JP6277114B2 - Power converter - Google Patents

Description

  The present invention relates to a power module and a power converter using the same, and more particularly to a power module used in a vehicle and a power converter using the same.

  A power conversion device is used in an electric vehicle or a hybrid vehicle, which is cooled by using a heat exchanger or the like, and is a power semiconductor element in a power module mounted on the power conversion device, for example, IGBT (Insulated Gate Bipolar). Transistors (insulated gate bipolar transistors), diodes must be protected against overtemperature. For the temperature protection control, the loss calculated using the temperature observed by the temperature detection element placed close to the power semiconductor element and the driving conditions of the power converter (output current, DC voltage, switching frequency, etc.) Based on the above, overtemperature protection or output limitation is performed.

Japanese Patent No. 5378293 2007-215250 gazette

  In a conventional power module in which a temperature detection element is arranged near the power semiconductor element, there is a difference between the temperature observed by the temperature detection element and the junction temperature of the power semiconductor element, and a response delay of the temperature detection element also occurs. Under the condition that the power semiconductor element located far from the temperature detection element generates heat, it is not suitable to use the temperature observed by the temperature detection element for temperature protection control. In addition, in a situation where the cooling conditions of the power conversion device fluctuate, for example, when the temperature of the cooling refrigerant is high and the flow rate is low, current output limitation as a temperature protection operation may act excessively depending on the set value of temperature protection control. There is a possibility that the performance of the power conversion device is deteriorated or the current output limit is insufficient. If the flow rate and temperature of the cooling refrigerant are used as input parameters for temperature protection control, the performance improvement of the temperature protection control can be expected. To add new detection means for directly detecting the flow rate and temperature of the cooling refrigerant, install it. There is a problem in that the power conversion device is increased in size due to the expansion of space and the cost is increased due to an increase in the number of parts.

In order to achieve the above object, a power converter according to the present invention includes a semiconductor element, a first conductor plate connected to one electrode of the semiconductor element via a solder material, and the first element sandwiching the semiconductor element. A second conductive plate disposed opposite to the conductive plate and connected to the other electrode of the semiconductor element via a solder material; a part of the first conductive plate; a part of the second conductive plate; and the semiconductor A sealing material for sealing the element; a case for housing the sealing material and serving as a heat dissipation path for the semiconductor element; and the first conductor plate exposed from the sealing material and the case. And a power module including an insulating member that contacts the first conductor plate and the inner wall of the case, and a temperature detection element disposed on the inner wall of the case, and includes a plurality of power modules and a flow path for flowing a refrigerant. Forming the plurality of pads. A module is arranged in series along the flow direction of the refrigerant, and among the plurality of power modules, the power module arranged at the most downstream side of the flow of the refrigerant and at least one other power module are an inner wall of the case The temperature detection element is disposed at a position, and a cooling refrigerant flow rate estimation unit that estimates a cooling refrigerant flow rate based on a temperature acquired by the temperature detection element is provided .

The power conversion device according to the present invention may further calculate the refrigerant temperature of the outlet pipe portion of the flow path based on the temperature acquired by the temperature detection element. The power conversion device according to the present invention may further include a loss calculation unit that calculates a loss of the power module based on a driving condition of the power conversion device. Further, the power conversion device according to the present invention further limits the output current of the power conversion device and protects the semiconductor element from over temperature so that the junction temperature of the semiconductor element does not exceed an allowable value. good.

The present invention, to improve the performance of a control function to protect the power semiconductor elements in the power conversion device from thermal damage due to excessive temperatures can be realized at low cost.

