Drive control device for controlling a power conversion device

Abstract

A drive control device of a power conversion device is provided. The drive control device (1) has a command value operation section (30) that controls a main drive control section (10 and 20) that performs drive control of a switching element. The main drive control section (10, 20) controls a rate of change of current flowing through the switching element in accordance with a first command value (DHr1 and DLr1) during a first period from when the switching element is to be turned on, and controls the rate of change of the current flowing through the switching element in accordance with a second command value (DHr2 and DLr2) during a second period after the first period. The command value operation section (30) controls the second command value (DHr2 and DLr2) based on temperatures of the two switching element sections.

Description

Technical Field

[0001] This disclosure relates to a drive control device for controlling a power conversion device. Background Technology

[0002] Active drive control is a technique for reducing losses caused by the switching of power switching elements included in a power conversion device. This technique is disclosed, for example, in Patent Document 1.

[0003] Patent Document 1 discloses a technique that detects the gate voltage or other parameters of a power switching element and controls the gate drive resistance or drive current of the power switching element based on the detected value. In this control, the gate drive resistance or drive current is controlled in two stages (e.g., resistance value decreasing → increasing) or three stages (e.g., resistance value decreasing → increasing → decreasing) by switching the switching element on / off. By varying the gate drive resistance or drive current during the on-time period in this way, switching losses in the power switching element are reduced.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent No. 5186095 Summary of the Invention

[0007] The problem the invention aims to solve

[0008] However, in the technology disclosed in Patent Document 1, due to accuracy errors in electrical components such as voltage detectors for measuring gate voltage and switching units for gate drive resistors, deviations occur in the switching timing of the gate drive resistor or drive current of the power switching element, or in the drive current of the power switching element. Therefore, in a power conversion device including an upper power switching element and a lower power switching element connected in series, the reduction in turn-on losses differs between the upper and lower power switching elements. Consequently, the temperature of each power switching element becomes unbalanced. As a result, there is a concern that the lifespan of the power switching element that generates more heat will be shortened. Furthermore, when designing with a margin in mind regarding the temperature imbalance of the power switching elements, the power conversion device may not be able to fully utilize its performance.

[0009] This disclosure was made in view of the problems described above, and its purpose is to suppress the heat generation of each switching element and to equalize the heat generation of each switching element in a power conversion device including two switching element sections connected in series.

[0010] Solution for solving the problem

[0011] As one method, a drive control device for controlling a power conversion device controls a power conversion device comprising two switching element sections connected in series. In this drive control device, each of the two switching element sections includes a switching element and a diode connected in reverse parallel with the switching element. The drive control device has an instruction value calculation unit that controls an active drive control unit that performs drive control of the switching element. During a first period starting from the activation of the target switching element (one of the two switching element sections), the active drive control unit controls the rate of change of the current flowing through the target switching element according to a first instruction value. During a second period following the first period, it controls the rate of change of the current flowing through the target switching element according to a second instruction value. The instruction value calculation unit controls the second instruction value based on the temperature of the two switching element sections and controls the first instruction value to a predetermined value independent of the temperature.

[0012] As another type of power conversion device, the drive control device controls a power conversion device comprising two switching element sections connected in series. In this drive control device, each of the two switching element sections includes a switching element and a diode connected in reverse parallel with the switching element. The drive control device has an instruction value calculation unit that controls an active drive control unit that performs drive control of the switching element. During a first period starting from the start of the switching element to be turned on (i.e., the target switching element) among the switching elements included in the two switching element sections, the active drive control unit controls the rate of change of the current flowing through the target switching element according to a first instruction value. During a second period following the first period, the active drive control unit controls the rate of change of the current flowing through the target switching element according to a second instruction value. If the target switching element is a switching element included in the switching element section with the lower temperature of the two switching element sections, the instruction value calculation unit reduces the second instruction value output to the active drive control unit.

[0013] Furthermore, as another method of controlling a power conversion device, a drive control device controls a power conversion device comprising two switching element sections connected in series. In this drive control device, each of the two switching element sections includes a switching element and a diode connected in reverse parallel with the switching element. The drive control device has an instruction value calculation unit that controls an active drive control unit that performs drive control of the switching element. During a first period starting from the start of the switching element to be turned on (i.e., the target switching element) among the switching elements included in the two switching element sections, the active drive control unit controls the rate of change of the current flowing through the target switching element according to a first instruction value. During a second period following the first period, it controls the rate of change of the current flowing through the target switching element according to a second instruction value. The instruction value calculation unit controls the second instruction value based on the temperature difference between the two switching element sections.

