not exceed the upper limit value; The values ​​a and b in the following (1) are values ​​obtained by deriving the duty ratios Dα and Dβ of the detection signal generated by detecting the forward voltage of the temperature sense diode when the temperature sense diode is preliminarily heated to different temperatures Tα and Tβ, and then substituting the duty ratios Dα and Dβ into the following equations (2) and (3): A power conversion device characterized by: T (°C) = a × (duty ratio D) + b (1) Tα (°C) = a × (duty ratio Dα) + b (2) Tβ(°C)=a×(duty ratio Dβ)+b (3).

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