JP2013240162A - Voltage conversion device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively reduce a loss due to a reduction in switching speed while implementing sufficient voltage withstanding performance in a switching element.SOLUTION: A voltage conversion device (12) converts a voltage by controlling a first switching element (Q1) and a second switching element (Q2) connected in series with each other. The voltage conversion device includes: surge voltage detection means (211, 212) for detecting a surge voltage (Vce) applied to at least either of the first switching element and the second switching element; and gate resistance value change means (213) for changing a gate resistance value (Rg) of at least either element on the basis of the surge voltage.

Description

  The present invention relates to a technical field of a voltage conversion device mounted on, for example, a vehicle.

  2. Description of the Related Art In recent years, as an environmentally-friendly vehicle, an electric vehicle that is mounted with a power storage device (for example, a secondary battery or a capacitor) and travels using a driving force generated from electric power stored in the power storage device has attracted attention. Examples of the electric vehicle include an electric vehicle, a hybrid vehicle, and a fuel cell vehicle.

  In these electric vehicles, a motor generator for generating driving force for traveling by receiving electric power from the power storage device when starting or accelerating, and generating electric power by regenerative braking during braking to store electric energy in the power storage device May be provided. Thus, in order to control a motor generator according to a driving | running | working state, an inverter is mounted in an electric vehicle.

  In such a vehicle, a voltage conversion device (converter) may be provided between the power storage device and the inverter in order to stably supply power used by the inverter that varies depending on the vehicle state. With this converter, the inverter input voltage can be made higher than the output voltage of the power storage device to increase the output of the motor and reduce the motor current at the same output, thereby reducing the size and cost of the inverter and motor Can be achieved.

  The converter is provided with a plurality of switching elements such as transistors, for example, and by performing switching control thereof, the voltage input from the power storage device is converted and output. The switching element is provided with a gate resistance. The higher the gate resistance value, the higher the breakdown voltage performance of the switching element. On the other hand, the higher the gate resistance value, the lower the switching speed of the switching element.

  A decrease in switching speed causes an increase in loss during switching control. In particular, when switching control is performed at a high frequency, the loss at the time of switching control increases with the multiplication factor of the frequency, so the influence cannot be ignored. Therefore, it is preferable that the gate resistance value of the switching element is designed as a value that can realize a switching speed as fast as possible while realizing an appropriate withstand voltage performance.

  Here, the characteristics of the switching elements and circuits are not limited due to manufacturing variations. For this reason, the switching element is designed, for example, with a slight margin for the gate resistance. That is, the gate resistance value is designed to be a little higher than the appropriate value so that sufficient withstand voltage performance can be ensured. In this case, there is a possibility that an unnecessary loss occurs in the switching element.

  As a technique for reducing the loss in such a switching element, for example, in Patent Document 1, the gate resistance value of the switching element is appropriately set based on the time until the voltage between the gate and the emitter of the switching element reaches a set voltage. A technique for changing to an appropriate value has been proposed.

JP 2001-314075 A

  For example, a surge voltage resulting from the parasitic inductance of the wiring is applied to the switching element in the converter. Since the surge voltage is higher than the voltage normally applied to the switching element, the gate resistance value corresponding to this surge voltage must be set in order to make the withstand voltage performance of the switching element appropriate. Is preferred.

  However, with the technique described in Patent Document 1 described above, no consideration is given to the surge voltage when changing the gate resistance value in the switching element. Therefore, even if the gate resistance value is variable, it is difficult to realize a gate resistance value corresponding to the surge voltage. That is, the technique described in Patent Document 1 has a technical problem that there is a possibility that sufficient withstand voltage performance that can withstand a surge voltage cannot be realized.

  The present invention has been made in view of the above-described problems, and provides a voltage conversion device capable of effectively reducing a loss due to a decrease in switching speed while realizing sufficient withstand voltage performance in a switching element. This is the issue.

  In order to solve the above-described problem, a voltage converter according to the present invention is a voltage converter that converts a voltage by controlling a first switching element and a second switching element connected in series with each other. Surge voltage detecting means for detecting a surge voltage applied to at least one of the second switching elements, and gate resistance value changing means for changing a gate resistance value of the at least one element based on the surge voltage With.

  The voltage converter according to the present invention is a converter mounted on a vehicle, for example, and includes a first switching element and a second switching element connected in series with each other. As the first switching element and the second switching element, for example, an IGBT (Insulated Gate Bipolar Transistor), a power MOS (Metal Oxide Semiconductor) transistor, or a power bipolar transistor can be used.

  For example, a diode is connected in parallel to each of the first switching element and the second switching element to form a first arm and a second arm, respectively. In other words, the first switching element forms a first arm, and the switching operation of the first arm can be switched on and off. Similarly, the second switching element forms a second arm, and on / off of driving in the second arm can be switched by the switching operation.

  More specifically, when the voltage conversion device according to the present invention operates, for example, gate signals for switching on and off of the first switching element and the second switching element are generated. The gate signal is generated by comparing, for example, a duty command signal corresponding to the duty ratio of the first switching element and the second switching element and a carrier signal corresponding to the switching frequency of the first switching element and the second switching element. Is done. The generated gate signal is supplied to the first switching element and the second switching element, whereby the driving of the first arm and the second arm of the voltage conversion device is controlled.