[0014] The effects of the invention

[0015] According to this disclosure, in a power conversion device including two switching element sections connected in series, the switching losses in each switching element section can be reduced, and the heat generation of each switching element section can be made equalized, thereby achieving a reduction in the failure rate caused by the temperature of the switching element section and equalization of the element life. Attached Figure Description

[0016] Figure 1 This is a circuit diagram showing the structure of a power conversion device having a drive control device as one embodiment.

[0017] Figure 2 This is a waveform diagram illustrating an example of the active drive control operation in the implementation method.

[0018] Figure 3 This is a block diagram showing the structure of the first example of the instruction value arithmetic unit in the embodiment.

[0019] Figure 4 This is a waveform diagram showing an example of the operation using the first implementation method.

[0020] Figure 5 This is a block diagram showing a portion of the structure of the second example of the instruction value arithmetic unit.

[0021] Figure 6 This is a block diagram showing a portion of the structure of the third example of the instruction value arithmetic unit. Detailed Implementation

[0022] The embodiments of the present invention will now be described with reference to the accompanying drawings.

[0023] Figure 1This is a circuit diagram showing the structure of a power conversion device 100 equipped with a drive control device 1 as one embodiment. In the power conversion device 100, the upper switching element section 110 is connected between the high-potential power supply line 101 and the output line 103. The high-potential power supply line 101 is connected to the positive terminal of a DC power supply (not shown). The output line 103 is connected to a load (not shown). The lower switching element section 120 is connected between the low-potential power supply line 102 and the output line 103. The low-potential power supply line 102 is connected to the negative terminal of the DC power supply.

[0024] Thus, in the power conversion device 100, an upper switching element section 110 and a lower switching element section 120 are connected in series between the high-potential power line 101 and the low-potential power line 102. The power conversion device 100 supplies power to the load connected to the output line 103 via the series-connected upper switching element section 110 and lower switching element section 120.

[0025] The upper switching element section 110 includes an upper power switching element 111. The lower switching element section 120 includes a lower power switching element 121. Both the upper power switching element 111 and the lower power switching element 121 are MOSFETs (Metal-Oxide Semiconductor Field Effect Transistors). The upper power switching element 111 and the lower power switching element 121 are respectively composed of wide-bandgap semiconductor elements such as SiC and GaN. An upper diode 112 is connected in reverse parallel to the upper power switching element 111. A lower diode 122 is connected in reverse parallel to the lower power switching element 121.

[0026] Temperature detector 131 detects the temperature STa1 of the upper switching element section 110. Temperature detector 132 detects the temperature STa2 of the lower switching element section 120.

[0027] A drive command DHa for the upper power switching element 111 and a drive command DLa for the lower power switching element 121 are supplied to the drive control device 1 from the upper-level device (not shown). The drive control device 1 is a device that performs drive control of the upper power switching element 111 and the lower power switching element 121 based on the drive commands Dha and DLa, the temperature STa1 of the upper switching element section 110, and the temperature STa2 of the lower switching element section 120.

[0028] like Figure 1 As shown, the drive control device 1 includes an upper active drive control unit 10, a lower active drive control unit 20, and an instruction value calculation unit 30.

[0029] The upper active drive control unit 10 is a device that selectively outputs either the gate voltage Vg that turns on the upper power switch element 111 or the gate voltage Vg that turns off the upper power switch element 111 to the upper power switch element 111 according to the drive command DHa. The lower active drive control unit 20 is a device that selectively outputs either the gate voltage Vg that turns on the lower power switch element 121 or the gate voltage Vg that turns off the lower power switch element 121 to the lower power switch element 121 according to the drive command DLa.

