POWER CONVERSION DEVICE

Abstract

A power conversion device (4) comprises a MOSFET (13), which is a switching element, an ECU (30), which is a control device that commands the switching speed of the switching element, and a drive circuit (20) that drives the switching element to switch on and off at a switching speed corresponding to a command speed. The power conversion device (4) includes a feedback circuit (23) as a feedback function and a monitoring unit (36) as an anomaly detection unit. The feedback circuit (23) outputs a signal, correlated with the actual switching speed, as a feedback signal to the control device. The anomaly detection unit (36) determines, by comparing the feedback signal with the command speed, whether the actual switching speed is in an anomalous state as opposed to the command speed.

Description

CROSS-REFERENCE TO RELATED REGISTRATIONS

[0001] This application is based on Japanese patent application No. 2023-131628, which was filed in Japan on August 10, 2023, and incorporates by reference the entire content of the application described above. TECHNICAL AREA

[0002] The present disclosure relates to a power conversion device. STATE OF THE ART

[0003] Patent document 1 discloses a power conversion device in which the switching speed of a switching element can be changed. The descriptions contained in patent document 1 are incorporated by reference as descriptions of technical elements in this document. DOCUMENT ACCORDING TO THE STATE OF THE TECHNOLOGY PATENT DOCUMENT

[0004] Patent document 1: JP 2015 - 65 742 A SUMMARY OF THE INVENTION

[0005] In a power conversion device with a variable switching speed, as described above, power consumption can be improved by increasing the switching speed. However, the faster the switching speed, the greater the surge voltage becomes, which raises concerns about potential damage to the switching element.

[0006] A disclosed problem is to provide a power conversion device that can reduce the risk of damage to a switching element while improving power consumption by making the switching speed variable.

[0007] A power conversion device according to one embodiment comprises: a plurality of switching elements that convert and output electrical power, a control device that commands a switching speed of the switching element, a drive circuit that drives the switching element for switching on and off at a switching speed that corresponds to a command speed from the control device, a feedback unit that outputs a signal correlated with an actual switching speed as a feedback signal to the control device, and an anomaly detection unit that determines, by comparing the feedback signal with the command rate, whether the actual switching rate is in an anomalous state as opposed to the command rate.

[0008] According to the disclosed power conversion device, the switching elements are switched on and off at a switching speed corresponding to the command speed, allowing the switching speed to be varied. Therefore, increasing the switching speed improves power consumption. Simultaneously, the anomaly detection unit determines whether the actual switching speed deviates from the command speed, enabling the implementation of measures to address the anomaly, such as a failsafe control. This reduces the risk of damage to the switching element.

[0009] The embodiments disclosed in this description employ different technical means to achieve their respective objectives. Reference numerals in parentheses in the claims and periods illustrate the relationship between sections of embodiments described later and are not intended to limit the technical scope. The objectives, features, and advantageous effects disclosed in this description will become clearer with reference to the detailed description below and the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 shows a representation illustrating a circuit configuration and drive system of a power conversion device according to a first embodiment. Fig. Figure 2 shows a diagram illustrating a configuration of a control circuit and an ECU. Fig. Figure 3 shows a representation illustrating differences in voltage waveforms as a function of switching speeds. Fig. Figure 4 shows a diagram illustrating a relationship between impulse voltage and power loss. Fig. Figure 5 shows a flowchart illustrating a process executed by a microcomputer of the ECU, Fig. Figure 6 shows a flowchart illustrating a process performed by a microcomputer according to a second embodiment, and Fig. Figure 7 shows a flowchart illustrating a process performed by a microcomputer according to a third embodiment. DETAILED DESCRIPTION

[0010] Several embodiments are described below with reference to the drawings. The same reference numerals are assigned to the corresponding elements in each embodiment, thus avoiding duplicate descriptions. If only part of the configuration is described in the respective embodiments, the configuration according to the other embodiments described previously can be applied to other parts of the configuration. Furthermore, it is possible not only to combine configurations as described in the description of the embodiments, but also to partially combine configurations from embodiments, even though this is not specified here, as long as the combination does not cause any difficulties.

[0011] The power conversion device according to the present embodiment is applicable, for example, to a moving object with a rotating electric machine as a drive source. The moving object is, for example, an electrically powered vehicle such as a battery electric vehicle (BEV), a hybrid electric vehicle (HEV), or a plug-in hybrid electric vehicle (PHEV), an electric flying object, a ship, a construction machine, or an agricultural machine. The electric flying object can, for example, be a drone or an electric vertical takeoff and landing aircraft (eVTOL). An example applied to a vehicle is described below. First embodiment

[0012] First, a schematic configuration of a vehicle drive system is shown with reference to Fig. 1 described. Vehicle propulsion system 1:

[0013] As it is in Fig. As shown in Figure 1, the vehicle drive system 1 is equipped with a direct current (DC) power supply 2, a motor generator 3 and a power conversion device 4.