  Here, particularly in the voltage conversion device according to the present invention, the surge voltage applied to at least one of the first switching element and the second switching element is detected by the surge voltage detecting means during operation. The surge voltage may be directly detected by a voltage sensor or the like provided in the first switching element and the second switching element, or may be indirectly detected (in other words, estimated) from other parameters.

  When the surge voltage is detected, the gate resistance value changing means converts the gate resistance values of the first switching element and the second switching element (more precisely, the gate resistance value of the switching element in which the surge voltage is detected) into the surge voltage. Changed to the base value. The gate resistance value changing means is configured as a digital potentiometer, for example, and reduces the gate resistance value if the detected surge voltage is lower than a predetermined threshold, and gate resistance if the detected surge voltage is higher than the predetermined threshold. Increase the value.

  If the gate resistance value is changed as described above, for example, when the surge voltage is relatively low, the switching speed is increased by decreasing the gate resistance value. Thereby, the loss at the time of switching control can be reduced. On the other hand, when the surge voltage is relatively high, the withstand voltage performance is improved by increasing the gate resistance value. Thereby, the pressure | voltage resistant performance which can endure a high surge voltage is realizable.

  The detection of the surge voltage and the change of the gate resistance value described above are repeatedly executed during the operation of the voltage converter. Thereby, even if the surge voltage applied to the switching element changes, an appropriate gate resistance value can be realized.

  As described above, according to the voltage converter of the present invention, the gate resistance value of the switching element is changed according to the surge voltage. Therefore, it is possible to effectively reduce a loss due to a decrease in switching speed while realizing a sufficient breakdown voltage performance in the switching element.

  In one aspect of the voltage converter according to the present invention, the surge voltage detection means includes an inductance voltage detection means for detecting a surge voltage generated in a parasitic inductance of a wiring electrically connected to the at least one element, and Surge voltage estimating means for estimating a surge voltage applied to the at least one element from a surge voltage generated in the parasitic inductance of the wiring.

  According to this aspect, when the surge voltage is detected by the surge voltage detecting means, first, the parasitic inductance of the wiring electrically connected to at least one of the first switching element and the second switching element by the inductance voltage detecting means. Is detected.

  Subsequently, the surge voltage applied to the switching element is estimated from the surge voltage generated in the detected parasitic inductance. That is, in this aspect, the surge voltage applied to the switching element is not directly detected, but is indirectly estimated from the surge voltage generated in the parasitic inductance. The surge voltage of the switching element can be estimated, for example, by adding the surge voltage in all the parasitic inductances to the system voltage output from the voltage converter.

  Here, the surge voltage applied to the switching element is a high voltage of, for example, about 1200 V. Therefore, if an attempt is made to directly detect the surge voltage, the size of the detection circuit increases, and the manufacturing cost increases due to an increase in the number of components. Specifically, since a voltage dividing circuit that divides a high voltage into a measurable voltage and an insulating circuit for protecting the circuit from dielectric breakdown are required, the circuit scale and area increase in proportion to the voltage value, Cost will also increase.

  However, in this embodiment, as described above, the surge voltage applied to the switching element is estimated from the surge voltage (for example, about 200 V) generated in the relatively low parasitic inductance. Therefore, the voltage detection operation may be performed by the inductance voltage detection means having a relatively simple configuration. Therefore, it is possible to prevent an increase in the size of the detection circuit and an increase in manufacturing cost.

  In the aspect including the inductance voltage detection means and the surge voltage estimation means described above, the inductance voltage detection means detects a surge voltage generated in a part of the parasitic inductance of the wiring, and the surge voltage estimation means A surge voltage generated in the other part of the parasitic inductance of the wiring is estimated from a surge voltage generated in a part of the parasitic inductance, and at least one of the surge voltage generated in a part of the parasitic inductance of the wiring and the other part. You may comprise so that the surge voltage applied to an element may be estimated.

  In this case, the inductance detection means detects not only the surge voltage generated in the entire parasitic inductance but only the surge voltage generated in a part. On the other hand, the surge voltage estimation means excludes other parts of the parasitic inductance of the wiring from the surge voltage generated in a part of the parasitic inductance of the wiring (that is, a part where the surge voltage is detected when viewed from the whole parasitic inductance). The surge voltage generated in the part) is estimated.

  The surge voltage generated in the other part of the parasitic inductance can be estimated from, for example, the proportion of the entire parasitic inductance in which the voltage is detected. Specifically, for example, a part of the parasitic inductance occupies 1/2 of the whole, and when a surge voltage of 100 V is detected, it is considered that the other part of the parasitic inductance also occupies 1/2 of the whole. Therefore, it can be presumed that a surge voltage of 100 V is generated similarly. Therefore, it can be estimated that a surge voltage of 200 V in total is generated in terms of the entire parasitic inductance.

  When the surge voltage generated in the other part of the parasitic inductance is estimated, the surge voltage estimation means further causes a part of the parasitic inductance of the wiring and the surge voltage generated in the other part (that is, the surge voltage generated in the entire parasitic inductance). Therefore, the surge voltage applied to the switching element is estimated. In this aspect, the detected surge voltage is lower than that in the case where the surge voltage generated in the entire parasitic inductance is detected. Therefore, an increase in the size of the detection circuit and an increase in manufacturing cost can be effectively prevented.

  The effect | action and other gain of this invention are clarified from the form for implementing invention demonstrated below.