[0030] In this embodiment, when the upper active drive control unit 10 turns on the upper power switch element 111, it divides the period after the start of the turn-on into an initial mode 1 (i.e., the first period) and a subsequent mode 2 (i.e., the second period). The upper active drive control unit 10 controls the gate voltage Vg supplied to the upper power switch element 111 in both mode 1 and mode 2. Here, for example, when the upper power switch element 111 is turned on, mode 2 is the period after the moment when reverse recovery begins in the lower diode 122. When the upper power switch element 111 is turned on, the upper power switch element 111 is an example of a target switch element.

[0031] More specifically, the instruction value calculation unit 30 supplies the upper active drive control unit 10 with a first instruction value DHr1 corresponding to mode 1 and a second instruction value DHr2 corresponding to mode 2 as instruction values ​​related to the rate of change dId / dt (i.e., time derivative) of the drain current Id flowing through the upper power switch element 111.

[0032] When the upper active drive control unit 10 turns on the upper power switch element 111, in mode 1, it controls the gate voltage Vg supplied to the upper power switch element 111 such that the rate of change dId / dt of the drain current Id flowing through the upper power switch element 111 follows a first command value DHr1. In mode 2, the upper active drive control unit 10 controls the gate voltage Vg supplied to the upper power switch element 111 such that the rate of change dId / dt of the drain current Id flowing through the upper power switch element 111 follows a second command value DHr2.

[0033] Similarly, the instruction value calculation unit 30 supplies the lower active drive control unit 20 with a first instruction value DLr1 corresponding to mode 1 and a second instruction value DLr2 corresponding to mode 2 as instruction values ​​related to the rate of change of the drain current Id flowing through the lower power switch element 121. When the lower power switch element 121 is turned on, in mode 1, the lower active drive control unit 20 controls the gate voltage Vg supplied to the lower power switch element 121 according to the first instruction value DLr1. In mode 2, the lower active drive control unit 20 controls the gate voltage Vg supplied to the lower power switch element 121 according to the second instruction value DLr2. When the lower power switch element 121 is turned on, the lower power switch element 121 is an example of a target switch element.

[0034] The command value calculation unit 30 is a device that controls the upper active drive control unit 10 and the lower active drive control unit 20. More specifically, the command value calculation unit 30 is a device that calculates command values ​​for the upper switch element unit 110 and the lower switch element unit 120 based on the temperature STa1 of the upper switch element unit 110 and the temperature STa2 of the lower switch element unit 120.

[0035] Before providing a detailed explanation of the function of the instruction value arithmetic unit 30, please refer to... Figure 2 This will be used to explain the active drive control performed in this embodiment. Figure 2 The waveforms of each part are shown when the upper power switch element 111 is turned on while the lower power switch element 121 is turned off.

[0036] When the drive command DHa is ON, indicating that the upper power switch element 111 is turned on, the upper active drive control unit 10 uses the command value DHr, which is related to the rate of change of the drain current Id flowing through the upper power switch element 111, as the first command value DHr1, and starts active drive control corresponding to mode 1. That is, the upper active drive control unit 10 controls the gate voltage Vg supplied to the upper power switch element 111 according to the first command value DHr1.

[0037] There are various ways to control the gate voltage Vg. In a preferred embodiment, a gate drive resistor corresponding to the first command value DHr1 supplied from the command value calculation unit 30 is selected from a variety of gate drive resistors provided corresponding to various first command values ​​DHr1, and the selected gate drive resistor is inserted into the input path of the gate voltage Vg in the upper power switch element 111. In other preferred embodiments, a variety of current sources with different current values ​​for charging the gate capacitance of the power switch element are used instead of the gate drive resistor.

[0038] When the active drive control corresponding to mode 1 starts, the gate voltage Vg of the upper power switch element 111 begins to rise with a slight delay. When the gate voltage Vg exceeds the threshold voltage Vth of the upper power switch element 111, the drain current Id begins to flow through the upper power switch element 111.

[0039] Then, the drain current Id increases as the gate voltage Vg rises. Additionally, the on-resistance of the upper power switch element 111 decreases as the gate voltage Vg rises, causing the drain-source voltage Vds to decrease. Moreover, when the effect of the increase in the drain current Id of the upper power switch element 111 outweighs the effect of the decrease in the on-resistance of the upper power switch element 111, the drain-source voltage Vds stops decreasing and begins to rise.