[0014] The DC power supply 2 is a DC voltage source with a rechargeable and dischargeable secondary battery. The secondary battery can be a lithium-ion battery, a nickel-hydrogen battery, or an organic radical battery. The motor-generator 3 is a rotating electric machine of the three-phase AC type. The motor-generator 3 functions as a vehicle propulsion source, i.e., as an electric motor. The motor-generator 3 also functions as a generator during regeneration. The power conversion device 4 performs an electrical power conversion between the DC power supply 2 and the motor-generator 3. Circuit configuration of the power conversion device 4:

[0015] Fig. Figure 1 shows a circuit configuration of the power conversion device 4. The power conversion device 4 comprises at least one power conversion circuit. The power conversion device according to the present embodiment is an inverter 5. The power conversion device 4 further comprises a smoothing capacitor 6, a drive circuit 20, an ECU 30 (control device), and the like. ECU is an abbreviation for electronic control unit.

[0016] The smoothing capacitor 6 primarily smooths the DC voltage supplied from the DC power supply 2. The smoothing capacitor 6 is connected between a P-line 8, which is a power line on a high-potential side, and an N-line 9, which is a power line on a low-potential side. The P-line 8 is connected to a positive electrode of the DC power supply 2, and the N-line 9 is connected to a negative electrode of the DC power supply 2. The positive electrode of the smoothing capacitor 6 is connected to the P-line 8 between the DC power supply 2 and the inverter 5. The negative electrode of the smoothing capacitor 6 is connected to the N-line 9 at a point between the DC power supply 2 and the inverter 5. The smoothing capacitor 6 is connected in parallel with the DC power supply 2.

[0017] Inverter 5 is a DC-AC conversion circuit. Inverter 5 converts the DC voltage into a three-phase AC voltage according to switching control by the ECU 30 and outputs the three-phase AC voltage to the motor-generator 3. This drives the motor-generator 3 to generate a predetermined torque. During regenerative braking of the vehicle, inverter 5 converts the three-phase AC voltage generated by the motor-generator 3 by receiving the rotational force from the wheels into a DC voltage according to switching control by the ECU 30 and outputs the DC voltage to the P-line. In this way, inverter 5 performs bidirectional power conversion between the DC power supply 2 and the motor-generator 3.

[0018] The inverter 5 is configured with upper and lower branch circuits 10 for each of the three phases. The upper and lower branch circuits 10 can be referred to as legs. Each of the upper and lower branch circuits 10 has an upper branch 10H and a lower branch 10L. The upper branch 10H and the lower branch 10L are connected in series between the P-line and the N-line 9, with the upper branch 10H positioned on the side of the P-line 8.

[0019] A connection point between the upper branch 10H and the lower branch 10L, i.e., a midpoint of the upper and lower branch circuit 10, is connected to a winding 3a of the corresponding phase in the motor-generator 3 via an output line 11. Of the upper and lower branch circuits 10, the U-phase upper and lower branch circuit 10U is connected to the U-phase winding 3a via the output line 11. The V-phase upper and lower branch circuit 10V is connected to the V-phase winding 3a via the output line 11. The W-phase upper and lower branch circuit 10W is connected to the W-phase winding 3a via the output line 11.

[0020] The upper and lower branch circuits 10 (10U, 10V, 10W) ​​each have a series connection 12. The series connection 12 contained in the upper and lower branch circuits 10 can be a single circuit or multiple circuits. In the case of multiple series connections 12, the series connections 12 are connected in parallel to each other to form the upper and lower branch circuit 10 for one phase. According to the present embodiment, each of the upper and lower branch circuits 10 has one series connection 12. The series connection 12 is formed by connecting a switching element on the side of the upper branch 10H and a switching element on the side of the lower branch 10L in series between the P line 8 and the N line 9.

[0021] The number of switching elements on the upper side and the number of switching elements on the lower side that form the series circuit 12 are not particularly limited. The number can be one or more. The series circuit 12 according to the present embodiment has one switching element on the upper side and one switching element on the lower side.

[0022] In the present embodiment, an n-channel MOSFET 13 is used for each switching element. MOSFET is an abbreviation for metal-oxide-semiconductor field-effect transistor. The MOSFET 13 is switched on and off by a drive signal (a gate voltage).

[0023] A freewheeling diode 14 (hereinafter referred to as FWD 14) is connected antiparallel to each of the MOSFETs 13. In the case of MOSFET 13, FWD 14 can be a parasitic diode (body diode) or an external diode. In the upper branch 10H, the drain of MOSFET 13 is connected to the P-line 8.

[0024] In the lower branch 10L, the source of MOSFET 13 is connected to the N-line 9. The drain of MOSFET 13 in the upper branch 10H and the drain of MOSFET 13 in the lower branch 10L are connected together. The anode of FWD 14 is connected to the source of the corresponding MOSFET 13, and the cathode is connected to the drain.

[0025] The switching element is not limited to MOSFET 13. For example, an IGBT can be used. IGBT stands for insulated-gate bipolar transistor. In the case of the IGBT, FWD 14 is also connected in reverse parallel. MOSFET 13 corresponds to one switching element.