1 is a schematic diagram illustrating an overall configuration of a vehicle in which a voltage conversion device according to a first embodiment is mounted. It is a partial block diagram which shows the specific structure of the voltage converter which concerns on 1st Embodiment. It is a flowchart which shows the change process of the gate resistance value in the voltage converter which concerns on 1st Embodiment. It is a partial block diagram which shows the specific structure of the voltage converter which concerns on 2nd Embodiment. It is a flowchart which shows the change process of the gate resistance value in the voltage converter which concerns on 2nd Embodiment. It is a conceptual diagram which shows the estimation method of the surge voltage which concerns on 2nd Embodiment. It is a partial block diagram which shows the specific structure of the voltage converter which concerns on 3rd Embodiment. It is a flowchart which shows the change process of the gate resistance value in the voltage converter which concerns on 3rd Embodiment. It is a conceptual diagram which shows the estimation method of the surge voltage which concerns on 3rd Embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

<First Embodiment>
First, the overall configuration of a vehicle on which the voltage conversion device according to the first embodiment is mounted will be described with reference to FIG. FIG. 1 is a schematic diagram showing the overall configuration of a vehicle on which the voltage conversion device according to the first embodiment is mounted.

  In FIG. 1, a vehicle 100 on which the voltage conversion device according to the present embodiment is mounted is configured as a hybrid vehicle using an engine 40 and motor generators MG1 and MG2 as power sources. However, the configuration of the vehicle 100 is not limited to this, and the vehicle 100 can be applied to a vehicle (for example, an electric vehicle or a fuel cell vehicle) that can be driven by electric power from the power storage device.

  Moreover, although this embodiment demonstrates the structure by which a voltage converter is mounted in the vehicle 100, if it is an apparatus driven by an alternating current motor other than a vehicle, it is applicable.

  The vehicle 100 includes a DC voltage generator 20, a load device 45, a smoothing capacitor C2, and an ECU 30.

  DC voltage generation unit 20 includes a power storage device 28, system relays SR1 and SR2, a smoothing capacitor C1, and a converter 12.

  The power storage device 28 includes a secondary battery such as nickel hydride or lithium ion, and a power storage device such as an electric double layer capacitor.

  System relay SR1 is connected between the positive terminal of power storage device 28 and power line PL1, and system relay SR2 is connected between the negative terminal of power storage device 28 and ground line NL. System relays SR <b> 1 and SR <b> 2 are controlled by a signal SE from ECU 30, and switch between supply and interruption of power from power storage device 28 to converter 12.

  Converter 12 is an example of the “voltage converter” of the present invention, and includes a reactor L1, switching elements Q1 and Q2, and diodes D1 and D2.

  The switching elements Q1 and Q2 are examples of the “first switching element” and the “second switching element” of the present invention, and are connected in series between the power line PL2 and the ground line NL. Switching elements Q1 and Q2 are controlled by a switching control signal PWC from ECU 30.

  As the switching elements Q1 and Q2, for example, an IGBT, a power MOS transistor, a power bipolar transistor, or the like can be used. Anti-parallel diodes D1 and D2 are arranged for switching elements Q1 and Q2.

  Reactor L1 is provided between a connection node of switching elements Q1 and Q2 and power line PL1. Smoothing capacitor C2 is connected between power line PL2 and ground line NL. Reactor current IL that is a current flowing through the reactor is detected by current sensor 18 and output to ECU 30.

  The converter 12 according to the present embodiment is provided with means for changing the gate resistance values of the switching elements Q1 and Q2, but is not shown here for convenience of explanation. The configuration of the means for changing the gate resistance value will be described in detail later.

  Load device 45 includes an inverter 23, motor generators MG <b> 1 and MG <b> 2, an engine 40, a power split mechanism 41, and drive wheels 42. Inverter 23 includes an inverter 14 for driving motor generator MG1 and an inverter 22 for driving motor generator MG2. As shown in FIG. 1, it is not essential to provide two sets of inverters and motor generators. For example, only one set of inverter 14 and motor generator MG1 or inverter 22 and motor generator MG2 may be provided.

  Motor generators MG1 and MG2 receive AC power supplied from inverter 23 and generate rotational driving force for vehicle propulsion. Motor generators MG1 and MG2 receive rotational force from the outside, generate AC power according to a regenerative torque command from ECU 30, and generate regenerative braking force in vehicle 100.

  Motor generators MG1 and MG2 are also coupled to engine 40 via power split mechanism 41. Then, the driving force generated by engine 40 and the driving force generated by motor generators MG1, MG2 are controlled to have an optimal ratio. Alternatively, either one of motor generators MG1 and MG2 may function exclusively as an electric motor, and the other motor generator may function exclusively as a generator. In the present embodiment, it is assumed that motor generator MG1 functions as a generator driven by engine 40, and motor generator MG2 functions as an electric motor that drives drive wheels 42.

  For the power split mechanism 41, for example, a planetary gear mechanism (planetary gear) is used in order to distribute the power of the engine 40 to both the drive wheels 42 and the motor generator MG1.

  Inverter 14 receives the boosted voltage from converter 12, and drives motor generator MG1 to start engine 40, for example. Inverter 14 also outputs regenerative power generated by motor generator MG <b> 1 by mechanical power transmitted from engine 40 to converter 12. At this time, converter 12 is controlled by ECU 30 to operate as a step-down circuit.