[0040] In the lower switching element section 120, which serves as the return current side component, the return current If flows through the lower diode 122 before the upper power switching element 111 is turned on. In Mode 1, the drain current Id begins to flow through the upper power switching element 111, and this drain current Id is supplied to the lower diode 122, thereby reducing the return current If flowing through the lower diode 122. Then, the return current If soon becomes 0. In Mode 1, the lower diode 122 is forward biased, and the voltage Vf across the lower diode 122 is maintained at a predetermined value. This is the operation in Mode 1.

[0041] When the return current If of the lower diode 122 becomes 0, the upper active drive control unit 10 begins active drive control corresponding to mode 2. That is, the upper active drive control unit 10 uses a command value DHr related to the rate of change of the current Id flowing through the upper power switch element 111 as a second command value DHr2, and controls the gate voltage Vg supplied to the upper power switch element 111 according to the second command value DHr2. Typically, the second command value DHr2 is set to a value lower than the first command value DHr1.

[0042] There are various methods for determining the timing of the transition from Mode 1 to Mode 2. In a preferred embodiment, the return current If flowing through the lower diode 122 is detected, and the transition from Mode 1 to Mode 2 occurs when the return current If becomes 0. In another preferred embodiment, the gate voltage Vg of the upper power switch element 111 is detected, and the transition from Mode 1 to Mode 2 occurs when the gate voltage Vg reaches a predetermined value. Furthermore, in yet another preferred embodiment, the transition from Mode 1 to Mode 2 occurs when a predetermined time has elapsed since the switch was first turned on.

[0043] In Mode 2, in the lower switching element section 120, which serves as the return current side element, the drain current Id flowing through the upper power switching element 111 is supplied to the lower diode 122, and the reverse recovery current If flows through the lower diode 122. The reverse recovery current If is the current that causes the minority carriers accumulated in the lower diode 122 to disappear during the forward bias period, and it is the current that flows in the opposite direction to the direction of the return current If.

[0044] The reverse recovery current If flowing through the lower diode 122 increases in mode 2, then decreases after reaching its peak. After the reverse recovery current If begins to flow, the voltage across the lower diode 122 (in this case, the reverse voltage) Vf rises with a slight delay. Moreover, this reverse voltage Vf becomes the reverse recovery surge voltage VAK.

[0045] The above describes the operation of turning on the upper power switch element 111. The operation of turning on the lower power switch element 121 is the same.

[0046] In the operations described above, in Mode 1, by maximizing the rate of change of the drain current Id flowing through the upper power switch element 111 (dId / dt), the turn-on loss in the upper power switch element 111 can be minimized. Conversely, in Mode 2, by minimizing the rate of change of the drain current Id flowing through the upper power switch element 111 (dId / dt), the reverse recovery surge voltage VAK generated in the lower diode 122 can be minimized. Therefore, in active drive control, by maximizing the first command value and minimizing the second command value, both the turn-on loss and the reverse recovery surge voltage VAK can be reduced.

[0047] However, when the characteristics of the upper active drive control unit 10 and the lower active drive control unit 20 differ due to manufacturing deviations in the components constituting the power conversion device 100 (e.g., differences in gate drive resistance or switching timing), the heat generation of the upper switching element unit 110 and the lower switching element unit 120 will differ. In this case, the problem arises that the one generating more heat, the upper switching element unit 110 or the lower switching element unit 120, is more prone to high temperature and is more easily damaged or has a shorter lifespan than the other.

[0048] Therefore, in this embodiment, the instruction value calculation unit 30 controls the first instruction value DHr1 and the second instruction value DHr2 for the upper active drive control unit 10 and the first instruction value DLr1 and the second instruction value DLr2 for the lower active drive control unit 20 in such a way that the temperature STa1 of the upper switch element unit 110 is the same as the temperature STa2 of the lower switch element unit 120, thereby solving the problem.