It is a vehicle system figure which mounted the power converter by this embodiment. It is a power converter circuit of the power converter by this embodiment. 2 is an external perspective view of a power module 300. FIG. It is sectional drawing seen from the arrow direction of the plane B of Fig.3 (a). FIG. 4 is a cross-sectional view that is simplified for easy understanding of the arrangement of the film type thermistor 335 and is viewed from the direction of the arrow on the plane C in FIG. The external shape of the film type thermistor 335 is shown. The mounting position of the mold type thermistor 336 of the conventional power module 300 is shown. The external appearance of the mold type thermistor 336 is shown. FIG. 4 is a schematic view of a flow path for flowing a refrigerant for cooling the power module 300. The cooling refrigerant temperature in the cooling refrigerant channel position of the power converter by this embodiment is shown. The relationship between the temperature detected by the mold type thermistor arranged in the vicinity of the power semiconductor element and the output limiting current is shown. It is a waveform at the time of the transition in the drive condition at the time of determining current limiting conditions. It is a waveform when the temperature at which the output restriction is started is adjusted so that the junction temperature of the power semiconductor element does not exceed the allowable continuous operation temperature even in the transient state. It is a waveform when the coolant flow rate is reduced under the driving conditions when the limiting conditions are determined. The cooling refrigerant temperature which can be detected with the film type thermistor in the double-sided cooling type power module of the power converter by this embodiment is shown. The control block diagram of the temperature protection control mounted in the power converter device by this embodiment is shown. The relationship of the outlet piping part cooling refrigerant | coolant temperature of the temperature protection control mounted in the power converter device by this embodiment and an output limiting current is shown. It is a waveform at the time of the transition in the drive condition at the time of determining a current limiting condition. It is a waveform when the temperature at which the output restriction is started is adjusted so that the junction temperature of the power semiconductor element does not exceed the allowable continuous operation temperature even in the transient state. It is a waveform when the coolant flow rate is reduced under the driving conditions when the limiting conditions are determined.

The numbers shown in the following description correspond to the numbers shown in each drawing.

  A power module according to an embodiment of the present invention has a double-sided cooling structure, and a power conversion device using the same will be described in detail below with reference to the drawings.

  The power conversion device 200 according to the embodiment of the present invention can be applied to a hybrid vehicle or a pure electric vehicle. Here, as a representative example, a control configuration and a circuit configuration of the power conversion device when the power conversion device according to the embodiment of the present invention is applied to an electric vehicle will be described with reference to FIGS. 1 and 2.

  As shown in FIG. 1, a vehicle including the power conversion device 200 of this example includes a battery 135, a power conversion device 200, an electric motor 192, a speed reducer 4, a drive shaft 5, wheels 6 and 7, and a rotation sensor for the electric motor 192. 199.

  The battery 135 is a power source for the vehicle. The power conversion apparatus 200 includes a power conversion circuit including a power module having a power semiconductor element for converting a direct current into an alternating current, and switches the semiconductor element on and off to allow a desired current to flow. Thus, the drive of the electric motor 192 is controlled, and the DC power and the AC power are converted between the battery 135 and the electric motor 192.

  The electric motor 192 is a drive source of the vehicle and transmits force to the drive wheels via the speed reducer 4 and the drive shaft 5. The battery 135 is discharged by powering of the electric motor 192 and charged by regeneration of the electric motor 192.

  The circuit configuration of the power conversion device 200 will be described with reference to FIG. The power conversion device 200 includes an inverter unit 140 that performs power conversion and a capacitor module 500 for smoothing a direct current. Inverter unit 140 is electrically connected to battery 135 via DC connector 138.

  The inverter unit 140 includes a plurality of power modules 300 having a double-sided cooling structure, three in this embodiment, and a three-phase bridge circuit is configured by connecting the power modules 300. When the current capacity is large, the power modules 300 are further connected in parallel, and these parallel connections correspond to the respective phases of the three-phase inverter circuit, so that the current capacity can be increased.

  The inverter circuit unit 144 includes a power module 300 having an upper and lower arm series circuit including an IGBT 328 (insulated gate bipolar transistor) and a diode 136 that operate as an upper arm, and an IGBT 330 and a diode 166 that operate as a lower arm. Three phases (U phase, V phase, W phase) are provided corresponding to each phase winding. Each of the upper and lower arm series circuits is connected to an AC power line 186 to the electric motor 192 through an AC terminal 159 and an AC connector 188 from the middle point portion (intermediate electrode 169).

  The collector electrode 153 of the upper arm IGBT 328 is connected to the positive electrode of the capacitor module 500 via the positive terminal 157, and the emitter electrode of the lower arm IGBT 330 is connected to the negative electrode of the capacitor module 500 via the negative terminal 158. Are electrically connected to each other.