  Inverter 14 is provided in parallel between power line PL2 and ground line NL, and includes U-phase upper and lower arms 15, V-phase upper and lower arms 16, and W-phase upper and lower arms 17. Each phase upper and lower arm is composed of a switching element connected in series between power line PL2 and ground line NL. For example, the U-phase upper and lower arms 15 are composed of switching elements Q3 and Q4, the V-phase upper and lower arms 16 are composed of switching elements Q5 and Q6, and the W-phase upper and lower arms 17 are composed of switching elements Q7 and Q8. Antiparallel diodes D3 to D8 are connected to switching elements Q3 to Q8, respectively. Switching elements Q3 to Q8 are controlled by a switching control signal PWI from ECU 30.

  For example, motor generator MG1 is a three-phase permanent magnet type synchronous motor, and one end of three coils of U, V, and W phases is commonly connected to a neutral point. Further, the other end of each phase coil is connected to a connection node of switching elements of upper and lower arms 15 to 17 for each phase.

  Inverter 22 is connected to converter 12 in parallel with inverter 14.

  Inverter 22 converts the DC voltage output from converter 12 into three-phase AC and outputs the same to motor generator MG2 that drives drive wheels. Inverter 22 also outputs regenerative power generated by motor generator MG2 to converter 12 along with regenerative braking. At this time, converter 12 is controlled by ECU 30 to operate as a step-down circuit. Although the internal configuration of the inverter 22 is not shown, it is the same as that of the inverter 14 and will not be described in detail.

  Converter 12 is basically controlled such that switching elements Q1 and Q2 are turned on and off in a complementary manner in each switching period. During the boosting operation, converter 12 boosts DC voltage VL supplied from power storage device 28 to DC voltage VH (this DC voltage corresponding to the input voltage to inverter 14 is also referred to as “system voltage” hereinafter). This boosting operation is performed by supplying the electromagnetic energy accumulated in the reactor L1 during the ON period of the switching element Q2 to the power line PL2 via the switching element Q1 and the antiparallel diode D1.

  Converter 12 steps down DC voltage VH to DC voltage VL during the step-down operation. This step-down operation is performed by supplying the electromagnetic energy accumulated in the reactor L1 during the ON period of the switching element Q1 to the ground line NL via the switching element Q2 and the antiparallel diode D2.

  The voltage conversion ratio (the ratio of VH and VL) in these step-up and step-down operations is controlled by the on-period ratio (duty ratio) of the switching elements Q1 and Q2 in the switching period. If switching elements Q1 and Q2 are fixed to ON and OFF, respectively, VH = VL (voltage conversion ratio = 1.0) can be obtained.

  In the present embodiment, the DC voltage VL before boosting is detected by the voltage sensor 10, and the DC voltage VH after boosting is detected by the voltage sensor 13. Each of the detected DC voltages VL and VH is configured to be output to the ECU 30.

  Smoothing capacitor C <b> 2 smoothes the DC voltage from converter 12 and supplies the smoothed DC voltage to inverter 23.

  When the torque command value of motor generator MG1 is positive (TR1> 0), inverter 14 responds to switching control signal PWI1 from ECU 30 when a DC voltage is supplied from smoothing capacitor C2, and switching elements Q3-Q8 The motor generator MG1 is driven so as to convert a DC voltage into an AC voltage and output a positive torque by the switching operation. Further, when the torque command value of motor generator MG1 is zero (TR1 = 0), inverter 14 converts the DC voltage into the AC voltage and the torque becomes zero by the switching operation in response to switching control signal PWI1. In this manner, motor generator MG1 is driven. Thereby, motor generator MG1 is driven to generate zero or positive torque designated by torque command value TR1.

  Furthermore, during regenerative braking of vehicle 100, torque command value TR1 of motor generator MG1 is set negative (TR1 <0). In this case, inverter 14 converts the AC voltage generated by motor generator MG1 into a DC voltage by a switching operation in response to switching control signal PWI1, and converts the converted DC voltage (system voltage) to smoothing capacitor C2. To the converter 12. The regenerative braking here refers to braking with regenerative power generation when the driver operating the electric vehicle performs a footbrake operation, or regenerative braking by turning off the accelerator pedal while driving, although the footbrake is not operated. This includes decelerating (or stopping acceleration) the vehicle while generating electricity.

  Similarly, inverter 22 receives switching control signal PWI2 from ECU 30 corresponding to the torque command value of motor generator MG2, receives a switching control signal PWI2, and converts the DC voltage into an AC voltage to a predetermined torque by a switching operation. The motor generator MG2 is driven so that

  Current sensors 24 and 25 detect motor currents MCRT1 and MCRT2 flowing through motor generators MG1 and MG2, and output the detected motor currents to ECU 30. Since the sum of the instantaneous values of the currents of the U-phase, V-phase, and W-phase is zero, the current sensors 24 and 25 are arranged to detect the motor current for two phases as shown in FIG. All you need is enough.

  Rotation angle sensors (resolvers) 26 and 27 detect rotation angles θ1 and θ2 of motor generators MG1 and MG2, and send the detected rotation angles θ1 and θ2 to ECU 30. ECU 30 can calculate rotational speeds MRN1, MRN2 and angular speeds ω1, ω2 (rad / s) of motor generators MG1, MG2 based on rotational angles θ1, θ2. Note that the rotation angle sensors 26 and 27 may not be arranged by directly calculating the rotation angles θ1 and θ2 from the motor voltage and current in the ECU 30.

  ECU 30 includes a CPU (Central Processing Unit), a storage device, and an input / output buffer, and controls each device of vehicle 100. Note that the control performed by the ECU 30 is not limited to processing by software, and can be constructed and processed by dedicated hardware (electronic circuit).