[0049] Figure 3 This is a block diagram showing the structure of the instruction value calculation unit 30a, which is a first example of the instruction value calculation unit 30 in this embodiment. Figure 3 As shown, the instruction value calculation unit 30a stores a first reference value Dr1def as a first instruction value. This first instruction value is optimized to sufficiently reduce the turn-on losses in the upper power switch element 111 and the lower power switch element 121 in mode 1. Additionally, the instruction value calculation unit 30a stores a second reference value Dr2def as a second instruction value. This second instruction value is optimized to appropriately suppress the reverse recovery surge voltage VAK generated in the upper diode 112 and the lower diode 122 in mode 2. The first reference value Dr1def is a value set according to the characteristics of the upper power switch element 111 and the lower power switch element 121, for example, it can be set to 4kA / μs. The second reference value Dr2def is also a value set according to the characteristics of the upper power switch element 111 and the lower power switch element 121, but it can be set to a value smaller than the first reference value Dr1def, such as 2kA / μs.

[0050] In this embodiment, the command value calculation unit 30a outputs a first reference value Dr1def as a first command value DHr1 for the upper active drive control unit 10 and a first command value DLr1 for the lower active drive control unit 20. That is, in this embodiment, the command value calculation unit 30a keeps the first command values ​​DHr1 and DLr1 corresponding to mode 1 constant, independent of the temperature STa1 of the upper switching element unit 110 and the temperature STa2 of the lower switching element unit 120.

[0051] On the other hand, the instruction value calculation unit 30a calculates the second instruction values ​​DHr2 and DLr2 in the calculation mode 2 based on the temperature STa1 of the upper switch element unit 110 and the temperature STa2 of the lower switch element unit 120, as follows.

[0052] Subtractor 300 subtracts the temperature STa2 of the lower switching element section 120 from the temperature STa1 of the upper switching element section 110 and outputs the subtraction result. For example, if the temperature STa1 is higher than the temperature STa2, subtractor 300 outputs a positive value. If the temperature STa2 is higher than the temperature STa1, subtractor 300 outputs a negative value. PI calculator 301 outputs an output signal obtained by applying the proportional element P and the integral element I to the subtraction result of subtractor 300. If the output signal of PI calculator 301 exceeds a predetermined upper limit value LMH, upper and lower limit limiter 302 outputs the upper limit value LMH. If the output signal of PI calculator 301 is lower than a predetermined lower limit value LML, upper and lower limit limiter 302 outputs the lower limit value LML. If the output signal of PI calculator 301 is between the upper limit value LMH and the lower limit value LML, upper and lower limit limiter 302 outputs the output signal of PI calculator 301. At this point, the upper limit LMH and the lower limit LML can also be determined based on the losses or temperature in the power switching elements.

[0053] When the output signal of the upper and lower limit limiters 302 is positive, the upper limit limiter 303 outputs 0 to the adder 305. When the output signal of the upper and lower limit limiters 302 is negative, the upper limit limiter 303 outputs the output signal of the upper and lower limit limiters 302 to the adder 305. The adder 305 outputs the value obtained by adding the second reference value Dr2def to the output signal of the upper limit limiter 303 as the second command value DHr2 for the upper active drive control unit 10.

[0054] Furthermore, when the output signal of the upper and lower limit limiters 302 is positive, the lower limit limiter 304 outputs the output signal of the upper and lower limit limiters 302 to the subtractor 306. When the output signal of the upper and lower limit limiters 302 is negative, the lower limit limiter 304 outputs 0 to the subtractor 306. The subtractor 306 outputs the value obtained by subtracting the output signal of the lower limit limiter 304 from the second reference value Dr2def as the second command value DLr2 for the lower active drive control unit 20.

[0055] In the above structure, when the temperature STa1 of the upper switch element section 110 is higher than the temperature STa2 of the lower switch element section 120, the value obtained by subtracting the positive value corresponding to the difference between the two temperatures from the second reference value Dr2def is output as the second command value DLr2 for the lower active drive control section 20, and the second reference value Dr2def is output as the second command value DHr2 for the upper active drive control section 10.

[0056] Conversely, when the temperature STa2 of the lower switching element section 120 is higher than the temperature STa1 of the upper switching element section 110, the value obtained by adding the negative value corresponding to the difference between the two temperatures to the second reference value Dr2def will be output as the second command value DHr2 for the upper active drive control section 10, and the second reference value Dr2def will be output as the second command value DLr2 for the lower active drive control section 20.

[0057] Thus, in this embodiment, the following control is performed: the second command value corresponding to the one with the lower temperature in the upper switch element section 110 and the lower switch element section 120 is reduced compared to the second reference value Dr2def.

