JP2011066989A - Power conversion device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To miniaturize a power conversion device as a whole by reducing the size of each switching element which constitutes a step-up/down converter and an inverter. <P>SOLUTION: The switching elements 21, 22 in the step-up/down converter 12 of the power conversion device 40 and the switching elements 34 to 39 in the inverter 13 are of types which are embedded with temperature sensitive diodes 41, respectively, as represented by the switching element 35. When temperatures of the switching elements 21 to 22, 34 to 39 detected by the temperature sensitive diodes 41 exceed preset thresholds, a drive control unit 43 lowers an output voltage Vcc of the step-up/down converter 12 (hereinafter called a boosting voltage) to a voltage value (prescribed value) which can secure a blocking tolerated dose of each switching element 21 to 22, 34 to 39 at the highest use temperature. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a power conversion device that drives an AC motor or a motor generator using a switching element for power conversion such as an IGBT (Insulated Gate Bipolar Transistor).

  Conventionally, there exists a thing of patent document 1 as a power converter device, for example. This power conversion device has a circuit configuration indicated by reference numeral 10 in FIG. 1, and includes a battery 11, a buck-boost converter 12, an inverter 13 that drives and controls a motor generator (load device) MG, and a surge voltage that also serves as a power storage. An absorption capacitor 15 is provided. In addition, the power converter device 10 is accommodated and comprised in one housing.

  The battery 11 is connected to the buck-boost converter 12, supplies DC power to the buck-boost converter 12, and stores DC power regenerated from the buck-boost converter 12.

  The step-up / down converter 12 boosts the DC power supplied from the battery 11 and outputs the boosted DC power to the inverter 13, and steps down the DC power output from the inverter 13 and outputs it to the battery 11. The buck-boost converter 12 is a capacitor 23, a reactor 24, an upper arm switching element (power conversion switching element) 21 which is a high voltage side semiconductor element, and a high voltage GND (ground) side semiconductor element. The lower arm switching element (power conversion switching element) 22 and diodes D1 and D2 are included.

  In these components, one end of the capacitor 23 and the reactor 24 is connected to the positive electrode side of the battery 11, and the other end of the capacitor 23 and the emitter terminal of the switching element 22 are connected to the negative electrode side. The switching element 21 and the switching element 22 are connected in series, and the other end of the reactor 24 is connected between them, that is, the emitter terminal of the switching element 21 and the collector terminal of the switching element 22.

  The collector terminal of the switching element 21 for the upper arm is connected to one end side of the inverter 13 described later. The emitter terminal of the switching element 22 for the lower arm is connected to the other end side of the inverter 13. Between the collector and emitter of the switching element 21, a diode D <b> 1 that allows current to flow from the emitter side to the collector side is connected. Similarly, a diode D <b> 2 is also connected between the collector and emitter of the switching element 22.

  Motor generator MG is connected to inverter 13 and is driven by electric power supplied from battery 11. When working as a generator, AC power is output to the inverter 13.

  The inverters 13 are connected in parallel to each other, convert the DC power boosted by the step-up / down converter 12 into three-phase AC, and output it to the motor generator MG. When motor generator MG functions as a generator, AC power output from motor generator MG is converted to DC and output to buck-boost converter 12.

  The inverter 13 includes a U phase 31, a V phase 32, and a W phase 33, and the U phase 31, the V phase 32, and the W phase 33 are connected to the step-up / down converter 12 in parallel. The U-phase 31 is formed by connecting a switching element 34 for the upper arm of the semiconductor element on the high voltage side and a switching element 35 for the lower arm of the semiconductor element on the high voltage GND side in series. Similarly, the switching element 36 for the upper arm and the switching element 37 for the lower arm are connected in the V phase, and the switching element 38 for the upper arm and the switching element 39 for the lower arm are connected in series in the W phase.

  Between the collectors and emitters of the respective switching elements 34 to 39, diodes D3 to D8 for passing a current from the emitter side to the collector side are respectively connected. An intermediate point of each UVW phase is connected to each phase end of each phase coil (not shown) of motor generator MG. Here, it is assumed that a power device such as an IGBT is used as the switching element included in each of the step-up / step-down converter 12 and the inverter 13.