  As a representative function, the ECU 30 receives the input torque command values TR1 and TR2, the system voltage VH detected by the voltage sensor 13 and the motor currents MCRT1 and MCRT2 from the current sensors 24 and 25, and the rotation angle sensors 26 and 27. Are controlled so that motor generators MG1 and MG2 output torques according to torque command values TR1 and TR2. That is, switching control signals PWC, PWI1, and PWI2 for controlling converter 12 and inverter 23 as described above are generated and output to converter 12 and inverter 23, respectively.

  During the boost operation of converter 12, ECU 30 feedback-controls system voltage VH, and generates switching control signal PWC so that system voltage VH matches the voltage command value.

  Further, when vehicle 100 enters the regenerative braking mode, ECU 30 generates switching control signals PWI1 and PWI2 so as to convert the AC voltage generated by motor generators MG1 and MG2 into a DC voltage, and outputs it to inverter 23. Thus, inverter 23 converts the AC voltage generated by motor generators MG1 and MG2 into a DC voltage and supplies it to converter 12.

  Further, when vehicle 100 enters the regenerative braking mode, ECU 30 generates a switching control signal PWC so as to step down the DC voltage supplied from inverter 23 and outputs it to converter 12. Thus, the AC voltage generated by motor generators MG1 and MG2 is converted into a DC voltage, and is further stepped down and supplied to power storage device 28.

  Next, a more specific configuration of the above-described converter 12 will be described with reference to FIG. FIG. 2 is a partial configuration diagram showing a specific configuration of the voltage conversion device according to the first embodiment.

  In FIG. 2, the switching element Q1 of the converter 12 according to the present embodiment is provided with a voltage measurement terminal 211a for detecting a surge voltage between the collector and the emitter. One end of the voltage measuring terminal 211a is electrically connected to the vicinity of the collector and the emitter of the switching element Q1, and the other end is electrically connected to the voltage measuring device 212.

  The voltage measuring device 212 is configured as an AD converter (Analog to Digital Converter), a comparator, or the like, for example, and outputs the measured voltage value to the switching element drive circuit 213. The voltage measuring device 212 here functions as an example of the “surge voltage detecting means” of the present invention together with the voltage measuring terminal 211a described above.

  The switching element drive circuit 213 is configured to include a digital potentiometer 214 that makes the gate resistance of the switching element Q1 variable, and changes the gate resistance value according to the voltage value measured by the voltage measuring device 212. That is, the switching element driving circuit 213 here functions as “gate resistance value changing means” of the present invention.

  On the other hand, the switching element Q2 side has the same configuration as the switching element Q1 side described above. That is, the switching element Q2 includes a voltage measuring terminal 221a and a voltage measuring device 222 that detect a surge voltage applied to the switching element Q2, and a switching that changes a gate resistance value according to the surge voltage applied to the switching element Q2. An element driving circuit 223 is provided.

  In addition, parasitic inductances L2, L3, L4, L5, L6, L7, L8, and L9 exist in the wiring connected to the switching elements Q1 and Q2.

  Next, the gate resistance value changing process executed during the operation of the converter 12 according to the present embodiment will be described with reference to FIG. FIG. 3 is a flowchart showing the gate resistance value changing process in the voltage converter according to the first embodiment.

  In FIG. 3, during the operation of the converter 12 of the present embodiment, the switching elements Q1 and Q2 are switching-controlled by first generating the switching control signal PWC (step S101). When the switching elements Q1 and Q2 are controlled, the voltage measuring devices 212 and 222 detect the surge voltage Vce applied to the switching elements Q1 and Q2, respectively (step S102).

  When the surge voltage Vce applied to the switching elements Q1 and Q2 is detected, the switching voltage drive circuit 213 and 223 compares the surge voltage Vce with a predetermined threshold value Vset (step S103). The predetermined threshold value Vset is a value set to realize a gate resistance value that can withstand the surge voltage Vce detected in the switching elements Q1 and Q2, and is determined in advance based on the characteristics of the device and the like. It is stored in a memory or the like included in the element driving circuits 213 and 223.

  In particular, when the detected surge voltage Vce is not greater than the predetermined threshold value Vset (step S103: NO), the gate resistance value Rg is decreased by the digital potentiometers 214 and 224 (step S104). In this way, the switching speed of the switching elements Q1 and Q2 is increased by the amount that the gate resistance value Rg is reduced. Thereby, the loss at the time of switching control can be reduced. Note that although the withstand voltage performance of the switching elements Q1 and Q2 is reduced by the reduction of the gate resistance value Rg, since the surge voltage Vce is equal to or less than the predetermined threshold value Vset, sufficient withstand voltage performance is realized.

  On the other hand, when the detected surge voltage Vce is larger than the predetermined threshold Vset (step S103: YES), the gate resistance value Rg is increased by the digital potentiometers 214 and 224 (step S105). In this way, the withstand voltage performance of the switching elements Q1 and Q2 is improved by the increase in the gate resistance value Rg. Therefore, even when the surge voltage Vce is larger than the predetermined threshold value Vset, sufficient withstand voltage performance is realized.

  The series of processes described above are repeatedly executed during the operation of converter 12. Thereby, even if it is a case where the gate resistance value Rg cannot be made into an appropriate value by one change, it can approach to an optimal value in steps. Even when the surge voltage Vce applied to the switching element changes, an appropriate gate resistance value Rg can be realized.