[0026] The drive circuit 20 drives switching elements that form the power conversion circuit, such as the inverter 5. The drive circuit 20 applies a gate voltage to the gate of the corresponding MOSFET 13 based on a drive command from the ECU 30. The drive circuit drives the corresponding MOSFET 13 by applying a gate voltage to switch the MOSFET 13 on and off. The drive circuit can also be referred to as a driver (a control device).

[0027] ECU 30 generates a drive command to operate MOSFET 13 and outputs this command to drive circuit 20. ECU 30 generates a drive command based on a torque request input from a (not illustrated) higher-level ECU and signals acquired by various sensors. ECU 30 also generates a speed command to change the switching speed of MOSFET 13 and outputs this command to drive circuit 20. ECU 30 may be located within a higher-level ECU.

[0028] The configuration of the drive circuit 20 and the ECU 30 is described in more detail below with reference to Fig. 2 described.

[0029] The drive circuit 20 comprises a drive IC 21 and an output circuit 24. The drive IC 21 functions as a switching circuit 22 and a feedback circuit (F / B circuit) 23. The output circuit 24 outputs a gate voltage to the gate terminal of the MOSFET 13. The output circuit 24 has a function to switch the magnitude of the gate voltage and output it. The switching circuit 22 outputs the drive signal Vg and the switching signals VH and VL to the output circuit 24.

[0030] The drive signal Vg is a voltage signal generated in response to a drive command from the ECU 30. The drive signal Vg is a square wave signal whose voltage changes in a pulse-like manner over time, as indicated by a solid line in Fig. Figure 3 shows that with a pulse input of the drive signal Vg, the MOSFET 13 is switched on and the motor current Im flows through winding 3a. With the pulse output of the drive signal Vg, the MOSFET 13 is switched off and the motor current Im becomes zero.

[0031] The switching signals VH and VL are voltage signals generated in response to a speed command from the ECU 30. These signals specify the type of waveform into which the drive signal Vg is converted. The dashed line in Fig. 3 is a drive signal that is converted into a waveform for high-speed switching, which is a high-speed drive signal VgH. The dashed line in Fig. 3 is a drive signal that has been converted into a waveform for low-speed switching, which is the low-speed drive signal VgL.

[0032] Output circuit 24 converts the drive signal Vg into the high-speed drive signal VgH when the switching signal VH is commanded, and converts the drive signal Vg into the low-speed drive signal VgL when the switching signal VL is commanded. The slope of the pulse edge is steeper with the high-speed drive signal VgH compared to the low-speed drive signal VgL. By switching the gate voltage waveform in this way, the waveform of the voltage (the motor voltage) of the motor current Im flowing through the MOSFET 13 also changes. The rising and falling slopes of the motor voltages are greater in the case of the high-speed drive signal VgH than in the case of the low-speed drive signal VgL.

[0033] As used here, switching speed refers to the rate of change (i.e., the slope) of the rise and fall of the motor voltage. The faster this rate of change, i.e., the greater the slope, the faster the switching speed and the less power loss occurs when MOSFET 13 is turned on and off. Conversely, the faster the switching speed, the greater the surge voltage that occurs when MOSFET 13 turns on and off. In other words, the amplitude of the surge waveform present in the motor voltage increases.

[0034] For example, according to the present embodiment, MOS transistors are used in output circuit 24, and the switching signals VH and VL are input to the gates of the MOS transistors. The drive signal Vg, which is input to the MOS transistor, is converted into a signal corresponding to the switching signals VH and VL and then output. For example, the switching signal VH is set to a higher voltage than the switching signal VL. When the switching signal VH is input to output circuit 24, the high-speed drive signal VgH is output from output circuit 24. As a result, the switching speed of the MOSFET 13 increases. When the switching signal VL is input to output circuit 24, the low-speed drive signal VgL is output from output circuit 24. As a result, the switching speed of the MOSFET 13 decreases.

[0035] The feedback circuit 23 outputs a signal, correlated with the actual switching speed of the MOSFET 13, to the ECU 30 as a feedback signal. The feedback circuit 23 corresponds to a feedback unit. The feedback signal output by the feedback circuit 23 indicates the nature of the switching signals VH and VL output by the switching circuit 22 to the output circuit 24. For example, if the switching signal VH is output to increase the switching speed, the high-speed signal VH is output as the feedback signal. If the switching signal VL is output to decrease the switching speed, the slow signal VL is output as a feedback signal.

[0036] The drive IC 21 and the output circuit 24 are provided for each MOSFET 13. Therefore, a feedback signal for each of the MOSFETs 13 is input into the ECU 30. This means that a multitude of feedback signals are input into the ECU 30.