[0058] Figure 4 This is a waveform diagram showing an example of the operation of a power conversion device 100 that uses the command value calculation unit 30a as the first example. Figure 2 same, Figure 4 The waveforms of each part are shown when the upper power switch element 111 is turned on while the lower power switch element 121 is off. Additionally, Figure 4 The waveforms of each part are shown with dashed lines when the temperature STa1 of the upper switching element section 110 is lower than the temperature STa2 of the lower switching element section 120.

[0059] As described above, in Mode 1, by increasing the rate of change of the drain current Id of the upper power switching element 111, did / dt, the turn-on loss in the upper power switching element 111 can be reduced. In Mode 2, by decreasing the rate of change of the drain current Id of the upper power switching element 111, did / dt, the reverse recovery surge voltage VAK can be reduced.

[0060] Here, the reverse recovery surge voltage VAK is determined by the rate of change dId / dt of the drain current Id of the upper power switching element 111 when the reverse recovery current If flowing through the lower diode 122 is 0. Therefore, the rate of change of current dId / dt in mode 1 is independent of the reverse recovery surge voltage VAK.

[0061] Therefore, in this embodiment, the first command values ​​DHr1 and DLr1 in Mode 1 are maintained at the first reference value Dr1def, which is the optimal value, regardless of the temperature STa1 of the upper switching element section 110 and the temperature STa2 of the lower switching element section 120. In this way, the turn-on loss in the upper power switching element 111 is reduced.

[0062] Next, in Mode 2, when the rate of change of the drain current Id of the upper power switch element 111 (which is on the turn-on side) decreases (dId / dt), the switching time of the upper power switch element 111 increases, thus increasing the turn-on loss. On the other hand, when the rate of change of the drain current Id of the upper power switch element 111 (dId / dt) decreases, the reverse recovery surge voltage VAK generated in the lower diode 122 on the return side decreases. Thus, in Mode 2, the turn-on loss in the upper power switch element 111 and the reverse recovery loss in the lower diode 122 are in a trade-off relationship where an increase in one leads to a decrease in the other.

[0063] Here, for example, if the temperature STa1 of the upper switching element section 110 is lower than the temperature STa2 of the lower switching element section 120, it is preferable to make the losses in the lower switching element section 120 less than the losses in the upper switching element section 110. This is because, in this way, the reduction in heat generation in the lower switching element section 120 is greater than the reduction in heat generation in the upper switching element section 110, and their temperatures are closer.

[0064] Therefore, in this example, the second command value DHr2 for the upper active drive control unit 10 corresponding to the upper switch element unit 110 with low temperature decreases to the second command value DHr2' (shown as a dashed line).

[0065] In this way, the drain current Id and drain-source voltage Vds of the upper power switching element 111 on the turn-on side become drain current Id' and drain-source voltage Vds' with a smoother time gradient (shown as dashed lines). As a result, the turn-on loss in the upper power switching element 111 increases.

[0066] On the other hand, in the lower switching element section 120, which serves as the return current side, the voltage Vf across the lower diode 122 and the reverse recovery current If become the voltage Vf' and the reverse recovery current If' (shown as dashed lines) with a smoother time gradient in their waveforms. As a result, the reverse recovery surge voltage VAK decreases to the reverse recovery surge voltage VAK', and the reverse recovery loss is reduced.

[0067] Therefore, the reduction in heat generation in the lower switching element section 120 is greater than the reduction in heat generation in the upper switching element section 110, and their temperatures are close.

[0068] As described above, according to this embodiment, in a power conversion device with two switching element sections connected in series, the switching losses in each switching element section can be reduced, and the heat generation of each switching element section can be made equalized, thereby reducing the failure rate caused by the temperature of the switching element section and equalizing the component life.

[0069] Next, refer to Figure 5Let's illustrate a second example of the instruction value arithmetic unit 30. In the second example, the first example ( Figure 3 The structure in the interval from subtractor 300 to PI operator 301 in the original text is replaced with... Figure 5 The structure shown.