  The IGBT 328 includes a collector electrode 153, a signal emitter electrode 155, and a gate electrode 154. The IGBT 330 includes a collector electrode 163, a signal emitter electrode 165, and a gate electrode 164. A diode 136 is electrically connected between the collector electrode 153 and the emitter electrode. A diode 166 is electrically connected between the collector electrode 163 and the emitter electrode.

  The capacitor module 500 is electrically connected to the battery 135 via the positive capacitor terminal 506, the negative capacitor terminal 504, and the DC connector 138. Note that the inverter unit 140 is connected to the positive capacitor terminal 506 via the DC positive terminal 314 and is connected to the negative capacitor terminal 504 via the DC negative terminal 316.

  The control unit 170 includes a driver circuit 174 that drives and controls the inverter circuit unit 144, and a control circuit 172 that supplies a control signal to the driver circuit 174 via the signal line 176. The IGBT 328 and the IGBT 330 operate in response to the drive signal output from the control unit 170, and DC power supplied from the battery 135 is converted into three-phase AC power and supplied to the electric motor 192.

  The control circuit 172 is mounted with a microcomputer (hereinafter referred to as “microcomputer”) in order to calculate the switching timing of the IGBT 328 and the IGBT 330. As input information to the microcomputer, a target torque value required for the electric motor 192, a current value supplied from the power module 300 to the electric motor 192, a magnetic pole position and a rotational speed of the rotor of the electric motor 192, and a capacitor A DC voltage between the positive side capacitor terminal 506 and the negative side capacitor terminal 504 of the module 500 is input.

  The target torque value is based on a command signal output from a host controller (not shown). The current value is based on a detection signal output from the current sensor 180 via the signal line 182. The rotor magnetic pole position and the rotation speed of the electric motor 192 are based on the detection signal output from the rotation sensor 199 mounted on the electric motor 192 via the signal line 198. In the present embodiment, the case where the current values of three phases are detected will be described as an example, but the current values for two phases may be detected.

  The microcomputer in the control circuit 172 is based on the target torque value, the rotation speed of the electric motor 192, and the DC voltage between the positive capacitor terminal 506 and the negative capacitor terminal 504 of the capacitor module 500 that is electrically connected to the battery 135. The current command value of the electric motor 192 is determined, and the voltage command value is calculated based on the difference between this current command value and the current value detected by the current sensor 180. Based on the calculated voltage command value based on the magnetic pole position detected by the rotation sensor 199, a U-phase, V-phase, and W-phase PWM (pulse width modulation) signal is generated, and is sent to the driver circuit 174 via the signal line 176. Output.

  The driver circuit 174 generates a drive signal for switching the IGBT 328 of the upper arm and the lower arm IGBT 330 based on the PWM signal output from the control circuit 172, and amplifies the PWM signal when driving the lower arm. The drive signal is output to the gate electrode of the corresponding lower arm IGBT 330. Further, when driving the upper arm, the driver circuit 174 amplifies the PWM signal after shifting the level of the reference potential of the PWM signal to the level of the reference potential of the upper arm, and uses this as a drive signal as a corresponding upper arm. Are output to the gate electrodes of the IGBTs 328 respectively. As a result, the upper arm IGBT 328 and the lower arm IGBT 330 perform a switching operation based on the input drive signal.

  In addition, the control unit 170 performs temperature protection control for limiting the output current so that an abnormality such as an overcurrent and an overtemperature is detected and a junction temperature of a power semiconductor element described later does not exceed an allowable value. For this reason, sensing information is input to the control unit 170.

  For example, information on the current flowing through the emitter electrodes of the IGBTs 328 and IGBTs 330 is input to the corresponding driver circuit 174 from the signal emitter electrode 155 and the signal emitter electrode 165 of each arm. As a result, the driver circuit 174 detects overcurrent, and when an overcurrent is detected, the switching operation of the corresponding IGBT 328 and IGBT 330 is safely stopped, and the corresponding IGBT 328 and IGBT 330 are overcurrent and a surge that is generated at the time of stop. Protect from voltage.

  As will be described later, in the power module 300, a film type thermistor or a mold type thermistor 336 is disposed as a temperature detecting element, and the junction temperature of the power semiconductor element exceeds the allowable continuous operation temperature based on the temperature detected by the film type thermistor 336. The temperature protection control for limiting the output current so that the output current is not exceeded and the over temperature detection for stopping the current output in order to prevent the temperature from reaching the maximum operating temperature can be detected.