  As described above, according to the voltage conversion device according to the first embodiment, the gate resistance value Rg of the switching elements Q1 and Q2 is changed according to the surge voltage Vce applied to the switching elements Q1 and Q2. Therefore, it is possible to effectively reduce a loss due to a decrease in switching speed while realizing sufficient withstand voltage performance in the switching elements Q1 and Q2.

Second Embodiment
Next, the voltage converter according to the second embodiment will be described. Note that the second embodiment differs from the first embodiment described above only in part of the configuration, and the other parts are substantially the same. For this reason, below, a different part from 1st Embodiment is demonstrated in detail, and description is abbreviate | omitted suitably about the overlapping part.

  First, a specific configuration of the converter 12 according to the second embodiment will be described with reference to FIG. FIG. 4 is a partial configuration diagram showing a specific configuration of the voltage conversion device according to the second embodiment.

  In FIG. 4, the switching element Q1 of the converter 12 according to the second embodiment is provided with a voltage measurement terminal 211b for detecting a surge voltage generated in the parasitic inductance L2. One end of the voltage measuring terminal 211b is electrically connected to both sides of the parasitic inductance L2, and the other end is electrically connected to the voltage measuring instrument 212. The voltage measuring device 212 outputs the surge voltage generated in the measured parasitic inductance L2 to the switching element driving circuit 213. That is, the voltage measuring terminal 211b and the voltage measuring device 212 here function as an example of the “inductance voltage detecting means” of the present invention.

  The switching element drive circuit 213 estimates the surge voltage applied to the switching element Q1 from the surge voltage generated in the parasitic inductance L2 measured by the voltage measuring device 212. That is, the switching element driving circuit 213 here functions as “surge voltage estimating means” of the present invention. Subsequently, the switching element drive circuit 213 changes the gate resistance value according to the estimated surge voltage of the switching element Q1.

  On the other hand, the switching element Q2 side has the same configuration as the switching element Q1 side described above. That is, the switching element Q2 estimates the surge voltage applied to the switching element Q2 from the voltage measurement terminal 221b and the voltage measuring device 222 for detecting the surge voltage generated in the parasitic inductance L2, and the surge voltage generated in the parasitic inductance L2. Thus, a switching element driving circuit 223 for changing the gate resistance value is provided.

  Next, the gate resistance value changing process executed during the operation of the converter 12 according to the second embodiment will be described with reference to FIG. FIG. 5 is a flowchart showing the process of changing the gate resistance value in the voltage conversion device according to the second embodiment.

  In FIG. 5, during the operation of the converter 12 of the second embodiment, the switching control signal PWC is first generated, so that the switching elements Q1 and Q2 are subjected to switching control (step S201). When the switching elements Q1 and Q2 are controlled, the voltage measuring devices 212 and 222 detect the surge voltage Vsrg generated in the parasitic inductance L2 (step S202).

  When the surge voltage Vsrg generated in the parasitic inductance L2 is detected, the switching element drive circuits 213 and 223 estimate the surge voltage Vce applied to the switching elements Q1 and Q2 (step S203).

  Hereinafter, a method for estimating the surge voltage Vce according to the second embodiment will be specifically described with reference to FIG. FIG. 6 is a conceptual diagram showing a surge voltage estimation method according to the second embodiment. In FIG. 6, for convenience of explanation, only members that affect the surge voltage applied to the switching element Q1 are shown, and other members are not shown as appropriate. For this reason, there is a part in which the configuration is partially different from that in FIG.

  In FIG. 6, it is assumed that the surge voltage Vsrg1 generated in the parasitic inductance La on the emitter side of the switching element Q1 is detected by the voltage measuring device 212 to be 200V. Here, since the current gradient is common on the emitter side and the collector side, if the surge voltage Vsrg1 generated in the parasitic inductance La on the emitter side is detected, the surge generated in the parasitic inductance Lb on the collector side using the L value. The voltage Vsrg2 can be calculated. Here, it is assumed that the surge voltage Vsrg2 generated in the parasitic inductance Lb is calculated as 200V.

  The surge voltage Vce applied to the switching element Q1 can be calculated as the sum of the surge voltage generated by all the parasitic inductances of the wirings electrically connected to the switching element Q1 and the output system voltage VH. Therefore, the surge voltage Vce applied to the switching element Q1 here can be estimated as 200 + 200 + 650 = 1050V. Similarly, on the switching element Q2 side, the surge voltage Vce applied to the switching element Q2 can be estimated using the surge voltage generated in the parasitic inductance.

  Returning to FIG. 5, when the surge voltage Vce applied to the switching elements Q1 and Q2 is estimated, the surge voltage Vce and the predetermined threshold value Vset are compared with each other in the switching element drive circuits 213 and 223 (step S204).

  In particular, when the detected surge voltage Vce is not greater than the predetermined threshold value Vset (step S204: NO), the gate resistance value Rg is decreased by the digital potentiometers 214 and 224 (step S205). On the other hand, when the detected surge voltage Vce is larger than the predetermined threshold Vset (step S204: YES), the gate resistance value Rg is increased by the digital potentiometers 214 and 224 (step S206).

  Since the surge voltage applied to the switching elements Q1 and Q2 is a high voltage of, for example, about 1200 V, if it is attempted to directly detect the surge voltage, the size of the detection circuit increases, and the manufacturing cost increases due to an increase in the number of components. Specifically, since a voltage dividing circuit that divides a high voltage into a measurable voltage and an insulating circuit for protecting the circuit from dielectric breakdown are required, the circuit scale and area increase in proportion to the voltage value, Cost will also increase.