[0070] In the second example, the absolute value operator 307 calculates the absolute value of the difference between temperatures STa1 and STa2 obtained from the subtractor 300. The comparator 308 compares the absolute value calculated by the absolute value operator 307 with a predetermined threshold thc. If the absolute value calculated by the absolute value operator 307 is greater than or equal to the threshold thc, the comparator 308 outputs True. If the absolute value calculated by the absolute value operator 307 is not greater than or equal to the threshold thc, the comparator 308 outputs False.

[0071] When the output signal of comparator 308 is true, that is, when the absolute value of the difference between temperatures STa1 and STa2 exceeds the threshold thc, switch 309 outputs the output signal of subtractor 300 to PI arithmetic unit 301. When the output signal of comparator 308 is false, switch 309 outputs 0 to PI arithmetic unit 301. The operation of other parts is the same as in the first example.

[0072] According to the second example, when the temperature difference between the upper switching element section 110 (STa1) and the lower switching element section 120 (STa2) is greater than or equal to a threshold value (thc), the command value calculation unit 30 adjusts the second command value (DHr2) or (DLr2). Therefore, it is possible to prevent frequent adjustments of the second command value (DHr2) or (DLr2) due to a small difference between the temperature difference between the upper switching element section 110 (STa1) and the lower switching element section 120 (STa2), thereby stabilizing the operation of the drive control device 1.

[0073] Next, refer to Figure 6 Let's illustrate the third example of the instruction value arithmetic unit 30. In this third example, the first example ( Figure 3 The structure in the interval from subtractor 300 to PI operator 301 in the original text is replaced with... Figure 6 The structure shown.

[0074] In the third example, the maximum value arithmetic unit 310 compares the temperature STa1 of the upper switching element section 110 with the temperature STa2 of the lower switching element section 120, and outputs the higher temperature to the comparator 308. The comparator 308 compares the temperature output by the maximum value arithmetic unit 310 with a predetermined threshold thd. If the temperature output by the maximum value arithmetic unit 310 is higher than the threshold thd, the comparator 308 outputs true to the switch 309. If the temperature output by the maximum value arithmetic unit 310 is lower than the threshold thd, the comparator 308 outputs false to the switch 309. Here, the threshold thd can be set to, for example, 150°C.

[0075] When the output of comparator 308 is true, switch 309 outputs the output signal of subtractor 300 to PI arithmetic unit 301. When the output of comparator 308 is false, switch 309 outputs 0 to PI arithmetic unit 301. The operation of other parts is the same as in the first example.

[0076] According to the third example, when the temperature of the upper switching element section 110 (STa1) and the temperature of the lower switching element section 120 (STa2), specifically, the higher of the temperatures (STa1 and STa2), exceeds a certain threshold, the command value calculation unit 30 adjusts the second command value DHr2 or DLr2. Therefore, it is possible to prevent frequent adjustments of the second command value DHr2 or DLr2 during periods when there is a temperature difference between the upper switching element section 110 and the lower switching element section 120, but the temperature of each switching element does not affect the characteristics of the switching elements, thereby stabilizing the operation of the drive control device 1.

[0077] <Variation Example>

[0078] The above describes one implementation method, but one implementation method may also be modified as follows.

[0079] (1) First variant

[0080] When the temperature of the higher of the upper switching element section 110 temperature STa1 and the lower switching element section 120 temperature STa2 is higher than the threshold thd, the third example of the instruction value calculation unit ( Figure 6 The second instruction value DHr2 or DLr2 is adjusted. Alternatively, if the temperature STa1 of the upper switch element section 110 or the lower switch element section 120 is higher than the threshold thd, for example, the third example of the instruction value calculation unit adjusts the second instruction value DHr2 or DLr2.

[0081] (2) Second variation

[0082] Regarding the command value calculation unit, the second and third examples described above can also be combined. That is, when the temperature of either the upper switching element 110 (STa1) or the lower switching element 120 (STa2) is higher than the threshold value thc, and the difference between the two temperatures is higher than the threshold value thd, the second command value DHr2 or DLr2 is adjusted. According to this variation, the second command value DHr2 or DLr2 is adjusted only during periods when the overall heat generation of the upper switching element 110 and the lower switching element 120 is high, the difference between their heat generation is large, and the necessity for adjusting the heat generation is high. Therefore, the operation of the drive control device 1 becomes more stable.

[0083] (3) Third variation

[0084] This disclosure can also be applied to power conversion devices other than inverters, such as DC / DC converters.