  However, in the conventional power module in which the mold type thermistor 336 is disposed in the vicinity of the power semiconductor element, there is a difference between the temperature detected by the mold thermistor 336 and the junction temperature of the power semiconductor element. Since the change in the junction temperature is extremely fast compared to the time constant of the temperature detected by the mold type thermistor 336, even if temperature protection control or overtemperature detection is performed based on the temperature detected by the mold type thermistor 336, the power semiconductor There was a possibility that the element exceeded the allowable continuous operation temperature.

  In particular, when the cooling refrigerant flow rate is controlled and fluctuates or the cooling refrigerant circulation stops when the temperature of the cooling refrigerant is high, the current output by the protection operation is set according to the set values of temperature protection control and overtemperature detection. The restriction acts excessively and the performance of the power conversion device deteriorates, or the temperature protection operation becomes insufficient.

  In order to improve the accuracy of temperature protection control and overtemperature detection, it is conceivable that the flow rate and temperature of the cooling refrigerant are used as input parameters for temperature protection control. In some cases, this information is transmitted to the power conversion device from the host control device (not shown) via the in-vehicle network. In other cases, a new measuring instrument for directly measuring the coolant flow rate and temperature is added. Therefore, there is a problem in that the power conversion device is increased in size by increasing the installation space, and the cost is increased due to an increase in the number of components.

  Accordingly, the double-sided cooling power module 300 that is inserted into the cooling refrigerant flow path configured in the power conversion device to form the flow path in order to solve the above problem detects the temperature of the cooling refrigerant flowing in the flow path. For this purpose, a film type thermistor 335 is provided as a temperature detecting element. Generally, the film type thermistor 335 has a lower operating temperature upper limit than the mold type thermistor 336, and is not suitable for temperature detection of power semiconductor elements. However, the film-type thermistor 335 is thin and has a relatively quick response and is suitable for detecting the temperature of the cooling refrigerant.

  Details of the power module 300 according to this embodiment will be described with reference to FIGS. 3 and 4. FIG. 3A is an external perspective view of the power module 300. FIG. 3B is a cross-sectional view as seen from the direction of the arrow on the plane B in FIG.

  The IGBT 328, IGBT 330, diode 133, and diode 166 (collectively referred to as power semiconductor elements) constituting the upper and lower arm series circuit are fixed by a conductor plate 315 and a conductor plate 319 from both sides and via a solder material. . To these conductor plates 315 and 319, an auxiliary mold body 600 is assembled which is formed by integrally transfer-molding signal wirings which are the signal terminals 325U and 325L. The conductor plate 315 and the like are sealed with the first sealing resin 348 with the heat dissipation surface exposed, and an insulating sheet 333 functioning as an insulating member is thermocompression bonded to the heat dissipation surface. The module primary sealing body 302 sealed with the first sealing resin 348 is inserted into the case 304 and sandwiched with the insulating sheet 333, and is thermocompression bonded to the inner surface of the case 304 that is a CAN type cooler. Here, the CAN-type cooler is a cooler having a cylindrical shape having an insertion port 306 on one surface and a bottom on the other surface, and has heat radiation bases 307A and 307B facing each other.

  The case 304 is made of an aluminum alloy material such as Al, AlSi, AlSiC, Al-C, or the like. The case 304 has a structure in which no opening other than the insertion port 306 is provided. Further, as shown in FIG. 3A, the heat dissipating base 307A and the second heat dissipating surface 307B having a surface wider than the other surfaces are arranged facing each other, and the facing heat dissipating base 307A and the second heat dissipating surface are arranged. The three surfaces connected to 307B constitute a surface sealed with a width narrower than that of the heat dissipation base 307A and the second heat dissipation surface 307B, and the insertion port 306 is formed on the surface of the other side. Further, the fins 305 are uniformly formed on the opposing heat dissipation base 307A and the second heat dissipation surface 307B, respectively.