  On the other hand, in 2nd Embodiment, as mentioned above, the surge voltage applied to switching element Q1 and Q2 is estimated from the surge voltage (for example, about 200V) which generate | occur | produces in a comparatively low parasitic inductance. Therefore, it is possible to prevent an increase in the size of the detection circuit and an increase in manufacturing cost.

  Here, the embodiment has been described in which the gate resistance value Rg is changed based on the surge voltage Vce applied to the switching elements Q1 and Q2 estimated from the surge voltage Vsrg generated in the parasitic inductance. If it is set to correspond to Vsrg, the gate resistance value Rg is changed based on the surge voltage Vsrg generated in the parasitic inductance without performing the process of estimating the surge voltage Vce applied to the switching elements Q1 and Q2. You can also.

  As described above, according to the voltage conversion device according to the second embodiment, since it is not necessary to directly detect the surge voltage Vce applied to the switching elements Q1 and Q2, the gates of the switching elements Q1 and Q2 are more preferably used. It is possible to change the resistance value Rg.

<Third Embodiment>
Next, a voltage conversion device according to a third embodiment will be described. Note that the third embodiment differs from the first embodiment and the second embodiment described above only in a part of the configuration, and the other parts are substantially the same. For this reason, below, a different part from 1st Embodiment and 2nd Embodiment is demonstrated in detail, and description shall be abbreviate | omitted suitably about the overlapping part.

  First, a specific configuration of the converter 12 according to the third embodiment will be described with reference to FIG. FIG. 7 is a partial configuration diagram showing a specific configuration of the voltage converter according to the third embodiment.

  In FIG. 7, the switching element Q1 of the converter 12 according to the third embodiment is provided with a voltage measurement terminal 211c for detecting a surge voltage generated in a part of the parasitic inductance L2. One end of the voltage measuring terminal 211c is electrically connected to the end and the center of the parasitic inductance L2, and the other end is electrically connected to the voltage measuring device 212. The voltage measuring device 212 outputs a surge voltage generated in a part of the measured parasitic inductance L2 to the switching element driving circuit 213.

  The switching element driving circuit 213 estimates the surge voltage generated in all of the parasitic inductance L2 from the surge voltage generated in a part of the parasitic inductance L2 measured by the voltage measuring device 212. Then, the switching element driving circuit 213 estimates the surge voltage applied to the switching element Q1 from the surge voltage generated in all of the estimated parasitic inductance L2. Finally, the switching element driving circuit 213 changes the gate resistance value according to the estimated surge voltage applied to the switching element Q1.

  On the other hand, the switching element Q2 side has the same configuration as the switching element Q1 side described above. That is, the switching element Q2 is applied to the switching element Q2 from the voltage measuring terminal 221c and the voltage measuring device 222 for detecting the surge voltage generated in a part of the parasitic inductance L2, and the surge voltage generated in a part of the parasitic inductance L2. A switching element driving circuit 223 is provided for estimating the surge voltage generated and changing the gate resistance value.

  Next, the gate resistance value changing process executed during the operation of the converter 12 according to the third embodiment will be described with reference to FIG. FIG. 8 is a flowchart showing the process of changing the gate resistance value in the voltage converter according to the third embodiment.

  In FIG. 8, during the operation of the converter 12 of the third embodiment, the switching elements Q1 and Q2 are switching-controlled by first generating the switching control signal PWC (step S301). When the switching elements Q1 and Q2 are controlled, the voltage measuring devices 212 and 222 detect the surge voltage Vsrgp generated in a part of the parasitic inductance L2 (step S302).

  When the surge voltage Vsrgp generated in a part of the parasitic inductance L2 is detected, the surge voltage Vsrg generated in the entire parasitic inductance L2 is estimated in the switching element drive circuits 213 and 223 (step S303).

  When the surge voltage Vsrg generated in the entire parasitic inductance L2 is estimated, the surge voltage Vce applied to the switching elements Q1 and Q2 is estimated in the switching element drive circuits 213 and 223 (step S304).

  Hereinafter, a method for estimating the surge voltage Vce according to the third embodiment will be specifically described with reference to FIG. FIG. 9 is a conceptual diagram showing a surge voltage estimation method according to the third embodiment. In FIG. 9, for convenience of explanation, only members that affect the surge voltage applied to the switching element Q1 are shown, and the other members are not shown as appropriate. For this reason, there is a part in which the configuration is partially different from FIG.

  In FIG. 9, it is assumed that the surge voltage Vsrgp generated in a part of the parasitic inductance La on the emitter side of the switching element Q1 is detected by the voltage measuring device 212 to be 100V. Here, assuming that a part of the parasitic inductance La in which the surge voltage Vsrgp is detected occupies 1/2 of the parasitic inductance La, the other parts excluding a part of the parasitic inductance La are also 1/2 of the parasitic inductance La. Therefore, the surge voltage Vsrgq generated in the other part of the parasitic inductance La can be estimated to be 100V. Incidentally, if a part of the parasitic inductance La occupies 1/3 of the parasitic inductance La, the surge voltage Vsrgq generated in the other part of the parasitic inductance La can be estimated to be 200V.