  In such a power conversion device 10, the DC power of the battery 11 is boosted by the step-up / down converter 12 and converted into three-phase AC by the inverter 13, and the motor generator MG is driven by this three-phase AC. On the other hand, when the motor generator MG functions as a generator, AC power output from the motor generator MG is converted into DC power by the inverter 13, further stepped down by the step-up / down converter 12, and regenerated to the battery 11.

JP 2005-204363 A

  However, in the conventional power conversion device 10 described above, as indicated by a cross in FIG. 2, for example, one switching element 34 of the inverter 13 is connected in series to the switching element 34 in a state where a short circuit has failed. When the switching element 35 is turned on, as indicated by an arrow Y1, an overcurrent corresponding to the voltage Vcc obtained by boosting the voltage of the battery 11 by the step-up / down converter 12 and the circuit impedance of each of the switching elements 34 and 35 flows. Therefore, in order to protect the normal switching element 35, the overcurrent is detected, and the switching element 35 is turned off without exceeding the cutoff withstand capability of the switching element 35.

  The withstand capability is the withstand capability until the switching element breaks, and has a characteristic that the withstand capability decreases as the temperature of the switching element rises, as indicated by a line segment L1 in FIG. Further, as indicated by a line segment L2 in FIG. 4, the withstand voltage has a characteristic of increasing as the area of the switching element increases.

  For this reason, when the temperature of the switching element 35 rises rapidly, the breaking resistance may decrease and the switching element 35 may be damaged. Therefore, after the overcurrent is detected, the switching element 35 is turned off without exceeding the breaking resistance. There is a case where it is impossible to do. Therefore, it is necessary to increase the area by increasing the size of each switching element of the power conversion device 10 to increase the withstand voltage. However, in this case, since each switching element becomes large, there is a problem that the power conversion device 10 that is required to be downsized becomes large.

  This invention is made | formed in view of such a situation, and provides the power converter device which can reduce the whole power converter device by making each switching element which comprises a buck-boost converter and an inverter small. The purpose is to do.

  In order to achieve the above object, the invention according to claim 1 is a buck-boost converter having a plurality of switching elements that boost the DC power of the battery, and converts the boost voltage in the buck-boost converter into an AC voltage. An inverter having a plurality of switching elements, and detecting the temperature of the step-up / down converter and the switching elements of the inverter in a power converter that drives a load device with an AC voltage converted by the inverter, and the detected temperature And a control means for performing control to lower the boosted voltage.

  According to this configuration, if the boosted voltage is lowered based on the detected temperature of the switching element, the boosted voltage also decreases the collector-emitter voltage of the switching element applied between the collector and the emitter. As a result of the increase, the interruption energy consumed until the element enters the interruption (destruction) state is reduced. If this shut-off energy is reduced to a level where the shut-off resistance at the maximum operating temperature of the switching element can be ensured, it is possible to secure a shut-off resistance that does not cause destruction of the element when the temperature rises without increasing the size of the switching element as in the past. Therefore, the element size can be reduced, and thus the entire power conversion device can be reduced.

  According to a second aspect of the present invention, when the control means performs the control to lower the boost voltage, the control device is configured to change the boost voltage to the switching element when the detected temperature exceeds a predetermined threshold. It is characterized in that control is performed to reduce to a predetermined value that can ensure the withstand voltage at the maximum operating temperature.

  According to this configuration, if the boosted voltage is lowered to a predetermined value, the collector-emitter voltage of the switching element to which the boosted voltage is applied between the collector and the emitter is also lowered. ) The cut-off energy spent to reach the state is lowered to a state where the cut-off resistance at the maximum operating temperature can be secured. Therefore, since it is possible to ensure a cutoff withstand capability that does not cause element destruction when the temperature rises without increasing the size of the switching element as in the prior art, the element size can be reduced. The whole can be reduced in size.

  According to a third aspect of the present invention, when the control means performs a control to lower the boost voltage, the boost voltage can be ensured so that a shut-off resistance of the switching element can be ensured while detecting a rising temperature of the switching element. It is characterized in that control is performed to gradually lower the value.

  Also in this configuration, since the control means controls to reduce the cutoff energy when the temperature of the switching element rises to ensure the cutoff tolerance, it is possible to prevent the switching element from being destroyed when the temperature rises even if the switching element is small. Therefore, the element size can be reduced, and thereby the entire power conversion device can be reduced.