  4A is a cross-sectional view that is simplified for easy understanding of the arrangement of the film type thermistor 335 and is viewed from the direction of the arrow on the plane C in FIG. As shown in FIG. 4A, the film-type thermistor 335 for detecting the coolant temperature does not come into contact with the module primary sealing body 302 sealed with the first sealing resin 348, and The insulating sheet 333 is directly attached to the heat dissipation base 307A where the fins 305 are formed without using the insulating sheet 333. Therefore, the film type thermistor 335 is not easily affected by heat generated by the power semiconductor element.

  In addition, the film type thermistor 335 has a thin structure and can be attached to the heat dissipation base 307A without any gap, so that the heat insulation effect of the gap layer is lost, and the temperature rise of the cooling refrigerant is slower than the thermal time constant of the film type thermistor 335. Therefore, the response delay of the film type thermistor 335 can be ignored. FIG. 4B shows the outer shape of the film type thermistor 335.

  4C shows the mounting position of the mold type thermistor 336 of the conventional power module 300, and FIG. 4D shows the outer shape of the mold type thermistor 336 to be mounted. The mold type thermistor 336 is mounted on the conductor plate 315 that is sealed with the first sealing resin 348 and is in contact with the insulating sheet 333.

  FIG. 5 is a schematic view of a flow path for flowing a refrigerant for cooling the power module 300. The refrigerant flow paths can be configured in series or in parallel, but when configured in series, the refrigerant flows into the inlet pipe 401 and flows out from the outlet pipe 402 in order to easily and uniformly control the refrigerant flow rate. In the power module 300 constituting each of the U phase, the V phase, and the W phase, the refrigerant is a U phase lower arm side circuit, a U phase upper arm side circuit, a V phase upper arm side circuit, and a V phase lower arm side circuit. The circuit is arranged so as to flow in the order of the circuit, the W-phase lower arm side circuit, and the W-phase upper arm side circuit.

  As shown in FIG. 6, the cooling refrigerant temperature in the power conversion device rises to sequentially cool the heat generated by the power semiconductor elements of the power module 300, and a temperature gradient is generated depending on the flow path position. In particular, when the flow rate of the cooling refrigerant is small, this temperature gradient becomes steep.

  The junction temperature of the power semiconductor element is based on the cooling refrigerant temperature at the flow path position where each power module 300 is inserted, and the loss of the power semiconductor element and the heat from the power semiconductor element to the cooling refrigerant based on the driving conditions of the power converter. Determined by resistance.

  In the normal drive mode of the power converter, if the PWM signal output from the control circuit 172 has a basic upper and lower arm symmetrical pattern, the losses in the upper and lower arms are equal, and the power disposed at the most downstream of the cooling refrigerant flow path. The junction temperature of the power semiconductor element mounted on the module 300 is the highest. In this embodiment, the power semiconductor element is mounted on the upper arm circuit of the W-phase power module 300.

  It is necessary to perform temperature protection control so that the junction temperature does not constantly exceed the allowable continuous operation temperature of the power semiconductor element. In order to prevent the junction temperature of the power semiconductor element from exceeding the allowable value, the junction temperature of the power semiconductor element is estimated based on the temperature obtained by the temperature detection element disposed in the vicinity of the power semiconductor element, for example, the mold type thermistor 336. It can be considered that the temperature is controlled so as not to exceed an allowable value.

  However, there is a difference between the temperature observed by the mold thermistor 336 and the junction temperature of the power semiconductor element, and a delay corresponding to the time constant of the mold thermistor 336 also occurs. Further, the vehicle drive power conversion device may not be able to obtain the cooling refrigerant temperature and flow rate information.In such a case, it is necessary to determine a representative drive condition in advance and determine a set value for temperature protection control. There is a possibility that the output limitation of the temperature protection operation acts excessively and the performance of the power conversion device deteriorates or the temperature protection operation becomes insufficient.

  FIG. 7 shows the temperature and output current detected by the film-type thermistor 335 when the junction temperature of the power semiconductor element mounted on the power module 300 arranged at the most downstream side of the cooling refrigerant flow path becomes the allowable continuous operation temperature. The relationship of limit values is shown. The power converter drive conditions for determining the current limit curve are selected so that the junction temperature is highest under the conditions in which the power converter is actually used. The microcomputer mounted on the control circuit 172 limits the output current according to the above relationship according to the temperature detected by the mold type thermistor 336.