[0037] Furthermore, according to the present embodiment, in addition to the high-speed signal VH and the low-speed signal VL, an element temperature T is also input into the ECU 30 as a feedback signal. The element temperature T is the temperature of the MOSFET 13, which is detected by the temperature sensor 40. The faster the switching speed, the higher the element temperature T. In other words, the element temperature T is a signal that correlates with the actual switching speed of the MOSFET 13. When the ECU 30 uses the element temperature T as a feedback signal, the temperature sensor 40 corresponds to a feedback unit.

[0038] The ECU 30 includes a microcomputer 31, which has a processor 32 and a memory 33. The processor 32 executes the programs stored in the memory 33, which cause the microcomputer 31 to perform a variety of functions. These functions include a power supply instruction unit 34, a speed instruction unit 35, a monitoring unit 36, and the like.

[0039] The power supply control unit 34 generates the drive command described above based on the torque request and signals acquired by the various sensors. For example, the power supply control unit 34 outputs a PWM signal as a drive command. PWM stands for pulse width modulation.

[0040] As it is in Fig. As shown in Figure 4, the surge voltage increases when the switching speed is increased to reduce power loss. If the surge voltage exceeds the breakdown voltage (element breakdown voltage) of MOSFET 13, there is a risk that MOSFET 13 could be damaged. If MOSFET 13 is damaged, the vehicle may become inoperable. Therefore, the speed control unit 39 generates a speed command to increase the switching speed to the extent that the surge voltage does not exceed the element's breakdown voltage, thereby reducing power loss and preventing damage to the element.

[0041] However, even if the switching speed remains the same, the surge voltage increases when the current flowing through MOSFET 13 increases. Therefore, the speed control unit 35 generates a speed command such that the switching speed decreases as the current flows through MOSFET 13 to prevent damage to the element.

[0042] Taking into account the points described above, the speed control unit 35 generates a speed command based on the magnitude of the motor current Im, which is detected by a current sensor (not shown). The motor current Im is the current flowing through the winding 3a of each phase. The speed command is generated such that the switching speed decreases as the motor current Im increases. According to the present embodiment, the switching speed is switched between two stages: a high speed and a low speed. The speed control unit 35 outputs either a high-speed signal or a low-speed signal as a speed command. The speed control unit 35 commands a common switching speed for the plurality of MOSFETs 13.

[0043] The monitoring unit 36 ​​compares the content of the speed command issued by the power supply control unit 34 with the actual switching speed, i.e., the feedback signal, to monitor whether an anomalous condition has occurred. Under normal conditions, the content of the speed command and the content of the feedback signal should match; if they do not match, an anomalous condition is determined. The feedback signals used for this monitoring can be the low-speed signal VL and the high-speed signal VH, or the element temperature T. The monitoring unit 36 ​​corresponds to an anomaly detection unit.

[0044] The monitoring unit 36 ​​according to the present embodiment performs monitoring using the low-speed signal VL and the high-speed signal VH as feedback signals. There are two patterns of anomalous conditions, as described below. One pattern is in which the feedback signal is the low-speed signal VL, even though the speed control unit 35 outputs a high-speed signal. The other pattern is in which the feedback signal is the high-speed signal VH, even though the speed control unit 35 outputs a low-speed signal.

[0045] One reason for the anomaly is a failure of the MOSFET 13 itself, including element damage, sticking, an open circuit, or a short circuit. Another reason is a failure of the signal lines L1, L2, and L3 that connect the ECU 30 and the drive circuit 20, such as a break or short circuit in the signal lines L1, L2, and L3.

[0046] The ECU 30 and the drive circuit 20 can communicate with each other via signal lines L1, L2, and L3. According to the present embodiment, the drive command and the speed command are transmitted via separate signal lines L1 and L2, but they can also be transmitted via a common signal line. The low-speed signal VL and the high-speed signal VH, as feedback signals, are transmitted from the drive circuit 20 to the ECU 30 via a signal line L4. According to the present embodiment, the feedback signal corresponding to each of the MOSFETs 13 is transmitted via separate signal lines L3, but can also be transmitted via a common signal line.

[0047] Temperature sensor 40 and ECU 30 are connected via signal line L4. The element temperature T is transmitted from temperature sensor 40 to ECU 30 using this signal line L4. Alternatively, the element temperature T can be transmitted from temperature sensor 40 to ECU 30 via drive circuit 20. In this case, the low-speed signal VL, the high-speed signal VH, and the element temperature T from drive circuit 20 can be transmitted to ECU 30 using the common signal line. The signal line for element temperature T can then be used to transmit a feedback signal from drive circuit 20 to ECU 30, thus reducing the number of signal lines. Control sequence by the microcomputer 31:

[0048] A in Fig. The control sequence shown in Figure 5 is repeatedly executed by the microcomputer 31 at a predetermined calculation period while the motor generator 3 is driven.

[0049] First, in step S10, the measured value of the motor current Im is obtained. In the subsequent step S20, it is determined whether the obtained motor current Im is greater than a threshold value Ith. If it is determined that the obtained motor current Im is greater than the threshold value Ith, it is considered that the current is large, as indicated in Fig. Figure 4 shows that in the following step S30, the speed command unit 35 outputs the low-speed signal as a speed command. Reducing the surge voltage with this configuration prevents damage to the MOSFET 13 components.