  According to a fourth aspect of the present invention, there is provided a temperature-sensitive diode as a means for detecting the temperature of the switching element, wherein the temperature is detected in the switching element and a current corresponding to the detected temperature is supplied to the control means. It is characterized by that.

  According to this configuration, the temperatures of the plurality of switching elements of the buck-boost converter and the inverter can be accurately detected.

  According to a fifth aspect of the present invention, as means for detecting the temperature of the switching element, the electric component including the switching element of the buck-boost converter and the inverter is disposed on a substrate, and the electric component is cooled. The water cooler is provided with a water temperature sensor that detects a temperature of the cooling water and supplies a current corresponding to the detected temperature to the control means.

  According to this configuration, the temperatures of the plurality of switching elements of the buck-boost converter and the inverter can be accurately detected.

  According to a sixth aspect of the present invention, as means for detecting the temperature of the switching element, an atmospheric temperature in the casing is detected in the casing that houses the step-up / down converter and the inverter, and according to the detected temperature. And a temperature sensor for supplying a current to the control means.

  According to this configuration, the temperatures of the plurality of switching elements of the buck-boost converter and the inverter can be accurately detected.

  The invention according to claim 7 is characterized in that the control means performs control to turn off the corresponding switching element when an overcurrent of the switching element is detected.

  According to this configuration, when an overcurrent flows through each switching element in the buck-boost converter and the inverter, the overcurrent is detected by the control means and the corresponding switching element is turned off. The switching element can be protected during an overcurrent.

It is a circuit diagram which shows the structure of the conventional power converter device. It is a circuit diagram which shows a mode that the switching element was damaged in the conventional power converter device. It is a figure which shows the interruption | blocking tolerance and temperature characteristic of a switching element. It is a figure which shows the relationship between the interruption | blocking tolerance of a switching element, and a switching element area. It is a circuit diagram which shows the structure of the power converter device which concerns on embodiment of this invention. It is a flowchart for demonstrating the characteristic control operation at the time of the temperature rise of the switching element in the power converter device of this embodiment. It is a figure for demonstrating reduction | decrease of the interruption | blocking energy at the time of the characteristic control operation | movement in the power converter device of this embodiment. It is a figure which shows an example of the map showing the relationship between the temperature of a switching element and the boost voltage in the power converter device of this embodiment. It is a figure which shows the water temperature sensor arrange | positioned at the cooler provided in the board | substrate of the buck-boost converter and inverter in the power converter device of this embodiment. It is a figure which shows the temperature sensor arrange | positioned in the housing of the buck-boost converter and inverter in the power converter device of this embodiment.

  Embodiments of the present invention will be described below with reference to the drawings. However, parts corresponding to each other in all the drawings in this specification are denoted by the same reference numerals, and description of the overlapping parts will be omitted as appropriate.

  FIG. 5 is a circuit diagram showing a configuration of the power conversion device according to the embodiment of the present invention. The power converter 40 shown in FIG. 5 is different from the conventional power converter 10 shown in FIG. 1 in the switching elements 21 and 22 in the buck-boost converter 12 and the switching elements 34 to 39 in the inverter 13. As shown as a representative of the switching element 35, a type having a built-in temperature sensitive diode 41 is used, and the temperature of each switching element 21-22, 34-39 detected by the temperature sensitive diode 41 is a predetermined threshold value. In this case, the output voltage (hereinafter referred to as boost voltage) Vcc of the step-up / down converter 12 is lowered to a predetermined value by the drive control unit (control means) 43. A predetermined value is a voltage value which can ensure the interruption | blocking tolerance at the time of the highest use temperature of each switching element 21-22, 34-39.

  That is, the drive control unit 43 detects the temperatures of the switching elements 21 to 22 and 34 to 39 detected by the temperature-sensitive diode 41 in step S1 shown in FIG. 6, and the detected temperatures are detected in step S2. When the threshold value is exceeded, in step S3, the boost voltage Vcc is lowered to a predetermined value by controlling the gate voltage of the switching elements 21 and 22 of the buck-boost converter 12. It should be noted that the temperature of each of switching elements 21 to 22 and 34 to 39 increases as the load on motor generator MG increases.