  FIG. 8 shows waveforms of the power semiconductor element junction temperature, the temperature detected by the molded thermistor 336, and the transient state of the output current.

  FIG. 8A shows a waveform at the time of transition in the driving condition when the current limiting condition is determined. In the steady state, the output current is properly limited, and the junction temperature of the power semiconductor element is the continuous operation allowable temperature. However, in the transient state, the output temperature is limited based on the temperature including the detection delay due to the mold thermistor 336 time constant, so that the junction temperature of the power semiconductor element may exceed the maximum operating temperature.

  FIG. 8B shows a waveform when the temperature at which the output restriction is started is adjusted so that the junction temperature of the power semiconductor element does not exceed the allowable continuous operation temperature even in the transient state. In the steady state, although the junction temperature of the power semiconductor element does not reach the allowable continuous operation temperature, the output restriction is performed, so that the performance of the power conversion device cannot be sufficiently exhibited.

  FIG. 8 (c) shows a waveform when the coolant flow rate is reduced under the driving conditions when the limiting conditions are determined. Since the junction temperature of the power semiconductor element cannot be limited to the allowable continuous operation temperature, and further exceeds the maximum operating temperature, there is a high possibility of failure.

  In order to solve these problems, the present embodiment detects the cooling refrigerant temperature using the power module 300 including the film type thermistor 335 for detecting the temperature of the cooling refrigerant flowing in the flow path, and the temperature of the cooling refrigerant. The flow rate is estimated based on the rising amount, and the current is limited by temperature protection control based on the cooling refrigerant temperature of the outlet pipe unit 402. Thereby, the reliability of the protection with respect to the thermal destruction by the overtemperature of a power semiconductor element can be improved, and the performance of a power converter device can also be improved.

As shown in FIG. 9, when the power converter is outputting current, the cooling refrigerant temperature in the power converter generates a temperature gradient because the power semiconductor element generated heat of the power module 300 is sequentially cooled. Based on the cooling refrigerant temperature detected by the film type thermistor 335 arranged in the power module 300, the microcomputer mounted in the control circuit 172 calculates the cooling refrigerant temperature rise amount in the power converter. In this embodiment, the cooling refrigerant temperature detected by the film-type thermistor 335 arranged in the power module 300 depends on the inlet temperature (T ₁ ) of the cooling refrigerant and the power module loss arranged in the V and W phases. The temperature after heat generation is received (T ₂ or T ₃ ) is calculated as the number (1) of the amount of cooling refrigerant temperature rise in the power converter.
ΔT _w3 : Cooling refrigerant temperature rise [℃] (Difference between inlet temperature and outlet temperature)
ΔT _w2 : Cooling refrigerant temperature rise [℃] (Temperature difference between inlet temperature T1 and T2 [or T3])
T ₁ : U-phase power module position cooling refrigerant temperature [℃]
T ₂ : V phase power module position cooling refrigerant temperature [℃] (or W phase)

Based on the loss of the three-phase power module 300 based on the amount of cooling refrigerant temperature rise in the power converter and the driving conditions of the power converter, DC voltage, current, switching frequency, modulation factor, and power factor, The flow rate of the cooling refrigerant can be estimated from the number (2). The cooling refrigerant density and the specific heat of the cooling refrigerant vary depending on the temperature of the cooling refrigerant.
Fr: Estimated coolant flow rate [L / min]
Q: Three-phase power module loss [W]
ΔT _w3 : Cooling refrigerant temperature rise [℃] (Difference between inlet temperature and outlet temperature)
ρ: Cooling refrigerant density [kg / L]
c: Specific heat of cooling refrigerant [J / gK]

In addition, the cooling refrigerant temperature of the outlet pipe section 402 serving as a reference temperature for temperature protection control realized by a microcomputer mounted on the control circuit 172 can be calculated by the equation (3).
T _{w_out} : Cooling refrigerant outlet piping temperature [℃]
T _{w_in} : Cooling refrigerant inlet piping temperature [℃] (T1 detected by thermistor)
T ₁ : U-phase power module position cooling refrigerant temperature [℃]
T ₂ : V phase power module position cooling refrigerant temperature [℃] (or W phase)