  The surge voltage Vsrg1 generated in the entire parasitic inductance La can be calculated as the sum of the surge voltage parasitic Vsrgp generated in a part of the parasitic inductance La and the surge voltage Vsrgq generated in the other part of the inductance La. Therefore, the surge voltage Vsrg1 generated across the entire parasitic inductance La can be estimated as 100 + 100 = 200V.

  Since the current slope is common on the emitter side and the collector side, if the surge voltage Vsrg1 generated in the parasitic inductance La on the emitter side is detected, the surge voltage Vsrg2 generated in the parasitic inductance Lb on the collector side is detected using the L value. It can be calculated. Here, it is assumed that the surge voltage Vsrg2 generated in the parasitic inductance Lb is calculated as 200V.

  The surge voltage Vce applied to the switching element Q1 can be calculated as the sum of the surge voltage generated in all parasitic inductances of the wiring electrically connected to the switching element Q1 and the output system voltage VH. Therefore, the surge voltage Vce applied to the switching element Q1 here can be estimated as 200 + 200 + 650 = 1050V. Similarly, on the switching element Q2 side, the surge voltage Vce applied to the switching element Q2 can be estimated using the surge voltage generated in a part of the parasitic inductance.

  Returning to FIG. 8, when the surge voltage Vce applied to the switching elements Q1 and Q2 is estimated, the surge voltage Vce and the predetermined threshold value Vset are compared with each other in the switching element drive circuits 213 and 223 (step S305).

  Here, in particular, when the detected surge voltage Vce is not greater than the predetermined threshold value Vset (step S305: NO), the gate resistance value Rg is decreased by the digital potentiometers 214 and 224 (step S306). On the other hand, when the detected surge voltage Vce is greater than the predetermined threshold Vset (step S305: YES), the gate resistance value Rg is increased by the digital potentiometers 214 and 224 (step S307).

  In the third embodiment, since the surge voltage generated in a part of the parasitic inductance is detected, the detected surge is compared with the case where the surge voltage generated in the entire parasitic inductance is detected as in the second embodiment described above. The voltage is lower. Therefore, it is possible to effectively prevent an increase in the size of the detection circuit and an increase in manufacturing cost due to an increase in the detected voltage.

  Here, the embodiment has been described in which the gate resistance value Rg is changed based on the surge voltage Vce applied to the switching elements Q1 and Q2 estimated from the surge voltage Vsrgp generated in a part of the parasitic inductance. If the threshold value Vset is set to correspond to Vsrgp, the gate resistance is determined based on the surge voltage Vsrgp generated in a part of the parasitic inductance without performing the process of estimating the surge voltage Vce applied to the switching elements Q1 and Q2. The value Rg can also be changed.

  As described above, according to the voltage conversion device according to the third embodiment, the gate resistance values Rg of the switching elements Q1 and Q2 can be changed more preferably.

  In each of the above-described embodiments, the processing in the switching elements Q1 and Q2 has been described together. However, a series of processing for changing the gate resistance value Rg is performed independently on the switching element Q1 side and the Q2 side. May be executed. Moreover, although the case where the means for changing the gate resistance value Rg is provided in both of the switching elements Q1 and Q2 has been described, the case where the means for changing the gate resistance value Rg is provided only in one of the switching elements Q1 and Q2. Even if it exists, the effect mentioned above is exhibited appropriately.

  The present invention is not limited to the above-described embodiments, and can be appropriately changed without departing from the gist or concept of the invention that can be read from the claims and the entire specification. Is also included in the technical scope of the present invention.

  DESCRIPTION OF SYMBOLS 10,13 ... Voltage sensor, 12 ... Converter, 18 ... Current sensor, 20 ... DC voltage generator, 22, 23 ... Inverter, 28 ... Power storage device, 30 ... ECU, 40 ... Engine, 41 ... Power split mechanism, 42 ... Drive wheel, 45 ... load device, 100 ... vehicle, 211a, 221a, 211b, 221b, 211c, 221c ... voltage measurement terminal, 212, 222 ... voltage measuring device, 213, 223 ... switching element drive circuit, 214, 224 ... digital Potentiometer, switching C2, smoothing capacitor, D1, D2 ... diode, IL ... reactor current, L1, reactor, L2, L3, L4, L5, L6, L7, L8, L9, La, Lb ... parasitic inductance, MG1, MG2 ... Motor generator, PWC ... gate signal, Q1, Q2 ... switching element, g ... gate resistance value, SR1, SR2 ... system relay.

Claims (3)

A voltage converter for converting a voltage by controlling a first switching element and a second switching element connected in series with each other,
Surge voltage detecting means for detecting a surge voltage applied to at least one of the first switching element and the second switching element;
A voltage conversion device comprising: a gate resistance value changing unit that changes a gate resistance value of the at least one element based on the surge voltage. The surge voltage detecting means is
Inductance voltage detecting means for detecting a surge voltage generated in a parasitic inductance of a wiring electrically connected to the at least one element;
The voltage converter according to claim 1, further comprising: a surge voltage estimating unit that estimates a surge voltage applied to the at least one element from a surge voltage generated in a parasitic inductance of the wiring. The inductance voltage detection means detects a surge voltage generated in a part of the parasitic inductance of the wiring,
The surge voltage estimating means estimates a surge voltage generated in the other part of the parasitic inductance of the wiring from a surge voltage generated in a part of the parasitic inductance of the wiring, and a part of the parasitic inductance of the wiring and the other part. The voltage conversion device according to claim 2, wherein a surge voltage applied to the at least one element is estimated from a surge voltage generated in the voltage.

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