  By reducing the boosted voltage Vcc to a predetermined value in this way, it is possible to reduce the interruption energy that is consumed until the element enters the interruption (destruction) state due to the temperature rise of the switching element. Here, the cutoff energy Esc of the switching element is expressed by the following equation (1).

  Esc = ∫ (ic × Vce) dt (1)

  Where ic is the collector current of the switching element, Vce is the voltage between the collector and emitter of the switching element, and t is the time until the switching element is cut off.

  Since the collector current ic of the switching element and the collector-emitter voltage Vce increase or decrease according to the boosted voltage Vcc applied to the collector side of the switching element, if the boosted voltage Vcc is lowered to a predetermined value as described above, the collector current ic and the collector-emitter voltage Vce also decrease. As a result, the cutoff energy Esc is lowered from the position indicated by Esc1 in FIG. 7 to a position where the cutoff tolerance at the maximum operating temperature of the switching element indicated by Esc2 can be secured. Since the cutoff energy indicated by Esc1 exceeds the cutoff tolerance at the maximum operating temperature in the switching element having a size having the cutoff tolerance-temperature characteristic indicated by the line segment L3, the switching element is destroyed when a predetermined time elapses. However, if the cut-off energy is lowered to the position of Esc2, the cut-off resistance at the maximum operating temperature of the switching element can be ensured, so that the destruction of the switching element is avoided.

  Here, if the switching element is a size having the cutoff tolerance-temperature characteristic indicated by the line segment L4, the cutoff tolerance at the maximum operating temperature can be secured even when the cutoff energy is at the position of Esc1, so that the destruction of the switching element can be avoided. There is a drawback that the size becomes larger than the switching element of the line segment L3.

  Moreover, in the power converter 40, the drive control part 43 detects the overcurrent of each switching element 21-22, 34-39 in the buck-boost converter 12 and the inverter 13, as represented by the switching element 35, Control is performed to turn off the corresponding switching element 35 when an overcurrent is detected.

  As described above, according to the power conversion device 40 of the present embodiment, the temperature sensing diode 41 is incorporated in each of the switching elements 21 to 22 and 34 to 39 in the buck-boost converter 12 and the inverter 13 to detect the element temperature, and this detection. When the temperature exceeds the threshold value, the boost control voltage Vcc is lowered by the drive control unit 43 to a predetermined value that can ensure the withstand voltage at the maximum use temperature of each of the switching elements 21 to 22 and 34 to 39.

  If the boosted voltage Vcc is lowered to a predetermined value in this way, the collector current ic and the collector-emitter voltage Vce of the switching element are also lowered, so that the cutoff energy Esc of the switching element is lowered to a state where the cutoff tolerance at the maximum use temperature can be secured. . As a result, it is possible to ensure the withstand voltage at the maximum operating temperature of the switching element, so that the switching element is not destroyed.

  Conventionally, when the temperature of the switching element rises, the withstand voltage decreases, and the interrupting energy Esc exceeds the reduced withstand voltage, thereby causing element destruction. For this reason, the device size is increased to ensure a withstand voltage that does not cause device destruction even when the temperature rises. However, in the present embodiment, since the control for lowering the boost voltage Vcc is performed so as to ensure a cutoff withstand capability that does not cause element destruction when the temperature rises without increasing the element size as described above, the element size is reduced. Can be Therefore, the whole power converter 40 can be reduced in size.

  Moreover, since the drive control part 43 detected the overcurrent of each switching element 21-22, 34-39 in the buck-boost converter 12 and the inverter 13, and turned off the corresponding switching element 35, each power converter 40 The switching elements 21 to 22 and 34 to 39 can be protected during an overcurrent.

  Moreover, in the said embodiment, when the temperature of each switching element 21-22, 34-39 exceeded a threshold value, the boosting voltage Vcc was lowered | hung to predetermined value by the drive control part 43, but the following control is carried out. May be performed. That is, a map representing the relationship between the boosted voltage Vcc and the temperature of the switching element, as indicated by a line segment L5 in FIG. And while the drive control part 43 detects the temperature which each switching element 21-22, 34-39 raises, the interruption | blocking tolerance is ensured by determining the boost voltage Vcc according to this detection temperature based on a map. Control is performed to gradually lower the boosted voltage Vcc so that it can be performed. Also by this control, the cutoff energy Esc is lowered when the temperature of the switching element rises to ensure the cutoff tolerance, so that even when the switching element is small, it can be prevented from being destroyed when the temperature rises. Therefore, the element size can be reduced, and thereby the entire power conversion device 40 can be reduced.