[0050] If, on the other hand, it is determined that the procured motor current Im is not greater than the threshold value Ith, it is taken into consideration that during the low-current period, the Fig. Figure 4 shows that the speed command unit 35 then outputs the high-speed signal as a speed command. This increases the switching speed and reduces power loss.

[0051] If a low-speed command is issued in step S30, the monitoring unit 36 ​​determines in the subsequent step S40 whether the feedback signal is the low-speed signal VL. If step S40 determines that the feedback signal is the low-speed signal VL, the command speed and the feedback signal match, so a normal state is assumed, and the process is terminated. Fig. 5 completed.

[0052] If a high-speed command is issued in step S31, the monitoring unit 36 ​​determines in the subsequent step S41 whether the feedback signal is the high-speed signal VH. If step S41 determines that the feedback signal is the high-speed signal VH, the command speed and the feedback signal match, so a normal state is assumed, and the process is terminated. Fig. 5 completed.

[0053] As described above, the feedback signal from the feedback circuit 23 is input to the ECU 30 for each of the MOSFETs 13. During the determination of steps S40 and S41, if at least one of the multiple feedback signals input to the ECU 30 does not match the command rate, a negative determination is made, and the process proceeds to step S50.

[0054] If, in step S40, it is determined that the feedback signal is the low-speed signal VL, the command speed and the feedback signal do not match. Similarly, if, in step S41, it is determined that the feedback signal is the high-speed signal VH, the command speed and the feedback signal do not match. In these cases, an anomalous condition is assumed, and the process proceeds to the next step S50.

[0055] In step S50, an anomalous condition is diagnosed, and an anomaly flag is set to ON. When the anomaly flag is set to ON, the power supply command unit 34 performs a failsafe control measure, such as limiting the output of the motor generator 3. When the anomaly flag is set to ON, the ECU 30 notifies the higher-level ECU of the anomalous condition. Upon receiving the notification of the anomalous condition, the higher-level ECU alerts the vehicle occupants to the anomalous condition by displaying a warning or emitting a warning sound. Summary of the first embodiment:

[0056] According to the present embodiment, the MOSFET 13 is switched on and off at a switching speed corresponding to the command speed, thus allowing the switching speed to be varied. Therefore, increasing the switching speed improves power consumption. Simultaneously, a feedback signal correlated with the actual switching speed is fed back to the ECU 30, enabling the ECU 30 to monitor whether the actual switching speed deviates from the command speed. This allows for the implementation of measures to address such anomalies, such as a fail-safe control to limit the output of the motor generator 3, or the issuance of a warning signal.As a result, while improving power consumption, it is possible to reduce the risk of the surge voltage exceeding the breakdown voltage of the element due to the actual switching speed being faster than intended.

[0057] According to the present embodiment, the ECU 30 commands the plurality of MOSFETs 13 to switch at a common speed. The feedback circuit 23 outputs a feedback signal to each of the plurality of MOSFETs 13. The monitoring unit 36 ​​determines that an anomalous condition exists if at least one of the many feedback signals is not in accordance with the command speed. This reduces the processing load on the microcomputer 31.

[0058] If the element temperature T is used as a feedback signal here, even if an anomalous condition occurs, it takes a certain amount of time for the element temperature T to change to an anomalous temperature. Therefore, it is difficult to detect an anomaly quickly. In contrast, according to this embodiment, the drive circuit 20 has an output circuit 24 that switches the magnitude of the gate voltage and outputs it to the gate terminal of the MOSFET 13. The drive circuit 20 also has the switching circuit 22, which commands the magnitude of the gate voltage of the output circuit 24. The feedback signal, which is used for monitoring by the monitoring unit 36, has the switching signals VH and VL, which represent the command content from the switching circuit 22.Therefore, even if an anomalous condition occurs where the content of the velocity command and the content of the feedback signal do not match, the anomaly can be quickly detected. Second example:

[0059] A second embodiment is a modification of the preceding embodiment as a basic configuration and may include the description of the preceding embodiment. According to the preceding embodiment, even if an anomaly is detected, the command speed is determined according to the magnitude of the motor current Im. Instead, according to the present embodiment, if the anomaly is detected, the command speed is set from the next time as described below, regardless of the magnitude of the motor current Im.

[0060] In particular, if in step S41 of Fig. 6. If a negative determination is made, an anomaly flag step is activated in S51, as in step S50, to issue an anomaly warning. Then, in step S30, a low-speed signal is output as a speed command. That is, if it is determined that an anomalous condition exists because the switching speed corresponding to the feedback signal is lower than the command speed, the speed command unit 35 changes the command speed to reduce it.

[0061] Then, if the actual speed becomes normally low, a positive determination is made in step S40, and if the motor current Im then remains below the threshold Ith, the command speed is switched back to the high-speed command in step S31.