[0085] (4) Fourth variation

[0086] In the above embodiment, the command value calculation unit 30 is provided together with the upper active drive control unit 10 and the lower active drive control unit 20 in the drive control device 1. However, alternatively, the drive control device that has the command value calculation unit 30 but does not have the upper active drive control unit 10 and the lower active drive control unit 20 can be set as a device independent of the power conversion device 100.

[0087] (5) Fifth variation

[0088] In the above embodiments, MOSFETs are listed as examples of power switching elements, but the power switching elements are not limited to this. For example, other power switching elements such as IGBTs (Insulated Gate Bipolar Transistors) can also be used.

[0089] Explanation of reference numerals in the attached figures

[0090] 100: Power conversion device; 1: Drive control device; 101: High-potential power line; 102: Low-potential power line; 103: Output line; 110: Upper switching element section; 120: Lower switching element section; 111: Upper power switching element; 112: Upper diode; 121: Lower power switching element; 122: Lower diode; 131, 132: Temperature detectors; 10: Upper active drive control section; 20: Lower active drive control section; 30, 30a: Command value calculation section; 300, 306: Subtractors; 301: PI arithmetic unit; 302: Upper and lower limit limiters; 303: Upper limit limiter; 304: Lower limit limiter; 305: Adder; 307: Absolute value calculation section; 308: Comparator; 309: Switch; 310: Maximum value calculation section.

Claims

1. A drive control device for controlling a power conversion device comprising two switching elements connected in series, characterized in that, The two switching elements each include a switching element and a diode connected in reverse parallel with the switching element. The drive control device includes an instruction value calculation unit, which controls an active drive control unit that performs drive control of the switching element. During a first period starting from the activation of the target switching element (one of the switching elements included in the two switching element units), the active drive control unit controls the rate of change of the current flowing through the target switching element according to a first command value. During a second period following the first period, it controls the rate of change of the current flowing through the target switching element according to a second command value. The instruction value calculation unit controls the second instruction value based on the temperature of the two switching element units, and controls the first instruction value to a predetermined value regardless of the temperature.

2. A drive control device for controlling a power conversion device comprising two switching elements connected in series, characterized in that, The two switching elements each include a switching element and a diode connected in reverse parallel with the switching element. The drive control device includes an instruction value calculation unit, which controls an active drive control unit that performs drive control of the switching element. During a first period starting from the activation of the target switching element (one of the switching elements included in the two switching element units), the active drive control unit controls the rate of change of the current flowing through the target switching element according to a first command value. During a second period following the first period, it controls the rate of change of the current flowing through the target switching element according to a second command value. When the target switching element is a switching element included in the switching element section of the two switching element sections with lower temperature, the command value calculation unit reduces the second command value output to the active drive control unit.

3. A drive control device for controlling a power conversion device comprising two switching elements connected in series, characterized in that... The two switching elements each include a switching element and a diode connected in reverse parallel with the switching element. The drive control device includes an instruction value calculation unit, which controls an active drive control unit that performs drive control of the switching element. During a first period starting from the activation of the target switching element (one of the switching elements included in the two switching element units), the active drive control unit controls the rate of change of the current flowing through the target switching element according to a first command value. During a second period following the first period, it controls the rate of change of the current flowing through the target switching element according to a second command value. The instruction value calculation unit controls the second instruction value based on the temperature difference between the two switching element units.

4. The drive control device according to claim 2 or 3, characterized in that, The instruction value calculation unit controls the first instruction value to a predetermined value regardless of the temperature.

5. The drive control device according to claim 3, characterized in that, When the target switching element is a switching element included in the switching element section of the two switching element sections with the lower temperature, the instruction value calculation unit reduces the second instruction value output to the active drive control unit.

6. The drive control device according to any one of claims 1 to 3, characterized in that, When the temperature difference between the two switching elements is above a certain threshold, the instruction value calculation unit adjusts the second instruction value.

7. The drive control device according to any one of claims 1 to 3, characterized in that, When the temperature of one of the two switching elements is above a certain threshold, the instruction value calculation unit adjusts the second instruction value.

8. The drive control device according to any one of claims 1 to 3, characterized in that, The switching element includes a wide-bandgap semiconductor element.

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