  In addition, in the said embodiment, although the temperature of each switching element 21-22, 34-39 was detected with the temperature sensitive diode 41, you may detect as follows. That is, the switching elements 21 to 22 and 34 to 39 in the buck-boost converter 12 and the inverter 13 of the power conversion device 40 are mounted on a printed board 51 as shown in FIG. A cooler 53 is fixed to the lower surface of the printed circuit board 51 via a cooling plate 52, and cooling water circulates in the cooler 53 to cool the switching elements 21 to 22 and 34 to 39. Yes. Therefore, a water temperature sensor 55 that measures the temperature of the cooling water is provided in the cooler 53, and the temperature detected by the water temperature sensor 55 is input to the drive control unit 43.

  In this configuration, when the temperature of each of the switching elements 21 to 22 and 34 to 39 rises, the temperature of the cooling water also rises. Therefore, the temperature at this time is detected by the water temperature sensor 55 and input to the drive control unit 43. When the input temperature exceeds the threshold value, the drive control unit 43 performs control to lower the boosted voltage Vcc to a predetermined value as described above.

  In addition, since the cooling water of the cooler 53 is supplied from a radiator of an automobile (not shown), a water temperature sensor 55 is provided in the radiator to measure the temperature of the cooling water of the radiator, and this is input to the drive control unit 43. You may do it.

  In addition, a temperature sensor 57 such as a thermistor is provided on the mounting surface of the switching elements 21 to 22 and 34 to 39 of the printed circuit board 51 shown in FIG. Also good. Also in this case, the temperature detected by the temperature sensor 57 is detected by the drive control unit 43, and when the detected temperature exceeds the threshold value, the boosted voltage Vcc is controlled to a predetermined value as described above.

DESCRIPTION OF SYMBOLS 10,40 Power converter 11 Battery 12 Buck-boost converter 13 Inverter 15 Surge voltage absorption capacitor 21, 22, 34-39 Switching element 23 Capacitor 24 Reactor 41 Temperature sensitive diode 43 Drive control part 51 Printed circuit board 52 Cooling plate 53 Cooling 55 Water temperature sensor 57 Temperature sensor D1-D8 Diode MG Motor generator

Claims (7)

A step-up / down converter having a plurality of switching elements for boosting the DC power of the battery, and an inverter having a plurality of switching elements for converting the boosted voltage at the step-up / down converter to an AC voltage, and the AC voltage converted by the inverter In the power converter that drives the load device at
A power conversion device comprising: control means for detecting temperatures of the switching elements of the step-up / step-down converter and the inverter and performing control for reducing the boosted voltage based on the detected temperatures.   The control means, when performing the control to lower the boost voltage, if the detected temperature exceeds a predetermined threshold, the boost voltage, the cutoff tolerance at the maximum operating temperature of the switching element The power conversion device according to claim 1, wherein control is performed to reduce the value to a predetermined value that can be secured.   When the control means performs control to lower the boost voltage, the control means performs control to gradually lower the boost voltage so that the switching element can be secured while detecting the temperature at which the switching element rises. The power converter according to claim 1, wherein   The means for detecting the temperature of the switching element includes a temperature-sensitive diode that detects a temperature in the switching element and flows a current corresponding to the detected temperature to the control means. 4. The power conversion device according to claim 1.   As a means for detecting the temperature of the switching element, the electric component including the switching element of the buck-boost converter and the inverter is disposed on a substrate, and the cooler that cools the electric part with cooling water The power converter according to any one of claims 1 to 3, further comprising a water temperature sensor that detects a temperature of the cooling water and supplies a current corresponding to the detected temperature to the control means.   As a means for detecting the temperature of the switching element, a temperature for detecting an ambient temperature in the casing in which the step-up / down converter and the inverter are housed, and supplying a current corresponding to the detected temperature to the control means. The power converter according to claim 1, further comprising a sensor.   The power conversion device according to claim 1, wherein the control unit performs control to turn off the corresponding switching element when an overcurrent of the switching element is detected.

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