[0062] Furthermore, according to the present embodiment, if the negative determination is made in step S40, the anomaly warning is issued in step S50, and then in the subsequent step S70, the speed command unit 35 is prevented from issuing a high-speed command. Summary of the second embodiment:

[0063] According to the present embodiment, it is possible to achieve the same effect as the configurations described in the previous embodiment. Additionally, the ECU 30 changes the command speed when it is determined that an anomalous condition exists. More precisely, if the actual speed is low despite the high-speed command, i.e., if a negative determination is made in step S41, the command is changed to a low-speed command. By changing from the high-speed command to the low-speed command in this way, it is possible to prevent an anomalous condition. Therefore, according to the present embodiment, there are cases in which the motor-generator 3 can be switched to a state in which it is driven normally.

[0064] Furthermore, according to the present embodiment, if it is determined that the anomalous condition exists, the ECU 30 fixes the command speed at a predetermined speed and prevents any change to it. More precisely, if the actual speed is high despite the low-speed command, i.e., if a negative determination is made in step S40, the low-speed command is fixed and a change to the high-speed command is prevented. This reduces the risk of the switching speed becoming unintentionally high and reduces the risk of damage to the MOSFET 13 due to a surge voltage. Third example

[0065] This embodiment is a modification of the preceding embodiment as a basic configuration and may include a description of the preceding embodiments. According to the preceding embodiment, one type of feedback signal is used to diagnose an anomaly. Alternatively, two or more types of feedback signals may be used to diagnose the anomaly.

[0066] In particular, according to the present embodiment, as it is in Fig. As shown in section 7, step S60 leads to the flowchart of Fig.Step S60 is added. This step is executed if the actual speed is high despite the low-speed command, i.e., if the determination in step S40 is negative. In step S60, the monitoring unit 36 ​​uses the second feedback signal to determine whether the anomaly has occurred. Specific examples of the second feedback signal include the element temperature T, the magnitude of the gate voltage applied to the gate terminal of MOSFET 13, and the waveform of an impulse voltage occurring in MOSFET 13 or winding 3a. In the present embodiment, the element temperature T is used as the second feedback signal. The first feedback signals are the switching signals VH and VL, whereas the element temperature T, as the second feedback signal, corresponds to the detection signal.

[0067] The first feedback signal is the one used in steps S40 and S41, i.e., the switching signals VH and VL. The second feedback signal is correlated with the actual switching speed and differs in type from the first feedback signal.

[0068] Steps S40 and S41 correspond to a first determination unit that identifies the anomalous condition using the first feedback signal. Step S60 corresponds to a second determination unit that uses the second feedback signal to determine whether an anomalous condition exists. The temperature sensor 40 corresponds to a detection unit that detects the second feedback signal. This detection unit and the feedback circuit 23 together constitute a feedback unit that outputs a feedback signal correlated with the actual switching speed.

[0069] The faster the switching speed, the higher the element temperature T becomes. Therefore, when the speed command switches from high-speed to low-speed and this state lasts for a predetermined time or longer, the element temperature T should decrease. Likewise, when the speed command switches from low-speed to high-speed and this state lasts for a predetermined time or longer, the element temperature T should increase. Taking these points into account, step S60 determines whether the actual speed is low or high based on the element temperature T. More precisely, the actual speed is determined based on the current value of the element temperature T and the change in the element temperature T up to the current time.

[0070] If step S40 determines that the speed is not low, even though the low-speed instruction is issued in step S30, the anomaly flag is set to ON in step S50. However, even if such an anomaly is diagnosed, if step S50 determines that the speed is low, the process returns to step S10 without suppressing the high-speed instruction in step S70. If step S50 determines that the speed is not low, the high-speed instruction is suppressed in step S70, as in step S40. Step S70 corresponds to a regulating unit that limits the instruction speed to suppress the high-speed instruction when the second determining unit determines that the anomalous condition exists. Summary of the third embodiment:

[0071] According to the present embodiment, it is possible to achieve the same effects as the configurations described in the preceding embodiments. Additionally, the power conversion device 4 includes the temperature sensor 40, and the feedback signal includes the element temperature T detected by the temperature sensor 40 in addition to the switching signals VH and VL. The anomaly detection unit by the monitoring unit 36 ​​comprises the first detection unit by steps S40 and S41 and the second detection unit by step S60. The first detection unit determines whether an anomalous condition exists by comparing the switching signals VH and VL with the command rate. The second detection unit determines whether an anomalous condition exists by comparing the element temperature T detected by the temperature sensor 40 with the command rate.Accordingly, since the anomaly determination is performed using two types of feedback signals, the accuracy of the anomaly determination can be improved.