FIG. 10 is a model for carrying out current limiting by temperature protection control of the power conversion device in the present embodiment. A current control unit 901 that determines a current command value in the normal mode, a three-phase power module loss calculation unit 902 that performs loss calculation in the power module 300 for three phases, a refrigerant flow rate estimation unit 903 that estimates the flow rate of the cooling refrigerant, A current limit calculation unit 904 that determines a current limit value based on the estimated coolant flow rate and the cooling refrigerant temperature of the outlet piping unit 402, and a current limit value determined by the current limit calculation unit 904 based on the current command value determined by the current control unit 901 If larger, the command switching unit 905 switches the current command value.

Three-phase power module loss can be calculated from the output current, switching frequency, DC voltage, modulation factor, and power factor, but when the drive conditions are known in advance, the parameter that has little fluctuation and little influence is set to a fixed value. Thus, the throughput of the microcomputer mounted on the control circuit 172 can be reduced.

  A method for determining the current limit value output by the current limit calculation unit 904 will be described. In each driving condition of the power conversion device in advance, power module loss calculation and cooling of the outlet piping section 402 when the power semiconductor element junction temperature of the power module 300 arranged at the most downstream of the cooling refrigerant flow path becomes the continuous operation allowable temperature. Find the relationship between refrigerant temperature and output current. At this time, the worst conditions of DC voltage, switching frequency, modulation factor, and power factor are used as driving conditions for the power converter. Therefore, even if the actual power converter driving conditions fluctuate, it is not necessary to limit the output current because the power semiconductor element junction temperature becomes lower than the continuous operation allowable temperature.

  FIG. 11 shows a limit curve of the output current used in the current limit calculation unit 904. The cooling refrigerant temperature of the outlet pipe section 402 that starts current limitation also changes due to the fluctuation of the cooling refrigerant flow rate. In order to reduce the throughput of the microcomputer mounted in the control circuit 172, the inclination of the current limit is obtained under the condition where the coolant flow rate is the highest and applied to all the coolant flow condition to start the current limit cooling of the outlet pipe section 402. The refrigerant temperature may be an approximate function of the estimated cooling refrigerant flow rate.

  FIG. 12 shows the waveform of the transient state of the junction temperature of the power semiconductor element, the temperature detected by the film-type thermistor 335 for detecting the coolant temperature mounted on the power module 300, and the output current.

  FIG. 12A shows a waveform at the time of transition in the driving condition when the current limiting condition is determined. In the steady state, the output current is properly limited, and the junction temperature of the power semiconductor element is the continuous operation allowable temperature. In the transient state, the output temperature is limited based on the temperature including the detection delay due to the film type thermistor 335 time constant, so that the junction temperature of the power semiconductor element exceeds the allowable continuous operation temperature. Compared to the current limit based on the temperature obtained from the mold type thermistor 336 arranged in the vicinity of the power semiconductor element, the amount of continuous operation allowable temperature exceeding the junction temperature of the power semiconductor element can be extremely small, and the maximum use temperature can not be exceeded. It becomes.

  FIG. 12B shows a waveform when the temperature at which the output restriction is started is adjusted so that the junction temperature of the power semiconductor element does not exceed the allowable continuous operation temperature even in the transient state. Since the output limit is performed based on the temperature including the detection delay due to the film type thermistor 335 time constant, the junction temperature of the power semiconductor element exceeds the allowable continuous operation temperature, but in the vicinity of the power semiconductor element shown in FIG. Compared with the current limit based on the temperature obtained from the placed mold type thermistor 336, the output limit amount in the steady state can be reduced, and the performance of the power converter can be improved.

  FIG. 12 (c) shows a waveform when the coolant flow rate is reduced under the driving conditions when the limiting conditions are determined. Compared to the current limit based on the temperature obtained from the mold type thermistor 336 arranged in the vicinity of the power semiconductor element shown in FIG. 8 (c), the amount of power semiconductor element junction temperature exceeding the allowable continuous operation temperature is extremely small. The range of driving and environmental conditions that do not exceed the maximum operating temperature can be expanded.

  By the temperature protection control described above, it is possible to improve the reliability of protection against thermal destruction due to overtemperature of the power semiconductor element of the power module 300, and to improve the performance of the power converter at low cost.