[0072] While the first detection unit can quickly identify an anomaly, there may be cases where a false detection occurs due to an anomaly in the signal line L3. Taking this into account, according to the present embodiment, even if the first detection unit determines that an anomalous condition exists, if the second detection unit does not, the control unit in step S70 is prevented from imposing a speed limit. This reduces concerns that excessive speed limits will prevent sufficient improvements in electricity efficiency. Therefore, it is possible to avoid MOSFET 13 failure while simultaneously improving power consumption. Other examples:

[0073] The disclosure in this description and the drawings is not limited to the illustrated embodiments. The disclosure includes the illustrated embodiments and modifications made by those skilled in the art based thereon. For example, the disclosure is not limited to the combinations of components and / or elements shown in the embodiments. The disclosure can be realized in various combinations. The disclosure may include additional sections added to the embodiments. The disclosure includes the omission of components and / or elements from the embodiments. The disclosure includes the substitution or combination of components and / or elements between one embodiment and another. The technical scope disclosed is not limited to the description of the embodiments.The various technical scopes disclosed are specified by the description of the claims and should further be understood to have meanings equivalent to the description of the claims and all modifications within the scope.

[0074] The disclosure in the description, drawings, and the like is not limited by the description of the patent claims. The disclosures in this description, the drawings, and the like encompass the technical ideas described in the patent claims and extend to a wider variety of technical ideas than those in the patent claims. Thus, various technical ideas can be extracted from the disclosure in the description, the drawings, and the like without being bound by the description of the patent claims.

[0075] According to the third embodiment, the first feedback signal and the second feedback signal are used to determine whether an anomaly has occurred. However, the first feedback signal can be omitted, and the second feedback signal can be used to determine whether an anomaly has occurred.

[0076] According to each of the embodiments described above, the switching speed is switched between two stages: a high speed and a low speed. In contrast to this configuration, the switching speed can be switched in three or more stages, or it can be changed linearly without stages.

[0077] According to the second embodiment described above, in the event of an anomalous condition, the ECU 30 fixes the speed command to a predetermined speed. Specifically, assuming that the switching speed is between two levels, high speed and low speed, in the event of an anomaly where the actual speed is high despite the low-speed command, the ECU 30 fixes the speed command to the low-speed command. Conversely, assuming that the speed is switching between three levels, high speed, medium speed, and low speed, the ECU 30 can fix the speed to either the low-speed or medium-speed command in the event of the anomaly described above.Furthermore, provided that the switching speed is changed linearly in a stepless manner, the ECU 30 can issue a speed command by fixing the speed at a level at which the MOSFET 13 will not be damaged. Specific examples of damage in this case include damage caused by excessive current flowing through the MOSFET 13, damage caused by excessive temperature of the MOSFET 13, and damage caused by applying excessive voltage to the MOSFET 13.

[0078] According to each of the embodiments described above, if a negative determination is made in step S41, and the motor current Im is subsequently greater than the threshold value Ith, the low-speed command in step S30 is permitted. Conversely, if a negative determination is made in step S41, the low-speed command can be suppressed regardless of the magnitude of the motor current Im.

[0079] According to each of the embodiments described above, if a negative value is determined in step S40, the switching speed is subsequently determined in step S20 according to the magnitude of the motor current Im. Conversely, if a negative value is determined in step S40, the motor current Im can then be fixed to the high-speed command, regardless of its magnitude.

[0080] According to each of the embodiments described above, the switching speed is changed according to the motor current Im. Alternatively, the switching speed can be changed depending on the temperature of the MOSFET 13 or the temperature of the cooling water that cools the MOSFET 13. For example, it is desirable that the higher these temperatures, the faster the switching speed becomes, in order to reduce power loss. Furthermore, the switching speed can be changed depending on the voltage applied to the MOSFET 13 and the voltage applied to the drive circuit 20. For example, it is desirable that the lower these voltages, the faster the switching speed becomes, in order to reduce power losses. Finally, the switching speed can be changed depending on the voltage of the power supply, which is used as the gate signal of the MOSFET 13.For example, low voltages for gate signals are desirable to increase switching speed and reduce power losses. Furthermore, the switching speed can be modified by combining parameters such as motor current Im, different temperatures, different voltages, and ambient pressure.

[0081] The power conversion device 4 may further include a converter as the power conversion circuit. The converter is a DC-DC converter circuit that converts a DC voltage to, for example, a DC voltage of a different value. The converter is located between the DC power supply 2 and the smoothing capacitor 6. The converter is configured, for example, to include an inductor and the above-described step-up and step-down circuit 10. This configuration can boost or reduce a voltage. The power conversion device 4 may further include a filter capacitor for removing power supply disturbances from the DC power supply 2. The filter capacitor is located between the DC power supply 2 and the converter. Examples of technical features:

[0082] This description reveals a multitude of technical features, which are described in a variety of sections listed below. Some features may be presented in multiply independent form, in which a subsequent feature selectively refers to preceding features. Furthermore, some features may be written in multiply dependent form, referring to other multiply dependent forms, which in turn depend on features of other multiply dependent forms. These sections written in multiply dependent form define multiple technical concepts. Technical feature 1:

[0083] A power conversion device has the following features: a variety of switching elements (13) configured to convert and output electrical power, a control device (30) configured to command a switching speed of the switching element, a drive circuit (20) configured to drive the switching element for switching on and off at a speed of sound corresponding to a command speed from the control device, a feedback unit (23, 40) which outputs a signal correlated with an actual switching speed as a feedback signal to the control device, and an anomaly detection unit (36) configured to determine, by comparing the feedback signal with the command rate, whether the actual switching rate is in an anomalous state as opposed to the command rate. Technical feature 2:

[0084] The power conversion device according to technical feature 1, wherein the control device changes the command speed when the anomalous condition is determined. Technical feature 3:

[0085] The power conversion device according to technical feature 2, wherein, if the anomalous condition is determined due to the fact that the switching speed corresponding to the feedback signal is slower than the command speed, the control device changes the command speed to reduce the command speed. Technical feature 4:

[0086] The power conversion device according to technical feature 1, wherein the control device fixes the command speed to a predetermined speed and prevents a change in the command speed when the anomalous condition is detected. Technical feature 5:

[0087] The power conversion device according to one of the technical features 1 to 4, wherein the drive circuit has an output circuit (24) that switches a magnitude of a gate voltage and outputs the gate voltage to the switching element, and a switching circuit (22) that switches a switching speed by instructing the output circuit to which gate voltage is to be switched, and The feedback signal has a switching signal that represents a command issued by the switching circuit. Technical feature 6:

[0088] The power conversion device according to the technical feature of claim 5, wherein the feedback unit comprises a detection unit (40) that detects a temperature of the switching element, and / or a gate voltage applied to the switching element and / or an impulse voltage waveform of the switching element, The feedback signal includes a detection signal, which is detected by the detection unit, in addition to the switching signal, and The anomaly detection unit comprises a first determination unit (S40, S41) that determines the anomalous state by comparing the switching signal with the command rate, and a second determination unit (S60) that determines the anomalous state by comparing the detection signal with the command rate. Technical feature 7:

[0089] The power conversion device according to technical feature 6 has a regulating unit (70) that limits a command speed from the control device when the second determining unit determines that the anomalous condition is present, wherein, even if the first determining unit determines that the anomalous condition is present, the regulating unit prevents a speed limitation if the second determining unit does not determine that the anomalous condition is present. Technical feature 8:

[0090] The power conversion device according to one of the technical features 1 to 7, wherein the control device commands a common switching speed to the plurality of switching elements, the feedback unit outputs the feedback signal for each of the multitude of switching elements, and The anomaly detection unit determines that the anomalous state is present if at least one of the multitude of feedback signals is contrary to the command rate. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] JP 2023

[0001] JP 131628

[0001] JP 2015 - 65 742 A

[0004]

Claims

[1] Power conversion device with: a variety of switching elements (13) configured to convert and output electrical power, a control device (30) which is configured to command a switching speed of the switching element, a drive circuit (20) configured to drive the switching element for switching on and off at a sound velocity corresponding to a command velocity from the control device, a feedback unit (23, 40) which outputs a signal correlated with an actual switching speed as a feedback signal to the control device, and an anomaly detection unit (36) configured to determine, by comparing the feedback signal with the command rate, whether the actual switching rate is in an anomalous state as opposed to the command rate. [2] Power conversion device according to claim 1, wherein the control device changes the command speed when the anomalous condition is determined. [3] Power conversion device according to claim 2, wherein, if the anomalous condition is determined due to the fact that the switching speed corresponding to the feedback signal is slower than the command speed, the control device changes the command speed to reduce the command speed. [4] Power conversion device according to claim 1, wherein the control device fixes the command speed to a predetermined speed and prevents a change in the command speed when the anomalous condition is determined. [5] Power conversion device according to claim 1, wherein The drive circuit includes an output circuit (24) that switches a gate voltage and outputs the gate voltage to the switching element, and a switching circuit (22) that switches a switching speed by instructing the output circuit which gate voltage to switch to, and The feedback signal has a switching signal that represents a command issued by the switching circuit. [6] Power conversion device according to claim 5, wherein the feedback unit includes a detection unit (40) that detects a temperature of the switching element, and / or a gate voltage applied to the switching element and / or an impulse voltage waveform of the switching element, The feedback signal includes a detection signal, which is detected by the detection unit, in addition to the switching signal, and The anomaly detection unit comprises a first determination unit (S40, S41) that determines the anomalous state by comparing the switching signal with the command rate, and a second determination unit (S60) that determines the anomalous state by comparing the detection signal with the command rate. [7] Power conversion device according to claim 6, further comprising: a regulating unit (70) that limits a command rate from the control device when the second determining unit determines that the anomalous condition is present, wherein, Even if the first unit of determination determines that the anomalous condition exists, the regulatory unit prevents a speed limit if the second unit of determination does not determine that the anomalous condition exists. [8] Power conversion device according to any one of claims 1 to 4, wherein The control device commands a common switching speed for the multitude of switching elements. the feedback unit outputs the feedback signal for each of the multitude of switching elements, and The anomaly detection unit determines that the anomalous state is present if at least one of the multitude of feedback signals is contrary to the command rate.

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