  In the second embodiment, the power module 300 including the film type thermistor 335 for detecting the temperature of the cooling refrigerant is arranged in the U phase and the V phase in FIG. 4, and the mold is arranged in the vicinity of the conventional power semiconductor element. A power module having a type thermistor 336 is arranged in the W phase.

  As a result, similarly to the first embodiment, the cooling refrigerant temperature and the cooling refrigerant flow rate estimated value of the outlet pipe section 402 can be obtained and detected by the mold thermistor 336 mounted on the power module arranged in the W phase. The junction temperature of the power semiconductor element can be obtained with high accuracy based on the temperature.

DESCRIPTION OF SYMBOLS 4 ... Reducer, 5 ... Drive shaft, 6 ... Wheel, 7 ... Wheel, 135 ... Battery, 136 ... Diode, 138 ... DC connector, 140 ... Inverter part, 144 ... Inverter circuit part, 153 ... Collector electrode, 154 ... Gate Electrode, 155... Signal emitter electrode, 156... Diode, 157... Positive terminal, 158... Negative terminal, 159... AC terminal, 163 ... Collector electrode, 164 ... Gate electrode, 165 ... Signal emitter electrode, 166 ... Diode, 169 ... middle point portion (intermediate electrode), 170 ... control unit, 172 ... control circuit, 174 ... driver circuit, 176 ... signal line, 180 ... current sensor, 182 ... signal line, 186 ... AC power line, 188 ... AC connector, 192 ... Electric motor, 198 ... Signal line, 199 ... Rotation sensor, 200 ... Power converter, 300 ... Power module , 302 ... Module primary sealing body, 304 ... Case, 305 ... Fin, 306 ... Insertion port, 307 A ... Heat dissipation base, 307 B ... Heat dissipation base, 314 ... DC positive terminal, 315 ... Conductor plate, 316 ... DC negative terminal, 319 ... Conductor plate, 325L ... Signal terminal, 325U ... Signal terminal, 328 ... IGBT, 330 ... IGBT, 335 ... Film type thermistor, 336 ... Mold type thermistor, 333 ... Insulating sheet, 348 ... First sealing resin, 401 ... Inlet Piping 402: Outlet piping 500 ... Capacitor module 504 ... Negative side capacitor terminal 506 ... Positive side capacitor terminal 600 ... Auxiliary mold body 901 ... Current control unit 902 ... Three-phase power module loss calculation unit 903 ... cooling refrigerant estimation unit, 904 ... current limit calculation unit, 905 ... command switching unit

Claims (4)

A semiconductor element;
A first conductor plate connected to one electrode of the semiconductor element via a solder material;
A second conductor plate disposed opposite to the first conductor plate across the semiconductor element and connected to the other electrode of the semiconductor element via a solder material;
A sealing material for sealing a part of the first conductor plate, a part of the second conductor plate, and the semiconductor element;
A case for housing the sealing material and serving as a heat dissipation path for the semiconductor element;
An insulating member disposed between the first conductor plate exposed from the sealing material and the case and in contact with the first conductor plate and the inner wall of the case;
A temperature detection element disposed on the inner wall of the case, and a power module comprising:
With multiple power modules,
Forming a flow path for the refrigerant,
The plurality of power modules are arranged in series along the flow direction of the refrigerant,
Among the plurality of power modules, the power module disposed at the most downstream side of the refrigerant flow and at least one other power module include the temperature detection element disposed on an inner wall of the case,
A power converter comprising a cooling refrigerant flow rate estimating unit that estimates a cooling refrigerant flow rate based on a temperature acquired by the temperature detection element . The power conversion device according to claim 1,
A power conversion device that calculates a refrigerant temperature of an outlet pipe portion of the flow path based on a temperature acquired by the temperature detection element. The power converter according to claim 1 or 2,
A power converter provided with the loss calculation part which calculates the loss of the said power module based on the drive conditions of the said power converter. The power conversion device according to any one of claims 1 to 3,
In order for the junction temperature of the semiconductor element not to exceed an allowable value,
A power conversion device that limits an output current of the power conversion device and protects the semiconductor element from over temperature.